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Quick Reference Guide to All 7 Answers

• 4 methods: plain soap & water, antiseptic soap & water, ABHR (most common), surgical antisepsis
• WHO 6-step technique detailed (20-30 sec for ABHR; 40-60 sec for soap & water)
• Products: alcohol (protein denaturation), chlorhexidine (membrane disruption, 6h persistence), povidone-iodine, triclosan
• WHO's 5 Moments: Before touching patient | Before aseptic procedure | After body fluid exposure | After touching patient | After touching patient surroundings

• Major HAIs: CAUTI (35-40%, most common), VAP, CLABSI, SSI, CDI
• CAUTI defined: UTI in catheterized patient, ≥10³ CFU/mL, symptoms present
• Pathogenesis: extraluminal route most common + biofilm formation; pathogens: E. coli, Klebsiella, Pseudomonas, Candida
• Diagnosis: urine culture (gold standard, ≥10³ CFU/mL), Gram stain, blood culture if septic
• Treatment: Remove catheter + empirical antibiotics (nitrofurantoin/fluoroquinolone for mild; IV piperacillin-tazobactam for sepsis)

• Risk factors: duration of ventilation (most important), MDR risk, prior antibiotics, altered consciousness
• Pathogenesis: aspiration of colonized oropharyngeal secretions past ET tube cuff + biofilm on ET tube
• Diagnosis: BAL (≥10⁴ CFU/mL), PSB (≥10³ CFU/mL), CPIS score, CXR infiltrate
• Treatment: Early VAP - ceftriaxone; Late/MDR - piperacillin-tazobactam/meropenem + vancomycin; 7-8 day course

• Sterilization = complete destruction of ALL life forms (absolute); Disinfection = less precise (spores may survive)
• Principle: Moist heat under pressure (121°C / 15 psi / 15-30 min); kills by protein denaturation
• Diagram provided with labelled components
• Uses: surgical instruments, lab glassware, culture media
• Advantages: reliable, non-toxic, rapid, penetrates packs
• Disadvantages: cannot sterilize heat-sensitive items, oils, powders; requires air expulsion

• High-level: Glutaraldehyde 2%, H₂O₂, Peracetic acid, Formaldehyde - for endoscopes, heat-sensitive critical items
• Intermediate: Alcohols 70%, Iodophors, Chlorine/Hypochlorite, Phenolics - skin antisepsis, surfaces, blood spills
• Low-level: QACs (benzalkonium chloride) - non-critical surfaces
• Spaulding's classification guides selection

• BMW Rules 2016 (India): 4-color coding
  • Yellow bag: Anatomical + soiled + microbiology → Incinerate
  • Red bag: Recyclable plastics/tubing → Autoclave + shred + recycle
  • White container: Sharps/needles → Autoclave + shred + landfill
  • Blue box: Glassware → Autoclave + shred + landfill
• Treatment methods: Incineration, Autoclaving, Microwaving, Chemical disinfection, Plasma pyrolysis

• Definition: Coordinated program to optimize antimicrobial use (right drug, dose, route, duration)
• Need: Rising AMR, C. difficile rates, adverse effects, costs, regulatory requirements
• CDC Core Elements: Leadership, Accountability, Pharmacy expertise, Action, Tracking, Reporting, Education
• Key strategies: Pre-authorization, Prospective audit & feedback, De-escalation, IV-PO switch, Antibiotic time-out, PK/PD optimization, Diagnostic stewardship, Antibiogram surveillance

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HOSPITAL INFECTION CONTROL - Short Structured Questions (All 24 Answers)

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Q1. Define HAI | Sources | Factors | Organisms

Definition

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Sources of HAIs

• Patient's own normal flora (oropharynx, gut, skin, genital tract)
• Microorganisms colonizing the patient before or after admission
• Example: E. coli from patient's gut causing CAUTI; S. aureus from patient's nasal carriage causing SSI

• Healthcare workers' hands (most important exogenous route - transient flora transmitted to patients)
• Other patients (cross-infection via HCW hands, equipment, droplets)
• Healthcare environment: Contaminated surfaces, floors, ventilation ducts, water (Legionella from cooling towers)
• Medical devices and equipment: Contaminated endoscopes, catheters, ventilator circuits, IV fluids
• Visitors (especially immunocompromised patients)
• Food and water supplies

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Factors Affecting HAIs

• Age extremes (neonates, elderly)
• Immunosuppression (HIV/AIDS, malignancy, transplant, steroids)
• Malnutrition
• Diabetes mellitus
• Chronic diseases (COPD, renal failure, hepatic failure)
• Skin breakdown, trauma, burns
• Prolonged hospitalization (longer stay = greater risk)

• Virulence, invasiveness, toxin production
• Ability to form biofilms (catheters, implants)
• Antimicrobial resistance (MRSA, ESBL, CRE)
• Environmental survival (enterococci, C. difficile spores survive for months)

• Invasive devices (urinary catheters, central lines, ET tubes, drains)
• Surgical procedures
• Broad-spectrum antibiotic use (disrupts normal flora, selects resistant organisms)
• ICU admission (sickest patients, most devices, most antibiotic pressure)
• Overcrowding, understaffing
• Poor hand hygiene compliance
• Inadequate sterilization/disinfection
• Lack of isolation facilities

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Organisms Implicated in HAIs

• Enterococcus faecium, S. aureus (MRSA), Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species

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Q2. Modes of Transmission | Standard Precautions | Blood Spill Management

Modes of Transmission of HAIs

• Direct contact: Physical transfer of microorganisms from patient to patient or HCW to patient (e.g., MRSA via hands)
• Indirect contact: Contaminated intermediate object (fomite) - stethoscopes, BP cuffs, door handles, bed rails

• Large respiratory droplets (>5 μm) generated by coughing, sneezing, talking, suctioning
• Settle within ~1 metre of source; do NOT remain suspended in air
• Examples: Streptococcus pyogenes, Neisseria meningitidis, Influenza, Mumps, Rubella, COVID-19

• Small particles ≤5 μm (droplet nuclei) remain suspended in air for prolonged periods and travel >1 metre
• Examples: Mycobacterium tuberculosis, Measles, Varicella-Zoster virus, Aspergillus

• Single contaminated source infects multiple persons
• Examples: Contaminated IV fluids, food, water, blood products

• Insects/arthropods (flies, mosquitoes, ticks)
• Rare in hospital settings

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Standard Precautions (Tier 1 - Apply to ALL patients)

1. Hand Hygiene - before and after every patient contact (WHO 5 Moments)
2. Personal Protective Equipment (PPE):
   • Gloves when touching blood, body fluids, mucous membranes, non-intact skin
   • Gown/apron when clothing may be soiled with blood/body fluids
   • Mask + eye protection/face shield during procedures likely to generate splashes
3. Respiratory/Cough Hygiene:
   • Cover mouth/nose with tissue when coughing/sneezing; dispose of tissue; perform hand hygiene
   • Surgical mask for patients with symptoms in common areas
4. Safe Injection Practices:
   • Use sterile, single-use needles and syringes
   • Never recap needles; use sharps containers
5. Safe Handling of Sharps - use puncture-proof containers; never bend/break needles
6. Patient Placement - single room if patient poses risk of contamination to others
7. Environmental Cleaning and Disinfection - routine cleaning and terminal cleaning of equipment
8. Handling of Linen and Waste - per biomedical waste rules; avoid shaking soiled linen
9. Handling of Patient-Care Equipment - clean and disinfect between patients
10. Safe Injection and Lumbar Puncture Practices

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Management of a Blood Spill

• Put on disposable gloves (double-glove if heavy contamination)
• Wear apron/gown; mask and eye protection if risk of splash

• Do NOT wipe blood with dry cloth (spreads contamination)
• Cover the spill with disposable absorbent paper/towels or sodium dichloroisocyanurate (NaDCC) granules (chlorine-releasing powder, 10,000 ppm available chlorine for blood spills)

• If using NaDCC granules: leave for 2 minutes, then wipe up
• If using liquid: apply 1% sodium hypochlorite (10,000 ppm) over the covered spill; leave for at least 3-10 minutes contact time

• Wipe up with disposable cloths/paper towels working from the outside of the spill inwards
• Place all contaminated materials into a yellow bag (biomedical waste)

• Wipe the area with a fresh cloth soaked in 1,000 ppm hypochlorite (for smooth surfaces)

• Remove gloves and apron carefully; dispose into yellow bag
• Perform thorough hand hygiene with soap and water

• If blood contacts skin/mucous membrane/eyes, wash immediately with copious water
• Report as occupational exposure and initiate PEP assessment if indicated

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Q3. PPE: Types, Donning, Doffing, Precautions

Personal Protective Equipment (PPE) Used in Healthcare

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Steps of DONNING PPE (putting on - in order)

1. Hand hygiene (wash hands or ABHR)
2. Wear gown: Pick up by neck opening; put arms through sleeves; fasten at neck and waist ties at the back
3. Wear mask/respirator: Place over nose, mouth and chin; mould the metal strip to nose; secure ties/straps; fit check (N95: positive/negative pressure check - cupped hands over mask, exhale/inhale)
4. Wear goggles/face shield: Place over eyes; ensure secure fit
5. Wear gloves: Pull over the cuff of the gown (gloves overlap cuffs)

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Steps of DOFFING PPE (removing - in order)

1. Remove gloves first (most contaminated item):
   • Grasp outside of one glove at the wrist
   • Peel off, turning inside out
   • Hold removed glove in gloved hand
   • Slide ungloved fingers inside the second glove; peel off inside out over the first glove
   • Discard both gloves together into waste bin
2. Hand hygiene
3. Remove goggles/face shield:
   • Grasp by headband/earpieces (outer edge)
   • Lift away from face without touching front
   • Place in designated container for reprocessing or discard
4. Hand hygiene
5. Remove gown:
   • Unfasten neck and waist ties
   • Pull gown off touching only inside, rolling it away from you
   • Bundle and discard; avoid contact of outer surface with clothing
6. Hand hygiene
7. Remove mask last (protects airway throughout doffing):
   • Surgical mask: untie bottom strings first, then top strings; hold by strings only
   • N95: remove bottom strap first, then top strap; hold straps
   • Do NOT touch front of mask
8. Final hand hygiene

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Precautions During Doffing

1. Never touch the front/outer surface of any PPE during removal (it is contaminated)
2. Perform hand hygiene between each step of doffing
3. Doff in a designated doffing area (outside the patient room/anteroom)
4. Doff slowly and carefully - no rushing
5. Have a buddy/trained observer watching and guiding the doffing process, especially for high-risk PPE (Ebola, COVID AGPs)
6. Never reuse single-use PPE
7. Dispose of all used PPE immediately into correct waste containers
8. Goggles/face shields (if reusable) go into designated container for cleaning and disinfection
9. If skin or mucous membrane is contaminated during doffing, follow occupational exposure protocol immediately

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Q4. Contact-Transmitted Agents and Infection Control

Agents Transmitted by Contact

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Infection Control Measures for Contact Precautions

1. Patient Placement:
   • Isolate in a single room (preferred) with the door closed
   • If single room unavailable, cohort patients with the same organism
   • Clearly display "Contact Precautions" signage outside the room
2. PPE:
   • Wear gloves upon entering the room (even before touching patient or environment)
   • Wear gown upon entering the room if direct patient contact anticipated
   • Remove gown and gloves before leaving the room
   • Perform hand hygiene immediately after removing PPE
3. Hand Hygiene:
   • For C. difficile and B. anthracis: soap and water (alcohol ABHR does NOT kill spores)
   • For MRSA/VRE/ESBL: ABHR is acceptable
4. Equipment:
   • Dedicate single-patient equipment (stethoscope, BP cuff, thermometer, tourniquet) to each isolated patient
   • If shared, clean and disinfect thoroughly before use on another patient
5. Patient Transport:
   • Limit transport to essential procedures only
   • Inform receiving department/staff of contact precautions
   • Patient should wear clean gown; any wounds should be covered
6. Environmental Cleaning:
   • Enhanced cleaning of the room - twice daily using appropriate disinfectant
   • For C. difficile: use sodium hypochlorite (bleach) 1,000-5,000 ppm (not quaternary ammonium - ineffective against spores)
   • Terminal cleaning (thorough deep clean) after patient discharge using sporicidal agents for C. diff
7. Duration of precautions:
   • MRSA/VRE: until 3 consecutive negative cultures from relevant sites
   • C. difficile: until 48 hours after diarrhea resolves (some guidelines recommend until discharge)
8. Visitor restrictions:
   • Educate visitors; instruct on hand hygiene and PPE use before entering room

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Q5. Droplet-Transmitted Agents and Infection Control

Agents Transmitted by Droplets (>5 μm)

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Infection Control for Droplet Precautions

1. Patient Placement:
   • Place in single room (door may remain open)
   • If no single room: maintain spatial separation of at least 1 metre from other patients; draw curtains
   • Display "Droplet Precautions" sign
2. PPE:
   • Wear a surgical/procedure mask (NOT necessarily N95) when working within 1 metre of the patient
   • Eye protection (goggles/face shield) if risk of droplet splash to eyes
3. Patient Transport:
   • Limit movement; if patient must be transported, have patient wear surgical mask
4. Hand Hygiene: After every patient contact
5. Cough hygiene: Patient should be educated on respiratory etiquette - cover mouth, use tissues, dispose properly
6. Duration: Maintain for the duration of illness (until patient no longer symptomatic/infectious based on pathogen)
7. No special air handling required (unlike airborne precautions)

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Q6. Aerosol-Transmitted Agents and TB Infection Control

Agents Transmitted by Aerosols (Airborne - ≤5 μm droplet nuclei)

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Infection Control for a TB Patient

• Admit to a Negative Pressure Room (Airborne Infection Isolation Room - AIIR):
  • Negative pressure relative to corridor (air flows from corridor INTO the room, not out)
  • Minimum 12 air changes per hour (ACH) - newer facilities; minimum 6 ACH in older facilities
  • Air exhausted directly outside or through HEPA filtration before recirculation
  • Keep door closed at all times
• If no AIIR available: place in closed room away from immunocompromised patients; use portable HEPA unit

• N95 respirator (or equivalent - FFP2) must be worn by ALL staff entering the room
• N95 must be fit-tested before use (qualitative or quantitative fit test)
• Regular surgical masks do NOT protect against airborne TB particles
• Gown and gloves for direct patient care

• Patient should wear a surgical mask (not N95) when being transported outside the room or when HCW is present
• Patient should perform respiratory hygiene (cover cough with tissue, dispose properly)
• Limit transport outside AIIR to essential procedures

• Maintain until:
  • Patient is on effective anti-TB therapy
  • Has shown clinical improvement, AND
  • Has 3 consecutive negative sputum smears for AFB (collected 8-24 hours apart, including one early morning sample)

• All staff in contact with TB patients should be TST/IGRA tested annually
• Newly positive test in HCW working in TB ward = occupational exposure, investigate and treat as appropriate
• BCG vaccination (in countries with routine BCG programs)

• HEPA filters in AIIR
• UV germicidal irradiation (UVGI) in upper-room air supplementation
• No recycling of unfiltered air from isolation rooms

• Restrict visitors; those who must enter wear N95 mask
• Educate on hand hygiene and respiratory precautions

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Q7. Hospital Infection Control Committee (HICC)

Constitution of HICC

• Biomedical waste management officer
• Occupational health physician
• Laundry supervisor

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Functions of HICC

• Formulate, review and update hospital IPC policies, SOPs, and guidelines
• Develop isolation policies (standard, contact, droplet, airborne precautions)
• Develop policies for device management (catheter care bundles, VAP bundles)

• Establish active ongoing surveillance of all HAI types (CAUTI, VAP, CLABSI, SSI, CDI)
• Calculate and monitor HAI rates (per 1000 device days)
• Identify trends, clusters, outbreaks; investigate and intervene

• Detect, investigate, and control outbreaks of nosocomial infection
• Implement case-finding, source identification, control measures
• Communicate with health authorities if needed

• Monitor antibiotic use and resistance patterns
• Develop formulary restrictions and prescribing guidelines
• Review local antibiogram data

• Regular training for all HCWs (hand hygiene, PPE, waste management, needlestick prevention)
• Orientation of new staff to IPC protocols
• Conduct hand hygiene compliance audits and improvement programs

• Microbiological monitoring of OT air, water quality, surfaces
• Oversee CSSD quality control and sterilization monitoring

• Management of needlestick injuries and occupational exposures
• PEP protocols; HCW vaccination programs (HBV, influenza)
• Annual tuberculin skin testing for TB ward staff

• Oversee compliance with BMW management rules
• Audit colour-coding, segregation, transport, and disposal

• Prepare and present periodic reports to hospital administration and quality committee
• Participate in NABH/JCI accreditation processes
• Benchmark HAI rates against national/international standards

• Ensure compliance with national guidelines (MoHFW, ICMR, CDC, WHO)
• Interface with accreditation bodies

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Q8. CRBSI - Risk Factors, Pathogenesis, Lab Diagnosis, Treatment

Definition

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Risk Factors

• Type of catheter: CVC > peripheral IV (femoral > internal jugular > subclavian, in decreasing risk order)
• Duration of catheterization (risk increases with time)
• Multi-lumen catheters (more ports = more entry points)
• Catheter material (polyvinyl chloride > polyurethane - biofilm adherence)
• Emergency insertion (non-sterile conditions)
• Catheter in femoral vein (highest infection risk due to proximity to groin flora)

• Extremes of age (neonates, elderly)
• Immunosuppression
• Total parenteral nutrition (TPN) through the catheter
• Burns, trauma
• ICU stay
• Skin colonization with MRSA or CoNS

• Non-sterile insertion technique (failure of "maximal sterile barrier precautions")
• Frequent catheter manipulation and connections
• Use of needleless connectors if not properly disinfected

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Pathogenesis

1. Extraluminal (skin-to-hub migration) - most common for short-term catheters (<2 weeks):
   • Skin organisms at insertion site (skin flora: CoNS, S. aureus) migrate along the external surface of catheter into the bloodstream
2. Intraluminal (hub contamination) - most common for long-term catheters (>2 weeks):
   • Contamination of catheter hub/connections during manipulation
   • Organisms (hands of HCW) colonize hub, migrate intraluminally
3. Hematogenous seeding:
   • Catheter tip colonized by bacteria from a remote site of infection (e.g., gut translocation)
4. Infusate contamination:
   • Rare; contaminated IV fluid, blood products, or TPN

• Organisms adhere to catheter surface; produce glycocalyx (biofilm)
• Biofilm is resistant to antibiotics and host immune response
• Bacteria detach from biofilm → bacteremia

• Coagulase-negative Staphylococci (CoNS) - most common (especially S. epidermidis)
• Staphylococcus aureus (including MRSA) - most virulent; metastatic complications
• Enterococcus spp.
• Gram-negative rods (Klebsiella, E. coli, Pseudomonas, Acinetobacter)
• Candida spp. (especially in TPN patients, immunocompromised)

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Lab Diagnosis

• Draw two sets of blood cultures before starting antibiotics:
  • One set from each lumen of the central catheter (through catheter hub)
  • One set from a peripheral vein (separate venipuncture)
• Differential Time to Positivity (DTP): If catheter blood culture turns positive ≥2 hours earlier than peripheral culture, it is highly suggestive of CRBSI (sensitivity ~90%, specificity ~85%)

• Remove catheter; cut the distal 5 cm of catheter tip using sterile scissors
• Roll over blood agar plate (Maki's roll plate technique) - ≥15 CFU = significant colonization
• Quantitative sonication method may also be used

• CBC: leukocytosis or neutropenia
• Serum procalcitonin (elevated in bacteremia)
• Echocardiogram if S. aureus bacteremia (rule out endocarditis)
• Ophthalmology review if Candida CRBSI (candidal endophthalmitis)

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Treatment

• Mandatory for: S. aureus, Candida, gram-negative bacteremia, tunnel/port-site infection, septic thrombosis

• Uncomplicated CoNS CRBSI (catheter removed): 5-7 days
• S. aureus CRBSI: minimum 14 days IV (longer if endocarditis/metastatic foci)
• Candida CRBSI: 14 days after first negative blood culture

• Hand hygiene before insertion
• Maximum sterile barrier precautions during insertion (cap, mask, sterile gown, sterile gloves, large sterile drape)
• Chlorhexidine skin antisepsis (2% CHG in alcohol) at insertion site
• Optimal catheter site selection (subclavian preferred over femoral)
• Daily review of catheter necessity and prompt removal when no longer needed
• Chlorhexidine-impregnated dressings
• Disinfect catheter hubs with 70% alcohol or CHG before each access ("scrub the hub" for 15 seconds)

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Q9. SSI - Risk Factors, Pathogenesis, Lab Diagnosis, Treatment

Definition

• Superficial incisional SSI: Involves skin and subcutaneous tissue only
• Deep incisional SSI: Involves deep soft tissue (fascia, muscle layers)
• Organ/space SSI: Involves any anatomy opened/manipulated during surgery (peritoneal cavity, joint space, pleural cavity)

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Risk Factors

• Age extremes; obesity (BMI >30)
• Diabetes mellitus (hyperglycemia impairs neutrophil function)
• Malnutrition (low serum albumin <3.5 g/dL)
• Immunosuppression (steroids, chemotherapy, HIV)
• Pre-existing remote infection (URTI, UTI, skin infection) at time of surgery
• Pre-operative hospitalization >3 days (colonization with hospital flora)
• MRSA nasal colonization
• Smoking (impairs wound healing and oxygenation)
• Chronic renal failure, liver disease

• Wound class (clean → clean-contaminated → contaminated → dirty - increasing SSI risk)
• Duration of surgery (>75th percentile for procedure type)
• Emergency surgery
• Inadequate skin preparation
• Inadequate antibiotic prophylaxis (wrong timing, wrong drug, not given)
• Surgical technique: inadequate hemostasis, excessive tissue trauma, dead space, use of drains
• Contamination of operative field

• Hyperglycemia (glucose >200 mg/dL in first 48 hours)
• Hypothermia during surgery
• Wound hematoma/seroma (culture medium for bacteria)
• Prolonged use of drain
• Inadequate wound care

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Pathogenesis

1. Microbial contamination of the surgical wound:
   • Sources: Patient's endogenous flora (skin, gut, respiratory tract - depending on procedure), OR exogenous (surgical team, instruments, environment)
2. Inoculum exceeds host defense:
   • Normally, a wound can handle small inocula of bacteria; SSI occurs when:
     • Bacterial load is high (heavily contaminated wound)
     • Host defenses are compromised (immunosuppression, poor blood supply, dead space, foreign material)
3. Bacterial multiplication in the wound:
   • Within 3-5 days post-op, bacteria multiply; local tissue invasion begins
   • Production of toxins, enzymes (collagenase, hyaluronidase) that break down tissue
   • Biofilm formation on implants/sutures
4. Inflammatory response:
   • Neutrophil influx → pus formation (abscess)
   • Or spreading cellulitis (diffuse inflammation)
   • Or deep plane involvement (fasciitis, myonecrosis)
5. Systemic consequences:
   • Bacteremia → sepsis → organ dysfunction (if untreated)

• Gram +ve: S. aureus (MRSA), CoNS (implant surgery), Streptococcus spp.
• Gram -ve: E. coli, Klebsiella, Pseudomonas (abdominal, urological surgery)
• Anaerobes: Bacteroides fragilis, Clostridium spp. (colorectal, biliary surgery)
• Fungi: Candida spp. (abdominal/GI surgery, immunocompromised)

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Lab Diagnosis

1. Wound swab culture: Swab of purulent discharge/wound exudate; Gram stain and culture
   • Gram stain: Rapid guide to organism type; report PMNs, organism morphology
   • Culture and sensitivity: Aerobic + anaerobic; 48-72 hours for final result
2. Tissue biopsy: Superior to swab for deep SSI; quantitative culture (>10⁵ CFU/g = significant)
3. Blood cultures: For systemic SSI with fever/sepsis (2 sets from peripheral veins)
4. Imaging:
   • Ultrasound: Detect fluid collections, abscesses (guide aspiration)
   • CT scan: Deep/organ space SSI (peritoneal abscess, mediastinitis, osteomyelitis)
5. CBC, CRP, procalcitonin: Elevated; assess severity; monitor treatment response

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Treatment

• Open and drain superficial SSI; wound packing with saline-moistened gauze
• For deep/organ-space SSI: surgical debridement, drainage, washout
• Negative pressure wound therapy (VAC therapy) for large wounds

• Antibiotic prophylaxis: single pre-operative dose 30-60 min before incision; stop within 24 hours
• Pre-op shower with CHG (2% chlorhexidine)
• Decolonize MRSA carriers pre-operatively (nasal mupirocin + CHG baths)
• Maintain normothermia and euglycemia intraoperatively
• Optimal tissue handling; minimize dead space
• Appropriate wound closure technique

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Q10. Care Bundle Approach for Device-Associated Infections

Definition of Care Bundle

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1. CAUTI Prevention Bundle (5-element bundle)

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2. CLABSI Prevention Bundle (Central Line Bundle)

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3. VAP Prevention Bundle

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4. SSI Prevention Bundle (Peri-operative)

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Key Principle of Bundle Compliance

• Bundles are monitored as "all-or-none" compliance (full compliance vs. any element missed)
• Regular audits of compliance; feedback to teams
• Zero tolerance for missed elements in high-risk patients
• Bundle compliance consistently reduces device-associated HAI rates by 50-70% in ICUs

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Q11. Objectives and Methods of HAI Surveillance

Objectives of HAI Surveillance

1. Establish baseline HAI rates for the facility (incidence density per 1000 patient-days or device-days)
2. Detect trends and changes in HAI rates over time
3. Identify outbreaks and clusters early for rapid investigation and control
4. Evaluate effectiveness of infection control interventions and care bundles
5. Identify risk factors for HAIs specific to the institution
6. Benchmark against other facilities and national/international standards (NHSN, CDC data)
7. Support antimicrobial stewardship - identify resistance patterns, MDROs
8. Provide data for accreditation (NABH, JCI)
9. Educate and motivate HCW through regular performance feedback

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Methods of HAI Surveillance

• Monitors all HAI types in all wards
• Most comprehensive but resource-intensive
• Useful for smaller hospitals

• Focus on high-risk areas (ICU) and high-risk infection types (CLABSI, VAP, CAUTI)
• Most cost-effective method
• CDC-NHSN protocol: ICU-specific device-associated infection surveillance

• Active (prospective): Infection control team proactively identifies cases through daily rounds, lab review, chart review - most sensitive and recommended
• Passive (retrospective): Reporting by clinicians/wards; tends to underestimate due to under-reporting

• Microbiologist reviews all culture reports daily
• Flags significant organisms (MRSA, ESBL, C. diff, fungemia)
• Detects clusters and outbreaks

• Infection Rate = (Number of HAIs / Total patient-days) × 1000
• Device Utilization Ratio = Device-days / Patient-days
• Device-associated Infection Rate = HAIs per 1000 device-days (used for CAUTI, VAP, CLABSI)
• SIR (Standardized Infection Ratio) = Observed infections / Predicted infections (used for benchmarking)

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Q12. Plasma Sterilization - Principle and Uses

Principle of Plasma Sterilization

1. Items are placed in the sterilization chamber (low-pressure sealed chamber)
2. Hydrogen peroxide solution (58%) is injected and vaporized throughout the chamber
3. Plasma is generated using radiofrequency (RF) energy or microwave energy, which creates an electromagnetic field that converts the H₂O₂ vapour into plasma
4. Reactive species are produced: hydroxyl radicals (·OH), hydroperoxyl radicals (·OOH), superoxide anions - these have extremely high oxidizing power
5. These reactive species attack microbial cell membranes, nucleic acids, and enzymes, causing rapid cell death
6. At the end of the cycle, the H₂O₂ breaks down to water and oxygen - no toxic residues

• Chamber temperature: 37-44°C (low-temperature process)
• Cycle time: 28-75 minutes
• H₂O₂ concentration: ~58%

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Uses

• Heat-sensitive surgical instruments: plastic/rubber components, powered instruments
• Endoscopes (rigid and some flexible)
• Fibre-optic cables, cameras, batteries
• Electronic devices (surgical navigation systems, ultrasound probes)
• Implants (as alternative to EO gas)
• Instruments with narrow lumens (some limitations with long, small-bore lumens)

Advantages:

• Low temperature - safe for heat-sensitive items
• Fast cycle time (28-75 minutes vs. 12 hours for ethylene oxide)
• No toxic residues (H₂O₂ decomposes to water + O₂)
• No aeration period needed
• Safe for environment and personnel

Limitations:

• Cannot process cellulose materials (paper, cotton, linen - absorb H₂O₂)
• Cannot process liquids or powders
• Instruments must be dry (moisture interferes with H₂O₂ vaporization)
• Not suitable for very long, narrow-bore lumens (H₂O₂ cannot penetrate adequately)
• More expensive per cycle than autoclave

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Q13. Hot Air Oven (Dry Heat Sterilization)

Functioning of Hot Air Oven

• Dry heat penetrates materials slowly
• Proteins denature at higher temperatures in the absence of moisture
• Hence, higher temperature and longer exposure time are required

• Insulated metal cabinet with electrically heated coils (nichrome wire)
• Fan (in forced-air/convection type) for even heat distribution
• Bimetallic thermostat controls temperature
• Timer for preset cycle duration
• Temperature monitoring with thermometer/thermocouple
• Perforated trays for items

1. Gravity convection oven: Natural convection; slower heat equilibration; less uniform
2. Forced-air/mechanical convection oven: Fan circulates hot air; faster, more uniform temperature - preferred

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Uses of Hot Air Oven

1. Glassware (Petri dishes, test tubes, pipettes, flasks, syringes) - items that cannot be autoclaved due to moisture
2. Oils, petroleum jelly (Vaseline), paraffin wax - cannot be autoclaved
3. Powders (zinc oxide, talcum powder, boric acid) - moisture would cause clumping
4. Metal surgical instruments (scissors, forceps) - where stainless steel is unaffected by high temperatures
5. Sharp instruments (dry heat does not dull cutting edges as moisture does)

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Advantages

1. Penetrates oils, waxes, powders (which steam cannot)
2. No corrosion of metals (no moisture)
3. Does not blunt sharp edges (unlike autoclaving)
4. Simple, cheap, no special plumbing required
5. Non-toxic process
6. Suitable for anhydrous materials

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Disadvantages

1. Cannot sterilize rubber, plastic, or heat-sensitive materials (temperatures >160°C would melt or deform these)
2. Slow - requires long exposure times
3. Poor penetration through wrapped packages or bulky loads
4. Not suitable for liquids (solutions would evaporate)
5. Uneven temperature distribution unless forced-air type is used
6. Not suitable for fabrics, dressings (may char/burn at high temperatures)
7. Monitoring is less reliable - no simple biological indicator equivalent to autoclave's Geobacillus stearothermophilus; uses Bacillus atrophaeus (ATCC 9372) as biological indicator

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Q14. Spaulding's Classification of Medical Devices

Spaulding's Classification

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Three Categories:

• Definition: Items that enter sterile body tissues, the vascular system, or through which sterile body fluids flow
• Risk: High - direct contact with normally sterile areas; any microbial contamination (including spores) can cause serious infection
• Required Level: STERILIZATION (complete destruction of ALL microorganisms)
• Methods: Autoclaving (preferred), dry heat, EO gas, H₂O₂ plasma, glutaraldehyde (10 hours)

• Surgical instruments (scalpels, scissors, forceps, retractors)
• Vascular catheters, needles
• Implants (prosthetic joints, cardiac valves, meshes)
• Urinary catheters (new/single-use)
• Cardiac and urological surgical devices
• Implantable drug delivery systems
• Biopsy forceps, cytoscopes (entering bladder through urethra - sterile tissue contact)

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• Definition: Items that come into contact with mucous membranes or non-intact skin
• Risk: Moderate - mucous membranes resist many common infections but are susceptible to some organisms
• Required Level: HIGH-LEVEL DISINFECTION (kills vegetative bacteria, fungi, mycobacteria, viruses; does NOT kill all spores)
• Methods: Glutaraldehyde 2% (20-45 min), H₂O₂ 6-7.5%, peracetic acid, automated endoscope reprocessors; thermal disinfection (pasteurization at 70°C for 30 min)

• Flexible endoscopes (gastroscope, colonoscope, bronchoscope)
• Laryngoscope blades
• Endotracheal tubes
• Respiratory therapy equipment (nebulizers, spirometer mouthpieces)
• Anaesthetic masks, breathing circuits
• Vaginal specula
• Anorectal manometry probes
• Tonometer tips (ophthalmology)
• Nasogastric tubes

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• Definition: Items that contact only intact skin (not mucous membranes or sterile tissues)
• Risk: Low - intact skin is an effective barrier to most organisms
• Required Level: INTERMEDIATE or LOW-LEVEL DISINFECTION (kills most vegetative bacteria, some viruses; may not kill Mycobacterium or spores)
• Methods: 70% alcohol, iodophor, phenolics, quaternary ammonium compounds, sodium hypochlorite

• Stethoscopes, blood pressure cuffs, thermometers (contact skin)
• Bedpans, urinals (if thoroughly cleaned)
• Crutches, splints, bed rails, call bells
• Hospital furniture surfaces, floors, walls
• ECG electrodes, pulse oximetry probes
• Wheelchairs, stretchers

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Summary Table

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Q15. Central Sterile Supply Department (CSSD)

Definition

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Objectives

1. Provide sterile instruments and equipment to all departments safely and efficiently
2. Centralise sterilization to ensure standardised quality control
3. Prevent cross-infection through systematic reprocessing of instruments
4. Reduce instrument damage by proper cleaning and handling
5. Maintain inventory and tracking of instruments

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Physical Layout (Unidirectional Traffic Flow - "Dirty to Clean")

DECONTAMINATION → CLEANING → INSPECTION/PACKAGING → STERILIZATION → STORAGE → DISTRIBUTION
 (dirty zone)    (wash)       (assembly zone)       (sterile zone)   (sterile)    (dispatch)

1. Receiving/Decontamination Zone (Dirty Zone):
   • Receives soiled instruments from wards/OT
   • Initial sorting, disassembly
   • Manual cleaning (enzymatic detergent soak, brushing), washer-disinfectors (automated)
   • Staff wear heavy-duty gloves, aprons, eye protection
2. Cleaning and Inspection Zone (Clean Zone):
   • Inspection of cleaned instruments (magnification loops)
   • Integrity check (no cracks, proper articulation of hinges)
   • Function testing
3. Assembly/Packing Zone:
   • Assembly of instrument sets/trays
   • Wrapping in double-layer crepe paper, non-woven fabric, or rigid containers
   • Placement of chemical indicators (CI) in each pack
   • Labelling with date, contents, expiry
4. Sterilization Zone:
   • Sterilizers: autoclave, EO gas sterilizer, H₂O₂ plasma sterilizer
   • Loading in standardized patterns
5. Sterile Storage Zone:
   • Temperature 18-22°C; humidity 35-70%
   • Items stored off the floor, away from walls, sinks
   • First In First Out (FIFO) system
   • Shelf life: depends on packaging (e.g., double-wrapped items: 6 months)
6. Distribution:
   • Dispatch to wards/OT in covered clean trolleys
   • Return of unsterile or outdated items tracked

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Quality Control in CSSD

1. Mechanical/Physical indicators: Temperature, pressure, time printouts from sterilizer
2. Chemical indicators (CI - Class 1-6):
   • Class 1: Process indicators (change colour to indicate item was processed)
   • Class 6: Emulating indicators (most specific - confirm all parameters met)
3. Biological indicators (BI): Geobacillus stearothermophilus spores for autoclave; Bacillus atrophaeus for EO; run weekly
4. Bowie-Dick test: Daily air removal test for pre-vacuum autoclaves - validates steam penetration
5. Traceability system: Barcode/RFID tracking of each instrument set to patient

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Q16. Indicators for Sterilization Efficacy and Tests for Chemical Disinfectants

Sterilization Efficacy Indicators

• Printouts of sterilization cycle parameters (temperature, pressure, time, humidity) from sterilizer's own sensors
• Provide real-time data; checked by operator after each cycle
• Limitations: Do not confirm product was sterilized if placed incorrectly

• Run frequency: At least weekly for routinely used sterilizers; with each load for implants
• Interpretation: BI placed in most challenging location of sterilizer; after cycle, incubate - no growth = sterilization achieved; growth = sterilization failure (recall affected loads)

• Run daily (first thing in the morning) before processing any loads
• Tests the air removal system of the vacuum phase
• A standard test pack with chemical indicator sheet is placed in the autoclave
• After cycle: even colour change = adequate air removal and steam penetration; uneven change = air pockets = failed air removal → do not use sterilizer; investigate

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Tests for Efficacy of Chemical Disinfectants

• Compares germicidal activity of a test disinfectant to phenol (reference standard) against Salmonella typhi and S. aureus
• Phenol Coefficient (PC) = MIC of phenol / MIC of test compound
• PC >1 = more effective than phenol; PC <1 = less effective
• Limitation: does not test in presence of organic matter

• Modification of Rideal-Walker; performed in the presence of added yeast (simulates organic matter/dirty conditions)
• More realistic test

• Standard gold test for disinfectants in USA
• Carriers (stainless steel cylinders) contaminated with organism, dried, then immersed in test disinfectant
• After contact time, carriers are transferred to growth media - no growth = bactericidal
• Tests against S. aureus, Salmonella choleraesuis, P. aeruginosa

• Organism suspended in test disinfectant for a defined contact time
• Count survivors; log reduction ≥5 log₁₀ = effective

• Tests disinfectant on contaminated surfaces

• Samples of disinfectant taken from actual use in the hospital tested for contamination

• 5 colonies per sample = disinfectant contaminated/inactivated = replace

• Kinetics of killing: measure bacterial counts at multiple time points after contact with disinfectant

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Q17. Disinfection of Operation Theatre and Membrane Filters

Disinfection of Operation Theatre (OT)

1. Damp dusting of all horizontal surfaces (OT table, instrument trolleys, light handles, anaesthetic machine, IV poles) with 1% hypochlorite or quaternary ammonium compound - all surfaces wiped with microfibre cloth soaked in disinfectant
2. Floor mopping with phenolic disinfectant or hypochlorite
3. Check air-handling unit (laminar airflow or AHU) is functioning; minimum 20 ACH for conventional OT; minimum 300 ACH for ultra-clean laminar airflow theatres

1. Remove soiled drapes, linen, instruments from OT table
2. Wipe OT table and all surfaces with 70% alcohol or 1% hypochlorite
3. Mop floor with disinfectant; allow drying
4. Dispose of all single-use materials; send instruments to CSSD
5. At least 10-15 minutes between cases for surface disinfection and air exchange

1. Thorough cleaning of all surfaces - OT table, walls, floor, lights, equipment
2. Disinfection with 1% sodium hypochlorite or 2% glutaraldehyde for equipment
3. Fumigation (if required): Formaldehyde fumigation (8 mL of 40% formalin per cubic metre, with heating to generate vapour) for 12-24 hours; then neutralised with ammonia - requires OT to be sealed; rarely done routinely due to toxicity
4. Modern alternative: Hydrogen peroxide vapour (HPV) fogging - automated, effective, non-toxic, shorter turnaround

• Deep cleaning of walls, ceilings, overhead lights, ducts, equipment
• Microbiological sampling (settle plates, air sampling) after cleaning

• HEPA filtration (removes ≥99.97% of particles ≥0.3 μm)
• Positive pressure relative to surrounding areas (prevents entry of contaminated air)
• Laminar Airflow (LAF) for ultra-clean environments (orthopaedic joint replacement surgery): unidirectional airflow 0.3-0.5 m/s; reduces SSI from ~5% to ~0.5%
• Minimum 20 ACH for conventional OT; up to 300 ACH in ultra-clean LAF theatres

• Formaldehyde (formalin): most traditional; toxic, carcinogenic, long aeration time
• Hydrogen peroxide vapour (HPV/VHP): preferred modern method; automated dispensers; no toxic residue; effective against spores; 30-60 min cycle; no aeration needed
• Glutaraldehyde spray: less commonly used for surfaces

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Membrane Filters

• Pore size 0.22 μm retains all bacteria (average bacterial size 1-2 μm) and fungi
• Pore size 0.45 μm retains most bacteria (standard microbiological membrane filter)
• Viruses (20-300 nm) are NOT retained by standard membrane filters
• Sterile filtration (0.22 μm) is used for heat-sensitive solutions

1. Sterilization of heat-sensitive solutions:
   • IV drug preparations (vitamins, insulin, certain cytotoxics)
   • Radiological contrast media, eye drops
   • Culture media components (serum, antibiotics added to media)
2. Water testing (bacteriological quality):
   • Large volume of water (100-1000 mL) filtered through 0.45 μm membrane
   • Membrane placed on selective agar (MacConkey for coliforms); incubated
   • Coliform count/100 mL of water (WHO standard: 0 coliforms/100 mL for drinking water)
3. Intravenous line filters:
   • In-line 0.22 μm filters on IV lines to prevent particulate matter and microorganisms entering patient
4. HEPA filters (High Efficiency Particulate Air):
   • Not membrane filters per se but work on similar filtration principles
   • 0.3 μm filtration of air; ≥99.97% efficiency
   • Used in: OT, AIIR (negative pressure rooms), CSSD, laminar airflow hoods, BSL-3/4 laboratories
5. Laboratory uses:
   • Sterilize sensitive reagents
   • Concentrate organisms from large volumes (water, milk testing)

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Q18. Needle Stick Injury - Agents, Precautions, PEP Steps

Agents Transmitted by Needle Stick Injury (NSI)

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Precautions While Handling Needles

1. Never recap needles with two hands (most common cause of NSI - 27% of NSIs)
2. If recapping is unavoidable: use one-handed scoop technique or mechanical recapping device
3. Never bend, break, or cut needles by hand
4. Dispose immediately after use into puncture-proof sharps container (never overfill beyond 3/4 mark)
5. Never pass needles hand-to-hand - use a kidney tray/neutral zone
6. Use safety-engineered sharps devices (retractable needles, shielded syringes) wherever available
7. Wear gloves during all venipuncture and IV procedures
8. Maintain clear workspace; avoid clutter and distractions
9. Announce to team when using sharps ("sharp on field")
10. Sharps containers must be at point of use (within arm's reach) - do not carry sharps across the room

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Steps of Post-Exposure Prophylaxis (PEP) - General

• Wash the wound immediately and thoroughly with soap and running water for at least 2-3 minutes
• Gently squeeze the wound to encourage bleeding
• Do NOT suck the wound (mucous membrane contact)
• For splash to eyes/mucous membranes: flush with copious sterile saline or water for 5-10 minutes
• Apply antiseptic (povidone-iodine or 70% alcohol) after washing

• Report to designated occupational health/infection control officer
• Fill incident report form (date, time, circumstance, source patient details, body part involved, depth of injury)

• Evaluate the injury: depth (deep laceration > superficial), visible blood on device, device type (hollow bore needle > solid needle)
• Identify and assess the source patient: obtain consent; test for HIV, HBsAg, anti-HCV (rapid tests)
• Assess HCW baseline: HIV status, HBV vaccination and anti-HBs titre, HCV status

• Do not delay - start PEP as soon as possible (ideally within 2 hours)
• PEP after 72 hours is generally not effective for HIV
• Refer to specific PEP protocols below (Q19, Q20)

• Counselling
• Repeat testing at 6 weeks, 3 months, 6 months for HIV; 3 and 6 months for HCV
• Monitoring for drug toxicity during PEP
• Psychological support

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Q19. PEP for HIV

HIV PEP Protocol

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• Tenofovir Disoproxil Fumarate (TDF) 300 mg + Emtricitabine (FTC) 200 mg once daily (as fixed-dose combination: TruvadaR)
• PLUS Raltegravir (RAL) 400 mg twice daily (preferred third drug - integrase inhibitor)

• Lopinavir/ritonavir (LPV/r) 400/100 mg twice daily, OR
• Atazanavir/ritonavir 300/100 mg once daily, OR
• Dolutegravir 50 mg once daily

• Baseline HIV Ag/Ab test at time of exposure
• Repeat at 6 weeks, 3 months, 6 months
• Liver function, renal function (for TDF toxicity monitoring) at baseline and at 2 weeks
• Test source patient (rapid HIV test) - if source is HIV negative (not window period), PEP may be discontinued
• If source has drug-resistant HIV: seek ID specialist consultation; modify PEP accordingly

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Q20. PEP for Hepatitis B

HBV PEP Protocol

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• Dose: 0.06 mL/kg IM (usually 5 mL for adult)
• Site: Anterolateral thigh or deltoid
• Timing: As soon as possible, ideally within 24 hours of exposure; maximum 7 days for percutaneous exposure; 14 days for sexual exposure
• Mechanism: Passive immunization - provides immediate anti-HBs antibodies

• Start at time of HBIG (different site)
• Complete full 3-dose series (0, 1, 6 months)
• Check anti-HBs titre 1-2 months after completing series

• Test for HBsAg and anti-HBs at 3 and 6 months post-exposure
• If HCW develops HBV infection: refer to hepatologist; consider antiviral therapy if chronic

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Q21. Monitoring AMSP Compliance | DDD and DOT

Monitoring Compliance with AMSP

• Days of Therapy (DOT) per 1000 patient-days - primary metric for antibiotic consumption
• Defined Daily Doses (DDD) per 1000 patient-days - WHO metric for antibiotic use
• Pre-authorization compliance rate: % of restricted antibiotic orders properly approved
• Time to antibiotic de-escalation after culture results
• IV-to-oral switch rate
• Rate of antibiotic "timeouts" performed at 48-72 hours
• Duration of prophylactic antibiotic use (% discontinued within 24 hours post-surgery)
• Antibiotic prescribing appropriateness rate (via audit of indications)

• HAI rates (CDI rate per 10,000 patient-days - most sensitive AMSP outcome)
• MDR organism acquisition rates (MRSA, ESBL, CRE)
• Antibiotic-related adverse event rates
• In-hospital mortality rates for infectious diagnoses
• Length of hospital stay

• Regular prescription audits (random sample review by ID pharmacist/physician)
• Point prevalence surveys (PPS) - cross-sectional survey of all patients on a given day; identify what percentage are on antibiotics and for what indication
• Daily stewardship rounds in ICU
• Electronic antimicrobial management systems (EAMS) with computerized physician order entry and clinical decision support

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DDD (Defined Daily Dose)

• Definition (WHO): The assumed average maintenance dose per day for a drug used for its main indication in adults.
• Set by the WHO Collaborating Centre for Drug Statistics Methodology
• Example: DDD for amoxicillin = 1 g/day; if a patient received 6 g over 3 days, this represents 6/1 = 6 DDDs
• Metric: DDD per 100 bed-days or DDD per 1000 patient-days
• Use: Comparing antibiotic use between hospitals, countries, or over time; aggregate/population-level metric
• Limitation: Does not reflect actual doses given to individual patients; less accurate for paediatric or renal-impaired patients

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DOT (Days of Therapy)

• Definition: The number of calendar days a patient receives an antibiotic, regardless of dose
• Example: A patient on ciprofloxacin for 7 days = 7 DOT for ciprofloxacin (regardless of 250 mg or 750 mg dose)
• Metric: Total DOT per 1000 patient-days (or per 100 patient-days)
• Use: Preferred metric for patient-level prescribing; recommended by IDSA/SHEA over DDD for AMSP monitoring
• Advantage: More accurate; accounts for actual number of days exposed; better at capturing paediatric prescribing

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Q22. Escalation, De-escalation and Hospital Antibiogram

Escalation Approach (Broad to Broader)

• In low-risk patients (community-acquired infections, no MDR risk factors)
• In mild-moderate infections where empirical coverage may be adequate

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De-escalation Approach (Broad to Narrow)

• Culture and sensitivity results are available
• Patient shows clinical improvement

1. Empirical therapy at 0-48h: Broad-spectrum IV antibiotics (e.g., meropenem + vancomycin for ICU patient with sepsis)
2. Antibiotic timeout at 48-72h: Review culture results
3. De-escalate based on culture:
   • If MSSA: switch vancomycin to nafcillin/cloxacillin
   • If ESBL-Klebsiella UTI: switch carbapenem to ceftriaxone if susceptible
   • If no organism grown + patient improving: stop antibiotics
4. Switch IV to oral when patient tolerating PO and clinically improving

• Reduces antibiotic resistance selection pressure
• Reduces CDI risk
• Reduces toxicity
• Reduces pharmaceutical costs
• Does NOT increase mortality or treatment failure when appropriately applied

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Hospital Antibiogram

1. Guide empirical antibiotic therapy selection (what drug is most likely to be active against local organisms)
2. Track trends in antimicrobial resistance over time
3. Inform institutional prescribing guidelines and drug formulary decisions
4. Benchmark against regional/national data (WHONET, AMASS)
5. Detect emerging resistance patterns and potential outbreaks

• Lists all commonly isolated organisms (rows) and antibiotics (columns)
• Shows % susceptibility for each organism-antibiotic combination
• Based on first isolate per patient per year (eliminates duplicate isolates)
• Minimum 30 isolates per organism-antibiotic combination for reliable data (CLSI M39 guidelines)

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Q23. Microbial Contamination of Water | Methods of Surveillance | Eijkman Test

Classification of Microbial Contamination of Water

• Indicator organisms (most important):
  • Escherichia coli - definitive indicator of recent fecal contamination
  • Coliforms (total coliforms): family Enterobacteriaceae including E. coli, Klebsiella, Enterobacter - general indicator
  • Fecal coliforms (thermotolerant coliforms): coliforms that grow at 44-44.5°C; include E. coli and some Klebsiella spp.
  • Fecal streptococci / Enterococcus spp.: indicate fecal pollution
• Pathogenic bacteria in water:
  • Vibrio cholerae (cholera)
  • Salmonella typhi and paratyphi (typhoid)
  • Shigella spp. (dysentery)
  • Campylobacter spp.
  • Legionella pneumophila (cooling towers, hot water systems)
  • Pseudomonas aeruginosa (hospital water supplies)
  • Cryptosporidium, Giardia (protozoa - not bacteria)

• Poliovirus, Hepatitis A virus, Norovirus, Rotavirus
• Standard water treatment removes most viruses; importance in immunocompromised

• Cryptosporidium parvum, Giardia intestinalis - resistant to chlorination
• Entamoeba histolytica, Cyclospora

• E. coli: 0 per 100 mL (drinking water)
• Total coliforms: 0 per 100 mL (drinking water)

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Methods of Surveillance of Water Quality

• Serial dilutions of water inoculated into MacConkey broth or lactose broth
• Incubated at 37°C for 24-48h
• Presumptive test: Gas production (CO₂) = presumptive coliform
• Confirmatory test: Subculture into brilliant green bile broth at 37°C; gas = confirmed coliform
• Completed test: Subculture on EMB/MacConkey agar; metallic sheen colonies confirm E. coli
• MPN tables give estimated count of coliforms per 100 mL

• 100 mL of water filtered through 0.45 μm membrane
• Membrane placed on MacConkey agar (coliforms) or mFC agar (fecal coliforms) or m-Endo agar
• Incubated; fecal coliforms on mFC agar at 44.5°C (Eijkman temperature)
• Count colonies; express as CFU/100 mL
• Advantages: More sensitive, faster, handles larger volumes, easier to perform

• Single tube test for 100 mL of water
• Simple; used for smaller supplies/field testing

• Rapid modern method; uses ONPG (for total coliforms) and MUG (for E. coli)
• Yellow colour = total coliforms; blue fluorescence under UV = E. coli
• Results in 24 hours; widely used now

• Assess overall bacterial load (not specifically fecal indicator)
• <500 CFU/mL is acceptable for treated water

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Eijkman Test

• E. coli and other fecal coliforms can ferment lactose with gas production at 44-44.5°C (elevated incubation temperature)
• Non-fecal coliforms (e.g., soil coliforms like Enterobacter, Klebsiella soil strains) cannot ferment lactose at this elevated temperature and are inhibited

1. Take a positive tube from the presumptive MPN test (gas in MacConkey/lactose broth at 37°C)
2. Subculture into MacConkey broth or EC broth (E. coli medium)
3. Incubate at 44-44.5°C (water bath with precise temperature control essential) for 24-48 hours
4. Observe for gas production (positive = fecal coliform present)

• Gas production at 44-44.5°C = Eijkman test positive = fecal coliforms present
• No gas = Eijkman test negative = no fecal coliforms (non-fecal coliforms only)

• Positive Eijkman test strongly indicates recent fecal contamination of water
• E. coli is the most common thermotolerant coliform; its presence confirms fecal pollution

• Below 44°C: false positives (non-fecal coliforms grow)
• Above 44.5°C: false negatives (E. coli inhibited)

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Q24. Evaluation of Quality of Air in Operation Theatre

Importance

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Parameters for Acceptable OT Air Quality

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Methods of Evaluating OT Air Quality

• Principle: Organisms in air settle by gravity onto open blood agar or nutrient agar plates
• Procedure:
  • Place 90 mm diameter blood agar settle plates at strategic positions in OT (operating table level, 4 corners, instrument trolley area)
  • Expose for 1 hour
  • Incubate at 37°C for 24-48 hours
  • Count colonies (CFU/plate/hour)
• Acceptable: <5 colonies/plate/hour (some guidelines: <35 CFU/m³ converted using Omerod's formula)
• Limitations: Does not sample very small or light particles; dependent on air turbulence; passive (not active sampling)

• Impingement method: Air is drawn through liquid medium; organisms collected in liquid; plated on agar
• Impaction method (RCS - Reuter Centrifugal Sampler, SAS - Surface Air Sampler):
  • Air drawn through slit/hole at known flow rate
  • Particles impacted onto rotating agar strip or plate
  • Known volume of air sampled = results expressed as CFU/m³
  • RCS: 100 L/min; most widely used portable active sampler
• More accurate than settle plates; gives CFU/m³

• Particle counters measure airborne particles by size (≥0.5 μm, ≥5 μm)
• Used for ISO classification of clean rooms
• Does not distinguish live from dead particles; needs to be correlated with microbiological data

• Surface swabs from OT table, lights, walls, floor after cleaning
• Detects environmental contamination

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When to Sample OT Air

1. Routine monitoring: Weekly/monthly settle plates in all OTs (part of HICC surveillance)
2. After installation of new HVAC/AHU or HEPA filters
3. After fumigation (to confirm decontamination effectiveness)
4. After outbreak of SSIs (investigate potential airborne source)
5. During accreditation assessments (NABH, JCI)

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Factors Affecting OT Air Quality (and how to control them)

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Key References:

• Harrison's Principles of Internal Medicine, 22nd Ed, 2025 (HIV PEP, CAUTI)
• Murray's Medical Microbiology, 9th Ed (Sterilization, Disinfection, Plasma sterilization)
• Bailey & Love's Short Practice of Surgery, 28th Ed (HAI, SSI)
• Goldman-Cecil Medicine, International Edition (AMSP, Stewardship)
• Sherris & Ryan's Medical Microbiology, 8th Ed (Sterilization definitions, disinfectants)
• Jawetz, Melnick & Adelberg's Medical Microbiology, 28th Ed (HAI prevention)
• WHO IPC Guidelines (Hand hygiene, Standard Precautions, OT air quality)
• CDC/NHSN Guidelines (HAI surveillance, PEP, care bundles)
• Biomedical Waste Management Rules, India 2016 (BMW)

• High-yield topics to revise thoroughly: CAUTI/VAP/CRBSI/SSI pathogenesis, WHO 5 Moments, Spaulding's classification, Care bundles, PEP for HIV/HBV, and BMW colour coding.
• Draw diagrams where asked - the autoclave diagram, hand hygiene steps, and OT air flow diagrams score well.
• For short answers, structure your response with a definition first, then subheadings - it makes it easier to read and score.
• The ESKAPE organisms mnemonic is worth remembering for HAI organism questions.