IMG_2067.jpg

Answers keep it Brief

Reading File

Given the budget constraints, I'll answer all questions directly from my medical knowledge. Here are brief answers to all exam questions:

LONG ESSAYS

Q1. Bronchoscope Disinfection (Spaulding's Classification)

A. Disinfectant Classes & Mechanism of Action:

Class	Example	Mechanism
High-level disinfectants	Glutaraldehyde 2%, OPA	Alkylates proteins/DNA
Intermediate-level	70% Alcohol, Iodophors	Protein denaturation, disrupts lipid membrane
Low-level	Quaternary ammonium compounds	Disrupts cell membrane

B. Spaulding's Classification:

Critical (enters sterile tissue): Sterilization required - e.g., surgical instruments
Semi-critical (contacts mucous membranes): High-level disinfection - e.g., bronchoscopes, endoscopes
Non-critical (contacts intact skin): Low/intermediate disinfection - e.g., BP cuffs, stethoscopes

C. Disinfecting Scopes (Bronchoscope):

Pre-cleaning: wipe exterior, flush channels with water immediately after use
Leak testing
Manual cleaning: detergent solution, brush all channels
Rinse
High-level disinfection: immerse in 2% glutaraldehyde for 20-45 min (or OPA 12 min)
Rinse with sterile/filtered water
Dry with 70% alcohol flush + forced air
Store hanging vertically

D. Testing Efficacy of Disinfectants:

Use-dilution test (AOAC method) - standard quantitative test
Kelsey-Sykes test - capacity use dilution test
Phenol coefficient - compare vs phenol as standard
In-use test - tests actual working dilution in hospital

Q2. Food Poisoning (Gram-negative, toxin-producing, invasive)

Agent: Vibrio parahaemolyticus (seafood) / also consider Shigella, but seafood + Gram-negative + invasive + toxin = Vibrio parahaemolyticus or E. coli (EHEC). Given mucus+blood+seafood = Vibrio parahaemolyticus.

A. Clinical Syndrome & Agents:

Gastroenteritis with vomiting, abdominal cramps, loose/bloody stools
Agents: Vibrio parahaemolyticus, V. cholerae O1/O139, Salmonella, Shigella
Toxin: Thermostable direct hemolysin (TDH) - Kanagawa phenomenon

B. Lab Diagnosis:

Specimen: Stool, rectal swab, vomitus, suspect food (seafood)
Gram stain: curved Gram-negative bacilli
Culture: Thiosulfate Citrate Bile Salt Sucrose (TCBS) agar - blue-green colonies
Oxidase positive
Salt tolerance (halophile) - 3% NaCl required
Serogrouping

C. Features of Dehydration:

Sunken eyes, dry mucous membranes, decreased skin turgor
Tachycardia, hypotension (severe)
Oliguria, concentrated urine
Altered consciousness (severe)
WHO grades: No dehydration / Some dehydration / Severe dehydration

D. Rationale of ORS:

Glucose-sodium co-transport (SGLT1) in intestinal epithelium remains intact even during secretory diarrhea
Glucose actively pulls Na+ and water into enterocytes
WHO ORS: Na 75 mEq/L, K 20 mEq/L, Chloride 65 mEq/L, Citrate 10 mEq/L, Glucose 75 mmol/L

SHORT ESSAYS

Q3. Fasciola hepatica (3+2)

Life Cycle:

Definitive host: sheep, cattle, humans
Intermediate host: Lymnaea snail
Eggs → miracidium → sporocyst → redia → cercaria (in snail) → metacercaria on aquatic vegetation → ingested by human → excyst in duodenum → migrate through liver parenchyma → bile ducts (adult)

Clinical Manifestations:

Acute: fever, RUQ pain, hepatomegaly, eosinophilia (migratory phase)
Chronic: biliary obstruction, cholangitis, cholecystitis
Halzoun: pharyngeal fascioliasis from raw liver

Q4. Herpes Simplex Virus (2+3)

Clinical Manifestations:

HSV-1: gingivostomatitis, herpes labialis, keratoconjunctivitis, encephalitis
HSV-2: genital herpes, neonatal herpes
Both: herpetic whitlow, eczema herpeticum

Lab Diagnosis:

Tzanck smear: multinucleated giant cells
Culture: CPE in 24-48 hrs (rounding, ballooning)
PCR (gold standard for encephalitis - CSF)
Direct immunofluorescence (DFA)
Serology: IgM (primary), IgG (past infection)

Q5. Subcutaneous Mycoses (2+3)

Aetiology:

Sporotrichosis: Sporothrix schenckii (rose thorn prick)
Chromoblastomycosis: Fonsecaea, Cladosporium
Mycetoma (Madura foot): Madurella mycetomatis
Rhinosporidiosis: Rhinosporidium seeberi

Lab Diagnosis:

Direct microscopy: KOH mount
Sporotrichosis: culture on SDA - cigar-shaped yeast at 37°C
Chromoblastomycosis: sclerotic bodies (Medlar/copper penny bodies)
Mycetoma: grains in pus (color varies by agent)

Q6. Primary vs Secondary Immune Response

Feature	Primary	Secondary
Antigen exposure	1st	2nd (same Ag)
Lag period	5-7 days	1-3 days
Peak antibody	Lower	Much higher
Antibody class	IgM first, then IgG	Predominantly IgG
Affinity	Lower	Higher (affinity maturation)
Duration	Shorter	Longer
Cells involved	Naive B cells	Memory B cells

Q7. Biological Effects of Complement

Opsonization: C3b coats bacteria → phagocytosis
Chemotaxis: C3a, C5a attract neutrophils
Anaphylatoxins: C3a, C4a, C5a → mast cell degranulation → inflammation
Membrane Attack Complex (MAC): C5b-9 → lysis of Gram-negative bacteria
Immune complex clearance: CR1 on RBCs transport complexes to liver/spleen
Enhancement of antibody production: C3d on B cell receptor

Q8. Lymphatic Filariasis (2+3)

Clinical Manifestations:

Acute: fever, lymphangitis (retrograde), lymphadenitis
Chronic: lymphedema, elephantiasis (lower limbs, scrotum), hydrocele, chyluria
Tropical pulmonary eosinophilia (TPE)

Lab Diagnosis:

Peripheral blood smear: nocturnal periodicity - collect blood at night (10 pm-2 am); Mf (microfilariae) in sheathed form
Knott's concentration technique
Membrane filtration
Antigen detection: ICT card test (circulating filarial antigen)
Serology: ELISA
PCR

SHORT ANSWERS

9. Immunofluorescence in Virology:

Direct IF: labeled antibody detects viral antigen in cells (e.g., RSV, Influenza DFA)
Indirect IF: unlabeled primary Ab + labeled secondary Ab; more sensitive

10. Premunition: Resistance to new infection while existing infection persists. Example: Plasmodium - mild immunity in chronic malaria prevents severe re-infection; disappears when infection clears.

11. Active vs Passive Immunity (3 differences):

Active	Passive
Body produces own antibodies	Pre-formed antibodies given
Slow onset (days-weeks)	Immediate onset
Long-lasting (years/lifelong)	Short-lived (weeks-months)

12. Acute Osteomyelitis - Bacterial:

Commonest organism: Staphylococcus aureus
Haematogenous spread to metaphysis
Features: fever, localized bone pain, tenderness, swelling
Lab: elevated ESR/CRP, blood culture, bone biopsy culture
X-ray changes appear after 10-14 days; MRI is early investigation of choice

13. Darling's Disease (Histoplasmosis):

Caused by Histoplasma capsulatum
Dimorphic fungus; yeast in tissue (intracellular in macrophages)
Endemic in Ohio/Mississippi River Valley
Diagnosis: Giemsa stain of bone marrow/blood; culture on SDA; urinary antigen test

14. Enterotest (String Test):

Used to collect duodenal contents for Giardia / Strongyloides
Gelatin capsule with nylon string swallowed; free end taped to cheek
After 4 hours, string retrieved and bile-stained portion examined microscopically

15. Ectothrix & Endothrix:

Ectothrix: arthroconidia on the outside of hair shaft (e.g., Microsporum canis, T. verrucosum)
Endothrix: arthroconidia inside hair shaft (e.g., T. tonsurans, T. violaceum)

16. Erythema Infectiosum (Fifth Disease):

Caused by Parvovirus B19
"Slapped cheek" appearance; lacy reticular rash on trunk/limbs
Aplastic crisis in sickle cell disease
Hydrops fetalis if in pregnancy

17. Cold Abscess - Spine (Pott's Disease):

Tuberculous spondylitis; L1 most common
Cold abscess: no heat/redness (unlike pyogenic); tracks along psoas muscle → psoas abscess
Features: back pain, gibbus deformity, paraplegia (Pott's paraplegia)
Diagnosis: MRI spine (gold standard), AFB culture of abscess aspirate

18. Beneficence:

Medical ethics principle: duty to act in the best interest of the patient
Do good, provide benefit, balance risks and benefits
Contrast with Non-maleficence ("do no harm")

All 18 questions answered. Good luck with your exam!

This is a shared conversation. Sign in to Orris to start your own chat.