30 type bacterial infection disease most important disease treatment investigation finding differential diagnosis contraindication ICU management OPD prescription and detail
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I'll compile a comprehensive clinical quick-reference covering the 30 most important bacterial diseases across all major categories, with treatment, investigations, key findings, differentials, contraindications, ICU management, and OPD prescriptions. Given the budget constraints, I'll deliver this from my consolidated clinical knowledge base.
30 Most Important Bacterial Infection Diseases — Clinical Quick Reference
RESPIRATORY INFECTIONS
1. COMMUNITY-ACQUIRED PNEUMONIA (CAP) — Streptococcus pneumoniae (most common)
| Feature | Details |
|---|---|
| Organism | S. pneumoniae, H. influenzae, Mycoplasma, Legionella, Klebsiella |
| Key Findings | Fever, productive cough, pleuritic chest pain, lobar consolidation on CXR, bronchial breath sounds, dullness to percussion |
| Investigations | CXR PA view, CBC (leukocytosis), sputum Gram stain & culture, blood cultures ×2, procalcitonin, BMP, urinary Legionella/pneumococcal antigen, ABG if SpO₂ <92% |
| Severity Score | CURB-65 (Confusion, Urea >7, RR ≥30, BP <90/60, Age ≥65); score ≥3 → ICU |
| Differential Dx | TB, lung abscess, PE with infarction, cardiac pulmonary edema, ARDS, Legionella, viral pneumonia |
| OPD Treatment | Amoxicillin 500 mg TDS × 5–7 days (mild); Azithromycin 500 mg OD × 5 days (atypical) |
| Hospital Treatment | IV Ceftriaxone 1–2 g OD + Azithromycin 500 mg IV OD or Levofloxacin 750 mg IV OD |
| ICU Management | IV Piperacillin-Tazobactam 4.5 g q8h + Azithromycin/Levofloxacin; O₂/mechanical ventilation; VAP bundle; de-escalate at 48–72 h based on cultures |
| Contraindications | Fluoroquinolones contraindicated in pregnancy; Tetracycline CI <8 years; Aminoglycosides—monitor renal function |
2. PULMONARY TUBERCULOSIS — Mycobacterium tuberculosis
| Feature | Details |
|---|---|
| Key Findings | Chronic cough >3 weeks, hemoptysis, night sweats, weight loss, low-grade fever, apical infiltrates/cavitation on CXR, AFB on sputum smear |
| Investigations | Sputum AFB smear ×3, GeneXpert MTB/RIF, CXR, Mantoux/TST, IGRA (QuantiFERON), LFTs, RFTs, HIV test, CBC |
| Differential Dx | Lung carcinoma, aspergillosis, pneumonia, histoplasmosis, sarcoidosis, lung abscess |
| OPD Treatment (DOTS) | Intensive phase (2 months): HRZE (Isoniazid + Rifampicin + Pyrazinamide + Ethambutol daily) → Continuation (4 months): HR daily |
| ICU Management | Respiratory isolation (negative pressure), IV Rifampicin if cannot swallow, pyridoxine 25 mg OD with INH; manage hemoptysis (bronchial artery embolization), ARDS protocol |
| Contraindications | Rifampicin — CI in severe hepatic disease; Ethambutol — CI in optic neuritis; Pyrazinamide — CI in gout, severe liver disease |
| Key Monitoring | LFTs monthly (hepatotoxicity), visual acuity (Ethambutol), uric acid, CBC |
3. WHOOPING COUGH (PERTUSSIS) — Bordetella pertussis
| Feature | Details |
|---|---|
| Key Findings | Paroxysmal cough with inspiratory "whoop," post-tussive vomiting, lymphocytosis (characteristic), infants may have apnea |
| Stages | Catarrhal (1–2 wk) → Paroxysmal (2–6 wk) → Convalescent |
| Investigations | Nasopharyngeal PCR (gold standard), culture (Bordet-Gengou agar), CBC (lymphocytosis >20,000) |
| Differential Dx | Viral croup, RSV, Mycoplasma, foreign body aspiration, adenovirus |
| OPD Treatment | Azithromycin 500 mg OD × 5 days (adults); 10 mg/kg/day in children; Clarithromycin 7 days alternative |
| ICU Management | O₂, suction, ECMO in severe neonatal pertussis with pulmonary hypertension, leukoreduction if WBC >100,000 |
| Contraindications | Erythromycin in neonates (risk of pyloric stenosis) |
4. LEGIONNAIRES' DISEASE — Legionella pneumophila
| Feature | Details |
|---|---|
| Key Findings | Severe pneumonia + hyponatremia + diarrhea + confusion; relative bradycardia; "Pontiac fever" (mild form) |
| Investigations | Urine Legionella antigen (serogroup 1, rapid), sputum culture (BCYE agar), DFA, serology, CXR (multilobar), hyponatremia, elevated LFTs, CPK |
| Differential Dx | Mycoplasma pneumonia, other atypical pneumonias, viral pneumonia |
| OPD/Hospital Treatment | Levofloxacin 750 mg OD × 5–14 days or Azithromycin 500 mg OD × 7–14 days |
| ICU Management | IV Levofloxacin 750 mg OD; correct hyponatremia; aggressive fluid management; no beta-lactams alone (ineffective) |
| Contraindications | Beta-lactams ineffective (no cell wall penetration into alveolar macrophages) |
GASTROINTESTINAL INFECTIONS
5. TYPHOID FEVER — Salmonella typhi
| Feature | Details |
|---|---|
| Key Findings | Stepladder fever, relative bradycardia (Faget's sign), rose spots (trunk), splenomegaly, coated tongue, constipation (early) then diarrhea |
| Investigations | Blood culture (1st week — gold standard), Widal test (>1:160 O, >1:80 H), Typhidot IgM, CBC (leukopenia), LFTs elevated, stool/urine culture (2nd–3rd week) |
| Differential Dx | Malaria, brucellosis, rickettsial fever, EBV, TB miliary, leptospirosis |
| OPD Treatment | Ceftriaxone 1–2 g IV OD × 10–14 days; Azithromycin 1 g/day × 5 days (uncomplicated) |
| ICU Management | IV Ceftriaxone; Dexamethasone 3 mg/kg then 1 mg/kg q6h × 48 h (severe/encephalopathy); monitor for intestinal perforation, hemorrhage; surgical consult if perforation |
| Contraindications | Chloramphenicol — avoided (aplastic anemia risk, increasing resistance); Fluoroquinolones — resistance rising; Ampicillin — resistance common |
6. CHOLERA — Vibrio cholerae
| Feature | Details |
|---|---|
| Key Findings | Profuse "rice-water" watery diarrhea without pain, "washerwoman's hands," hypokalemia, metabolic acidosis, severe dehydration, sunken eyes, poor skin turgor |
| Investigations | Stool dark-field microscopy (darting motility), stool culture (TCBS agar), RDT, electrolytes (hypokalemia), ABG (metabolic acidosis) |
| Differential Dx | ETEC diarrhea, rotavirus, cryptosporidium, other secretory diarrheas |
| OPD Treatment | Oral rehydration solution (ORS) + Doxycycline 300 mg single dose (adults); Azithromycin 1 g single dose |
| ICU Management | Ringer's lactate IV rapid replacement (100 mL/kg in 3 h); K⁺ replacement; correct acidosis; Doxycycline or Azithromycin IV; monitor urine output |
| Contraindications | Doxycycline — CI in pregnancy and <8 years (use Azithromycin instead) |
7. C. DIFFICILE COLITIS — Clostridioides difficile
| Feature | Details |
|---|---|
| Key Findings | Watery diarrhea ≥3/day after antibiotics, abdominal cramps, fever, leukocytosis (WBC >15,000), "thumbprinting" on CT, pseudomembranes on colonoscopy |
| Investigations | Stool GDH antigen + toxin A/B EIA (or PCR), CT abdomen (megacolon, colonic thickening), CBC, CMP, sigmoidoscopy |
| Differential Dx | IBD flare, ischemic colitis, other antibiotic-associated diarrhea, infectious colitis |
| OPD Treatment | Fidaxomicin 200 mg BD × 10 days (preferred, lower recurrence) or Vancomycin PO 125 mg QDS × 10 days |
| ICU Management | Vancomycin PO 500 mg QDS + Metronidazole IV 500 mg TDS; colectomy for toxic megacolon/perforation; fecal microbiota transplant (FMT) for recurrent |
| Contraindications | Antiperistaltics (loperamide) — absolutely contraindicated (risk of toxic megacolon); PPI — avoid if possible (risk factor) |
8. SALMONELLOSIS (Non-typhoidal) — Salmonella enteritidis/typhimurium
| Feature | Details |
|---|---|
| Key Findings | Bloody/watery diarrhea, abdominal cramps, fever 8–72 h after contaminated food (eggs, poultry) |
| Investigations | Stool culture, CBC, CMP; blood cultures if bacteremia suspected |
| Differential Dx | Campylobacter, Shigella, EHEC, IBD |
| OPD Treatment | Supportive ORS (antibiotics usually NOT recommended in uncomplicated cases — prolong carrier state); Ciprofloxacin for high-risk (immunocompromised, prosthetic valves, infants) |
| ICU Management | IV Ceftriaxone 2 g OD for bacteremia/sepsis; surgical if intestinal complication |
| Contraindications | Antibiotics in uncomplicated cases — increase carrier state and resistance |
9. SHIGELLOSIS (BACILLARY DYSENTERY) — Shigella dysenteriae
| Feature | Details |
|---|---|
| Key Findings | Bloody mucoid diarrhea, tenesmus, high fever, leukocytosis; HUS complication (S. dysenteriae type 1) |
| Investigations | Stool culture (gold standard), CBC, CMP, stool microscopy (RBCs, PMNs, no trophozoites) |
| Differential Dx | Amoebic dysentery, EHEC, C. difficile, Campylobacter, IBD |
| OPD Treatment | Azithromycin 500 mg OD × 3 days; Ciprofloxacin 500 mg BD × 3 days (resistance increasing) |
| ICU Management | IV hydration; Ceftriaxone 2 g IV OD if severe; avoid antiperistaltics; treat HUS if present |
| Contraindications | Antiperistaltics (loperamide) — CI; antibiotics in HUS — controversial (may worsen) |
CNS INFECTIONS
10. BACTERIAL MENINGITIS — N. meningitidis, S. pneumoniae, L. monocytogenes
| Feature | Details |
|---|---|
| Key Findings | Fever + headache + neck stiffness (Kernig's & Brudzinski's signs), photophobia, petechial/purpuric rash (meningococcal), bulging fontanelle (infants), altered consciousness |
| Investigations | LP (opening pressure, CSF: cloudy, ↑WBC >1000 PMNs, ↑protein, ↓glucose, Gram stain & culture), blood cultures ×2, CT head before LP if papilledema/focal signs, CBC, CRP, procalcitonin, glucose (simultaneous) |
| CSF Profile | Bacterial: WBC >1000 PMN, protein >100, glucose <45 or CSF:serum <0.4, Gram stain +ve 60–90% |
| Differential Dx | Viral (HSV/entero) meningitis, TB meningitis, fungal (cryptococcal), brain abscess, subarachnoid hemorrhage |
| OPD/ER Treatment | Ceftriaxone 2 g IV q12h + Dexamethasone 0.15 mg/kg q6h × 4 days (before or with 1st dose ATB); Add Ampicillin 2 g q4h if Listeria risk (age >50, immunocompromised, pregnancy) |
| ICU Management | ICP monitoring, seizure prophylaxis/treatment, maintain CPP >60 mmHg, head elevation 30°, avoid hypotonic fluids, early DVT prophylaxis |
| Contraindications | LP contraindicated if papilledema, focal neuro signs, or coagulopathy (get CT first); Steroids — CI if no ATB given first |
11. TETANUS — Clostridium tetani
| Feature | Details |
|---|---|
| Key Findings | Trismus (lockjaw), risus sardonicus, opisthotonus, board-like rigidity, reflex spasms triggered by stimuli, autonomic dysfunction |
| Investigations | Clinical diagnosis; wound culture (unreliable); tetanus Ab levels; EEG (to R/O epilepsy) |
| Differential Dx | Strychnine poisoning, meningitis, hypocalcemia, dystonic reactions, oculogyric crisis, rabies |
| OPD | Prevention: TIG + tetanus toxoid booster; wound debridement; Metronidazole 500 mg TDS × 7–10 days |
| ICU Management | TIG 3000–6000 U IM (neutralize unbound toxin); Metronidazole IV 500 mg TDS; diazepam/midazolam infusion for spasms; propofol/vecuronium for severe spasms; intubation if laryngospasm; dark quiet room; autonomic support (MgSO₄, labetalol) |
| Contraindications | Penicillin — increases GABA antagonism (avoid); succinylcholine — risk of hyperkalemia in chronic spasm |
12. BOTULISM — Clostridium botulinum
| Feature | Details |
|---|---|
| Key Findings | Descending flaccid paralysis (cranial nerves first: diplopia, dysarthria, dysphagia → descending), no fever, no sensory loss, normal mentation, dilated pupils, dry mouth |
| Investigations | Serum/stool/food toxin assay (mouse bioassay — gold standard), EMG (incremental response at high-frequency stimulation, unlike MG), LP (normal) |
| Differential Dx | Guillain-Barré, myasthenia gravis, stroke, organophosphate poisoning, Eaton-Lambert |
| Treatment | Heptavalent botulinum antitoxin (HBAT) IV ASAP; respiratory support; ICU monitoring |
| ICU Management | Early intubation (respiratory failure), NG feeds, bowel care, DVT prophylaxis; NO antibiotics for food botulism (lysis releases more toxin); Penicillin for wound botulism |
| Contraindications | Aminoglycosides — contraindicated (worsen neuromuscular blockade); antitoxin not indicated post recovery |
SKIN / SOFT TISSUE INFECTIONS
13. CELLULITIS / ERYSIPELAS — S. pyogenes (GAS), S. aureus
| Feature | Details |
|---|---|
| Key Findings | Erysipelas: sharply demarcated raised red plaque, face/leg, butterfly pattern; Cellulitis: diffuse, indistinct borders, warmth, tenderness, no epidermal involvement |
| Investigations | Clinical primarily; CBC, CRP, blood cultures if systemic; swab if entry wound; CK (rule out necrotizing fasciitis) |
| Differential Dx | DVT, contact dermatitis, lipodermatosclerosis, necrotizing fasciitis, gout |
| OPD Treatment | Amoxicillin-Clavulanate 625 mg TDS × 5–7 days; Flucloxacillin 500 mg QDS × 5–7 days; MRSA coverage: TMP-SMX or Doxycycline |
| ICU/Hospital | IV Flucloxacillin 2 g q6h (MSSA); IV Vancomycin 15–20 mg/kg q12h (MRSA); surgical debridement if necrotizing fasciitis suspected |
| Contraindications | Penicillin allergy — use Clindamycin or Vancomycin |
14. NECROTIZING FASCIITIS — S. pyogenes (Type II), Polymicrobial (Type I)
| Feature | Details |
|---|---|
| Key Findings | Severe pain out of proportion to skin findings, "wooden hard" subcutaneous tissue, skin necrosis, crepitus (gas-forming organisms), LRINEC score ≥6 |
| Investigations | LRINEC score (CRP, WBC, Hb, Na, Cr, glucose), CT/MRI (gas tracking fascial planes — gold standard), frozen section biopsy, blood cultures, CBP |
| Differential Dx | Cellulitis, pyomyositis, compartment syndrome, gas gangrene |
| Treatment | SURGICAL EMERGENCY — aggressive wide debridement + IV Piperacillin-Tazobactam 4.5 g q8h + Clindamycin 600–900 mg q8h (anti-toxin) + Vancomycin (MRSA cover) |
| ICU Management | Repeat debridement q24–48h; hyperbaric O₂ adjunct; IVIG (GAS); vasopressors for septic shock; ICU-level monitoring |
| Contraindications | Delay in surgery is the critical contraindication; conservative management alone — fatal |
15. LEPROSY — Mycobacterium leprae
| Feature | Details |
|---|---|
| Key Findings | Hypopigmented anesthetic skin patches, thickened peripheral nerves (ulnar, peroneal), claw hand, lagophthalmos, Leonine facies (lepromatous), AFB in slit-skin smear |
| Types | Tuberculoid (TT) — strong CMI, few lesions; Lepromatous (LL) — weak CMI, many lesions, positive smear; Borderline |
| Investigations | Slit-skin smear (AFB), skin biopsy (histology), Lepromin test (Mitsuda), nerve conduction study |
| Differential Dx | Vitiligo, tinea versicolor, granuloma annulare, lupus, sarcoidosis |
| OPD Treatment (MDT WHO) | PB (Paucibacillary): Rifampicin 600 mg monthly + Dapsone 100 mg daily × 6 months; MB (Multibacillary): Rifampicin 600 mg + Clofazimine 300 mg monthly + Dapsone 100 mg + Clofazimine 50 mg daily × 12 months |
| ICU | Rarely needed; manage Type 1 reactions with Prednisolone 40 mg/day tapering; Type 2 (ENL): Thalidomide (males)/Clofazimine/Prednisolone |
| Contraindications | Thalidomide — absolutely CI in women of childbearing age (teratogenic); Dapsone — CI in G6PD deficiency |
16. ANTHRAX — Bacillus anthracis
| Feature | Details |
|---|---|
| Key Findings | Cutaneous: painless black eschar with surrounding edema; Inhalation: flu-like → mediastinal widening on CXR, hemorrhagic mediastinitis; GI: severe hemorrhagic gastroenteritis |
| Investigations | Blood/wound culture, PCR, CXR/CT chest (mediastinal widening, pleural effusion), nasal swab, LFTs, CBC |
| Differential Dx | Cutaneous: spider bite, orf, plague; Inhalation: community pneumonia, mediastinal lymphoma |
| OPD Treatment | Ciprofloxacin 500 mg BD × 60 days or Doxycycline 100 mg BD × 60 days (cutaneous) |
| ICU Management | IV Ciprofloxacin 400 mg q12h + Clindamycin 900 mg q8h + Rifampicin 300 mg q12h (triple therapy inhalation/systemic); anthrax antitoxin; pleural drainage |
| Contraindications | Monotherapy for systemic anthrax; prophylactic antibiotics should be completed full 60 days |
SEXUALLY TRANSMITTED INFECTIONS
17. SYPHILIS — Treponema pallidum
| Feature | Details |
|---|---|
| Key Findings | Primary: painless chancre + regional lymphadenopathy; Secondary: maculopapular rash (palms/soles), condyloma lata, alopecia, mucous patches; Tertiary: gummas, neurosyphilis, aortitis; Latent: asymptomatic |
| Investigations | Non-treponemal (VDRL/RPR — screening, titer reflects activity); Treponemal (TPHA/FTA-ABS — confirm, stays positive life-long); CSF VDRL for neurosyphilis; LP if neurosyph suspected |
| Differential Dx | Chancroid, herpes, LGV, Behçet's; rash: drug rash, pityriasis, viral exanthem |
| OPD Treatment | Primary/Secondary/Early latent: Benzathine Penicillin G 2.4 million IU IM single dose; Late latent/Tertiary (non-neuro): 3 weekly doses; Allergy: Doxycycline 100 mg BD × 14 days |
| ICU/Neurosyphilis | Aqueous Penicillin G 18–24 million IU/day IV × 10–14 days (3–4 MU q4h) |
| Contraindications | Doxycycline — CI in pregnancy (use Penicillin, desensitize if allergic) |
| Jarisch-Herxheimer | Warn patients — fever, myalgia 2–8 h after 1st dose; manage with Aspirin; do NOT stop antibiotics |
18. GONORRHEA — Neisseria gonorrhoeae
| Feature | Details |
|---|---|
| Key Findings | Males: purulent urethral discharge, dysuria; Females: cervicitis, PID, often asymptomatic; Disseminated: septic arthritis, skin pustules, tenosynovitis; Neonates: ophthalmia neonatorum |
| Investigations | NAAT (urine/swab — gold standard), Gram stain (Gram-negative diplococci in PMNs, useful in males), culture (Thayer-Martin medium), concurrent STI screen (HIV, chlamydia, syphilis) |
| Differential Dx | Chlamydia, NGU, trichomoniasis, reactive arthritis |
| OPD Treatment | Ceftriaxone 500 mg IM single dose (uncomplicated); dual therapy no longer routinely needed if Ceftriaxone alone used per updated guidelines |
| ICU/Hospital | Disseminated: IV Ceftriaxone 1–2 g OD × 7 days; PID: IV Cefoxitin + Doxycycline or IV Clindamycin + Gentamicin |
| Contraindications | Fluoroquinolone monotherapy — global resistance; Penicillin monotherapy — resistance |
19. CHLAMYDIA — Chlamydia trachomatis
| Feature | Details |
|---|---|
| Key Findings | Urethritis (NGU), cervicitis, often asymptomatic (70% females); PID, epididymo-orchitis; neonatal conjunctivitis/pneumonia; LGV (serovars L1–L3): genital ulcer → inguinal adenopathy → proctitis |
| Investigations | NAAT (urine/swab — most sensitive/specific), culture (intracellular, difficult), serology (LGV) |
| Differential Dx | Gonorrhea, NGU, trichomoniasis, HSV |
| OPD Treatment | Doxycycline 100 mg BD × 7 days (preferred) or Azithromycin 1 g single dose; LGV: Doxycycline × 21 days |
| ICU | PID/systemic: IV Doxycycline + Cefoxitin; neonatal: Erythromycin PO × 14 days |
| Contraindications | Doxycycline — CI in pregnancy (use Azithromycin 1 g); Erythromycin — GI intolerance |
SYSTEMIC / SEPSIS / ZOONOTIC
20. SEPSIS / SEPTIC SHOCK — Polymicrobial (E. coli, Klebsiella, S. aureus, others)
| Feature | Details |
|---|---|
| Definition | Sepsis: life-threatening organ dysfunction (SOFA ≥2) due to infection; Septic shock: Sepsis + vasopressor to maintain MAP ≥65 + lactate >2 mmol/L despite fluids |
| Key Findings | Fever/hypothermia, tachycardia, tachypnea, altered sensorium, hypotension, oliguria, mottled skin |
| Investigations | Blood cultures ×2 (before antibiotics), CBC, CMP, lactate, LFTs, coagulation (DIC screen), procalcitonin, ABG, urine cultures, CXR, SOFA score |
| "Hour-1 Bundle" (Surviving Sepsis) | 1) Measure lactate; 2) Blood cultures before antibiotics; 3) Broad-spectrum ATB within 1 hour; 4) 30 mL/kg IV crystalloid for hypotension/lactate ≥4; 5) Vasopressors if MAP <65 despite fluids |
| OPD/ER | Immediate hospitalization; oral management not appropriate |
| ICU Management | Norepinephrine (vasopressor of choice, 0.1–0.3 mcg/kg/min); vasopressin 0.03 U/min add-on; Piperacillin-Tazobactam + Vancomycin empirically; source control (drain/surgery); ARDS-protective ventilation; RRT if AKI; hydrocortisone 200 mg/day if refractory shock |
| Contraindications | Dopamine (↑arrhythmia vs NE); high-volume fluids beyond resuscitation (SMART trial); early corticosteroids in non-refractory shock |
21. BRUCELLOSIS — Brucella melitensis/abortus
| Feature | Details |
|---|---|
| Key Findings | Undulant fever, profuse sweating, arthralgia, hepatosplenomegaly, orchitis, sacroiliitis, Malta fever; exposure to animals/unpasteurized dairy |
| Investigations | Blood culture (gold standard, BACTEC; prolonged incubation), serology (Rose Bengal test, Standard Agglutination Test ≥1:160), Brucella PCR, CBC (pancytopenia), LFTs |
| Differential Dx | Typhoid, malaria, TB, infective endocarditis, visceral leishmaniasis |
| OPD Treatment | Doxycycline 100 mg BD + Rifampicin 600–900 mg OD × 6 weeks (first line); Doxycycline 6 wk + Gentamicin IM × 7–14 days (superior for relapse) |
| ICU/Endocarditis | Triple therapy: Doxycycline + Rifampicin + TMP-SMX × 3–6 months; surgical valve replacement often needed |
| Contraindications | Monotherapy — high relapse rate; Doxycycline CI in pregnancy (use TMP-SMX + Rifampicin) |
22. LEPTOSPIROSIS — Leptospira interrogans
| Feature | Details |
|---|---|
| Key Findings | Weil's disease: jaundice + AKI + hemorrhage (thrombocytopenia) + uveitis; Anicteric (majority): flu-like, conjunctival suffusion (pathognomonic), calf muscle tenderness |
| Investigations | MAT (gold standard, paired sera), ELISA IgM (early), PCR (blood/urine), blood culture (EMJH medium), CBC (thrombocytopenia, leukocytosis), LFTs (↑bilirubin), RFTs, urinalysis (hematuria, proteinuria) |
| Differential Dx | Malaria, dengue, hepatitis A/E, rickettsia, hantavirus, viral hepatitis |
| OPD Treatment | Mild: Doxycycline 100 mg BD × 7 days or Amoxicillin 500 mg TDS × 7 days |
| ICU/Severe | IV Penicillin G 1.5 MU q6h × 7 days or Ceftriaxone 1 g OD × 7 days; RRT for AKI; platelet transfusion; ventilatory support for pulmonary hemorrhage syndrome |
| Contraindications | Doxycycline — CI in pregnancy |
23. PLAGUE — Yersinia pestis
| Feature | Details |
|---|---|
| Key Findings | Bubonic: tender fluctuant bubo (inguinal/axillary), fever, rapid onset; Septicemic: DIC, purpura, "Black Death"; Pneumonic: cough, bloody sputum — most dangerous, person-to-person |
| Investigations | Blood/bubo culture, PCR, Gram stain (safety pin bipolar staining), CXR, CBC (leukocytosis), DIC panel |
| Differential Dx | Tularemia, anthrax, scrub typhus, cat-scratch disease, LGV |
| Treatment | Streptomycin 1 g IM BD × 10 days (gold standard); Gentamicin 5 mg/kg OD IV; Doxycycline 100 mg BD × 14 days; Ciprofloxacin as alternative |
| ICU | Strict isolation (pneumonic plague); supportive for DIC; vasopressors; ICP monitoring if meningitis |
| Contraindications | Chloramphenicol for plague meningitis only (others have poor CNS penetration); monotherapy failure in pneumonic plague |
24. LYME DISEASE — Borrelia burgdorferi
| Feature | Details |
|---|---|
| Key Findings | Stage 1: Erythema migrans ("bull's eye" rash at tick bite); Stage 2: Carditis (heart block), facial palsy, aseptic meningitis; Stage 3: Lyme arthritis (large joints), encephalopathy |
| Investigations | ELISA (screen) + Western blot confirmation (2-tier testing); ECG (AV block), CSF analysis, joint fluid PCR/culture |
| Differential Dx | Reactive arthritis, fibromyalgia, RMSF, viral meningitis, rheumatoid arthritis |
| OPD Treatment | Early: Doxycycline 100 mg BD × 10–21 days; Amoxicillin 500 mg TDS; Carditis/Neurolyme (mild): Doxycycline PO |
| ICU/Hospital | Complete heart block/Neuroborreliosis: IV Ceftriaxone 2 g OD × 14–28 days; temporary pacing if HR <45 or Mobitz II/3rd degree block |
| Contraindications | Doxycycline CI <8 years and pregnancy (use Amoxicillin); prolonged antibiotics (>28 days) — no evidence benefit, increases risk |
URINARY TRACT INFECTIONS
25. URINARY TRACT INFECTION (UTI) / PYELONEPHRITIS — E. coli (80%), Klebsiella, Proteus
| Feature | Details |
|---|---|
| Key Findings | Uncomplicated UTI: dysuria, frequency, urgency, suprapubic pain; Pyelonephritis: fever, costovertebral angle tenderness, nausea/vomiting, systemic symptoms |
| Investigations | Urinalysis (pyuria, nitrites, leukocyte esterase), midstream urine culture (gold standard, ≥10⁵ CFU/mL), CBC, CMP, blood cultures (pyelonephritis/sepsis), renal ultrasound/CT if obstruction suspected |
| Differential Dx | STI/PID (women), appendicitis, renal calculus, bladder/renal TB, prostatitis |
| OPD Treatment | Uncomplicated UTI (female): Nitrofurantoin 100 mg BD × 5 days or TMP-SMX × 3 days; Pyelonephritis (outpatient): Ciprofloxacin 500 mg BD × 7 days or Levofloxacin 750 mg OD × 5 days |
| ICU/Hospital | IV Ceftriaxone 1–2 g OD (moderate); IV Piperacillin-Tazobactam/Meropenem for ESBL/complicated |
| Contraindications | Nitrofurantoin — CI in pyelonephritis (inadequate tissue levels), eGFR <30, pregnancy at term; Fluoroquinolones — resistance rates high in many regions; avoid in pregnancy |
VECTOR-BORNE / TICK / RICKETTSIAL
26. ROCKY MOUNTAIN SPOTTED FEVER (RMSF) — Rickettsia rickettsii
| Feature | Details |
|---|---|
| Key Findings | Triad: fever + headache + rash; rash starts wrists/ankles → centripetal spread → palms/soles (petechial/maculopapular); thrombocytopenia, hyponatremia, elevated LFTs |
| Investigations | Clinical (treat empirically — do NOT wait); serology (IFA — gold standard, positive after 7 days); skin biopsy (PCR/IHC), CBC (thrombocytopenia, normal WBC), CMP (hyponatremia) |
| Differential Dx | Meningococcemia, dengue, viral exanthem, ehrlichiosis, drug rash, ITP |
| Treatment | Doxycycline 100 mg BD × 7 days (first choice ALL ages including children — benefits outweigh risks); treat empirically without waiting for confirmation |
| ICU Management | IV Doxycycline; aggressive vasopressor support; platelet transfusion; DIC management; dialysis if AKI |
| Contraindications | Chloramphenicol — inferior and causes aplastic anemia; delay in treatment is the key danger; do NOT withhold Doxycycline in children due to dental fear |
27. SCRUB TYPHUS — Orientia tsutsugamushi
| Feature | Details |
|---|---|
| Key Findings | Eschar at mite bite site (pathognomonic), fever, headache, lymphadenopathy, maculopapular rash; complications: ARDS, myocarditis, meningoencephalitis |
| Investigations | Weil-Felix test (OX-K positive, low sensitivity), IFA (gold standard), PCR, CBC (thrombocytopenia, atypical lymphocytes), LFTs elevated |
| Differential Dx | Typhoid, dengue, leptospirosis, malaria, EBV |
| OPD Treatment | Doxycycline 100 mg BD × 7 days (first line); Azithromycin 500 mg OD × 3 days (pregnancy/children) |
| ICU | IV Doxycycline + supportive (O₂, vasopressors, RRT); rifampicin for refractory cases |
| Contraindications | Penicillin/beta-lactams — completely ineffective (no cell wall in rickettsiae); Chloramphenicol — second line only |
MULTI-DRUG RESISTANT / HOSPITAL-ACQUIRED
28. MRSA INFECTION — Methicillin-resistant Staphylococcus aureus
| Feature | Details |
|---|---|
| Key Findings | HA-MRSA: post-surgical wound, IV line, ventilator-associated; CA-MRSA: skin/soft tissue ("spider bite"), necrotizing pneumonia; PVL toxin (CA-MRSA), fever, purulent material |
| Investigations | Culture + sensitivity (chromogenic agar, PCR for mecA gene), blood cultures, MRSA nasal/wound swab, CBC, CRP |
| Differential Dx | MSSA, gram-negative sepsis, fungal infection (immunocompromised) |
| OPD Treatment | CA-MRSA skin: TMP-SMX 160/800 mg BD × 5–7 days or Doxycycline 100 mg BD × 5 days |
| ICU/Hospital | Vancomycin IV (15–20 mg/kg q8–12h, target AUC/MIC 400–600); Linezolid 600 mg IV q12h (superior for pneumonia — better lung penetration); Daptomycin 6–10 mg/kg OD (bacteremia); Tedizolid, Ceftaroline alternatives |
| Contraindications | Vancomycin for MRSA pneumonia alone — poor lung penetration (Linezolid preferred); Daptomycin — CI in pneumonia (inactivated by surfactant) |
29. KLEBSIELLA PNEUMONIAE (Hypervirulent/MDR)
| Feature | Details |
|---|---|
| Key Findings | Lobar pneumonia (upper lobe, alcoholics), "currant jelly sputum," lung abscess, liver abscess (hypervirulent KP — endogenous endophthalmitis), UTI, HAP, ESBL/KPC-producing strains |
| Investigations | Sputum/blood/urine culture with sensitivity (ESBL/MBL testing — E-test/combined disc), CXR/CT (abscess, cavitation), string test (hypervirulent), CBC |
| Differential Dx | S. pneumoniae pneumonia, anaerobic lung abscess, TB, lung cancer |
| OPD Treatment | Non-ESBL: Amoxicillin-Clavulanate or Cephalosporins |
| ICU/MDR | ESBL: Ertapenem or Meropenem; KPC (carbapenem-resistant): Ceftazidime-Avibactam ± Aztreonam; Colistin (last resort); Cefiderocol for NDM producers; source control (drainage) |
| Contraindications | ESBL organisms — cephalosporins unreliable (inoculum effect); Colistin — nephrotoxic, monitor closely; monotherapy for CRE |
30. PSEUDOMONAS AERUGINOSA (HAP/VAP/Burn Wound)
| Feature | Details |
|---|---|
| Key Findings | HAP/VAP: green purulent sputum, ecthyma gangrenosum (pathognomonic skin lesion in bacteremia — black necrotic ulcer with erythematous halo), burn wound sepsis, external otitis malignans (diabetics) |
| Investigations | BAL/tracheal aspirate culture (quantitative >10⁴ CFU/mL for VAP), blood cultures, sensitivity (Pseudomonas susceptibility panel: Pip-Tazo, carbapenems, fluoroquinolones, aminoglycosides, colistin), CBC, CPIS score |
| Differential Dx | Other Gram-negative HAP (Klebsiella, Acinetobacter), MRSA, fungal (neutropenic) |
| Treatment | Pip-Tazo 4.5 g q6h (extended infusion); Cefepime 2 g q8h; Meropenem 1–2 g q8h; Ciprofloxacin 400 mg q8h IV |
| ICU/MDR-Pseudomonas | Combination therapy for MDR: Meropenem (extended infusion) + Tobramycin; Ceftolozane-Tazobactam; Imipenem-Cilastatin-Relebactam; Colistin (salvage) |
| Contraindications | Monotherapy for MDR-Pseudomonas (high resistance emergence); Ertapenem — no Pseudomonas activity; Azithromycin alone — ineffective |
QUICK REFERENCE SUMMARY TABLE
| # | Disease | Organism | First-Line Treatment | Key Contraindication |
|---|---|---|---|---|
| 1 | CAP | S. pneumoniae | Amoxicillin / Ceftriaxone + Azithromycin | FQ in pregnancy |
| 2 | TB | M. tuberculosis | HRZE × 2m → HR × 4m | Rifampicin in hepatic failure |
| 3 | Pertussis | B. pertussis | Azithromycin | Erythromycin in neonates |
| 4 | Legionella | L. pneumophila | Levofloxacin / Azithromycin | Beta-lactam monotherapy |
| 5 | Typhoid | S. typhi | Ceftriaxone / Azithromycin | Chloramphenicol (resistance) |
| 6 | Cholera | V. cholerae | ORS + Doxycycline | Doxycycline in pregnancy |
| 7 | C. diff | C. difficile | Fidaxomicin / Vancomycin PO | Loperamide |
| 8 | Salmonellosis | S. enteritidis | Supportive ± Ciprofloxacin | Antibiotics (uncomplicated) |
| 9 | Shigellosis | Shigella sp | Azithromycin | Loperamide, antibiotics in HUS |
| 10 | Meningitis | N. meningitidis / S. pneumoniae | Ceftriaxone + Dexamethasone | LP without CT if focal signs |
| 11 | Tetanus | C. tetani | TIG + Metronidazole | Penicillin (GABA effect) |
| 12 | Botulism | C. botulinum | HBAT antitoxin | Aminoglycosides |
| 13 | Cellulitis | GAS / S. aureus | Flucloxacillin / Amoxiclav | Penicillin allergy → Vancomycin |
| 14 | Necrotizing fasciitis | GAS / Polymicrobial | Surgery + Pip-Tazo + Clindamycin | Delayed surgery = fatal |
| 15 | Leprosy | M. leprae | Rifampicin + Dapsone (MDT) | Thalidomide in females |
| 16 | Anthrax | B. anthracis | Ciprofloxacin × 60 days | Monotherapy (systemic) |
| 17 | Syphilis | T. pallidum | Benzathine Penicillin G | Doxycycline in pregnancy |
| 18 | Gonorrhea | N. gonorrhoeae | Ceftriaxone 500 mg IM | FQ (resistance) |
| 19 | Chlamydia | C. trachomatis | Doxycycline / Azithromycin | Doxycycline in pregnancy |
| 20 | Sepsis/Septic shock | Polymicrobial | Pip-Tazo + Vancomycin | Dopamine (1st vasopressor) |
| 21 | Brucellosis | Brucella sp | Doxycycline + Rifampicin | Monotherapy |
| 22 | Leptospirosis | L. interrogans | Doxycycline / Penicillin G IV | Doxycycline in pregnancy |
| 23 | Plague | Y. pestis | Streptomycin / Gentamicin | Delay in treatment |
| 24 | Lyme disease | B. burgdorferi | Doxycycline / Ceftriaxone IV | Prolonged ATB (>28 days) |
| 25 | UTI/Pyelonephritis | E. coli | Nitrofurantoin / Ciprofloxacin | Nitrofurantoin in pyelonephritis |
| 26 | RMSF | R. rickettsii | Doxycycline | Chloramphenicol; delay in Rx |
| 27 | Scrub typhus | O. tsutsugamushi | Doxycycline / Azithromycin | Beta-lactams (ineffective) |
| 28 | MRSA | MRSA | Vancomycin / Linezolid | Daptomycin in pneumonia |
| 29 | Klebsiella (MDR) | K. pneumoniae | Meropenem / Ceftaz-Avibactam | Cephalosporins (ESBL) |
| 30 | Pseudomonas | P. aeruginosa | Pip-Tazo / Ceftolozane-Tazo | Ertapenem; monotherapy (MDR) |
GENERAL ICU PRINCIPLES FOR BACTERIAL INFECTIONS
- Source control — drain abscesses, remove infected lines/devices, debride necrotic tissue
- Empiric ATB within 1 hour of sepsis/septic shock recognition
- De-escalate at 48–72 h based on cultures
- Procalcitonin-guided duration — helps shorten ATB courses
- VAP bundle — HOB 30°, daily SAT/SBT, oral chlorhexidine, subglottic suctioning
- ARDS — lung-protective ventilation (TV 6 mL/kg IBW, Pplat <30 cmH₂O, PEEP)
- AKI — early RRT, avoid nephrotoxins, dose-adjust ATB
- DIC — treat underlying infection; FFP, platelets, cryoprecipitate as needed
STANDARD OPD PRESCRIPTION FORMAT
Rx
Date: ___
Patient: ___ Age/Sex: ___ Weight: ___
1. [Antibiotic] [dose] [route] [frequency] × [duration]
2. [Antipyretic] Paracetamol 500 mg PO TDS PRN fever/pain
3. [Probiotic] Lactobacillus preparation BD during/after ATB course
4. [ORS] if diarrheal disease
5. [Vitamin B6/Pyridoxine] 25 mg OD if INH prescribed
6. [PPI] if prolonged ATB / GI risk
Advice:
- Complete full antibiotic course
- Return if: fever >72 h, worsening symptoms, rash, difficulty breathing
- Hydration: 2–3 L water/day
- Isolation precautions if applicable
Note: This reference is organized for clinical use. Always adjust empiric therapy based on local antibiogram data, culture results, patient allergies, renal/hepatic function, pregnancy status, and patient age. Antibiotic resistance patterns vary significantly by region.
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