IM26.1-35 | Infectious Diseases — Graded Quiz

Correct. Temporal lobe encephalitis with herpetic labialis, lymphocytic CSF, and MRI temporal signal change = herpes simplex encephalitis (HSE) until proven otherwise. IV acyclovir 10 mg/kg every 8 hours must be started IMMEDIATELY — treatment delay worsens outcomes dramatically. PCR has 95%+ sensitivity but takes hours to days; clinical diagnosis drives treatment. Continue acyclovir for 14-21 days for confirmed HSE.

HSE: temporal lobe MRI changes + lymphocytic CSF + altered sensorium. Start IV acyclovir 10 mg/kg 8-hourly IMMEDIATELY; do not delay for PCR (sensitivity 95%+, but result takes hours). Duration: 14 days (immunocompetent), 21 days (immunocompromised). HSV-1 accounts for >90% of encephalitis.

Temporal lobe encephalitis + labial herpes + lymphocytic CSF = HSE until proven otherwise. IV acyclovir 10 mg/kg every 8 hours must start immediately — waiting for PCR results in preventable brain damage and death. PCR is used to confirm and guide duration of therapy, not to initiate it.

Correct. Necrotising fasciitis (NF) with subcutaneous gas = surgical emergency. Mortality doubles with every 6 hours of surgical delay. The cornerstone of management is urgent wide surgical debridement (go beyond visible margins) combined with broad-spectrum IV antibiotics covering polymicrobial organisms (Gram-positive, Gram-negative, anaerobes): piperacillin-tazobactam + clindamycin (to inhibit toxin synthesis) is appropriate, with addition of vancomycin if MRSA suspected. IV fluid resuscitation and ICU. Antibiotics alone without surgery = fatal.

Necrotising fasciitis: gas in soft tissues, rapid spread, haemodynamic compromise. Treat with urgent surgical debridement (within 6 hours) + IV antibiotics (piperacillin-tazobactam + clindamycin). The 'wooden plank' feel under deceptively normal-looking skin is pathognomonic. LRINEC score ≥6 warrants surgical exploration. Antibiotics alone are NEVER sufficient.

Necrotising fasciitis: subcutaneous gas + purple discolouration + haemodynamic instability = surgical emergency. Urgent wide debridement is mandatory — antibiotics alone without surgery are inadequate and fatal. Each 6-hour delay doubles mortality. Hyperbaric oxygen is an adjunct, not first-line.

Correct. Empyema thoracis: pH <7.2 + glucose <60 + LDH >1000 + turbid/purulent fluid with organisms on Gram stain = definitive empyema requiring drainage. Gram-positive cocci in clusters suggest Staphylococcus aureus — in healthcare/post-hospital context with alcoholic liver disease, MRSA coverage with vancomycin is appropriate. Chest drain is mandatory; intrapleural fibrinolytics (alteplase) reduce need for surgical decortication in loculated empyema. Surgery (VATS/decortication) is reserved for failure of medical + drainage management.

Pleural empyema criteria requiring drainage: pH <7.2 OR glucose <3.3 mmol/L OR LDH >1000 IU/L OR positive Gram stain/culture OR frank pus. Management: chest drain + antibiotics. Add intrapleural fibrinolytics for loculation. Surgical decortication for failed medical management.

Empyema criteria met: pH <7.2, glucose <60, LDH >1000, organisms on Gram stain, turbid fluid = chest drain is MANDATORY. Antibiotics alone without drainage = treatment failure. Vancomycin covers potential MRSA Staph aureus (Gram-positive cocci in clusters). Fibrinolytics (alteplase) are added for loculated collections.

Correct. Tuberculous meningitis (TBM) profile: subacute onset (7 days), lymphocytic pleocytosis, very low glucose (<50% of serum = ~21%), high protein, raised ADA, raised pressure — in an immunocompetent person from India. AFB smear is only 40-50% sensitive. India ink negative makes cryptococcal less likely (also not immunocompromised). Start antitubercular therapy (NTEP 2HRZE intensive + 4HRE continuation, 12 months total for TBM) plus dexamethasone (reduces mortality by 30%). Do NOT await culture confirmation in TBM — clinical-CSF profile is sufficient to start.

TBM CSF: lymphocytic pleocytosis, glucose <50% serum, high protein, raised ADA, high pressure. Start NTEP ATT (2HRZE+4HRE, 12 months for TBM) + dexamethasone empirically. AFB smear sensitivity only 40-50%; culture takes 4-6 weeks. Xpert MTB/RIF on CSF increases diagnostic yield. Compare: bacterial (neutrophils, glucose <40 mg/dL, very high protein); viral (lymphocytes, normal glucose, low protein).

This CSF profile — subacute onset, lymphocytic pleocytosis, glucose <50% serum, high protein, elevated ADA, raised pressure — is characteristic of TBM in India. AFB smear is 40-50% sensitive; clinical diagnosis justifies empirical NTEP ATT (2HRZE+4HRE, 12 months total) + dexamethasone. Waiting for culture confirmation (takes 4-6 weeks) is dangerous.

Correct. Complete tetanus management: (1) HTIG 500 IU IM (human preparation preferred — lower risk of anaphylaxis vs equine ATS; neutralises unbound toxin); (2) wound debridement with H2O2 irrigation (creates aerobic environment); (3) penicillin G IV or metronidazole (to eradicate Clostridium tetani and reduce further toxin production); (4) diazepam or midazolam for spasm control; (5) tetanus toxoid at a DIFFERENT site to begin active immunisation; (6) ICU with airway management readiness.

Tetanus management: HTIG 500 IU IM (separate site from toxoid) + wound debridement + penicillin G IV (or metronidazole) + diazepam. HTIG preferred over equine ATS. Incubation 3-21 days; trismus is the earliest sign; autonomic instability (tachycardia, hypertension) is the most common cause of death in ICU. Neonatal tetanus: HTIG 500 IU IM + penicillin.

Complete tetanus management requires all four components: HTIG 500 IU IM (neutralises unbound toxin) + toxoid at a separate site (active immunisation) + penicillin G or metronidazole IV (kills the organism) + benzodiazepines (spasm control) + wound debridement. HTIG is preferred over equine ATS to avoid anaphylaxis. Antispasmodics alone are insufficient.

Correct. ABPA diagnostic criteria (modified ISHAM): (1) predisposing condition (asthma or CF); (2) mandatory: positive Aspergillus skin test OR elevated IgE; (3) total IgE >1000 IU/mL; (4) elevated IgE or IgG anti-Af; (5) consistent CXR (fleeting shadows, central bronchiectasis). This patient has asthma, eosinophilia, elevated IgE >1000, positive skin test, migratory infiltrates, and sputum Aspergillus culture. Treatment: prednisolone + itraconazole (steroid-sparing). IPA requires immunosuppression; CPA has cavitary lesions in pre-existing lung disease; aspergilloma is a fungal ball in a cavity.

ABPA: asthma + IgE >1000 IU/mL + positive Aspergillus skin test + eosinophilia + migratory infiltrates/central bronchiectasis. Treat: prednisolone + itraconazole (steroid-sparing). Contrast with IPA (immunocompromised + halo sign) and CPA (pre-existing lung disease, not asthmatic, IgG elevated, cavities).

This is ABPA: asthma + eosinophilia + IgE >1000 + positive skin test + migratory infiltrates. IPA requires significant immunosuppression (neutropenia, transplant). CPA presents in pre-existing lung cavities in non-asthmatic patients. Aspergilloma = fungal ball in a cavity without this allergic background. ABPA treatment: prednisolone + itraconazole.

Correct. Rising haematocrit ≥20% rise = plasma leakage = dengue critical phase (days 3-6). No frank shock yet, but she has warning signs (rising haematocrit, thrombocytopaenia). WHO dengue classification: dengue with warning signs requires close monitoring and early IV fluid. The critical monitoring parameter is haematocrit (≥20% rise signals plasma leakage) AND narrow pulse pressure (<20 mmHg = early shock). Platelet transfusion is NOT indicated unless platelet <10,000 or active severe bleeding. FFP has no role. The bolus fluid protocol is for Dengue Shock Syndrome, not this stage.

Dengue critical phase (days 3-6): haematocrit rises ≥20% as plasma leaks. Monitor: haematocrit hourly (leakage) and pulse pressure (narrows <20 mmHg = early shock). Platelet transfusion NOT prophylactic (threshold <10,000 or active severe bleeding). Isotonic fluid is mainstay — avoid aggressive bolus. The critical phase lasts 24-48 hours; recovery phase brings fluid reabsorption and risk of pulmonary oedema.

Rising haematocrit ≥20% = plasma leakage = dengue critical phase. This is dengue with warning signs requiring hospitalisation and IV fluid titration. The key parameters are: haematocrit (leakage marker) and pulse pressure (shock marker — narrows before BP falls). Platelet transfusion is NOT given prophylactically; only if <10,000/microL or active severe bleed.

Correct. WHO category III = single or multiple transdermal bites or scratches, or contamination of mucous membranes. India NIP (updated schedule): Category III in previously unvaccinated person requires BOTH RIG (20 IU/kg human RIG or 40 IU/kg equine RIG) infiltrated into the wound as much as possible, with remaining given IM + 4-dose Essen schedule vaccine (days 0, 3, 7, 28). NEVER withhold RIG for Category III regardless of dog's health status or availability. The dog should be quarantined and observed for 10 days (if healthy throughout, the 28-day and later doses may be stopped — per some regional protocols — but the initial doses with RIG must start immediately).

Rabies PEP India: Category I (touching/feeding) = wash only. Category II (minor scratch) = wash + vaccine. Category III (transdermal bite/mucous membrane) = wash + RIG (20 IU/kg human or 40 IU/kg equine, infiltrate wound) + 4-dose vaccine (days 0, 3, 7, 28). Once symptomatic, rabies is universally fatal — no treatment exists. Pre-exposure prophylaxis for veterinarians: days 0, 7, 21/28.

WHO Category III (transdermal bite): BOTH RIG (infiltrated into wound + remaining IM) AND 4-dose vaccine (days 0, 3, 7, 28) are mandatory. Never withhold PEP pending dog observation for Category III — rabies is 100% fatal once symptomatic. RIG without vaccine OR vaccine without RIG for Category III are both incomplete management.

Correct. VAP with Pseudomonas aeruginosa sensitive to meropenem: use meropenem 2 g IV every 8 hours (antipseudomonal carbapenem). Ceftriaxone (3rd-gen cephalosporin) has no reliable Pseudomonas activity. Ciprofloxacin is resistant on culture. Amoxicillin-clavulanate is NOT active against Pseudomonas — intrinsic resistance via OprD efflux. Colistin is reserved for carbapenem-resistant Pseudomonas (XDR strains). For confirmed sensitive Pseudomonas VAP, monotherapy with the appropriate beta-lactam is sufficient; combination therapy (with aminoglycoside) is considered only for severe septic shock.

Pseudomonas aeruginosa: intrinsic resistance to amoxicillin-clavulanate, ceftriaxone, most 3rd-gen cephalosporins. Active agents: antipseudomonal penicillins (piperacillin-tazobactam), carbapenems (meropenem, imipenem), ceftazidime, cefepime, ciprofloxacin, aminoglycosides, colistin. MDR Pseudomonas: colistin + meropenem. Three mechanisms of resistance: efflux pumps, porin loss (OprD), beta-lactamases.

Pseudomonas aeruginosa VAP: use the appropriate antipseudomonal antibiotic guided by sensitivity. Meropenem is correct here (sensitive on culture). Ceftriaxone has no Pseudomonas activity. Ciprofloxacin is resistant. Amoxicillin-clavulanate has intrinsic no activity against Pseudomonas. Colistin is for XDR (carbapenem-resistant) strains.

Correct. Brucellosis: undulant fever + goat/sheep contact + Brucella agglutination ≥1:160 is diagnostic. WHO and standard guidelines for uncomplicated brucellosis: doxycycline 100 mg twice daily + rifampicin 600-900 mg daily for 6 weeks (the oral combination regimen). Doxycycline + gentamicin IM for the first 2 weeks is preferred by some experts for complicated/severe brucellosis (neurobrucellosis, endocarditis). Doxycycline monotherapy has high relapse rates. Azithromycin is not effective.

Brucellosis: undulant fever + occupational exposure (goats, cattle, raw dairy) + Brucella agglutination ≥1:160. Treat: doxycycline + rifampicin x6 weeks (uncomplicated) or doxycycline + gentamicin x6 weeks (preferred for severe/complicated). Blood culture gold standard but slow. Relapse (not re-infection) is the main complication of inadequate therapy.

Brucellosis treatment: doxycycline + rifampicin for 6 weeks (standard oral regimen for uncomplicated disease). Monotherapy with doxycycline has unacceptably high relapse rates. Doxycycline + gentamicin is an alternative for complicated disease. Brucella agglutination ≥1:160 in endemic context with compatible history is diagnostic.

Correct. Scrub typhus: eschar (necrotic, painless) in axilla + post-monsoon season + thrombocytopaenia/leucopaenia + positive OX-K Weil-Felix (Orientia tsutsugamushi). Doxycycline 100 mg twice daily for 7 days is the first-line treatment — it causes rapid defervescence within 24-48 hours (a therapeutic diagnostic test). If doxycycline is contraindicated (pregnancy, children <8 years), azithromycin is the safe alternative. Co-trimoxazole and beta-lactams are ineffective (Orientia is an obligate intracellular organism insensitive to these drugs).

Scrub typhus: mite-bite eschar (axilla, groin, popliteal fossa, scalp) + thrombocytopaenia + positive OX-K Weil-Felix. Treat: doxycycline 100 mg twice daily x7 days. Azithromycin for pregnancy/children. Clinical response within 24-48 hours is diagnostic. Complications: ARDS, multi-organ failure, meningoencephalitis — all preventable with early doxycycline.

Scrub typhus: axillary eschar + thrombocytopaenia + positive OX-K = Orientia tsutsugamushi. Doxycycline 100 mg twice daily x7 days is first-line — rapid defervescence in 24-48 hours confirms the diagnosis. Azithromycin is the alternative in pregnancy or children <8 years. Co-trimoxazole and beta-lactams are ineffective for intracellular Rickettsia/Orientia.

Correct. India's National Kala-Azar Elimination Programme (NKEP) has designated single-dose liposomal amphotericin B 10 mg/kg IV as the FIRST-LINE treatment for visceral leishmaniasis (VL) in India. This replaced SSG due to widespread SSG resistance in Bihar, Jharkhand, and West Bengal (SSG primary resistance >60% in some districts). Single-dose L-AmB achieves cure rates >97% in the Indian subcontinent. Miltefosine is an oral alternative but is teratogenic and has emerging resistance. Paromomycin is used in combination regimens.

Kala-azar India (NKEP 2020): first-line = single-dose liposomal amphotericin B 10 mg/kg IV (SSG resistance >60% in Bihar). Alternatives: miltefosine 2.5 mg/kg/day x28 days (teratogenic, avoid in pregnancy) or combination regimens. Diagnosis: clinical + rK39 RDT (sensitivity >97% in India) or splenic/bone marrow aspirate. Post-kala-azar dermal leishmaniasis (PKDL): treat with miltefosine x12 weeks.

India's NKEP (2020): first-line for VL = single-dose liposomal amphotericin B 10 mg/kg IV (due to >60% SSG resistance in Bihar). SSG is no longer first-line in India. Miltefosine (oral) is an alternative but teratogenic. Single-dose L-AmB achieves >97% cure in Indian subcontinent VL.