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IM26.1-35 | Infectious Diseases — Practice Quiz
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A 28-year-old construction worker presents in October with fever for 5 days, severe headache, bilateral conjunctival suffusion, myalgia, and oliguria. He worked in a waterlogged site after recent floods in Chennai. Serum creatinine is 3.2 mg/dL, bilirubin 4.8 mg/dL, and urine shows granular casts. Which single investigation is MOST likely to confirm the diagnosis at this stage of illness?
Correct. The triad of conjunctival suffusion, jaundice, and acute kidney injury (Weil's disease) after waterlogged-soil exposure is classical leptospirosis. Leptospira IgM ELISA becomes positive from day 5-7 of illness and is the best non-invasive confirmatory test at this stage. MAT (microscopic agglutination test) is the gold standard but requires reference laboratory facilities.
Leptospirosis (Weil's disease): conjunctival suffusion + jaundice + AKI after waterlogged exposure; diagnose with Leptospira IgM ELISA (day 5-7) or MAT; treat mild disease with doxycycline, severe with IV penicillin G or ceftriaxone.
The combination of conjunctival suffusion, jaundice, AKI, and flood-water exposure after 5 days of fever points to Weil's disease (severe leptospirosis). Leptospira IgM ELISA becomes positive from day 5-7 and is the appropriate confirmatory test at this stage. BCYE agar is for Legionella; Widal for enteric fever; smear for malaria; NS1 for dengue — none match this full syndromic picture.
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A 22-year-old college student is brought to casualty with sudden-onset severe headache, fever 39.8°C, neck stiffness, and a non-blanching petechial rash on both lower limbs. He is drowsy but arousable. Blood pressure is 90/60 mmHg. Which is the MOST APPROPRIATE immediate sequence of actions?
Correct. Non-blanching petechial rash with meningismus and haemodynamic instability in a young adult is meningococcaemia — a life-threatening emergency. The correct sequence is: blood cultures → IV dexamethasone + IV ceftriaxone (both within 30 minutes of presentation) → defer LP if there are signs of raised ICP or haemodynamic instability. Never delay antibiotics for LP or imaging in this scenario.
Bacterial meningitis emergency protocol: blood cultures → IV dexamethasone → IV ceftriaxone all within 30 min. Non-blanching rash = meningococcaemia; LP deferred if haemodynamically unstable or raised ICP signs. Add ampicillin for Listeria if age >50 years or immunocompromised.
Non-blanching petechial rash with meningitis signs and hypotension = meningococcal septicaemia. The guideline is: blood cultures → dexamethasone → ceftriaxone ALL within 30 minutes. LP is deferred when there is haemodynamic instability or signs of raised ICP. Delaying antibiotics for LP or CT in this scenario is dangerous.
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A 35-year-old farmer from Rajasthan presents with high fever, painful swelling in the right groin with overlying erythema, and rapidly worsening malaise. He recalls being bitten by fleas while working in fields with rodent infestation 4 days ago. The lymph node is fluctuant and extremely tender. Which drug is the treatment of choice?
Correct. Bubonic plague (Yersinia pestis) presenting as a painful inguinal bubo after flea bite in a rodent-endemic area. Streptomycin is the first-line treatment (1 g IM twice daily for 10 days); gentamicin IV is the preferred alternative when streptomycin is unavailable. Doxycycline is an alternative but is second-line; it is the drug of choice for prophylaxis in contacts.
Plague (Yersinia pestis): flea bite from rodents → bubonic (painful lymphadenopathy) or pneumonic (haemoptysis, highly contagious) forms. Treatment: streptomycin IM or gentamicin IV; doxycycline for prophylaxis. Notifiable disease — immediate isolation and reporting required.
This is bubonic plague — painful fluctuant inguinal bubo after flea bite in a rodent-endemic area (Rajasthan). The treatment of choice is streptomycin IM (or gentamicin IV). Doxycycline is used for post-exposure prophylaxis of contacts, not as first-line treatment. Azithromycin and amoxicillin-clavulanate have no role in plague.
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A 19-year-old student presents with fever for 10 days, relative bradycardia, rose spots on the abdomen, and mild splenomegaly. Widal test shows O titre 1:160 and H titre 1:80. Blood culture is pending. What is the MOST APPROPRIATE treatment?
Correct. Enteric fever (typhoid) is treated with ceftriaxone 2 g IV once daily for 7-14 days — this is the preferred treatment in India where nalidixic acid-resistant Salmonella Typhi (NARST) and now multidrug-resistant (MDR) strains are widespread. Fluoroquinolones (ciprofloxacin) are no longer first-line due to high rates of reduced susceptibility. Chloramphenicol has largely been replaced due to MDR strains. Azithromycin is an oral option for uncomplicated typhoid but ceftriaxone is preferred for this severity.
Enteric fever treatment in India: ceftriaxone 2 g IV daily (7-14 days) is first-line due to widespread NARST/MDR strains. Azithromycin is an oral alternative for uncomplicated typhoid. Fluoroquinolones have limited role due to resistance. Widal serology has low specificity; blood culture remains the gold standard.
Enteric fever in India should be treated with ceftriaxone 2 g IV daily due to widespread nalidixic acid-resistant and multidrug-resistant Salmonella Typhi. Fluoroquinolones have limited efficacy due to emerging resistance. Chloramphenicol is no longer first-line. Azithromycin is an option for uncomplicated mild-moderate disease.
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A 45-year-old immunocompromised patient on long-term corticosteroids presents with productive cough, fever, and pleuritic chest pain. CXR shows a right-upper-lobe cavitary lesion with a 'halo sign' on HRCT chest. Serum galactomannan is positive. BAL shows septate hyphae with 45-degree angle branching. What is the MOST APPROPRIATE first-line treatment?
Correct. Invasive pulmonary aspergillosis (IPA): halo sign on HRCT + positive galactomannan + septate hyphae with 45-degree branching (characteristic of Aspergillus) in an immunocompromised host. Voriconazole is the first-line treatment per IDSA and ESCMID guidelines, with loading dose 6 mg/kg IV 12-hourly on day 1, then maintenance 4 mg/kg IV 12-hourly. Fluconazole has no activity against Aspergillus. Amphotericin B is an alternative but second-line due to superior outcomes with voriconazole.
Invasive aspergillosis: halo sign on HRCT + galactomannan + 45-degree septate hyphae. Treat with voriconazole (first-line); amphotericin B or isavuconazole if voriconazole not tolerated. Fluconazole has no anti-Aspergillus activity. Neutropenia and corticosteroid use are the major risk factors.
The combination of halo sign, positive galactomannan, and septate 45-degree branching hyphae = invasive pulmonary aspergillosis. First-line treatment is voriconazole (loading 6 mg/kg IV 12-hourly day 1, then 4 mg/kg 12-hourly). Fluconazole has NO activity against Aspergillus. Caspofungin is a salvage option. Amphotericin B is second-line.
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A 30-year-old HIV-positive man (CD4 60 cells/microL) presents with fever, severe headache, and confusion. CSF shows: opening pressure 280 mm H2O, WBC 20/mm3 (lymphocytes 90%), glucose 45 mg/dL (serum 90 mg/dL), protein 80 mg/dL, India ink positive. CSF CrAg is positive. What is the MOST APPROPRIATE induction treatment?
Correct. Cryptococcal meningitis in HIV (CD4 <100): India ink positive + positive CrAg with raised CSF pressure confirms the diagnosis. Induction therapy: amphotericin B deoxycholate 0.7-1 mg/kg/day IV PLUS flucytosine 25 mg/kg orally four times daily for 2 weeks (combination superior to monotherapy). Consolidation: fluconazole 400 mg/day for 8 weeks. Maintenance: fluconazole 200 mg/day until CD4 >200 on ART. Serial lumbar punctures are needed for raised ICP management.
Cryptococcal meningitis in HIV: India ink + CrAg positive CSF; treat with amphotericin B + flucytosine induction (2 weeks) → fluconazole consolidation (8 weeks) → fluconazole maintenance. Raised ICP: therapeutic LPs to keep opening pressure <200 mm H2O. Do NOT start ART immediately — defer 4-6 weeks to avoid IRIS.
Cryptococcal meningitis (India ink positive, CrAg positive, raised ICP) in HIV needs combination induction: amphotericin B deoxycholate + flucytosine for 2 weeks (superior to fluconazole monotherapy in reducing early mortality). Fluconazole alone is inferior for induction. Voriconazole and caspofungin have no role in cryptococcal meningitis.
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A 7-year-old boy from Assam presents in June with fever for 4 days, headache, and one episode of generalised convulsion. Peripheral blood smear shows ring forms with multiple rings per RBC, banana-shaped gametocytes, and no enlarged erythrocytes. His mother is pregnant (32 weeks). What is the CORRECT treatment for the child in India?
Correct. Multiple ring forms per RBC and banana-shaped gametocytes = P. falciparum. India's NVBDCP (National Vector-Borne Disease Control Programme) recommends ACT: artesunate + sulfadoxine-pyrimethamine (AS+SP) for 3 days plus a single low dose of primaquine (0.75 mg/kg) on day 1 as a gametocytocidal agent for uncomplicated falciparum malaria. This child does not have features of severe malaria (single convulsion in febrile illness is not itself a severity criterion; would need repeated convulsions or other criteria). The pregnant mother should NOT receive primaquine.
India malaria treatment (NVBDCP): P. falciparum uncomplicated = ACT (AS+SP) x3 days + primaquine single dose 0.75 mg/kg. P. vivax = chloroquine x3 days + primaquine 0.25 mg/kg/day x14 days (G6PD test mandatory; contraindicated in pregnancy). Severe malaria = IV artesunate. Primaquine contraindicated in pregnancy and G6PD deficiency.
Multiple rings per RBC + banana gametocytes = P. falciparum. India's NVBDCP regimen: ACT (artesunate + SP) for 3 days + single-dose primaquine 0.75 mg/kg (day 1) for uncomplicated falciparum. Chloroquine alone is no longer effective against P. falciparum due to resistance. IV artesunate is reserved for severe malaria criteria.
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A 55-year-old farmer from Bihar presents with progressive painless swelling of the left leg for 2 years, scrotal swelling, and fever. Nocturnal blood smear shows microfilariae with a sheath and nuclei not extending to the tip of the tail. What is the CORRECT treatment?
Correct. Wuchereria bancrofti microfilariae: sheathed with nuclei that do NOT extend to tip of tail (distinguish from Brugia malayi where nuclei extend to tail tip). The drug of choice for treatment of symptomatic lymphatic filariasis is DEC 6 mg/kg/day in three divided doses for 12 days. DEC has both macrofilaricidal and microfilaricidal activity. For mass drug administration (MDA) in India, DEC + albendazole single dose annually is used.
Lymphatic filariasis (W. bancrofti): sheathed microfilariae, nuclei absent from tail tip; nocturnal periodicity. Treat with DEC 6 mg/kg/day x12 days. MDA in India: DEC + albendazole annual single dose. Distinguish from Brugia malayi (nuclei extend to tail tip, sub-periodic in South India).
Sheathed microfilariae with nuclei not extending to the tail tip = Wuchereria bancrofti. Treatment: DEC 6 mg/kg/day in divided doses for 12 days. Ivermectin is used for onchocerciasis and as part of MDA in co-endemic areas. Praziquantel is for schistosomiasis/tapeworm. Albendazole is added for MDA programmes, not sufficient alone for treatment.
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A 25-year-old woman presents with recurrent white vaginal discharge, vulval pruritus, and erythema. She has been on amoxicillin for a chest infection for 5 days. KOH wet mount shows pseudohyphae and budding yeast cells. What is the MOST APPROPRIATE treatment?
Correct. Vulvovaginal candidiasis (VVC) — white discharge + vulval pruritus + pseudohyphae on KOH mount. First-line treatment is topical antifungal: clotrimazole 500 mg vaginal pessary (single dose) or 100 mg for 7 days. Oral fluconazole 150 mg single dose (not 400 mg) is an alternative. Voriconazole and caspofungin are reserved for invasive candidiasis, not mucocutaneous VVC. Metronidazole is for bacterial vaginosis/trichomonas, not candidiasis.
VVC treatment: topical clotrimazole (500 mg single-dose pessary) or oral fluconazole 150 mg single dose. Complicated/recurrent VVC (4+ episodes/year): fluconazole 150 mg every 72h x3 doses, then weekly for 6 months. Oropharyngeal thrush: fluconazole 100 mg/day x7 days or clotrimazole troches. Oesophageal candidiasis (AIDS-defining): fluconazole 200 mg/day x14-21 days.
VVC: pseudohyphae + budding yeast on KOH, post-antibiotic. Treat with topical clotrimazole 500 mg single-dose pessary or oral fluconazole 150 mg (single dose). Voriconazole and caspofungin are for invasive candidiasis. Metronidazole is for bacterial vaginosis — has no anti-candidal activity.
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A 40-year-old man presents with a 3-week history of dyspepsia, epigastric pain worsened by eating, and a duodenal ulcer on endoscopy. Rapid urease test (CLO test) is positive. He has no prior antibiotic exposure. What is the MOST APPROPRIATE first-line eradication regimen in India?
Correct. H. pylori eradication in India: standard 7-day triple therapy (PPI + clarithromycin + amoxicillin) has eradication rates below 80% in India due to high clarithromycin resistance (>15%). Current Indian Society of Gastroenterology (ISG 2023) guidelines recommend concomitant quadruple therapy (PPI + amoxicillin + clarithromycin + metronidazole) for 10-14 days as first-line, achieving >90% eradication. Bismuth quadruple therapy is an alternative but less available.
H. pylori India: high clarithromycin resistance (>15%) makes 7-day triple therapy suboptimal. First-line: concomitant quadruple therapy (PPI + amoxicillin + clarithromycin + metronidazole) 10-14 days. Confirm eradication 4 weeks post-treatment with urea breath test or faecal antigen test (not serology — antibodies persist after eradication). MALT lymphoma stage I: antibiotics alone achieve remission.
Standard 7-day triple therapy has <80% efficacy in India due to high clarithromycin resistance. ISG 2023 recommends concomitant quadruple therapy (PPI + amoxicillin + clarithromycin + metronidazole) for 10-14 days as first-line in India. Eradication must ALWAYS be confirmed 4 weeks after completing therapy (urea breath test or faecal antigen test).
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