Infectious Diseases — MCQs
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An HIV-positive man presents with a high-grade fever. Examination reveals a positive Kernig's sign. CSF shows reduced glucose, increased protein, and increased leukocytes. A diagnosis of cryptococcal meningitis is made. What is the appropriate management for this patient?
A patient presented with a fever for 11 days with neck rigidity. A lumbar puncture was done, and it showed predominantly lymphocytes, sugar- 50mg, and protein- 3000mg/dl. Gram-staining was negative. The patient's chest X-ray shows upper lobe involvement with hilar lymph node enlargement. What is the probable diagnosis?
A 65-year-old male presented with unexplained fever and prolonged respiratory distress despite appropriate treatment. A diagnosis of cryptic tuberculosis was made. Which of the following is the correct statement related to this condition?
Which of the following is least likely to cause mucormycosis?
What is the role of Procalcitonin in pneumonia?
A 20-year-old male presents with fever, severe headache, vomiting, and photophobia. On examination, neck rigidity and Brudzinskis sign are positive. CT scan of the brain shows hydrocephalus. What is the most likely diagnosis?
A 58-year-old male presents with burning micturition. Prostatic examination is normal. Urinalysis shows >50 pus cells per high power field, but urine culture shows no growth. What is the most likely diagnosis?
A patient underwent cardiac surgery and was admitted to the ICU. He later developed ventilator-associated pneumonia and was started on empirical antibiotics. A few hours later, the patient developed acute kidney injury. Serum procalcitonin was sent. Which of the following statements regarding procalcitonin is correct?
A 25-year-old sewage worker presents with fever for 1 week and weakness for 1 day. Laboratory evaluation reveals elevated bilirubin and decreased urine output. Conjunctival redness? What is the most likely diagnosis?
A patient with HIV develops tuberculosis. When should ART be initiated?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 721: An HIV-positive man presents with a high-grade fever. Examination reveals a positive Kernig's sign. CSF shows reduced glucose, increased protein, and increased leukocytes. A diagnosis of cryptococcal meningitis is made. What is the appropriate management for this patient?
- A. High dose fluconazole with flucytosine
- B. Voriconazole
- C. Liposomal amphotericin B (Correct Answer)
- D. Vancomycin
Explanation: ***Liposomal amphotericin B***- **Liposomal amphotericin B** (often combined with **flucytosine**) is the standard of care for the **induction phase** (first 2 weeks) of severe cryptococcal meningitis treatment in HIV-positive patients due to its potent fungicidal activity [1].- The severity of the presentation (high fever, positive **Kernig's sign**, and abnormal CSF findings) necessitates this regimen to rapidly reduce the fungal burden in the central nervous system.*Vancomycin*- **Vancomycin** is an antibiotic used specifically to treat severe infections caused by **Gram-positive bacteria**, notably **MRSA**.- This drug has absolutely no therapeutic efficacy against the fungal pathogen *Cryptococcus neoformans*.*High dose fluconazole with flucytosine*- While fluconazole is an effective antifungal against *Cryptococcus*, this regimen is typically reserved for the **consolidation phase** (post-induction) or for milder disease.- Severe meningitis, indicated by the clinical signs and CSF profile, requires the superior fungicidal activity of **amphotericin B** during the induction phase [1].*Voriconazole*- **Voriconazole** is a broad-spectrum triazole mainly used for treating invasive **Aspergillus** and some *Candida* infections [1], [2].- It has **limited efficacy** against *Cryptococcus neoformans* and is not recommended as primary induction therapy for cryptococcal meningitis.
Question 722: A patient presented with a fever for 11 days with neck rigidity. A lumbar puncture was done, and it showed predominantly lymphocytes, sugar- 50mg, and protein- 3000mg/dl. Gram-staining was negative. The patient's chest X-ray shows upper lobe involvement with hilar lymph node enlargement. What is the probable diagnosis?
- A. Bacterial meningitis
- B. Fungal meningitis
- C. Viral meningitis
- D. Tuberculous meningitis (Correct Answer)
Explanation: ***Tuberculous meningitis***- The CSF analysis combines **lymphocytic predominance** (suggesting non-pyogenic cause), subacute onset (11 days of fever), and critically high protein (3000 mg/dL), which are hallmarks of TBM [1]. - The chest X-ray findings of **upper lobe involvement** and **hilar lymph node enlargement** confirm active systemic tuberculosis, providing the strongest evidence for TBM as the underlying cause of meningitis [4].*Bacterial meningitis*- Typically presents acutely (hours to a few days) and CSF analysis shows a predominance of **neutrophils** (neutrophilic pleocytosis) [3].- Although CSF protein is high and glucose is low, the presence of lymphocytes and a negative Gram stain makes typical pyogenic bacterial meningitis less likely [3].*Fungal meningitis*- Fungal infections like **Cryptococcosis** can cause lymphocytic pleocytosis and elevated protein, but the protein level (3000 mg/dL) is excessively high, even for fungal causes.- While systemic involvement can occur, the specific pulmonary findings (upper lobe infiltrates, hilar nodes) are classic diagnostic features of **Mycobacterium tuberculosis**.*Viral meningitis*- Viral meningitis typically causes an acute, self-limiting illness and is generally associated with relatively low protein levels (usually <100 mg/dL) and normal CSF glucose [2].- The protein level of 3000 mg/dL in this patient is incompatible with a typical viral etiology, which mostly resolves spontaneously [2].
Question 723: A 65-year-old male presented with unexplained fever and prolonged respiratory distress despite appropriate treatment. A diagnosis of cryptic tuberculosis was made. Which of the following is the correct statement related to this condition?
- A. Positive skin tuberculin test and negative chest X-ray
- B. Positive skin tuberculin test and positive chest X-ray
- C. Negative skin tuberculin test and negative chest X-ray (Correct Answer)
- D. Negative skin tuberculin test and positive chest X-ray
Explanation: ***Negative skin tuberculin test and negative chest X-ray***- **Cryptic tuberculosis (TB)**, or occult TB, often presents with non-specific systemic symptoms (like prolonged unexplained fever) without typical clinical or radiological signs expected in classic TB [1].- In older patients or those with disseminated disease, the immune response is often diminished, leading to a false negative result (anergy) on the **tuberculin skin test (TST)**, alongside a frequently normal chest X-ray (CXR) [1]. *Positive skin tuberculin test and negative chest X-ray*- A **positive TST** indicates prior exposure to *M. tuberculosis* but doesn't necessarily confirm active, symptomatic disease like cryptic TB. - Although the CXR is negative (consistent with cryptic TB), the positive TST contradicts the common finding of **anergy** seen in severely ill or elderly patients with cryptic disease. *Positive skin tuberculin test and positive chest X-ray*- This combination is characteristic of typical, **active pulmonary tuberculosis**, where the disease is localized and clinically/radiologically apparent. - By definition, cryptic TB lacks the **classic radiological findings** on chest X-ray, making this option incorrect. *Negative skin tuberculin test and positive chest X-ray*- While a **negative TST** can occur in active TB due to anergy or immunosuppression, a **positive CXR** strongly indicates radiologically apparent TB. - If the TB is radiologically apparent, the designation "cryptic" (meaning hidden or obscure) is inappropriate.
Question 724: Which of the following is least likely to cause mucormycosis?
- A. Neutropenia
- B. Broad spectrum antibiotics (Correct Answer)
- C. Uncontrolled diabetes without DKA
- D. Prolonged use of steroid
Explanation: ***Broad spectrum antibiotics*** - While broad-spectrum antibiotics predispose to many fungal infections (especially *Candida* infections) by disrupting the normal **microbiome**, they are not typically considered a direct, primary risk factor for **mucormycosis** [1]. - *Mucorales* are ubiquitous molds, and their pathogenicity is primarily related to defects in **phagocytic function** (like in neutropenia) [2] or **acidosis/iron overload** (like in DKA), not bacterial flora changes [2]. *Neutropenia* - Profound **neutropenia** (low neutrophil count) significantly impairs the host's ability to clear fungal spores, making it one of the most important risk factors for invasive mold infections, including **mucormycosis** [2]. - Neutrophils are crucial for the primary defense against **Mucorales** by killing the spores and hyphae. *Uncontrolled diabetes without DKA* - Even without **diabetic ketoacidosis (DKA)**, poorly controlled diabetes leads to impaired phagocyte function and immunosuppression, increasing the risk of invasive fungal infections like *Mucorales* and **Candida** [2], [3]. - The high glucose environment, especially in the **nasal mucosa**, can facilitate the growth and invasion of these fungi. *Prolonged use of steroid* - Glucocorticoids cause generalized **immunosuppression** by impairing the function of phagocytes and T-lymphocytes, thereby increasing susceptibility to opportunistic infections [3]. - High-dose or prolonged corticosteroid use is a well-established risk factor for severe and disseminated **mucormycosis** as it compromises the innate immune response.
Question 725: What is the role of Procalcitonin in pneumonia?
- A. Requirement of further investigation
- B. Guiding initiation of antibiotic
- C. Early antibiotic discontinuation (Correct Answer)
- D. No role
Explanation: ***Early antibiotic discontinuation*** - Procalcitonin (PCT) is a validated biomarker used to monitor clinical response and guide the safe cessation of antibiotics in patients with **Community-Acquired Pneumonia (CAP)** and other lower respiratory tract infections. - A significant decrease in PCT levels (typically <0.25 ng/mL or a substantial drop from peak) suggests the infection is resolving, facilitating **de-escalation** and reducing unnecessary antibiotic exposure. ***Guiding initiation of antibiotic*** - While elevated PCT levels (e.g., >0.5 ng/mL) strongly suggest a **bacterial etiology** over a viral one, clinical guidelines often mandate immediate empiric antibiotic initiation based on the severity of illness (e.g., **CURB-65** criteria) [1]. - Although useful for differentiating bacterial vs. viral causes, the strongest evidence and clinical application of PCT in pneumonia focus on the timing of **stopping** treatment rather than starting [2]. ***Requirement of further investigation*** - PCT is a specific **biomarker** that helps establish the presence of a **systemic bacterial infection** or sepsis, thus serving as a diagnostic aid itself rather than just indicating the need for additional, generic investigations [2]. - If PCT levels are high, it confirms the likelihood of a bacterial etiology, directing the clinician towards definitive **antibiotic therapy** and close monitoring rather than simply delaying treatment with more tests. ***No role*** - This statement is incorrect; PCT-guided algorithms for antibiotic management are integrated into many international guidelines (like those from the Infectious Diseases Society of America/American Thoracic Society) to reduce the **duration of therapy**. - Its measurable sensitivity and specificity in distinguishing bacterial infections from non-infectious causes or viral infections provide a substantial clinical role in improving **antibiotic stewardship** [2].
Question 726: A 20-year-old male presents with fever, severe headache, vomiting, and photophobia. On examination, neck rigidity and Brudzinskis sign are positive. CT scan of the brain shows hydrocephalus. What is the most likely diagnosis?
- A. Viral Encephalitis
- B. Bacterial Meningitis (Correct Answer)
- C. Subarachnoid Hemorrhage
- D. Normal Pressure Hydrocephalus
Explanation: ***Bacterial Meningitis*** - The clinical triad of **fever**, **headache**, and **neck rigidity** (nuchal rigidity) is classic for acute meningitis [1]. - Positive meningeal signs like **Brudzinski's sign** confirm meningeal irritation, and hydrocephalus may occur due to impaired CSF flow or absorption (communicating or non-communicating) [1]. ***Normal Pressure Hydrocephalus*** - Characterized by the triad of gait disturbance, urinary incontinence, and **dementia** (Wacky, Wobbly, Wet). - Does not typically present with acute systemic symptoms like **fever** or acute signs of meningeal irritation (neck rigidity/Brudzinski's). ***Viral Encephalitis*** - While it presents with fever and headache, the hallmark is altered mental status (confusion, seizures) and focal neurological deficits, indicating **parenchymal involvement**. - Severe, rigid **neck stiffness** (a major sign of meningeal irritation) is usually less prominent compared to bacterial meningitis [1]. ***Subarachnoid Hemorrhage*** - Presents with a sudden worst headache of life (**thunderclap headache**) and meningeal signs (neck rigidity, photophobia) [1]. - **Fever** is usually low-grade (if present) and develops later, unlike the often high fever seen in bacterial meningitis.
Question 727: A 58-year-old male presents with burning micturition. Prostatic examination is normal. Urinalysis shows >50 pus cells per high power field, but urine culture shows no growth. What is the most likely diagnosis?
- A. Granulomatous prostatitis
- B. Chronic bacterial prostatitis
- C. Acute bacterial prostatitis
- D. Sterile pyuria (Correct Answer)
Explanation: ***Sterile pyuria*** - The combination of **pyuria** (>50 pus cells/HPF) and a **negative urine culture (no growth)** is known as sterile pyuria. This can be idiopathic or indicate conditions like **urethritis**, **tuberculosis**, or non-bacterial infections [1]. - The presence of symptoms (burning micturition) combined with pyuria and a normal prostate examination rules out typical bacterial prostatitis scenarios [1]. ***Chronic bacterial prostatitis*** - While chronic bacterial prostatitis involves recurrent symptomatic episodes and may sometimes show pyuria, it is characterized by **recurrent positive urine cultures** (often *E. coli*) and localization of bacteria to prostatic fluid. - The prostatic examination is often normal, but the hallmark is the presence of bacteria in the urine/prostatic fluid, which is absent here. ***Acute bacterial prostatitis*** - This presents with signs of systemic infection (fever, chills) and a very tender, boggy prostate, which is not mentioned, and the exam here is noted as **normal** [1]. - It always involves a **positive urine culture** due to the high bacterial load in the urine. ***Granulomatous prostatitis*** - This is a rare inflammatory condition, often related to fungal infections or **BCG therapy**, and typically manifests as a firm, nodular prostate that mimics prostate cancer. - While it can cause sterile pyuria, the presentation is usually dominated by prostatic enlargement or hardness, which is contradicted by the **normal prostatic examination** given in the prompt.
Question 728: A patient underwent cardiac surgery and was admitted to the ICU. He later developed ventilator-associated pneumonia and was started on empirical antibiotics. A few hours later, the patient developed acute kidney injury. Serum procalcitonin was sent. Which of the following statements regarding procalcitonin is correct?
- A. It helps in determining the duration of antibiotic therapy (Correct Answer)
- B. It can be used to confirm source of infection
- C. It is used to differentiate bacterial from fungal cause
- D. It helps in identifying which empirical antibiotics to be started
Explanation: ***It helps in determining the duration of antibiotic therapy*** - Procalcitonin (PCT) levels **decrease rapidly** (half-life of 24 hours) as a patient responds to effective antibiotic treatment, making it an excellent biomarker for guiding antibiotic **de-escalation** and **discontinuation**. [1] - Serial measurement of PCT is a core component of many **antibiotic stewardship** protocols to safely shorten the duration of therapy in patients with conditions like VAP or sepsis, reducing antibiotic exposure and resistance. ***It helps in identifying which empirical antibiotics to be started*** - PCT indicates the **likelihood, severity, and prognosis** of a bacterial infection, but it does **not** provide information about the **susceptibility** profile or Gram stain characteristics of the pathogen, which are crucial for selecting empirical antibiotics. - PCT levels should be used to support the decision to **initiate** antibiotics, not to select the specific agent; this selection requires clinical assessment and local **resistance patterns**. ***It can be used to confirm source of infection*** - PCT is a systemic marker elevated in response to most **bacterial infections**, especially those leading to sepsis, and its elevation does not localize the site or **source** of infection (e.g., lung, urinary tract, abdomen). [2] - The source of infection must still be confirmed using **radiology**, cultures, and clinical examination (e.g., **chest X-ray** for VAP). ***It is used to differentiate bacterial from fungal cause*** - PCT is primarily released by C-cells of the thyroid and neuroendocrine cells in response to **bacterial endotoxins** and inflammatory cytokines (like IL-6 and TNF-α) produced during bacterial infection. - Although PCT levels remain **low** in most **viral** and **fungal** infections, its primary clinical utility is differentiating bacterial infection from non-infectious inflammation (like surgery or trauma), not specifically distinguishing bacteria from fungi, for which markers like **beta-D-glucan** are more relevant.
Question 729: A 25-year-old sewage worker presents with fever for 1 week and weakness for 1 day. Laboratory evaluation reveals elevated bilirubin and decreased urine output. Conjunctival redness? What is the most likely diagnosis?
- A. Enteric fever
- B. Acute Viral Hepatitis
- C. Weil's disease (Correct Answer)
- D. Brucellosis
Explanation: ***Weil's disease*** - The clinical triad of fever, **jaundice (elevated bilirubin)**, and **acute kidney injury (decreased urine output)**, particularly in an individual with exposure to contaminated water (**sewage worker**), is the classical presentation of the severe form of leptospirosis, also known as Weil's disease [1]. - **Conjunctival suffusion/redness** without inflammation or discharge is a pathognomonic physical sign highly suggestive of Weil's disease, caused by the spirochete **Leptospira interrogans** [1], [2]. *Brucellosis* - Usually presents with an undulating fever, night sweats, and localized infection in the bones (**spondylitis**) or reticuloendothelial system; it is often linked to consumption of **unpasteurized dairy**. - While mild hepatic involvement can occur, it rarely causes the severe combination of **acute renal failure** and deep jaundice seen in this patient. *Enteric fever* - Characterized by a gradually rising fever, **relative bradycardia**, and often features a dry cough, abdominal discomfort, and sometimes **rose spots**. [2] - Severe organ damage like acute kidney injury and profound jaundice simultaneously is unusual in typhoid fever, and **conjunctival suffusion** is not a feature. *Acute Viral Hepatitis* - Presents with fever, malaise, and eventually **jaundice (elevated bilirubin)**; the primary pathology is hepatocyte necrosis. [2] - It typically does not cause simultaneous severe **acute renal failure** and the specific finding of **conjunctival suffusion**, which are hallmarks of Weil's disease.
Question 730: A patient with HIV develops tuberculosis. When should ART be initiated?
- A. Start ART followed by ATT
- B. ART alone
- C. Start ART and ATT simultaneously
- D. Start ATT, then ART after 2 weeks (Correct Answer)
Explanation: ***A. Start ATT, then ART after 2 weeks*** - This strategy is the standard recommendation, particularly for patients with CD4 counts >50 cells/mm³, to reduce the risk of **Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome (IRIS)** [1]. - Delaying ART by 2 weeks allows patients to establish tolerance to **Anti-Tubercular Treatment (ATT)** and simplifies the management of potential overlapping drug toxicities [2]. *B. Start ART and ATT simultaneously* - Simultaneous initiation significantly increases the risk and severity of developing **IRIS**, which can worsen the patient's clinical status due to paradoxical worsening of TB symptoms [1]. - This approach also makes it challenging to identify the source of **drug-related toxicities** (e.g., hepatotoxicity), as many ATT and ART drugs are metabolized by the liver [2]. *C. Start ART followed by ATT* - Delaying the initiation of **ATT** is dangerous as active tuberculosis is the immediate life-threatening condition that requires urgent treatment [2]. - Treatment priority in HIV-TB co-infection must first focus on effectively treating the active infection to prevent **disseminated disease** and death. *D. ART alone* - Administering **ART alone** will lead to the progression of active tuberculosis, resulting in significant morbidity and high mortality rates. - ART is necessary but must be combined with effective **ATT** as it is not a treatment for Mycobacterium tuberculosis itself.
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Principles of Antimicrobial Therapy
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Fever of Unknown Origin
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HIV/AIDS and Related Infections
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Tuberculosis and Mycobacterial Diseases
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Tropical and Parasitic Infections
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Viral Infections (Hepatitis, Herpes, etc.)
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Healthcare-Associated Infections
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Fungal Infections
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Sepsis and Septic Shock
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Infection in Immunocompromised Hosts
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Emerging and Re-emerging Infections
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Antimicrobial Resistance
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Vaccination Principles
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