Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1091: A 25-year-old woman presents with fever, rash, and joint pain after returning from Southeast Asia. What is the most likely diagnosis?

A. Dengue fever (Correct Answer)
B. Malaria
C. Typhoid fever
D. Leptospirosis

Explanation: ***Dengue fever*** - The classic triad of **fever**, **rash**, and **arthralgia** (joint pain) following travel to endemic areas like Southeast Asia is highly suggestive of dengue [1]. - Dengue is a **mosquito-borne viral infection** common in tropical and subtropical regions. *Malaria* - Characterized by **cyclic fevers**, chills, and sweats [2], but rash and prominent joint pain are not typical features. - Diagnosed by **microscopic examination** of blood smears for parasites or rapid diagnostic tests. *Typhoid fever* - Presents with a **prolonged fever**, headache, abdominal pain, and often a **"rose spot" rash**, but significant joint pain is uncommon. - Caused by **Salmonella Typhi** and transmitted through contaminated food or water. *Leptospirosis* - Typically causes **fever**, headache, muscle pain (myalgia), and sometimes jaundice, but a widespread rash and prominent arthralgia are less characteristic. - Transmitted through contact with **urine of infected animals** or contaminated water.

Question 1092: Which test is used to diagnose active tuberculosis?

A. Mantoux test
B. Sputum culture (Correct Answer)
C. Chest X-ray
D. ELISA

Explanation: ***Sputum culture*** - **Sputum culture** for *Mycobacterium tuberculosis* is considered the **gold standard** for diagnosing **active pulmonary tuberculosis** because it directly detects the presence of viable bacteria [2]. - A positive culture confirms active disease and allows for **drug susceptibility testing**, which is crucial for guiding treatment [1]. *Mantoux test* - The **Mantoux test** (tuberculin skin test) detects exposure to *Mycobacterium tuberculosis* and subsequent **immune sensitization**, indicating latent infection or past exposure, not necessarily active disease [3]. - It does not differentiate between **latent tuberculosis infection (LTBI)** and **active TB**, and a positive result requires further investigation to rule out active disease. *Chest X-ray* - A **chest X-ray** can show abnormalities consistent with tuberculosis (e.g., infiltrates, cavities, hilar lymphadenopathy), but it is not definitive for **active TB** [1]. - Abnormal findings on a chest X-ray must be correlated with clinical symptoms and often require **microbiological confirmation** to diagnose active disease. *ELISA* - **ELISA-based tests** are primarily used for detecting **antibodies** to *Mycobacterium tuberculosis* antigens, which can indicate exposure but do not reliably distinguish between **active** and **latent TB**. [3] - Their sensitivity and specificity for diagnosing active TB, particularly in immunocompromised individuals, are generally **lower** than direct microbiological methods, making them unsuitable as a primary diagnostic tool for active disease.

Question 1093: A patient presents with fever, headache, and a bull's-eye rash. What is the most likely diagnosis, and which vector is associated with this disease?

A. Lyme disease, Ixodes tick (Correct Answer)
B. Rocky Mountain spotted fever, Dermacentor tick
C. Ehrlichiosis, Amblyomma tick
D. Babesiosis, Ixodes tick

Explanation: ***Lyme disease, Ixodes tick*** - The classic triad of **fever**, **headache**, and a **bull's-eye rash** (erythema migrans) is highly characteristic of Lyme disease [1]. - **Lyme disease** is transmitted by the **Ixodes tick**, also known as the deer tick [1]. *Rocky Mountain spotted fever, Dermacentor tick* - Rocky Mountain spotted fever presents with a **maculopapular rash** that typically starts on the extremities and spreads centrally, often involving palms and soles, but not a bull's-eye pattern [2]. - It is transmitted by the **Dermacentor tick** (dog tick or wood tick). *Ehrlichiosis, Amblyomma tick* - Ehrlichiosis typically presents with **fever**, **headache**, **myalgia**, and thrombocytopenia, but usually no rash, or a non-specific rash, rather than a bull's-eye [1]. - It is primarily transmitted by the **Amblyomma americanum tick** (lone star tick). *Babesiosis, Ixodes tick* - Babesiosis can cause **fever**, **fatigue**, **malaise**, and **hemolytic anemia**, but it does not cause a bull's-eye rash. - While it is transmitted by the **Ixodes tick**, the clinical presentation is distinct from Lyme disease [1].

Question 1094: Which hepatitis virus is most commonly associated with chronic liver disease and hepatocellular carcinoma?

A. Hepatitis B (Correct Answer)
B. Hepatitis A
C. Hepatitis D
D. Hepatitis C

Explanation: ***Hepatitis C*** - Hepatitis C is known for its high potential to cause **chronic liver disease**, leading to cirrhosis and hepatocellular carcinoma. - It often remains asymptomatic for years, allowing for the progression to **chronic infection** and liver complications [1]. *Hepatitis D* - Hepatitis D primarily occurs in individuals already infected with **Hepatitis B**, and is not the main cause of chronic liver disease by itself. - It leads to more severe liver disease but is **dependant** on Hepatitis B for its propagation. *Hepatitis A* - Hepatitis A typically causes **acute** liver disease with symptoms like fever and jaundice, and it does not lead to chronic infection. - It is primarily spread through **fecal-oral route** and resolved completely in most cases, with no associated risk for liver cancer. *Hepatitis B* - While Hepatitis B is associated with chronic liver disease, it is **Hepatitis C** that has a higher incidence of leading to hepatocellular carcinoma. - Chronic Hepatitis B infection has significant liver disease implications but is less common than Hepatitis C in terms of **liver cancer association**, though the HBx protein has been implicated in hepatocellular carcinoma pathogenesis.

Question 1095: A patient with a history of HIV presents with multiple ring-enhancing lesions in the brain, and serology is positive for IgG antibodies against Toxoplasma. What is the most likely diagnosis?

A. Cryptococcal meningitis
B. Toxoplasmosis (Correct Answer)
C. Cerebral malaria
D. Cysticercosis

Explanation: ***Toxoplasmosis*** - **Ring-enhancing lesions** in the brain of an **HIV patient** with **positive IgG antibodies against *Toxoplasma*** is highly characteristic of central nervous system toxoplasmosis [1]. - This opportunistic infection is common in individuals with **severe immunosuppression**, where dormant *Toxoplasma gondii* cysts reactivate [1]. *Cryptococcal meningitis* - While common in HIV patients, it typically presents with **meningeal symptoms** and diffuse enhancement or hydrocephalus on imaging, rather than distinct ring-enhancing lesions. - Diagnosis usually involves detecting **Cryptococcal antigen** in CSF or blood. *Cerebral malaria* - This is a rare complication of malaria, primarily seen in **endemic areas**, and is characterized by coma, seizures, and other neurological signs. - It does not typically present with **ring-enhancing lesions** and is not directly associated with HIV. *Cysticercosis* - Caused by the larval stage of **Taenia solium**, it can cause ring-enhancing lesions but is usually acquired through ingestion of contaminated food. - While possible, the combination of **HIV** and **positive *Toxoplasma* serology** makes toxoplasmosis a much more likely diagnosis in this clinical context.

Question 1096: A patient with a history of hematopoietic stem cell transplantation presents with fever and sinus pain. Imaging reveals sinusitis with possible fungal involvement. What is the most appropriate management?

A. Initiate amphotericin B and consider surgical debridement (Correct Answer)
B. Perform a biopsy and wait for histopathology results
C. Start empirical antibacterial therapy and monitor response
D. Administer corticosteroids to reduce inflammation

Explanation: A patient with a history of hematopoietic stem cell transplantation presents with fever and sinus pain. Imaging reveals sinusitis with possible fungal involvement. What is the most appropriate management? ***Initiate amphotericin B and consider surgical debridement*** - In a **hematopoietic stem cell transplant (HSCT) recipient** with fever, sinus pain, and imaging suggestive of fungal sinusitis, prompt initiation of **broad-spectrum antifungal therapy**, such as **amphotericin B**, is crucial due to their severe immunocompromise and the high mortality risk of invasive fungal infections [1]. - **Surgical debridement** is often necessary to remove necrotic tissue and reduce fungal burden, especially in invasive fungal sinusitis where medical therapy alone may be insufficient [1]. *Perform a biopsy and wait for histopathology results* - While a **biopsy** is essential for definitive diagnosis, waiting for the results before initiating treatment in a severely immunocompromised patient with suspected invasive fungal sinusitis can lead to **rapid disease progression** and worse outcomes [1]. - Due to the **rapidly progressive nature** of invasive fungal sinusitis in transplant patients, delayed treatment can be fatal; thus, empirical therapy based on strong clinical suspicion and imaging is warranted [1]. *Start empirical antibacterial therapy and monitor response* - The patient's presentation and imaging findings specifically point to **fungal involvement**, making empirical antibacterial therapy insufficient and inappropriate as the primary treatment. - Delaying antifungal treatment would allow the fungal infection, which is often more aggressive in **immunocompromised patients**, to worsen rapidly [2]. *Administer corticosteroids to reduce inflammation* - **Corticosteroids** are generally contraindicated in active or suspected fungal infections, especially in immunocompromised patients, as they can further **suppress the immune system** and worsen fungal dissemination and proliferation. - While inflammation is present, the underlying cause is likely a severe fungal infection, and addressing the infection with appropriate antifungals is paramount rather than simply suppressing the inflammatory response.

Question 1097: A patient with a history of heart valve replacement presents with fever and a new onset of a heart murmur. Blood cultures are pending. What is the most appropriate empiric antibiotic therapy?

A. Vancomycin and gentamicin (Correct Answer)
B. Penicillin and rifampin
C. Ceftriaxone and doxycycline
D. Linezolid and azithromycin

Explanation: Vancomycin and gentamicin - This combination provides broad-spectrum coverage, targeting Gram-positive organisms (common in prosthetic valve endocarditis) with vancomycin and using gentamicin for synergistic activity [4] and coverage against potential gram-negative or difficult-to-treat organisms [3]. - The patient's history of heart valve replacement [2] and a new murmur strongly suggest infective endocarditis [5], requiring immediate empiric therapy covering common causative agents like staphylococci and streptococci [3]. [1] Penicillin and rifampin - Penicillin alone would not provide adequate coverage for MRSA or other resistant Gram-positive organisms commonly seen in prosthetic valve endocarditis [3]. - Rifampin is typically added later in the course of prosthetic valve endocarditis [2], often after initial de-escalation, due to its ability to penetrate biofilms, but it's not a first-line empiric choice due to rapid resistance development. Ceftriaxone and doxycycline - Ceftriaxone provides good coverage for streptococci [3] but lacks reliable activity against MRSA, a significant concern in prosthetic valve endocarditis. - Doxycycline has limited utility as a primary empiric agent for severe infective endocarditis, as its spectrum and bactericidal activity are not sufficient for this indication. Linezolid and azithromycin - Linezolid is effective against Gram-positive bacteria, including MRSA [3], but it is typically reserved for cases where vancomycin is contraindicated or ineffective, and its use as a primary empiric agent in this setting is less common. - Azithromycin has a narrow spectrum against common endocarditis pathogens and is generally not recommended for the treatment of severe bacterial endocarditis.

Question 1098: A traveler returning from a tropical country presents with fever and a single enlarging ulcer on the leg. Culture reveals gram-negative rods. Assess the diagnosis and consider the regional epidemiology.

A. Buruli ulcer
B. Cutaneous leishmaniasis
C. Tularemia
D. Melioidosis (Correct Answer)

Explanation: ***Melioidosis*** - **Melioidosis** is caused by the gram-negative bacterium *Burkholderia pseudomallei*, which is endemic in tropical regions, particularly Southeast Asia and Northern Australia. - The presentation of a **single enlarging ulcer** with accompanying **fever** in a traveler returning from a tropical country is highly consistent with localized invasive melioidosis [1]. *Buruli ulcer* - **Buruli ulcer** is caused by *Mycobacterium ulcerans* and is characterized by a painless, progressively destructive skin lesion, but it is not typically associated with fever in its early stages. - The causative agent is an acid-fast bacillus, not a gram-negative rod, which would differentiate it from the culture findings. *Cutaneous leishmaniasis* - **Cutaneous leishmaniasis** presents as skin lesions, often ulcers, after exposure in endemic areas, but it is caused by *Leishmania* parasites, not bacteria [1]. - Culture would reveal parasites, not gram-negative rods, and treatment would differ significantly. *Tularemia* - **Tularemia** can cause an ulceroglandular disease, but it is typically associated with exposure to infected animals (e.g., rabbits, rodents, ticks) in temperate regions like North America. - While *Francisella tularensis* is a gram-negative rod, the geographic context and the specific presentation of a single enlarging ulcer are less typical for tularemia compared to melioidosis.

Question 1099: A 35-year-old HIV-positive patient presents with a chronic cough and bloody sputum. A chest X-ray shows cavitary lesions. Which diagnostic test is the most appropriate?

A. Sputum culture for Mycobacterium (Correct Answer)
B. Blood culture for fungi
C. PCR for HIV viral load
D. CT scan of the chest

Explanation: ***Sputum culture for Mycobacterium*** - Given the patient's **HIV-positive status**, **chronic cough**, **bloody sputum**, and **cavitary lesions** on chest X-ray, **tuberculosis** is highly suspected [1]. - A **sputum culture for Mycobacterium tuberculosis** is the definitive diagnostic test to confirm the presence of the bacteria and determine drug susceptibility [2]. *Blood culture for fungi* - While fungal infections can occur in HIV patients, **chronic cough**, **bloody sputum**, and **cavitary lesions** are not the primary or most characteristic presentation for common opportunistic fungal infections like PCP or cryptococcosis [1]. - **Microbiological sputum examination (e.g., fungal culture or staining)** might be considered if initial tests for TB are negative, but it is not the most appropriate initial diagnostic test given the strong suspicion for TB. *PCR for HIV viral load* - An **HIV viral load test** measures the amount of HIV in the blood and is used to monitor disease progression and response to antiretroviral therapy [3]. - It does **not directly diagnose the cause of the respiratory symptoms** and cavitary lesions in this patient. *CT scan of the chest* - A **CT scan of the chest** would provide more detailed anatomical information about the cavitary lesions and lung involvement. - However, it is an **imaging study** and does not provide a definitive microbiological diagnosis of the underlying infection.

Question 1100: A patient with known rheumatoid arthritis presents with new-onset fever, fatigue, and a significant drop in hemoglobin. What is the most likely cause, and how should it be managed?

A. Rheumatoid vasculitis; increase immunosuppression
B. Infection; initiate broad-spectrum antibiotics (Correct Answer)
C. Iron deficiency anemia; start iron supplements
D. Gastrointestinal bleed; perform endoscopy

Explanation: Infection; initiate broad-spectrum antibiotics - A patient with **rheumatoid arthritis (RA)** is commonly on **immunosuppressive therapy**, which increases the risk of infection [1]. - The triad of **fever**, **fatigue**, and new-onset **anemia** in an immunosuppressed patient strongly suggests an undiagnosed infection requiring prompt and aggressive treatment with **broad-spectrum antibiotics** [1]. *Rheumatoid vasculitis; increase immunosuppression* - While rheumatoid vasculitis can cause systemic symptoms and anemia, **fever** is not its primary feature, and it typically presents with other organ involvement such as **skin ulcers**, **neuropathy**, or **glomerulonephritis**. - Without clear evidence of vasculitis, simply increasing immunosuppression could worsen an underlying infection [1]. *Iron deficiency anemia; start iron supplements* - **Iron deficiency anemia** can cause fatigue and a drop in hemoglobin, but it does **not typically present with fever** as a primary symptom. - While RA patients can develop chronic disease anemia, new-onset significant anemia with fever is less likely to be solely due to iron deficiency [2]. *Gastrointestinal bleed; perform endoscopy* - A **gastrointestinal bleed** can certainly cause a drop in hemoglobin and fatigue, and GI complications are common in RA patients due to NSAID use [2]. - However, GI bleeding typically presents with **melena**, **hematochezia**, or **hemodynamic instability**, and **fever** is not a characteristic symptom of an uncomplicated GI bleed.

Practice by Chapter

Principles of Antimicrobial Therapy

Practice Questions

Fever of Unknown Origin

Practice Questions

HIV/AIDS and Related Infections

Practice Questions

Tuberculosis and Mycobacterial Diseases

Practice Questions

Tropical and Parasitic Infections

Practice Questions

Viral Infections (Hepatitis, Herpes, etc.)

Practice Questions

Healthcare-Associated Infections

Practice Questions

Fungal Infections

Practice Questions

Sepsis and Septic Shock

Practice Questions

Infection in Immunocompromised Hosts

Practice Questions

Emerging and Re-emerging Infections

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Antimicrobial Resistance

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Vaccination Principles

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