Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1191: What is the most commonly recommended COMPLETE antiretroviral regimen for a pregnant woman with HIV infection?

A. Abacavir/lamivudine
B. Didanosine/stavudine
C. Tenofovir disoproxil fumarate/emtricitabine/dolutegravir (Correct Answer)
D. Tenofovir disoproxil fumarate/emtricitabine (2-drug regimen)

Explanation: ***Tenofovir disoproxil fumarate/emtricitabine/dolutegravir*** - This is a **highly effective, well-tolerated, and recommended first-line complete regimen** for pregnant women with HIV due to its established efficacy in suppressing viral load and preventing mother-to-child transmission. - **Dolutegravir**, an integrase strand transfer inhibitor (INSTI), is favored due to its rapid viral suppression and high barrier to resistance, while **tenofovir disoproxil fumarate/emtricitabine (TDF/FTC)** provides a robust nucleoside reverse transcriptase inhibitor (NRTI) backbone [1]. *Abacavir/lamivudine* - While **abacavir/lamivudine (ABC/3TC)** is an NRTI backbone sometimes used, it is less preferred than TDF/FTC as a first-line option in pregnancy, especially if the patient's HLA-B*5701 status is unknown (due to potential for hypersensitivity reaction with abacavir). - This option represents only a **two-drug NRTI backbone**, not a complete antiretroviral regimen, which typically includes at least three active drugs from two different classes. *Didanosine/stavudine* - **Didanosine and stavudine** are older NRTIs that are no longer recommended for routine use in HIV treatment due to their **significant toxicity profiles**, including peripheral neuropathy and pancreatitis, and inferiority compared to newer agents. - These drugs are associated with **lactic acidosis** and other severe side effects, making them unsuitable for pregnant women or general HIV treatment today. *Tenofovir disoproxil fumarate/emtricitabine (2-drug regimen)* - While **tenofovir disoproxil fumarate/emtricitabine (TDF/FTC)** is an excellent NRTI backbone, it is a **two-drug regimen only** and thus not a complete antiretroviral regimen. - A **complete regimen** for HIV treatment requires at least **three active drugs from at least two different classes** to effectively suppress viral replication and prevent resistance, making this option incomplete without a third agent (e.g., an INSTI, NNRTI, or protease inhibitor) [1].

Question 1192: Pneumocystis jirovecii, typically seen in immunocompromised patients, is a:

A. Parasite
B. Virus
C. Bacteria
D. Fungus (Correct Answer)

Explanation: ***Fungus*** - *Pneumocystis jirovecii* is a **yeast-like fungus** that causes severe lung infections, particularly in individuals with **compromised immune systems**, such as those with HIV/AIDS. - Its classification has evolved, but it is now firmly established as a fungus based on its **genetic makeup** and cell wall structure. *Bacteria* - Bacteria are single-celled microorganisms that belong to the kingdom **Prokaryotae**, lacking a true nucleus and membrane-bound organelles. - While bacteria can cause pneumonia in immunocompromised patients, *Pneumocystis jirovecii* has a distinct **eukaryotic cell structure** and genetic characteristics of fungi. *Virus* - Viruses are **acellular infectious agents** that replicate only inside the living cells of other organisms. - Viruses cause a wide range of infections, but *Pneumocystis jirovecii* possesses its own **cellular machinery** and metabolic pathways, classifying it outside the viral domain. *Parasite* - Parasites are organisms that live on or in a host organism and obtain their food at the expense of their host. - Although *Pneumocystis jirovecii* was historically misclassified as a protozoan parasite due to its morphology, molecular studies have since confirmed its **fungal lineage**.

Question 1193: Most common organism associated with reactive arthritis is:

A. Staphylococcus
B. Shigella
C. Chlamydia (Correct Answer)
D. Yersinia

Explanation: ***Chlamydia*** - **Chlamydia trachomatis** is a commonly identified pathogen causing **genitourinary infections** that can trigger reactive arthritis [1]. - The organism itself is not present in the joint, but its antigens trigger an immune response leading to sterile arthritis [1]. *Staphylococcus* - **Staphylococcus aureus** is a common cause of septic arthritis, which involves direct bacterial invasion of the joint. - Reactive arthritis is a **sterile arthritis** triggered by an infection elsewhere, not directly caused by staphylococcal joint infection. *Shigella* - While **Shigella** is a known enteric pathogen that can trigger reactive arthritis, it is less commonly associated with the condition globally compared to Chlamydia [1]. - Reactive arthritis often follows episodes of **dysentery** caused by Shigella species [1]. *Yersinia* - **Yersinia enterocolitica** is another enteric bacterium that can induce reactive arthritis, typically after **gastrointestinal infections**. - Its prevalence as a trigger for reactive arthritis is generally lower than that of Chlamydia.

Question 1194: What does the acronym I.R.I.S. stand for in the context of immunology?

A. Immune reconstitution idiopathic syndrome
B. Immune reconstitution immunological syndrome
C. Inflammatory reconstitution immune syndrome
D. Immune reconstitution inflammatory syndrome (Correct Answer)

Explanation: ***Immune reconstitution inflammatory syndrome*** - **IRIS** refers to a paradoxical worsening, unmasking, or new manifestation of opportunistic infections or inflammatory disorders during **immune recovery**, typically following the initiation of **antiretroviral therapy (ART)** in HIV-infected individuals [1]. - It occurs when a weakened immune system, suddenly bolstered by treatment, mounts an excessive inflammatory response to pre-existing or newly recognized pathogens or antigens [1]. *Immune reconstitution idiopathic syndrome* - The term **"idiopathic"** implies an unknown cause, which is not accurate for IRIS, as its pathophysiology is linked to **immune recovery**. - While some cases might have less clear triggers, the overall syndrome is understood to be inflammation driven by specific **immune responses**. *Immune reconstitution immunological syndrome* - This option uses the redundant term **"immunological"** after "immune reconstitution," which does not form the correct acronym or accurately describe the syndrome's hallmark: **inflammation** [1]. - The key feature of IRIS is the **inflammatory response**, not merely an "immunological" event [1]. *Inflammatory reconstitution immune syndrome* - This arrangement of words reverses the correct order and meaning of the acronym **IRIS**, placing "inflammatory" before "reconstitution." - The syndrome describes **immune reconstitution** leading to **inflammatory** manifestations, not the other way around [1].

Question 1195: Which condition is associated with Streptococcus bovis infection?

A. Colorectal cancer (Correct Answer)
B. Chronic lymphocytic leukemia (CLL)
C. Hairy cell leukemia (HCL)
D. Multiple myeloma (MM)

Explanation: ***Colorectal cancer*** - *Streptococcus gallolyticus* (formerly known as *Streptococcus bovis* biotype I) infection, particularly **bacteremia** or **endocarditis**, has a strong association with underlying **colorectal cancer**. - It is hypothesized that the bacteria may play a role in **tumorigenesis** or that the cancerous lesions provide an entry point for the bacteria into the bloodstream. *Chronic lymphocytic leukemia (CLL)* - While patients with CLL are **immunocompromised** and prone to infections, there is no specific association between *Streptococcus bovis* and CLL. - Infections in CLL patients are typically due to encapsulated bacteria, such as *Streptococcus pneumoniae* or *Haemophilus influenzae*. *Hairy cell leukemia (HCL)* - Patients with HCL often experience **immunosuppression** due to neutropenia and monocytopenia, leading to increased susceptibility to infections. - However, there is no direct or specific link between *Streptococcus bovis* infection and HCL itself. *Multiple myeloma (MM)* - Patients with multiple myeloma have **impaired humoral immunity** and are at risk for infections, especially from encapsulated bacteria. - There is no established specific association between *Streptococcus bovis* infection and multiple myeloma.

Question 1196: What is the most common cause of lung abscess in comatose patients?

A. Staph aureus
B. Oral anaerobes (Correct Answer)
C. Klebsiella
D. Tuberculosis

Explanation: Oral anaerobes - **Comatose patients** are at high risk for **aspiration** of oropharyngeal flora, which predominantly consists of anaerobic bacteria. [1] - Aspiration of these organisms, especially in compromised lung tissue, frequently leads to **necrotizing pneumonia** and subsequent abscess formation. [1] *Staph aureus* - While *Staphylococcus aureus* can cause lung abscesses, particularly in the context of **hematogenous spread** (e.g., endocarditis) or nosocomial infections, it is not the most common cause in *comatose patients* who typically aspirate oral flora. [2] - *S. aureus* lung abscesses are often associated with multiple, smaller lesions rather than a single, large abscess from aspiration. *Klebsiella* - *Klebsiella pneumoniae* can cause severe, **rapidly progressive pneumonia** that may lead to abscess formation, especially in individuals with **alcoholism** or **diabetes**. - However, it is less common than oral anaerobes as the primary cause of abscess in the general population of comatose patients, whose main risk factor is aspiration of normal oral flora. [1] *Tuberculosis* - **Mycobacterium tuberculosis** can cause cavitary lung lesions, but these are typically chronic and result from primary or reactivated tuberculosis disease, not acute aspiration. [3] - Lung abscesses caused by tuberculosis are histologically distinct from pyogenic abscesses and are characterized by **granulomatous inflammation** and caseous necrosis.

Question 1197: What is the causative agent of trench fever?

A. Q-fever
B. Boutonneuse fever
C. Indian tick typhus
D. Bartonella quintana (Correct Answer)

Explanation: ***Bartonella quintana*** - **Trench fever** is a **rickettsial-like illness** primarily transmitted by the human body louse. - The causative agent is the bacterium **Bartonella quintana**, which causes recurrent fever, headache, and body pains. *Q-fever* - Q-fever is caused by the bacterium **Coxiella burnetii** and is typically transmitted through airborne exposure to contaminated aerosols from infected animals. - It presents with fever, headache, and atypical pneumonia, and is not associated with human body lice. *Boutonneuse fever* - This fever is caused by **Rickettsia conorii**, transmitted by the **brown dog tick**. - Characterized by a **maculopapular rash** and an **eschar (tache noire)** at the site of the tick bite. *Indian tick typhus* - This is a form of spotted fever group rickettsiosis caused by **Rickettsia conorii subspecies indica**, transmitted by ticks [1]. - It presents with fever, rash, and an eschar, similar to boutonneuse fever, but is specified for the Indian subcontinent [1].

Question 1198: Buboes form is which stage of LGV?

A. Secondary (Correct Answer)
B. Tertiary
C. Latent
D. Primary

Explanation: ***Secondary*** - Buboes, which are swollen, painful lymph nodes, are a hallmark of the **secondary stage** of **Lymphogranuloma Venereum (LGV)** [1]. - This stage typically develops weeks after the initial infection, following the unnoticed or transient primary lesion. *Primary* - The primary stage of LGV is characterized by a **small, painless papule or ulcer** at the site of inoculation, which often goes unnoticed. - **Buboes are not formed** during this initial, often asymptomatic, phase. *Tertiary* - The tertiary stage of LGV involves **chronic inflammation** and **tissue destruction**, leading to complications like **genital elephantiasis**, rectal strictures, and fistulas. - While there is chronic lymphedema, the acute, painful buboes are characteristic of the secondary stage, not this late, destructive phase. *Latent* - The concept of a latent stage is not typically used to describe the progression of LGV in the same way as other infections like syphilis. - LGV progresses through distinct symptomatic primary, secondary, and potentially tertiary stages without a prolonged asymptomatic latency period between symptom presentations.

Question 1199: Most common complication of diphtheria is -

A. Myocarditis (Correct Answer)
B. Pneumonia
C. Meningitis
D. Endocarditis

Explanation: ***Myocarditis*** - Diphtheria toxin can directly damage myocardial cells, leading to inflammation and dysfunction of the heart muscle, making **myocarditis** the most common and serious complication. - This can result in **heart failure**, arrhythmias, and even death, highlighting its significance in diphtheria. *Pneumonia* - While respiratory complications can occur in diphtheria, **pneumonia** is not the most common or life-threatening complication associated with the diphtheria toxin itself. - Secondary bacterial infections might lead to pneumonia, but it is not a direct toxic effect like myocarditis. *Meningitis* - **Meningitis**, an inflammation of the membranes surrounding the brain and spinal cord, is an extremely rare complication of diphtheria. - Diphtheria primarily affects the upper respiratory tract and heart [1], with neurological complications typically manifesting as neuropathies rather than meningitis. *Endocarditis* - Although diphtheria can cause cardiac complications, **endocarditis** (inflammation of the heart's inner lining, including the valves) is not a common complication. - Myocarditis, due to the direct toxic effect on heart muscle, is far more prevalent than endocarditis in diphtheria.

Question 1200: What is the most common form of leptospirosis?

A. Icteric form
B. Hepatorenal form
C. Anicteric form (Correct Answer)
D. Weil's disease

Explanation: ***Anicteric form*** - The **anicteric form** accounts for about 90% of all leptospirosis cases, presenting with milder, flu-like symptoms without jaundice. - Patients typically experience **fever, headache, myalgia**, and conjunctival suffusion during the initial septicemic phase [1], followed by an immune phase that can involve meningitis or uveitis [1]. *Icteric form* - The **icteric form** (Weil's disease) is a severe manifestation, characterized by jaundice, renal failure, and hemorrhage, occurring in a minority of cases (5-10%). - Although more severe and often life-threatening, it is **less common** than the anicteric presentation [1]. *Hepatorenal form* - This term describes the severe complications of leptospirosis, including **liver and kidney dysfunction**, specifically associated with Weil's disease. - While a critical aspect of severe leptospirosis, it is a description of the organ involvement rather than a distinct common form of the disease. *Weil's disease* - **Weil's disease** is the most severe and potentially fatal form of leptospirosis, characterized by **jaundice, renal failure, hemorrhage, and myocarditis**. - It is a severe subset of the icteric form, making it a very serious but **uncommon variant** of the overall disease.

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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