Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1321: Which of the following is NOT a recognized gastrointestinal tract infection in AIDS patients?

A. HSV
B. Atypical mycobacteria
C. CMV
D. Cryptococcus neoformans (Correct Answer)

Explanation: ***Cryptococcus neoformans*** - While *Cryptococcus neoformans* is a significant opportunistic infection in AIDS patients, it primarily causes **meningitis** and **pulmonary infections**, not typically a primary gastrointestinal tract infection [1]. - Though dissemination can occur, direct involvement of the GI tract as a primary site of infection is **uncommon** compared to other pathogens listed. *HSV* - **Herpes simplex virus (HSV)** commonly causes **esophagitis** in AIDS patients, leading to painful swallowing and ulcerations. - It can also cause **perianal ulcers** and proctitis in immunocompromised individuals [2]. *CMV* - **Cytomegalovirus (CMV)** is a frequent cause of severe GI disease in AIDS patients, leading to **colitis**, esophagitis, and gastritis [1]. - CMV infection can cause **ulcerations**, bleeding, and perforation throughout the gastrointestinal tract. *Atypical mycobacteria* - **Atypical mycobacteria**, such as *Mycobacterium avium complex (MAC)*, are common causes of widespread **disseminated disease** in AIDS patients, frequently involving the gastrointestinal tract [3]. - MAC infection in the GI tract can cause **malabsorption**, chronic diarrhea, and abdominal pain [3].

Question 1322: A pulled-up caecum is typically associated with which condition?

A. Colorectal cancer
B. Intestinal obstruction
C. Crohn's disease
D. Tuberculosis (Correct Answer)

Explanation: **Tuberculosis** - **Abdominopelvic tuberculosis**, particularly of the ileocecal region, is a common cause of a **pulled-up caecum** due to inflammatory adhesions and fibrosis. - The inflammatory process and subsequent scarring can lead to contracture and retraction of the caecum. *Colorectal cancer* - While it can cause mass effect and obstruction, **colorectal cancer** does not typically result in a "pulled-up caecum." - It more commonly presents with symptoms like **hematochezia**, changes in bowel habits, or abdominal pain. *Intestinal obstruction* - **Intestinal obstruction** is a functional or mechanical blockage of the bowel, leading to symptoms like abdominal distension, vomiting, and obstipation. - It does not inherently cause a **pulled-up caecum**; instead, it's a consequence of the obstruction itself, often involving a distended small bowel. *Crohn's disease* - **Crohn's disease** can affect any part of the gastrointestinal tract and may cause inflammation, strictures, and fistulas. - While it can cause inflammation in the ileocecal region, a **pulled-up caecum** is not a classic or defining feature in the same manner as with tuberculosis.

Question 1323: Which of the following is typically not associated with allergic pulmonary aspergillosis?

A. High IgE level
B. Pleural effusion
C. Recurrent pneumonia
D. Occurrence in patients with old cavitary lesions (Correct Answer)

Explanation: Occurrence in patients with old cavitary lesions - Allergic bronchopulmonary aspergillosis (ABPA) primarily affects patients with **asthma** or **cystic fibrosis**, causing an allergic response to *Aspergillus* spores within the airways. - The presence of old cavitary lesions is a hallmark of **aspergilloma**, a distinct form of aspergillus infection, rather than ABPA [1]. *High IgE level* - ABPA is characterized by an intense **T-helper 2 immune response** to *Aspergillus* antigens, leading to significantly elevated total and *Aspergillus*-specific **IgE levels**. - **Serological tests** showing high IgE are a key diagnostic criterion for ABPA. *Pleural effusion* - While less common, **pleural effusions** can occur in severe cases of ABPA, typically due to associated **pneumonitis** or bronchial obstruction. - It indicates significant inflammatory involvement beyond the airways. *Recurrent pneumonia* - Patients with ABPA often experience recurrent episodes of **pulmonary infiltrates**, which can clinically present as recurrent pneumonia. - These episodes are due to **bronchial obstruction** by mucus plugs and inflammatory reactions to the fungus, leading to localized inflammation and consolidation [1].

Question 1324: Which one of the following tests would be most useful in determining the chances of an HIV-positive patient progressing to symptomatic AIDS?

A. HIV antibody test
B. Neopterin
C. HIV PCR
D. CD4 lymphocyte count (Correct Answer)

Explanation: ***CD4 lymphocyte count*** - A **low CD4 count** is inversely correlated with the risk of developing **opportunistic infections** and cancers characteristic of AIDS [1]. - Monitoring changes in CD4 count over time provides crucial information about **disease progression** and the efficacy of antiretroviral therapy [1]. *HIV antibody test* - An **HIV antibody test** indicates the presence of HIV infection but does not provide information about the **disease stage** or progression to AIDS [1]. - It primarily detects the body's immune response to the virus, not the viral load or immune damage. *HIV PCR* - **HIV PCR** (polymerase chain reaction) measures the **viral load**, which indicates the amount of HIV in the blood. - While a high viral load is associated with faster progression, the **CD4 count** is a more direct and universally accepted indicator of immune system damage and risk of AIDS-defining conditions [1]. *Neopterin* - **Neopterin** is a marker of **immune activation** and inflammation, often elevated in HIV infection. - While elevated neopterin can indicate disease activity, it is not as specific or as strong a predictor of progression to AIDS as the CD4 lymphocyte count.

Question 1325: What is the optimum duration of antibacterial treatment for acute bacterial prostatitis?

A. 3 days
B. 4-6 weeks (Correct Answer)
C. 7-14 days
D. 2-14 days

Explanation: ***4-6 weeks*** - Treatment for **acute bacterial prostatitis** requires a prolonged course of antibiotics to ensure eradication of the infection from the prostate gland, which often has poor antibiotic penetration. - A duration of **4 to 6 weeks** is recommended to prevent recurrence and progression to chronic prostatitis. *3 days* - A 3-day course of antibiotics is **too short** for acute bacterial prostatitis. - Such a short duration would likely lead to incomplete bacterial eradication and a high risk of **relapse or chronic infection**. *7-14 days* - A 7-14 day course of antibiotics is typically sufficient for more superficial or readily accessible infections, but it is **insufficient for acute bacterial prostatitis**. - The prostate's unique anatomy and vascular supply necessitate a **longer treatment period** to achieve therapeutic drug levels and eliminate pathogens. *2-14 days* - While suitable for some acute urinary tract infections, a 2-14 day regimen is **inadequate for acute bacterial prostatitis**. - This duration does not account for the **depth and complexity of prostate infection**, increasing the risk of treatment failure.

Question 1326: What does XDR-TB stand for in the context of tuberculosis resistance?

A. Resistance to at least isoniazid and rifampicin, with possible resistance to other drugs.
B. Resistance to any of the three first-line drugs used in tuberculosis treatment.
C. Resistance to at least isoniazid and rifampicin, plus any fluoroquinolone and at least one injectable second-line drug. (Correct Answer)
D. Resistance to all first-line drugs and any three second-line injectable drugs.

Explanation: ***Resistance to at least isoniazid and rifampicin, plus any fluoroquinolone and at least one injectable second-line drug.*** - **XDR-TB (Extensively Drug-Resistant Tuberculosis)** is defined by resistance to both **isoniazid** and **rifampicin** (making it MDR-TB), plus resistance to any **fluoroquinolone** and at least one of the three injectable second-line drugs (amikacin, capreomycin, or kanamycin) [1]. - This level of resistance indicates a significantly more challenging and prolonged treatment regimen, often with poorer outcomes. *Resistance to at least isoniazid and rifampicin, with possible resistance to other drugs.* - This definition primarily describes **Multidrug-Resistant Tuberculosis (MDR-TB)**, which is a precursor to XDR-TB but does not specifically include resistance to fluoroquinolones and injectable second-line drugs. - While other resistances might be present, they are not part of the core definition of MDR-TB and are insufficient to classify it as XDR-TB. *Resistance to any of the three first-line drugs used in tuberculosis treatment.* - This describes **monoresistance** or **polyresistance** (resistance to more than one first-line drug, but not both isoniazid and rifampicin simultaneously). - It is a much milder form of drug resistance compared to XDR-TB, which requires resistance to both key first-line drugs and specific second-line agents. *Resistance to all first-line drugs and any three second-line injectable drugs.* - While XDR-TB involves resistance to **isoniazid and rifampicin** (two key first-line drugs), it does not necessarily mean resistance to *all* first-line drugs (e.g., ethambutol or pyrazinamide might still be effective). - The definition specifically requires resistance to *any* fluoroquinolone and *at least one* (not necessarily three) injectable second-line drug, making this option too broad and inaccurate regarding the specific second-line drug criteria.

Question 1327: All are true about disseminated nocardial infection, except which of the following?

A. Brain abscess are usually supratentorial
B. The typical manifestation is subacute abscess
C. The most common site of dissemination is liver (Correct Answer)
D. Sulfonamides are not the drug of choice.

Explanation: ***The most common site of dissemination is liver*** - This statement is incorrect because the **brain** is the most common site for disseminated nocardial infection, particularly in immunocompromised patients. - While nocardial infections can affect various organs, **hepatic involvement** is relatively rare compared to CNS involvement. *Brain abscess are usually supratentorial* - **Cerebral nocardiosis** typically presents as single or multiple abscesses, which are indeed most commonly located in the **supratentorial compartment** of the brain. - This pattern of brain lesion is characteristic of disseminated Nocardia. *The typical manifestation is subacute abscess* - Nocardial infections, especially in their disseminated form, often progress insidiously, leading to the formation of **subacute abscesses** in various organs over weeks to months. - This **slow progression** makes the diagnosis challenging and necessitates a high index of suspicion. *Sulfonamides are not the drug of choice.* - This statement is incorrect because **trimethoprim-sulfamethoxazole (TMP-SMX)**, a type of sulfonamide, is actually the **drug of choice** for treating nocardial infections. - Nocardia species are generally susceptible to sulfonamides, which are crucial for effective treatment.

Question 1328: Pea soup stool (atrophic stool), characterized by greenish-brown or khaki-colored appearance, is characteristically seen in which of the following conditions?

A. Cholera
B. Botulism
C. Typhoid (Correct Answer)
D. Polio

Explanation: ***Typhoid*** - **Pea soup stool** is a classic feature of **typhoid fever**, reflecting the characteristic severe intestinal inflammation. [2] - The greenish, watery, and foul-smelling nature is due to the sloughing of intestinal lining and bacterial overgrowth from *Salmonella typhi*. *Cholera* - Characterized by **rice water stools**, which are profuse, watery, and contain flecks of mucus, rather than pea soup-like stools. [1], [4] - The primary mechanism is enterotoxin-mediated fluid secretion without significant inflammation or tissue damage. *Botulism* - Primarily causes **neurological symptoms** such as **flaccid paralysis**, rather than gastrointestinal symptoms like characteristic stools. [3] - While constipation can occur, "pea soup stool" is not associated with botulism. [3] *Polio* - Primarily affects the **nervous system**, leading to **paralysis**; it does not typically cause characteristic diarrheal stools like pea soup stool. - Gastrointestinal symptoms, if present, are usually non-specific and not related to diarrhea with a specific appearance.

Question 1329: How many blood samples should be drawn in cases of fever of unknown origin to optimize detection of intermittent bacteremia?

A. 2
B. 3 (Correct Answer)
C. 1
D. 4

Explanation: ***3*** - Drawing **three separate blood samples** significantly increases the likelihood of detecting intermittent bacteremia, as bacteria may not always be present in high concentrations in the bloodstream. - This practice maximizes the diagnostic yield while minimizing the risk of false positives from contamination. *1* - A single blood sample has a **low sensitivity** for detecting intermittent bacteremia, as transient presence of bacteria might be missed. - Relying on one sample increases the chance of a **false negative**, delaying appropriate treatment. *2* - While two samples are better than one, they still may not be sufficient to reliably detect **intermittent bacteremia** which can fluctuate. - This quantity might be acceptable for some conditions but is suboptimal for robust exclusion of **bacteremia in FUO** [1]. *4* - While four samples might slightly increase sensitivity over three, the **incremental benefit** in diagnostic yield is often negligible. - This approach adds to the **patient discomfort** and increases resource utilization without substantial additional diagnostic value.

Question 1330: What is the most common and serious cause of infection by Pseudomonas aeruginosa in hospitalized patients?

A. None of the options
B. Burn injuries
C. Patients with indwelling catheters (Correct Answer)
D. Neutropenic patients

Explanation: ***Patients with indwelling catheters*** - **Indwelling catheters** (e.g., urinary catheters, central venous catheters) provide a direct route for *Pseudomonas aeruginosa* to enter the body, making them the most common source of serious infections in hospitalized patients due to widespread use [1]. - The biofilm formation on catheter surfaces by *P. aeruginosa* makes these infections difficult to treat and a major cause of **catheter-associated urinary tract infections (CAUTIs)** and **catheter-related bloodstream infections (CRBSIs)** [1]. *Burn injuries* - While *Pseudomonas aeruginosa* is a significant cause of **wound infections** in patients with severe **burns**, these are not the most common source of *P. aeruginosa* infections in the overall hospital setting. - Burn wounds provide a large, open surface for bacterial colonization and systemic infection, but the prevalence of burn patients is lower than that of patients with indwelling catheters. *Neutropenic patients* - **Neutropenic patients** are highly susceptible to severe infections from *Pseudomonas aeruginosa* due to their compromised immune system, often leading to **bacteremia** or **pneumonia**. - Although *P. aeruginosa* infections in neutropenic patients are serious and life-threatening, the initial source of infection can often be linked to environmental exposure or compromised skin/mucosal barriers, rather than directly to neutropenia as the primary cause or common entry point. *None of the options* - This option is incorrect because **indwelling catheters** are a well-established and highly prevalent source of *Pseudomonas aeruginosa* infections in hospitalized patients [1]. - The routine use of various catheters across different patient populations makes them a leading cause of nosocomial infections.

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

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Tropical and Parasitic Infections

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Viral Infections (Hepatitis, Herpes, etc.)

Practice Questions

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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