Infectious Diseases Practice Questions

Q: Which of the following chest X-ray findings is least likely to be associated with tuberculosis in patients with HIV?

Lupus vulgaris. ***Lupus vulgaris*** * **Lupus vulgaris** is a form of **cutaneous tuberculosis** that affects the skin and is not a chest X-ray finding. * It is a localized skin lesion, typically on the face or neck, and does not manifest with pulmonary radiographic changes. *Miliary pattern* * **Miliary pattern** on chest X-ray appears as diffuse **small nodular infiltrates** (1-3 mm) distributed throughout both lung fields, representing hematogenous dissemination of *Mycobacterium tuberculosis*. * This finding is common in HIV patients with **disseminated (miliary) tuberculosis** and reflects severely impaired cell-mediated immunity. * The term "miliary" refers to the millet seed-like appearance of the nodules. *Pleural effusion* * **Pleural effusion** is a common manifestation of tuberculosis, especially in immunocompromised individuals like those with HIV, often appearing as blunting of the **costophrenic angles** on chest X-ray. * It is caused by an inflammatory reaction to mycobacterial antigens in the pleural space. *Hilar lymphadenopathy* * **Hilar lymphadenopathy** is a common chest X-ray finding in both primary and reactivated tuberculosis, particularly in HIV-infected patients due to an altered immune response. * Enlarged lymph nodes near the **hilum** are often prominently visible and can be a sole chest X-ray finding in early or atypical presentations.

Q: True regarding the presentation of primary tuberculosis is

U/L hilar lymphadenopathy. ***U/L hilar lymphadenopathy*** - A **unilateral hilar lymphadenopathy** is a classic radiographic finding in **primary pulmonary tuberculosis** in children and often in adults, representing the enlargement of lymph nodes draining the primary lung lesion. - The disease typically begins with a primary lesion (Ghon focus) in the lung parenchyma and regional **lymph node involvement** constitutes the primary complex [1]. *B/L pleural effusion with negative Tuberculin test* - **Bilateral pleural effusion** is an uncommon presentation for primary tuberculosis; typically, effusions are unilateral. - A **negative Tuberculin test** (PPD) would make a diagnosis of tuberculosis less likely, although it can be negative in immunocompromised individuals or in the very early stages of infection. *Sustained chronic pyrexia* - While fever (pyrexia) is a common symptom of tuberculosis, **sustained chronic pyrexia** is more characteristic of secondary (post-primary) or disseminated tuberculosis, not necessarily primary infection which is often asymptomatic or mildly symptomatic [2]. - Fevers in primary TB, if present, can be low-grade and intermittent rather than sustained and chronic. *B/L pleural effusion with positive tuberculin test* - Although a **positive Tuberculin test** indicates prior exposure to M. tuberculosis, **bilateral pleural effusion** is an unusual initial presentation of primary tuberculosis. - Pleural effusions in TB are typically unilateral and usually result from a hypersensitivity reaction or direct spread from a primary lesion, but bilateral involvement is less common.

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

The most common site of dissemination is liver. ***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.

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

3. ***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.

Q: Which condition is characterized by bacteremia?

Typhoid fever. ***Typhoid fever*** - Typhoid fever, caused by **Salmonella Typhi**, is characterized by **bacteremia**, as the bacteria invade the bloodstream from the gut. - The systemic spread of bacteria leads to classic symptoms such as **high fever**, headache, and abdominal pain. *Shigella infection* - Shigella infections, primarily cause **dysentery** by invading the colonic mucosa, leading to **bloody diarrhea**. - While localized to the gut, **bacteremia is rare** and typically seen only in severely immunocompromised individuals. *Cholera infection* - Cholera, caused by **Vibrio cholerae**, is a **non-invasive** infection that primarily affects the small intestine. - It produces a **toxin** that causes massive fluid and electrolyte loss, leading to severe **watery diarrhea**, but **does not typically involve bacteremia**. *Diphtheria infection* - Diphtheria is caused by **Corynebacterium diphtheriae**, which produces a **toxin** that enters the bloodstream and can affect distant organs (heart, nerves). - The bacterial infection itself is usually localized to the upper respiratory tract; **bacteremia is not a characteristic feature** of diphtheria.

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

Typhoid. ***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.

Q: A thirty-year-old man presented with nausea, fever, and jaundice of 5 days' duration. Biochemical tests revealed a bilirubin level of 6.7 mg/dl, with 5.0 mg/dl being conjugated, and SGOT/SGPT (AST/ALT) levels of 1230/900 IU/ml. Serological tests showed the presence of HBsAg, IgM anti-HBc, and HBeAg. What is the most likely diagnosis?

Acute hepatitis B infection with high infectivity. ***Acute hepatitis B infection with high infectivity*** - The presence of **HBsAg** and **IgM anti-HBc** indicates an **acute infection**, not chronic [1]. - **HBeAg** positivity signifies **active viral replication** and therefore **high infectivity** [1]. *Chronic hepatitis B infection* - **Chronic hepatitis B** is defined by the persistence of **HBsAg** for **more than six months** [1]. - The presence of **IgM anti-HBc** specifically points to **acute infection**, distinguishing it from chronic forms [1]. *Acute hepatitis B infection with low infectivity* - **Low infectivity** in acute hepatitis B is indicated by the absence of **HBeAg** and the presence of **anti-HBe** (HBe antibody) [1]. - The patient's **HBeAg positivity** confirms high infectivity [1]. *Chronic hepatitis B infection with low infectivity* - Although **low infectivity** in chronic hepatitis B is characterized by the absence of **HBeAg** and presence of **anti-HBe**, the **IgM anti-HBc** rules out chronicity [1]. - **Chronic infection** would typically involve **IgG anti-HBc** rather than IgM anti-HBc [1].

Q: A 24-year-old patient complains of diarrhea, vomiting, and abdominal pain that is exacerbated by food ingestion since one week. Stool microscopy reveals rhabditiform larvae. What is the appropriate treatment for this condition?

Ivermectin. ***Ivermectin*** - The presence of **rhabditiform larvae** in stool, accompanied by diarrhea, vomiting, and abdominal pain exacerbated by food ingestion, is highly indicative of **strongyloidiasis** [1]. - **Ivermectin** is the drug of choice for treating **Strongyloides stercoralis** infections due to its high efficacy and good safety profile [1]. *Tinidazole* - **Tinidazole** is an antimicrobial drug typically used to treat infections caused by protozoa (e.g., Giardia, Entamoeba) and anaerobic bacteria. - It is not effective against parasitic roundworms like **Strongyloides stercoralis**. *Praziquantel* - **Praziquantel** is an anthelmintic medication primarily used to treat infections caused by **flukes** (e.g., Schistosomiasis) and **tapeworms** [2]. - It does not have significant activity against **nematodes** such as Strongyloides stercoralis. *Niclofolan* - **Niclofolan** is an anthelmintic agent that was historically used in veterinary medicine, particularly for liver fluke infections in animals. - It is **not approved for human use** and is not a treatment option for **strongyloidiasis**.

Q: Which of the following statements regarding falciparum malaria is false?

Adequately prevented with chloroquine therapy. ***Adequately prevented with chloroquine therapy*** - This statement is **false** because many strains of *Plasmodium falciparum* are now **resistant to chloroquine**, making it ineffective for prevention or treatment in most endemic areas [1]. - The widespread **drug resistance** of *P. falciparum* to chloroquine means it is no longer considered an adequate preventative measure. *Haemoglobinuria and renal failure* - These are **true** complications of severe *Falciparum malaria*, often termed **"blackwater fever"**, due to massive **intravascular hemolysis** and subsequent **acute kidney injury** [1]. - Renal failure can result from **hemoglobinuria**, **hypovolemia**, and **acidosis** associated with severe infection. *Hypoglycemia* - **Hypoglycemia** is a **true** and life-threatening complication of severe *Falciparum malaria*, particularly in children, pregnant women, and patients treated with **quinine** [1]. - It occurs due to increased **glucose consumption** by parasites and host cells, impaired **gluconeogenesis**, and drug-induced **insulin secretion**. *Cerebral malaria* - **Cerebral malaria** is a **true**, severe, and often fatal neurological complication of *Falciparum malaria*, characterized by **impaired consciousness** or **coma** [1]. - It is caused by **sequestration** of parasitized red blood cells in the **cerebral microvasculature**, leading to **microcirculatory obstruction** and inflammation.

Question 1

Which of the following chest X-ray findings is least likely to be associated with tuberculosis in patients with HIV?

Accepted Answer

Lupus vulgaris

Answer

Pleural effusion

Answer

Hilar lymphadenopathy

Answer

Miliary pattern

Question 2

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

Accepted Answer

Resistance to at least isoniazid and rifampicin, plus any fluoroquinolone and at least one injectable second-line drug.

Answer

Resistance to at least isoniazid and rifampicin, with possible resistance to other drugs.

Answer

Resistance to any of the three first-line drugs used in tuberculosis treatment.

Answer

Resistance to all first-line drugs and any three second-line injectable drugs.

Question 3

True regarding the presentation of primary tuberculosis is

Accepted Answer

U/L hilar lymphadenopathy

Answer

B/L pleural effusion with negative Tuberculin test

Answer

Sustained chronic pyrexia

Answer

B/L pleural effusion with positive tuberculin test

Question 4

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

Accepted Answer

The most common site of dissemination is liver

Answer

Brain abscess are usually supratentorial

Answer

The typical manifestation is subacute abscess

Answer

Sulfonamides are not the drug of choice.

Question 5

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

Accepted Answer

3

Answer

2

Answer

1

Answer

4

Question 6

Which condition is characterized by bacteremia?

Accepted Answer

Typhoid fever

Answer

Shigella infection

Answer

Cholera infection

Answer

Diphtheria infection

Question 7

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

Accepted Answer

Typhoid

Answer

Cholera

Answer

Botulism

Answer

Polio

Question 8

A thirty-year-old man presented with nausea, fever, and jaundice of 5 days' duration. Biochemical tests revealed a bilirubin level of 6.7 mg/dl, with 5.0 mg/dl being conjugated, and SGOT/SGPT (AST/ALT) levels of 1230/900 IU/ml. Serological tests showed the presence of HBsAg, IgM anti-HBc, and HBeAg. What is the most likely diagnosis?

Accepted Answer

Acute hepatitis B infection with high infectivity

Answer

Chronic hepatitis B infection

Answer

Acute hepatitis B infection with low infectivity

Answer

Chronic hepatitis B infection with low infectivity

Question 9

A 24-year-old patient complains of diarrhea, vomiting, and abdominal pain that is exacerbated by food ingestion since one week. Stool microscopy reveals rhabditiform larvae. What is the appropriate treatment for this condition?

Accepted Answer

Ivermectin

Answer

Tinidazole

Answer

Praziquantel

Answer

Niclofolan

Question 10

Which of the following statements regarding falciparum malaria is false?

Accepted Answer

Adequately prevented with chloroquine therapy

Answer

Haemoglobinuria and renal failure

Answer

Hypoglycemia

Answer

Cerebral malaria

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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