Infectious Diseases Practice Questions

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: 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: 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 boy is suffering from acute pyelonephritis. The most specific investigation to confirm the diagnosis is:

Urine culture. Urine culture - A **urine culture** is considered the gold standard for diagnosing urinary tract infections, including pyelonephritis, as it identifies the specific **pathogen** and its **antibiotic susceptibility** [1]. - It quantifies the number of bacteria present (colony-forming units/mL), confirming significant bacteriuria indicative of infection [2]. *Leucocyte esterase test* - The **leucocyte esterase test** detects enzymes produced by neutrophils, indicating the presence of **white blood cells (pyuria)** in the urine. - While suggestive of inflammation and infection, it is not specific to pyelonephritis and can be positive in other conditions like cystitis or contamination. *Nitrite test* - The **nitrite test** detects nitrites produced by some gram-negative bacteria (e.g., *E. coli*) that convert urinary nitrates to nitrites. - A positive result suggests bacteriuria but is not specific, as some pathogens do not produce nitrite, and it doesn't quantify bacterial load or identify the organism. *Bacteria in gram stain* - Direct visualization of **bacteria in a Gram stain** of uncentrifuged urine can indicate bacteriuria, especially if numerous organisms are seen [1]. - However, it provides preliminary information and cannot definitively identify the species, quantify bacterial load, or determine antibiotic sensitivity, which are crucial for confirming pyelonephilitis and guiding treatment [1].

Q: A 36-year-old man presents to his primary care physician's office complaining of fever and headache. On examination, he has leucopenia, increased liver enzymes, and inclusion bodies are seen in his monocytes. Given his history of removing a tick from his leg, which of the following is the most likely diagnosis?

Ehrlichiosis. ***Ehrlichiosis*** - This diagnosis is strongly supported by the patient's history of a **tick bite**, presenting symptoms of **fever** and **headache**, and laboratory findings of **leukopenia** and **elevated liver enzymes**. - The presence of **inclusion bodies (morulae) in monocytes** is a classic diagnostic feature of ehrlichiosis, as *Ehrlichia chaffeensis* specifically infects monocytes and macrophages [1]. *Lyme disease* - While Lyme disease is also a **tick-borne illness**, it typically presents with an **erythema migrans rash** (bull's-eye rash), which is not mentioned in this case [1]. - Unlike ehrlichiosis, Lyme disease is caused by *Borrelia burgdorferi* and does not commonly feature **leukopenia** or **monocytic inclusion bodies** [1]. *Q fever* - Q fever is caused by *Coxiella burnetii* and is usually transmitted through **inhalation of aerosols** from infected animals, not typically by tick bites. - Although it can cause **fever** and **headache**, it is not associated with **monocytic inclusion bodies** or the specific leukopenia profile seen here. *Rocky Mountain spotted fever* - This **tick-borne illness** is caused by *Rickettsia rickettsii* and is characterized by a **rash** that typically starts on the ankles and wrists and spreads centrally. - While it can cause **fever** and **headache**, it does not involve **monocytic inclusion bodies**; instead, it affects endothelial cells.

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.

Q: What is the drug of choice for diarrhea in AIDS?

Loperamide. ***Loperamide*** - **Loperamide** is the **drug of choice** for symptomatic relief of **diarrhea in AIDS** due to its effectiveness in reducing stool frequency and volume. - It works as an **opioid receptor agonist** in the gut, decreasing intestinal motility and allowing for greater water and electrolyte absorption. *Lactulose* - **Lactulose** is a **laxative** used to treat constipation and **hepatic encephalopathy**, not diarrhea. - Its osmotic effect draws water into the colon, which would worsen, not alleviate, diarrhea. *Octreotide* - **Octreotide** is a **somatostatin analog** used to treat secretory diarrhea, especially in conditions like **carcinoid syndrome** or **VIPomas**. - Its use for general diarrhea in AIDS is typically reserved for cases that are refractory to conventional therapies like loperamide and other anti-motility agents. *Codeine* - **Codeine** can be used as an **antidiarrheal agent** due to its opioid effects, but it is generally **not the first-line choice** for diarrhea in AIDS. - It carries a **higher risk of side effects** such as sedation and dependency compared to loperamide, which has localized gut effects.

Q: All of the following are seen in cerebral malaria, except:

Hyperglycaemia. All of the following are seen in cerebral malaria, except: ***Hyperglycaemia*** - **Hypoglycemia**, not hyperglycemia, is a common complication of cerebral malaria, especially in children and pregnant women, due to increased glucose consumption by red blood cells with high parasitic load and quinine treatment. - While extremely rare, **hyperglycemia** is an atypical finding in severe malaria and would warrant investigation for co-existing conditions, as it is not directly caused by the disease pathophysiology. *Thrombocytopaenia* - **Thrombocytopaenia** is a very common hematologic abnormality in both uncomplicated and severe malaria, including cerebral malaria. - It is thought to occur due to increased platelet destruction, splenic sequestration, and bone marrow suppression. *Acute respiratory distress syndrome* - **Acute respiratory distress syndrome (ARDS)** is a severe pulmonary complication that can occur in cerebral malaria, particularly in adults. - It is often associated with fluid overload, inflammation, and pulmonary edema. *Heavy parasitemia* - **Heavy parasitemia** (high parasitic load) is a hallmark of severe malaria, including cerebral malaria [1]. - It involves a significant percentage of red blood cells being infected, leading to widespread microvascular obstruction and organ dysfunction [1].

Q: In multibacillary leprosy, what is the recommended follow-up examination period after adequate treatment?

5 years. ***5 years*** - Follow-up for **multibacillary leprosy** after adequate treatment is recommended for **5 years** to monitor for relapse. - This extended period is crucial due to the higher bacterial load and potential for late recurrence in multibacillary forms. *3 years* - A 3-year follow-up period is typically recommended for **paucibacillary leprosy**, which has a lower risk of relapse compared to multibacillary forms. - This duration is insufficient for multibacillary cases, as relapse can occur later. *10 years* - A 10-year follow-up period is generally considered excessive and not the standard recommendation for routine monitoring of treated leprosy cases. - While relapse can occur, 5 years is deemed sufficient for most multibacillary cases. *2 years* - A 2-year follow-up period is too short for multibacillary leprosy, as it significantly increases the risk of missing a potential relapse. - The latency for relapse in multibacillary leprosy can extend beyond this timeframe.

Q: Which condition is associated with pseudobronchiectasis?

Atelectasis. ***Atelectasis*** - **Pseudobronchiectasis** refers to the apparent dilation of bronchi due to surrounding lung collapse, which is characteristic of **atelectasis** [1]. - As the collapsed lung tissue reduces in volume, the airways within that segment can appear relatively wider on imaging, mimicking true bronchiectasis [1]. *Lung abscess* - A **lung abscess** is a localized collection of pus within the lung parenchyma, often with a cavity. - While it can cause inflammatory changes, it does not typically lead to the radiographic appearance of dilated bronchi in the same way that surrounding lung collapse does. *Bronchopneumonia* - **Bronchopneumonia** is a patchy inflammation of the lung involving the bronchi and bronchioles and the adjacent alveoli. - It causes consolidation and inflammation, but not the *apparent* bronchial dilation seen in pseudobronchiectasis. *Emphysema* - **Emphysema** is characterized by permanent enlargement of the airspaces distal to the terminal bronchioles, with destruction of their walls. - This condition involves airspace destruction and airway collapse during expiration, not bronchial dilation caused by surrounding lung collapse.

Question 1

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 2

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 3

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 4

A boy is suffering from acute pyelonephritis. The most specific investigation to confirm the diagnosis is:

Accepted Answer

Urine culture

Answer

Leucocyte esterase test

Answer

Nitrite test

Answer

Bacteria in gram stain

Question 5

A 36-year-old man presents to his primary care physician's office complaining of fever and headache. On examination, he has leucopenia, increased liver enzymes, and inclusion bodies are seen in his monocytes. Given his history of removing a tick from his leg, which of the following is the most likely diagnosis?

Accepted Answer

Ehrlichiosis

Answer

Lyme disease

Answer

Q fever

Answer

Rocky Mountain spotted fever

Question 6

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

Question 7

What is the drug of choice for diarrhea in AIDS?

Accepted Answer

Loperamide

Answer

Lactulose

Answer

Codeine

Answer

Octreotide

Question 8

All of the following are seen in cerebral malaria, except:

Accepted Answer

Hyperglycaemia

Answer

Acute respiratory distress syndrome

Answer

Heavy parasitemia

Answer

Thrombocytopaenia

Question 9

In multibacillary leprosy, what is the recommended follow-up examination period after adequate treatment?

Accepted Answer

5 years

Answer

3 years

Answer

10 years

Answer

2 years

Question 10

Which condition is associated with pseudobronchiectasis?

Accepted Answer

Atelectasis

Answer

Lung abscess

Answer

Emphysema

Answer

Bronchopneumonia

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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