Infectious Diseases — MCQs
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How many blood samples should be drawn in cases of fever of unknown origin to optimize detection of intermittent bacteremia?
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?
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?
Which of the following statements regarding falciparum malaria is false?
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?
A boy is suffering from acute pyelonephritis. The most specific investigation to confirm the diagnosis is:
What is the drug of choice for diarrhea in AIDS?
All of the following are seen in cerebral malaria, except:
In multibacillary leprosy, what is the recommended follow-up examination period after adequate treatment?
Which condition is associated with pseudobronchiectasis?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 1331: 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 1332: 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?
- A. Tinidazole
- B. Ivermectin (Correct Answer)
- C. Praziquantel
- D. Niclofolan
Explanation: ***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**.
Question 1333: 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?
- A. Chronic hepatitis B infection
- B. Acute hepatitis B infection with high infectivity (Correct Answer)
- C. Acute hepatitis B infection with low infectivity
- D. Chronic hepatitis B infection with low infectivity
Explanation: ***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].
Question 1334: Which of the following statements regarding falciparum malaria is false?
- A. Haemoglobinuria and renal failure
- B. Hypoglycemia
- C. Cerebral malaria
- D. Adequately prevented with chloroquine therapy (Correct Answer)
Explanation: ***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 1335: 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?
- A. Ehrlichiosis (Correct Answer)
- B. Lyme disease
- C. Q fever
- D. Rocky Mountain spotted fever
Explanation: ***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.
Question 1336: A boy is suffering from acute pyelonephritis. The most specific investigation to confirm the diagnosis is:
- A. Urine culture (Correct Answer)
- B. Leucocyte esterase test
- C. Nitrite test
- D. Bacteria in gram stain
Explanation: 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].
Question 1337: What is the drug of choice for diarrhea in AIDS?
- A. Lactulose
- B. Codeine
- C. Octreotide
- D. Loperamide (Correct Answer)
Explanation: ***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.
Question 1338: All of the following are seen in cerebral malaria, except:
- A. Acute respiratory distress syndrome
- B. Heavy parasitemia
- C. Hyperglycaemia (Correct Answer)
- D. Thrombocytopaenia
Explanation: 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].
Question 1339: In multibacillary leprosy, what is the recommended follow-up examination period after adequate treatment?
- A. 3 years
- B. 5 years (Correct Answer)
- C. 10 years
- D. 2 years
Explanation: ***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.
Question 1340: Which condition is associated with pseudobronchiectasis?
- A. Lung abscess
- B. Emphysema
- C. Bronchopneumonia
- D. Atelectasis (Correct Answer)
Explanation: ***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.
Practice by Chapter
Principles of Antimicrobial Therapy
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Fever of Unknown Origin
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HIV/AIDS and Related Infections
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Tuberculosis and Mycobacterial Diseases
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Tropical and Parasitic Infections
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Viral Infections (Hepatitis, Herpes, etc.)
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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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