Infectious Diseases — MCQs
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A boy presented with multiple non suppurative osteomyelitis with sickle cell anaemia. What will be the causative organism?
Which condition is most commonly associated with cryoglobulinemia?
What does the acronym I.R.I.S. stand for in the context of immunology?
Most common organism associated with reactive arthritis is:
Which condition is associated with Streptococcus bovis infection?
Buboes form is which stage of LGV?
What is the causative agent of trench fever?
Which of the following statements is true regarding amoebic liver abscess?
Recrudescences are commonly seen in which type of malaria:
What is the most common form of leptospirosis?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 1191: A boy presented with multiple non suppurative osteomyelitis with sickle cell anaemia. What will be the causative organism?
- A. Salmonella (Correct Answer)
- B. H. influenzae
- C. Enterobacter species
- D. Staphylococcus aureus
Explanation: ***Salmonella*** - **Salmonella species** are a well-known cause of **osteomyelitis** in patients with **sickle cell anemia**, due to factors like gut mucosal damage and functional asplenia. [1] - The unique pathophysiology of sickle cell disease, including areas of bone infarction and compromised reticulendothelial system function, predisposes these patients to **Salmonella infections**. [1] *Staphylococcus aureus* - While **Staphylococcus aureus** is the most common cause of osteomyelitis in the general population, it is less likely to be the causative organism in patients with **sickle cell anemia** compared to Salmonella. - Its presence usually indicates other predisposing factors like trauma or prosthetic devices. *H. influenzae* - **Haemophilus influenzae** was a common cause of osteomyelitis in children before widespread vaccination but is now rare, especially with routine immunizations. - It is not specifically associated with a higher risk in patients with **sickle cell disease** for osteomyelitis compared to other pathogens. *Enterobacter species* - **Enterobacter species** can cause osteomyelitis, particularly in immunocompromised individuals or following surgery, but they are not uniquely associated with **sickle cell anemia** as a primary cause compared to Salmonella. - Their involvement in non-suppurative osteomyelitis in this specific patient population is less common.
Question 1192: Which condition is most commonly associated with cryoglobulinemia?
- A. Ovarian cancer
- B. Diabetes
- C. Leukemia
- D. Hepatitis C (Correct Answer)
Explanation: **Hepatitis C** - **Hepatitis C virus (HCV) infection** is the most common cause of mixed cryoglobulinemia, with cryoglobulins being detected in a high percentage of infected individuals. - The chronic immune stimulation caused by HCV leads to the production of **monoclonal or polyclonal immunoglobulins** (cryoglobulins) that precipitate in the cold. *Ovarian cancer* - While certain malignancies can be associated with paraneoplastic syndromes, **ovarian cancer** is not typically linked to cryoglobulinemia. - Cryoglobulinemia is more commonly associated with **lymphoproliferative disorders** or chronic infections rather than solid tumors like ovarian cancer. *Diabetes* - **Diabetes mellitus** is not directly associated with cryoglobulinemia; it is a metabolic disorder affecting glucose regulation. - Complications of diabetes include microvascular and macrovascular disease, but not primary cryoglobulin formation. *Leukemia* - Certain hematological malignancies, particularly **lymphoproliferative disorders like Waldenström macroglobulinemia or multiple myeloma**, can be associated with cryoglobulinemia. - However, **leukemia** (especially acute forms) is less commonly linked to cryoglobulinemia than chronic infections like hepatitis C or certain B-cell lymphomas.
Question 1193: 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 1194: 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 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: 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 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: Which of the following statements is true regarding amoebic liver abscess?
- A. May rupture into the pleural cavity.
- B. Mostly involving the right lobe of the liver. (Correct Answer)
- C. For asymptomatic luminal carriers, metronidazole is the drug of choice.
- D. Multiple abscesses is less common than a single abscess.
Explanation: ***Mostly involving the right lobe of the liver*** - The **right lobe** of the liver is the most common site for an amoebic liver abscess due to its larger size and preferential blood flow from the portal venous system, which drains the intestines where *Entamoeba histolytica* resides. - The **superior mesenteric vein**, draining the cecum and ascending colon (common sites for amebiasis), primarily feeds the right hepatic lobe. *May rupture into the pleural cavity* - While rupture can occur, the **peritoneal cavity** is a more common site of rupture for amoebic liver abscesses. - Rupture into the pleural cavity or lung is less frequent but can lead to **empyema** or **bronchopleural fistula** [1]. *For asymptomatic luminal carriers, metronidazole is the drug of choice* - **Metronidazole** is effective against invasive amoebiasis (like liver abscess or dysentery) but is not the drug of choice for asymptomatic luminal carriers. - For **asymptomatic luminal carriers**, **luminal amebicides** such as **paromomycin** or **diloxanide furoate** are used to eradicate cysts from the intestine [1]. *Multiple abscesses is less common than a single abscess* - **A single amoebic liver abscess** is more common than multiple abscesses [1]. - Multiple abscesses are typically seen in disseminated disease or immunocompromised individuals, though even then a solitary lesion is more frequent.
Question 1199: Recrudescences are commonly seen in which type of malaria:
- A. P. vivax
- B. P. falciparum (Correct Answer)
- C. P. malariae
- D. P. ovale
Explanation: ***P. falciparum*** - **Recrudescence** refers to the reappearance of malaria symptoms after a period of remission, due to the survival and subsequent increase of asexual parasites in the blood [1]. - This is common in *P. falciparum* due to the high parasite burden and its ability to sequester in deep capillaries, evading splenic clearance and developing drug resistance. *P. vivax* - *P. vivax* is known for **relapses**, which are caused by the activation of dormant liver stages called **hypnozoites**, rather than a recrudescence of blood-stage parasites [1]. - Relapses can occur months or years after the initial infection, even after the blood-stage parasites have been cleared. *P. malariae* - *P. malariae* is uniquely characterized by infections that can persist for many years, even decades, causing symptoms of **recrudescence**, although less frequently than *P. falciparum* [1]. - It has a prolonged erythrocytic cycle, which can lead to chronic low-level parasitemia and sporadic symptomatic episodes. *P. ovale* - Similar to *P. vivax*, *P. ovale* also causes **relapses** due to the presence of **hypnozoites** in the liver [1]. - While it can manifest with symptoms similar to *P. vivax*, it is generally less common and causes milder disease.
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
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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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