Infectious Diseases — MCQs
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Pneumocystis jirovecii, typically seen in immunocompromised patients, is a:
What is the most commonly recommended COMPLETE antiretroviral regimen for a pregnant woman with HIV infection?
Most common organism associated with reactive arthritis is:
Which condition is associated with Streptococcus bovis infection?
What does the acronym I.R.I.S. stand for in the context of immunology?
What is the most common cause of lung abscess in comatose patients?
Recrudescences are commonly seen in which type of malaria:
Which of the following statements is true regarding amoebic liver abscess?
ABO non- secretors are more prone to ?
Eschar is seen in all the Rickettsial diseases except:
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 1191: Pneumocystis jirovecii, typically seen in immunocompromised patients, is a:
- A. Parasite
- B. Virus
- C. Bacteria
- D. Fungus (Correct Answer)
Explanation: ***Fungus*** - *Pneumocystis jirovecii* is a **yeast-like fungus** that causes severe lung infections, particularly in individuals with **compromised immune systems**, such as those with HIV/AIDS. - Its classification has evolved, but it is now firmly established as a fungus based on its **genetic makeup** and cell wall structure. *Bacteria* - Bacteria are single-celled microorganisms that belong to the kingdom **Prokaryotae**, lacking a true nucleus and membrane-bound organelles. - While bacteria can cause pneumonia in immunocompromised patients, *Pneumocystis jirovecii* has a distinct **eukaryotic cell structure** and genetic characteristics of fungi. *Virus* - Viruses are **acellular infectious agents** that replicate only inside the living cells of other organisms. - Viruses cause a wide range of infections, but *Pneumocystis jirovecii* possesses its own **cellular machinery** and metabolic pathways, classifying it outside the viral domain. *Parasite* - Parasites are organisms that live on or in a host organism and obtain their food at the expense of their host. - Although *Pneumocystis jirovecii* was historically misclassified as a protozoan parasite due to its morphology, molecular studies have since confirmed its **fungal lineage**.
Question 1192: What is the most commonly recommended COMPLETE antiretroviral regimen for a pregnant woman with HIV infection?
- A. Abacavir/lamivudine
- B. Didanosine/stavudine
- C. Tenofovir disoproxil fumarate/emtricitabine/dolutegravir (Correct Answer)
- D. Tenofovir disoproxil fumarate/emtricitabine (2-drug regimen)
Explanation: ***Tenofovir disoproxil fumarate/emtricitabine/dolutegravir*** - This is a **highly effective, well-tolerated, and recommended first-line complete regimen** for pregnant women with HIV due to its established efficacy in suppressing viral load and preventing mother-to-child transmission. - **Dolutegravir**, an integrase strand transfer inhibitor (INSTI), is favored due to its rapid viral suppression and high barrier to resistance, while **tenofovir disoproxil fumarate/emtricitabine (TDF/FTC)** provides a robust nucleoside reverse transcriptase inhibitor (NRTI) backbone [1]. *Abacavir/lamivudine* - While **abacavir/lamivudine (ABC/3TC)** is an NRTI backbone sometimes used, it is less preferred than TDF/FTC as a first-line option in pregnancy, especially if the patient's HLA-B*5701 status is unknown (due to potential for hypersensitivity reaction with abacavir). - This option represents only a **two-drug NRTI backbone**, not a complete antiretroviral regimen, which typically includes at least three active drugs from two different classes. *Didanosine/stavudine* - **Didanosine and stavudine** are older NRTIs that are no longer recommended for routine use in HIV treatment due to their **significant toxicity profiles**, including peripheral neuropathy and pancreatitis, and inferiority compared to newer agents. - These drugs are associated with **lactic acidosis** and other severe side effects, making them unsuitable for pregnant women or general HIV treatment today. *Tenofovir disoproxil fumarate/emtricitabine (2-drug regimen)* - While **tenofovir disoproxil fumarate/emtricitabine (TDF/FTC)** is an excellent NRTI backbone, it is a **two-drug regimen only** and thus not a complete antiretroviral regimen. - A **complete regimen** for HIV treatment requires at least **three active drugs from at least two different classes** to effectively suppress viral replication and prevent resistance, making this option incomplete without a third agent (e.g., an INSTI, NNRTI, or protease inhibitor) [1].
Question 1193: 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 1194: 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 1195: 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 1196: What is the most common cause of lung abscess in comatose patients?
- A. Staph aureus
- B. Oral anaerobes (Correct Answer)
- C. Klebsiella
- D. Tuberculosis
Explanation: Oral anaerobes - **Comatose patients** are at high risk for **aspiration** of oropharyngeal flora, which predominantly consists of anaerobic bacteria. [1] - Aspiration of these organisms, especially in compromised lung tissue, frequently leads to **necrotizing pneumonia** and subsequent abscess formation. [1] *Staph aureus* - While *Staphylococcus aureus* can cause lung abscesses, particularly in the context of **hematogenous spread** (e.g., endocarditis) or nosocomial infections, it is not the most common cause in *comatose patients* who typically aspirate oral flora. [2] - *S. aureus* lung abscesses are often associated with multiple, smaller lesions rather than a single, large abscess from aspiration. *Klebsiella* - *Klebsiella pneumoniae* can cause severe, **rapidly progressive pneumonia** that may lead to abscess formation, especially in individuals with **alcoholism** or **diabetes**. - However, it is less common than oral anaerobes as the primary cause of abscess in the general population of comatose patients, whose main risk factor is aspiration of normal oral flora. [1] *Tuberculosis* - **Mycobacterium tuberculosis** can cause cavitary lung lesions, but these are typically chronic and result from primary or reactivated tuberculosis disease, not acute aspiration. [3] - Lung abscesses caused by tuberculosis are histologically distinct from pyogenic abscesses and are characterized by **granulomatous inflammation** and caseous necrosis.
Question 1197: 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 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: ABO non- secretors are more prone to ?
- A. Increased risk of infections (Correct Answer)
- B. Autoimmune diseases
- C. Cardiovascular diseases
- D. Cancer
Explanation: Increased risk of infections - Non-secretors of ABO antigens exhibit an increased susceptibility to a variety of infections, particularly bacterial and viral pathogens. - This is thought to be due to the absence of ABO antigens in secretions, which typically act as decoy receptors to prevent pathogen adhesion to host cells. Autoimmune diseases - While some associations between ABO blood groups and autoimmune diseases exist, non-secretor status is not consistently linked to a higher overall risk of autoimmune conditions. Cardiovascular diseases - ABO blood groups have been associated with cardiovascular risk, with non-O blood types generally having a slightly higher risk of certain cardiovascular events. - However, secretor status (the ability to secrete ABO antigens into bodily fluids) itself is not a prominent independent risk factor for cardiovascular diseases. Cancer - There are some documented associations between specific ABO blood types and certain types of cancer (e.g., non-O blood types with pancreatic cancer), but this is distinct from secretor status. - Being an ABO non-secretor is not a primary, broadly recognized risk factor for developing cancer.
Question 1200: Eschar is seen in all the Rickettsial diseases except:
- A. Scrub typhus
- B. Rickettsial pox
- C. Indian tick typhus
- D. Endemic typhus (Correct Answer)
Explanation: ***Endemic typhus*** - **Endemic typhus**, caused by *Rickettsia typhi*, is transmitted by **fleas** and typically presents without an eschar. - The disease is characterized by fever, headache, and a maculopapular rash, but the **inoculation site lesion (eschar) is rare or absent**. *Scrub typhus* - **Scrub typhus**, caused by *Orientia tsutsugamushi*, is known for causing a prominent **eschar** [1] at the site of the **chigger mite bite**. - This **painless black scab** is a classic diagnostic feature of the disease [1]. *Rickettsial pox* - **Rickettsial pox**, caused by *Rickettsia akari*, almost invariably presents with an **eschar**, often referred to as an **inoculation lesion**. - This lesion appears as a papule that vesiculates and then forms a scab, indicating the site of the **mite bite**. *Indian tick typhus* - **Indian tick typhus** (part of the **spotted fever group rickettsioses**), caused by *Rickettsia conorii*, frequently presents with a characteristic **eschar** at the site of the **tick bite**. - This eschar, known as a **tache noire**, is a valuable diagnostic clue in affected patients.
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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