Infectious Diseases — MCQs
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Which of the following statements about herpes zoster complications is incorrect?
A woman with recurrent diarrhea is prescribed a broad-spectrum antibiotic. Which of the following statements is not true regarding Clostridium difficile infection?
A bronchial asthma patient on inhalational steroids presented with white patchy lesions on the tongue and buccal mucosa. What condition is likely to be present in this patient?
In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?
A young male came to the hospital with a clean-cut wound without any bleeding. The patient received a full course of tetanus vaccination 10 years ago. What is the best management for this patient?
A male patient diagnosed with tuberculosis took complete treatment. Sputum examination was done after the completion of the intensive and the continuation phases. It was found to be negative. What is the status of the patient?
A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
A patient diagnosed to be HIV-positive was started on highly active antiretroviral therapy (HAART). Which of the following can be used to monitor treatment efficacy?
A 30-year-old male is found to be positive for HBsAg and HBeAg and is diagnosed with chronic hepatitis B. The patient's viral load is 2 × 10^5 IU/mL and ALT is elevated (2× upper limit of normal). What is the appropriate management in this patient?
An 11-year-old boy presented with a cough for 15 days. On examination, he was found to have cervical lymphadenopathy. Lymph node biopsy showed the following findings. What could be the diagnosis?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 1171: Which of the following statements about herpes zoster complications is incorrect?
- A. Chickenpox and herpes zoster are caused by the same virus (VZV)
- B. Herpes zoster typically occurs in a dermatomal distribution
- C. Chickenpox vaccination prevents both primary varicella and herpes zoster reactivation completely
- D. Postherpetic neuralgia is the most common complication of herpes zoster (Correct Answer)
Explanation: ***Chickenpox vaccination prevents both primary varicella and herpes zoster reactivation completely*** - While the **chickenpox vaccine** (varicella vaccine) is highly effective at preventing primary varicella (chickenpox) and significantly reduces the risk of herpes zoster (shingles), it does not offer **complete prevention** against either [1]. - Vaccinated individuals can still get a milder form of chickenpox, and they can still develop shingles, albeit at a reduced rate and often with less severe symptoms and a **lower risk of postherpetic neuralgia**. *Chickenpox and herpes zoster are caused by the same virus (VZV)* - This statement is correct; both conditions are caused by the **Varicella-Zoster Virus (VZV)**, a human herpesvirus [1]. - VZV causes primary infection (chickenpox) and then establishes latency in **sensory ganglia**, reactivating later as herpes zoster [1]. *Herpes zoster typically occurs in a dermatomal distribution* - This statement is correct; herpes zoster rash characteristically presents as a **unilateral vesicular eruption** confined to one or more contiguous **dermatomes** [1]. - This distribution reflects the reactivation of the virus from a single or adjacent **sensory ganglion** [1]. *Postherpetic neuralgia is the most common complication of herpes zoster* - This statement is correct; **postherpetic neuralgia (PHN)** is defined as pain that persists for at least 90 days after the onset of the zoster rash. - It is the **most frequent and debilitating long-term complication** of herpes zoster, particularly in older adults [1].
Question 1172: A woman with recurrent diarrhea is prescribed a broad-spectrum antibiotic. Which of the following statements is not true regarding Clostridium difficile infection?
- A. Pseudomembrane is a layer of inflammatory debris
- B. Oral fidaxomicin is used for treatment
- C. It is toxin mediated
- D. IgM assay is used to confirm the diagnosis of Clostridium difficile infection. (Correct Answer)
Explanation: ***IgM assay is used to confirm the diagnosis of Clostridium difficile infection*** - An **IgM assay** is **not** the standard or recommended method for diagnosing *Clostridium difficile* infection (CDI). - Diagnosis typically relies on detecting **toxins (A and B)** in stool samples through antigen-based tests, PCR, or enzyme immunoassays [1]. *Oral fidaxomicin is used for treatment* - **Fidaxomicin** is an **oral macrolide antibiotic** specifically approved and highly effective for treating *C. difficile* infection, especially recurrent cases. - It works by inhibiting bacterial RNA polymerase, leading to bactericidal activity against *C. difficile* with minimal systemic absorption. *It is toxin mediated* - The pathogenicity of *C. difficile* is primarily mediated by its **exotoxins, Toxin A (enterotoxin)** and **Toxin B (cytotoxin)** [1]. - These toxins cause mucosal inflammation, increased permeability, and cell death in the colon, leading to the characteristic symptoms of CDI. *Pseudomembrane is a layer of inflammatory debris* - **Pseudomembranes** are a hallmark pathological feature of severe *C. difficile* colitis, visible during colonoscopy [1]. - They consist of an inflammatory exudate composed of **necrotic epithelial cells, fibrin, neutrophils, and mucus**, forming raised yellow-white plaques on the colonic mucosa.
Question 1173: A bronchial asthma patient on inhalational steroids presented with white patchy lesions on the tongue and buccal mucosa. What condition is likely to be present in this patient?
- A. Oral lichen planus
- B. Aphthous ulcers
- C. Oral leukoplakia
- D. Oral candidiasis (Correct Answer)
Explanation: **Oral candidiasis** - **Inhaled corticosteroids** can suppress the local immune response in the oral cavity, creating an environment conducive to the overgrowth of *Candida albicans*. - The classic presentation includes **white patchy lesions** on the tongue and buccal mucosa, which can often be scraped off. *Oral lichen planus* - Characterized by **reticular (Wickham's striae)**, papular, or erosive lesions, which are often bilateral and symmetric [1]. - While it can present with white lesions, they are typically not easily scraped off and are not primarily associated with inhaled corticosteroid use [1]. *Aphthous ulcers* - These are typically **painful, solitary, or multiple ulcers** with a red halo and a yellowish-gray center [2]. - They are distinct from widespread white patchy lesions and are not directly caused by inhaled corticosteroid use [2]. *Oral leukoplakia* - Defined as a **white patch or plaque** on the oral mucosa that cannot be characterized clinically or pathologically as any other disease, and which is not removable by scraping. - It is often associated with tobacco use and alcohol consumption, and carries a risk of malignancy; it does not typically appear as a direct side effect of inhaled corticosteroids.
Question 1174: In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?
- A. Bone marrow biopsy
- B. DEC provocation test
- C. Detection of microfilariae in the blood smear (Correct Answer)
- D. Ultrasound of the scrotum
Explanation: ***Detection of microfilariae in the blood smear*** - A positive **filarial antigen test** indicates the presence of adult worms, and the next step is to confirm active infection by identifying **microfilariae**. [1] - **Nocturnal blood samples** are crucial because microfilariae of *Wuchereria bancrofti* and *Brugia malayi* exhibit **nocturnal periodicity**, meaning they are most abundant in peripheral blood between 10 PM and 2 AM. [1] *Bone marrow biopsy* - This procedure is typically used to diagnose **hematological disorders**, such as leukemia or lymphoma, or investigate causes of unexplained fever, but it is not indicated for filariasis. - While filariasis can rarely lead to **eosinophilia**, a bone marrow biopsy is not a diagnostic tool for filarial infection itself. *DEC provocation test* - The **diethylcarbamazine (DEC) provocation test** is used to bring out microfilariae into the peripheral blood during the daytime for species that exhibit nocturnal periodicity. [1] - However, it carries a risk of severe adverse reactions due to rapid killing of microfilariae, especially in cases of heavy infection, and is generally avoided when antigen tests are positive. [1] *Ultrasound of the scrotum* - Scrotal ultrasound can detect the characteristic "filarial dance sign" (motile adult worms) in the **lymphatic vessels of the scrotum and epididymis**, confirming lymphatic filariasis. [2] - While useful for assessing advanced disease manifestations like **hydrocele**, it does not quantify microfilaremia or replace the need for microscopic confirmation of circulating microfilariae to guide treatment.
Question 1175: A young male came to the hospital with a clean-cut wound without any bleeding. The patient received a full course of tetanus vaccination 10 years ago. What is the best management for this patient?
- A. Single-dose tetanus toxoid (Correct Answer)
- B. Human tetanus immunoglobulin only
- C. Human tetanus immunoglobulin and a full course of vaccine
- D. No treatment required
Explanation: ***Single-dose tetanus toxoid*** - For a **clean-cut wound** in a patient who completed a **primary tetanus vaccination series** and received their last dose more than 5 years ago but less than 10 years ago, a **single booster dose** of tetanus toxoid is recommended. [1] - A booster ensures continued protection, as vaccine-induced immunity wanes over time, but the prior full course provides a robust anamnestic response with a single dose. *Human tetanus immunoglobulin and a full course of vaccine* - This regimen (tetanus immunoglobulin + vaccine) is typically reserved for patients with **unvaccinated status**, an **unknown vaccination history**, or a **severely contaminated wound** (e.g., rusty nail, soil contamination) who have not been fully vaccinated. - The patient had a **clean-cut wound** and completed a full course of vaccination 10 years ago, making immunoglobulin unnecessary and a full course of vaccine excessive. *Human tetanus immunoglobulin only* - Administering **tetanus immunoglobulin alone** is appropriate for immediate, passive immunity in situations where a patient is unvaccinated or has an unknown vaccination status and has a significant risk of tetanus from a contaminated wound. [2] - This patient has a clean wound and a history of full vaccination, so a booster is sufficient to stimulate active immunity. *No treatment required* - While the patient was fully vaccinated 10 years ago, the protection from tetanus vaccination can **wane over time**, especially after 5-10 years. - A **booster dose** is crucial to maintain adequate protection against tetanus, even for a clean wound, given the 10-year interval since the last dose.
Question 1176: A male patient diagnosed with tuberculosis took complete treatment. Sputum examination was done after the completion of the intensive and the continuation phases. It was found to be negative. What is the status of the patient?
- A. Cured (Correct Answer)
- B. Treatment completed
- C. Lost to follow up
- D. Treatment failed
Explanation: ***Cured*** - A patient is declared **cured** if they have completed the full course of treatment and have achieved **two negative sputum smear results**, with one at the end of the intensive phase and another at the completion of the treatment [1]. - This indicates that the **infection has been eradicated**, and the patient is no longer infectious. *Treatment completed* - This status applies when a patient has **completed the full treatment course** but does not have documented sputum smear results that meet the criteria for "cured." - While treatment was completed, the **bacteriological status is not confirmed** in the same way as for a cured patient. *Lost to follow up* - This term describes a patient who was **enrolled in treatment but was interrupted** for a specific period (e.g., two consecutive months or more) and their outcome cannot be determined. - They **ceased to attend follow-up appointments** and their treatment completion or success is unknown. *Treatment failed* - This status is assigned when a patient remains **sputum smear-positive at the end of the intensive phase** or at the end of the treatment, or if they initially converted to negative but later became positive again [1]. - It signifies that the **treatment regimen was ineffective** in eradicating the infection.
Question 1177: A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
- A. Dengue (Correct Answer)
- B. Malaria
- C. Scrub typhus
- D. Typhoid
Explanation: Dengue - The combination of **fever, arthralgia, extensive petechial rash**, and severe **thrombocytopenia** (platelet count 20,000/mm³) with **prolonged bleeding time** is highly characteristic of severe dengue infection, especially in an endemic area like Delhi [1]. - While leukocytosis (WBC 9000/mm³) is not typical for dengue (usually causes leukopenia), the other features strongly point to dengue hemorrhagic fever [1]. *Malaria* - Typically presents with **intermittent high fever**, chills, and sweats. While it can cause some thrombocytopenia and anemia, the **extensive petechial rash** is not a characteristic feature. - **Thrombocytopenia** in malaria is usually milder than observed here, and prolonged bleeding time is less common [2]. *Scrub typhus* - Caused by Orientia tsutsugamushi, it is characterized by **fever, headache, myalgia, and a characteristic eschar** (necrotic ulcer) at the bite site, which is not mentioned. - While it can cause rash and some thrombocytopenia, the **petechial rash** and such severe thrombocytopenia with prolonged bleeding time are less typical. *Typhoid* - Presents with **sustained high fever**, headache, bradycardia, and sometimes a **rose spot rash** (maculopapular), which is different from a petechial rash. - Typhoid typically causes **leukopenia** and can lead to gastrointestinal complications like intestinal bleeding, but severe thrombocytopenia and extensive petechiae are not common presenting features.
Question 1178: A patient diagnosed to be HIV-positive was started on highly active antiretroviral therapy (HAART). Which of the following can be used to monitor treatment efficacy?
- A. CD4+ T cell count
- B. Viral load (Correct Answer)
- C. p24 antigen
- D. Viral serotype
Explanation: ***Viral load*** - **Viral load** (HIV RNA copies per milliliter of plasma) is the most direct and sensitive measure of HAART efficacy, as it indicates the amount of actively replicating virus [1]. - A successful HAART regimen aims to reduce the **viral load** to undetectable levels, signaling effective suppression of viral replication [1]. *CD4+ T cell count* - While important for monitoring immune status and disease progression, **CD4+ T cell count** changes more slowly than viral load [1]. - An increase in **CD4+ T cell count** is a positive sign of immune reconstitution but is a lagging indicator of immediate treatment efficacy [1]. *p24 antigen* - **p24 antigen** is a core structural protein of HIV, primarily detectable early in acute infection and in advanced stages when viral replication is very high. - It is generally not used for routine monitoring of HAART efficacy in chronic HIV infection because its levels fluctuate and become undetectable as the immune system produces antibodies. *Viral serotype* - **Viral serotype** refers to the specific strain or subtype of HIV (e.g., HIV-1 vs. HIV-2, or different clades within HIV-1). - It is determined at diagnosis to understand the specific virus but does not change significantly during the course of treatment and is not used to monitor HAART efficacy.
Question 1179: A 30-year-old male is found to be positive for HBsAg and HBeAg and is diagnosed with chronic hepatitis B. The patient's viral load is 2 × 10^5 IU/mL and ALT is elevated (2× upper limit of normal). What is the appropriate management in this patient?
- A. Combined pegylated interferon with lamivudine
- B. Pegylated interferon
- C. Lamivudine
- D. Tenofovir (Correct Answer)
Explanation: Tenofovir - This patient presents with chronic hepatitis B (HBsAg positive for >6 months), evidence of active viral replication (HBeAg positive, high viral load), and liver inflammation (elevated ALT). [3] This signifies chronic active hepatitis B, requiring treatment. [1] - Tenofovir is a highly potent nucleotide analog with a high barrier to resistance, making it a first-line treatment for chronic hepatitis B. *Lamivudine* - While an antiviral for HBV, lamivudine has a low genetic barrier to resistance, meaning resistance mutations can rapidly develop, reducing its long-term efficacy. - Due to the high risk of resistance, lamivudine is generally not recommended as a first-line monotherapy for treatment-naive patients with chronic hepatitis B, especially with a high viral load. *Pegylated interferon* - Pegylated interferon is an option for chronic hepatitis B, but it causes significant side effects (e.g., fatigue, depression, bone marrow suppression) and is usually administered by injection. [2] - Its efficacy in achieving sustained HBeAg seroconversion or HBsAg loss can be variable, and it is often reserved for patients who prefer a finite course of treatment and can tolerate the side effects, or for those without advanced liver disease. [2] *Combined pegylated interferon with lamivudine* - There is no significant evidence that combining pegylated interferon with lamivudine offers superior efficacy compared to monotherapy with a potent nucleos(t)ide analog like tenofovir or entecavir. - This combination would increase the side effect burden from interferon and still carry the risk of lamivudine resistance without substantial added benefit.
Question 1180: An 11-year-old boy presented with a cough for 15 days. On examination, he was found to have cervical lymphadenopathy. Lymph node biopsy showed the following findings. What could be the diagnosis?
- A. Leprosy
- B. Sarcoidosis
- C. Syphilis
- D. Tuberculosis (Correct Answer)
Explanation: ***Tuberculosis*** - The image likely displays **granulomatous inflammation** with **caseous necrosis**, which is highly characteristic of **tuberculosis**, especially in someone presenting with a persistent cough and lymphadenopathy. - The presence of **cervical lymphadenopathy** along with a **cough** for 15 days in an 11-year-old boy points towards extrapulmonary tuberculosis or primary tuberculosis infection affecting the mediastinal lymph nodes with cervical involvement. *Leprosy* - While leprosy also causes granulomas, it typically manifests as skin lesions and nerve involvement, and lymphadenopathy is less common or specific as the primary initial presentation. - The granulomas in leprosy are often **epithelioid** with **foamy histiocytes** and numerous acid-fast bacilli, which are not explicitly described or obvious in the provided context for a definitive diagnosis without special stains. *Sarcoidosis* - Sarcoidosis involves **non-caseating granulomas**, meaning there is no central necrosis, which is a key differentiating feature from the caseating necrosis often seen in tuberculosis. - Although sarcoidosis can cause lymphadenopathy and cough, the microscopic features in the image, particularly if showing necrosis, would argue against sarcoidosis. *Syphilis* - Syphilis can cause lymphadenopathy (especially in secondary syphilis), but the characteristic histological finding is usually a **plasma cell-rich infiltrate** with **endarteritis obliterans**, not typically prominent granulomas with caseous necrosis. - Clinical presentation with cough and chronic lymphadenopathy in an 11-year-old would also make syphilis a less likely primary consideration without other suggestive signs.
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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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