Infectious Diseases — MCQs
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Tropical pulmonary eosinophilia is specifically associated with which of the following conditions?
Most common cause of diarrhea in AIDS patients?
A 10-year-old boy presents with an ulcerated lesion with undermined edges over the upper chest, accompanied by a satellite lesion in the anterior axillary fold for two months. Axillary lymph nodes are palpable. Histopathology reveals a dermal abscess with ill-defined histiocytes. AFB staining of the tissue is positive. Chest X-ray shows infiltrations and cavities. Mantoux test is positive. What is the most likely diagnosis?
The most common cause of seizures in a patient of AIDS is
Most common presentation of extra- pulmonary TB
Which type of pulmonary TB is most likely to give sputum positive ?
What is a rare condition associated with Hepatitis B infection?
What serum markers are indicative of a high level of Hepatitis B virus (HBV) infection?
Which of the following is the most common bacterial cause of community-acquired pneumonia?
A 17 years old female presents with sore throat and lymphadenopathy. A diagnostic test reveals the presence of heterophile antibodies. Diagnosis is?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 1161: Tropical pulmonary eosinophilia is specifically associated with which of the following conditions?
- A. Occult filariasis (Correct Answer)
- B. Asthmatic bronchitis
- C. Pneumonic plague
- D. Cerebral malaria
Explanation: ***Occult filariasis*** - **Tropical pulmonary eosinophilia (TPE)** is a hypersensitivity reaction specifically caused by infection with **filarial parasites**, primarily *Wuchereria bancrofti* or *Brugia malayi*, in individuals living in endemic areas [1]. - The disease involves migration of microfilariae to the lungs, stimulating a strong **IgE-mediated immune response** leading to high eosinophil counts in the blood and lung tissue [1]. *Cerebral malaria* - **Cerebral malaria** is caused by the parasite *Plasmodium falciparum* and is characterized by neurological complications, not pulmonary eosinophilia. - It involves sequestration of parasitized red blood cells in the brain's microvasculature, leading to coma and other neurological symptoms. *Pneumonic plague* - **Pneumonic plague** is a severe bacterial infection caused by *Yersinia pestis*, affecting the lungs and leading to pneumonia. - It is not associated with eosinophilia and requires antibiotic treatment. *Asthmatic bronchitis* - **Asthmatic bronchitis** is a general term referring to inflammation of the bronchi combined with features of asthma, often triggered by allergens, irritants, or infections. - While it can involve eosinophilic inflammation, it is a broader syndrome and not specifically linked to occult filariasis in the way TPE is.
Question 1162: Most common cause of diarrhea in AIDS patients?
- A. Salmonella typhimurium
- B. Cryptosporidium (Correct Answer)
- C. Candida
- D. Isospora
Explanation: ***Cryptosporidium*** - **Cryptosporidium parvum** is a common opportunistic pathogen in AIDS patients, causing chronic, watery diarrhea, especially when the **CD4 count is low** [1]. - This parasite is resistant to routine chlorination, making **waterborne transmission** a significant concern. *Salmonella typhimurium* - While *Salmonella* can cause severe and recurrent gastroenteritis in AIDS patients, it is **not the most common cause** of chronic diarrhea in this population. - Salmonella infections in immunocompromised individuals often disseminate, leading to **bacteremia** beyond just diarrheal symptoms. *Candida* - *Candida albicans* is a common opportunistic pathogen in AIDS, primarily causing **oral candidiasis (thrush)** or esophagitis [2]. - While it can sometimes cause gastrointestinal symptoms, **Candida is not typically a prominent cause of diarrhea** in AIDS patients [2]. *Isospora* - **Isospora belli** is another coccidian parasite that causes chronic diarrhea in AIDS patients, particularly in tropical and subtropical regions [1]. - Although significant, it is **less common overall** compared to *Cryptosporidium* as a primary cause of diarrhea in this population [1].
Question 1163: A 10-year-old boy presents with an ulcerated lesion with undermined edges over the upper chest, accompanied by a satellite lesion in the anterior axillary fold for two months. Axillary lymph nodes are palpable. Histopathology reveals a dermal abscess with ill-defined histiocytes. AFB staining of the tissue is positive. Chest X-ray shows infiltrations and cavities. Mantoux test is positive. What is the most likely diagnosis?
- A. Scrofuloderma (Correct Answer)
- B. Skin abscess
- C. Furuncle
- D. Cellulitis
- E. Erysipelas
Explanation: ### Scrofuloderma - The combination of an **ulcerated lesion with undermined edges**, **satellite lesions**, palpable **axillary lymph nodes** [1], positive **AFB staining** in tissue (indicating mycobacteria), and **pulmonary infiltrations/cavities** on chest X-ray are classic signs of scrofuloderma, a contiguous spread of tuberculosis from underlying structures to the skin. - A **positive Mantoux test** further supports a diagnosis of tuberculosis [1], and the histopathology showing a **dermal abscess with ill-defined histiocytes** is consistent with a tuberculous granulomatous reaction. ### Skin abscess - A skin abscess would typically present as a localized collection of **pus** and inflammation but would not usually have undermined edges, satellite lesions, or systemic involvement like pulmonary infiltrates or positive AFB staining for mycobacteria. - While histopathology might show an abscess, the presence of **ill-defined histiocytes** along with systemic signs points away from a simple bacterial abscess. ### Furuncle - A furuncle (boil) is a **deep folliculitis**, an infection of the hair follicle, usually caused by *Staphylococcus aureus*, presenting as a painful, red, pus-filled lump [2]. - It does not typically present with **undermined edges**, satellite lesions, or systemic findings such as pulmonary involvement or positive AFB staining for mycobacteria. ### Erysipelas - Erysipelas is a superficial skin infection, typically caused by **Group A Streptococcus**, characterized by a rapidly spreading, bright red, well-demarcated, and painful rash with a raised border. - It does not involve deep ulceration with undermined edges, satellite lesions, or the systemic pulmonary findings and positive AFB staining seen in this case. ### Cellulitis - Cellulitis is a bacterial infection of the subcutaneous tissue, manifesting as a poorly demarcated, red, swollen, and tender area that is usually not raised. - Unlike scrofuloderma, it does not typically present with **undermined ulcers**, satellite lesions, regional lymphadenopathy specifically related to tuberculosis, or the systemic and histopathological findings of mycobacterial infection.
Question 1164: The most common cause of seizures in a patient of AIDS is
- A. Toxoplasmosis (Correct Answer)
- B. Cryptococcal meningitis
- C. Progressive multifocal leucoencephalopathy
- D. CNS lymphoma
Explanation: ***Toxoplasmosis*** - **Cerebral toxoplasmosis** is the most common cause of focal neurological deficits and seizures in patients with AIDS [1]. - It typically presents with multiple **ring-enhancing lesions** on MRI, often in the basal ganglia [1]. *Cryptococcal meningitis* - While common in AIDS, **cryptococcal meningitis** primarily causes headache, fever, and altered mental status, but seizures are less frequent. - It is diagnosed by identifying **Cryptococcus neoformans** in CSF. *Progressive multifocal leucoencephalopathy* - PML is a demyelinating disease caused by the **JC virus** and results in progressive neurological deficits due to white matter lesions [2]. - Seizures can occur, but this condition primarily affects **cognition** and motor function [2]. *CNS lymphoma* - **Primary CNS lymphoma** is another common CNS complication in AIDS, often presenting as a solitary or multiple ring-enhancing lesion [1]. - While it can cause seizures, it is less common than toxoplasmosis as the primary cause of seizures in this population [1].
Question 1165: Most common presentation of extra- pulmonary TB
- A. Tubercular lymphadenitis (Correct Answer)
- B. Peritoneal TB
- C. Pericardial TB
- D. Tubercular meningitis
Explanation: ***Tubercular lymphadenitis*** - This is the **most common form** of extrapulmonary tuberculosis, often presenting as painless, swollen lymph nodes, especially in the cervical region [1]. - It develops when *Mycobacterium tuberculosis* disseminates from a primary pulmonary focus to regional lymph nodes, leading to granulomatous inflammation [1], [3]. *Peritoneal TB* - While a significant form of extrapulmonary TB, it is **less common** than lymphadenitis, typically presenting with abdominal pain, distension, and ascites. - Involvement of the peritoneum usually indicates hematogenous spread or direct extension from adjacent organs. *Pericardial TB* - This is a **rare but serious** form of extrapulmonary TB, often leading to pericardial effusion, constriction, or tamponade [2]. - It results from retrograde lymphatic spread or direct extension from mediastinal lymph nodes and is not the most common presentation. *Tubercular meningitis* - A **severe and life-threatening** form of extrapulmonary TB, involving the meninges of the brain and spinal cord, but it is less frequent than lymphadenitis [2]. - It is often seen in immunocompromised individuals or young children and presents with neurological symptoms [4].
Question 1166: Which type of pulmonary TB is most likely to give sputum positive ?
- A. Fibronodular
- B. Pleural effusion
- C. Cavitary (Correct Answer)
- D. None of the options
Explanation: ***Cavitary*** - **Cavitary lesions** in pulmonary tuberculosis indicate extensive tissue destruction and high bacterial load, leading to a much higher likelihood of finding **acid-fast bacilli** in the sputum [1]. - The communication of these cavities with the airways allows for the expulsion of bacilli-laden material, making sputum microscopy a sensitive diagnostic tool [1]. *Fibronodular* - While fibronodular lesions indicate pulmonary TB, they typically represent areas of **healing or chronic, lower-grade infection** where the bacterial load may be lower. - Sputum positivity is possible but less frequent compared to cavitary disease, as the organisms are more contained within **granulomas** [2]. *Pleural effusion* - **Pleural effusions** in TB are often a result of a hypersensitivity reaction to mycobacterial antigens rather than direct mycobacterial invasion of the pleural space with high bacterial load. - Sputum smears are typically **negative** in cases of isolated tuberculous pleural effusion because the infection is primarily contained within the pleural space, not actively expelled from the lungs. *None of the options* - This option is incorrect because **cavitary pulmonary TB** is well-established as the form most frequently associated with sputum positivity [1]. - The presence of open cavities directly correlates with the ability to detect bacteria in expectorated samples.
Question 1167: What is a rare condition associated with Hepatitis B infection?
- A. Wegener's granulomatosis
- B. Systemic lupus erythmatosus
- C. Polyarteritis nodosa (Correct Answer)
- D. Sjogren syndrome
Explanation: ***Polyarteritis nodosa*** - **Polyarteritis nodosa (PAN)** is a **necrotizing vasculitis** [1] strongly associated with **Hepatitis B virus (HBV)** infection, particularly in areas where HBV is endemic. - The circulating **immune complexes** formed by HBV antigens and antibodies are deposited in the walls of small and medium-sized arteries, leading to inflammation and tissue damage. *Wegener's granulomatosis* - Now known as **Granulomatosis with Polyangiitis (GPA)**, this condition is primarily associated with **antineutrophil cytoplasmic antibodies (ANCAs)**, particularly **c-ANCA**, and is not typically linked to Hepatitis B infection. - It is characterized by necrotizing granulomatous inflammation and vasculitis affecting the respiratory tract and kidneys. *Systemic lupus erythematosus* - **Systemic lupus erythematosus (SLE)** is an **autoimmune disease** characterized by widespread inflammation and damage to various organ systems, often involving **antinuclear antibodies (ANAs)** [2], [3]. - While it can be triggered by various factors, a direct and strong association with Hepatitis B infection is not a known characteristic. *Sjogren syndrome* - **Sjogren syndrome** is a chronic autoimmune disorder primarily affecting the **exocrine glands**, leading to **dry eyes** and **dry mouth**, and is associated with **anti-Ro/SSA** and **anti-La/SSB antibodies** [2]. - While autoimmune conditions can rarely coexist or be triggered by viral infections, a direct or common association between Sjogren syndrome and Hepatitis B infection is not established.
Question 1168: What serum markers are indicative of a high level of Hepatitis B virus (HBV) infection?
- A. HBsAg only
- B. HBsAg and HBV DNA
- C. HBsAg, HBeAg, and HBV DNA (Correct Answer)
- D. Anti-HBsAg and HBV DNA
Explanation: **HBsAg, HBeAg, and HBV DNA** - The presence of **HBsAg** indicates ongoing HBV infection [1], while **HBeAg** signifies active viral replication and high infectivity [1]. - **HBV DNA levels** directly quantify the amount of viral genetic material, providing a direct measure of viral load and disease activity [1]. *HBsAg only* - While **HBsAg** indicates the presence of HBV infection, it doesn't provide a complete picture of viral replication or load [1]. - It doesn't differentiate between active replication and chronic carriage with low viral activity [1]. *HBsAg and HBV DNA* - This combination is better than HBsAg alone, as **HBV DNA** directly measures viral load [1]. - However, it misses **HBeAg**, which is a crucial marker for active viral replication and high infectivity, especially in the early phases of chronic infection [2]. *Anti-HBsAg and HBV DNA* - **Anti-HBsAg** (HBsAb) indicates immunity to HBV, either from vaccination or resolved infection, and its presence suggests the absence of active infection [1]. - Therefore, the co-existence of **Anti-HBsAg** with significant **HBV DNA** levels is contradictory and unlikely to represent a high level of active HBV infection.
Question 1169: Which of the following is the most common bacterial cause of community-acquired pneumonia?
- A. Staphylococcus aureus
- B. Streptococcus pneumoniae (Correct Answer)
- C. Staphylococcus epidermidis
- D. Staphylococcus saprophyticus
Explanation: ***Streptococcus pneumoniae*** - **_Streptococcus pneumoniae_** is the most frequent bacterial cause of **community-acquired pneumonia (CAP)**, responsible for a significant percentage of cases [1]. - It often leads to classical lobar pneumonia with acute onset of fever, chills, cough with purulent sputum, and pleuritic chest pain [2]. *Staphylococcus aureus* - While a cause of pneumonia, **_Staphylococcus aureus_** is more commonly associated with **hospital-acquired pneumonia** or pneumonia in individuals with predisposing factors such as influenza, IV drug use, or cystic fibrosis [1]. - It can cause severe necrotizing pneumonia and empyema, but it is not the most common cause of CAP. *Staphylococcus epidermidis* - **_Staphylococcus epidermidis_** is a common **commensal organism** of the skin and a frequent contaminant in cultures. - It is rarely a primary cause of pneumonia in immunocompetent individuals but can cause infections in the presence of **foreign bodies** like prosthetic devices [1]. *Staphylococcus saprophyticus* - **_Staphylococcus saprophyticus_** is primarily known as a cause of **urinary tract infections (UTIs)**, especially in young women. - It is not a common pathogen for respiratory tract infections or pneumonia.
Question 1170: A 17 years old female presents with sore throat and lymphadenopathy. A diagnostic test reveals the presence of heterophile antibodies. Diagnosis is?
- A. Tuberculosis (TB)
- B. Infectious mononucleosis (IM) (Correct Answer)
- C. Cytomegalovirus infection
- D. Streptococcal throat infection
Explanation: ***Infectious mononucleosis (IM)*** - The presence of **heterophile antibodies** in a patient with **sore throat** and **lymphadenopathy** is the diagnostic hallmark of infectious mononucleosis, commonly caused by the **Epstein-Barr virus (EBV)** [1]. - This clinical presentation, especially in a young adult, is highly suggestive of IM [1]. *Tuberculosis (TB)* - While TB can cause **lymphadenopathy** (e.g., scrofula), it typically presents with other systemic symptoms like **fever**, **night sweats**, and **weight loss**, and its diagnosis relies on microbial cultures, PCR, or biopsy, not heterophile antibodies [2]. - A sore throat is not a characteristic primary symptom of TB lymphadenitis. *Cytomegalovirus infection* - **Cytomegalovirus (CMV)** can cause a mononucleosis-like syndrome with symptoms similar to EBV, including fever, fatigue, and lymphadenopathy [3]. - However, CMV infection does **not typically produce heterophile antibodies**, which differentiates it from IM [3]. *Streptococcal throat infection* - **Streptococcal pharyngitis** causes a sore throat and can lead to cervical lymphadenopathy but is diagnosed by **rapid strep test** or **throat culture**. - It does **not involve heterophile antibody production** and typically lacks the widespread lymphadenopathy and fatigue seen in IM.
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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