Infectious Diseases — MCQs

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?

Q1159

Which of the following is NOT more commonly seen in Klebsiella Pneumonia compared to Pneumococcal Pneumonia?

Q1160

Most common cause of diarrhea in AIDS patients?

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1151: Non-parasitic eosinophilia is caused by infection with -

A. Coccidioidomycosis (Valley Fever) (Correct Answer)
B. Ehrlichiosis
C. Candidiasis (Yeast infection)
D. Staphylococcal infection

Explanation: ***Coccidioidomycosis (Valley Fever)*** - **Coccidioidomycosis** is a systemic fungal infection that characteristically causes **non-parasitic eosinophilia**. This is a classic association frequently tested. - The host immune response to this specific fungal pathogen often involves a significant increase in **eosinophil count**. *Ehrlichiosis* - **Ehrlichiosis** is a bacterial infection transmitted by ticks, which typically causes **leukopenia** (low white blood cell count), sometimes with relative lymphocytosis. - While it affects various blood cell lines, it does not characteristically lead to **eosinophilia**; rather, it's more associated with low platelet and white cell counts. *Candidiasis (Yeast infection)* - **Candidiasis** is a common fungal infection, but it almost never causes **eosinophilia** [1]. - Systemic candidiasis is more likely to cause **neutrophilia**, rather than an increase in eosinophils [1]. *Staphylococcal infection* - **Staphylococcal infections** are bacterial and typically cause **neutrophilia** as the primary response.

Question 1152: Bloody diarrhea in HIV infected patient is mostly due to ?

A. Cryptosporidium
B. Isospora
C. CMV (Correct Answer)
D. Salmonella

Explanation: ***CMV*** - **Cytomegalovirus (CMV) colitis** is a common opportunistic infection in advanced HIV, causing **bloody diarrhea**, abdominal pain, and fever. - CMV infection can lead to **ulcerations** and inflammation of the colonic mucosa, resulting in blood in the stool. *Cryptosporidium* - **Cryptosporidiosis** causes profuse, **watery diarrhea** in HIV patients, not typically bloody [1]. - While it can be severe and persistent, it primarily affects the small intestine, leading to malabsorption. *Isospora* - **Isosporiasis** (caused by *Isospora belli*) primarily presents as **unrelenting watery diarrhea** in immunocompromised individuals [1]. - It affects the small bowel and does not commonly result in bloody stools. *Salmonella* - **Salmonella gastroenteritis** can cause bloody diarrhea, but in HIV patients, it is often associated with **bacteremia** and systemic infection. - While possible, **CMV colitis** is a more classic and frequent cause of bloody diarrhea in advanced HIV in the absence of other focal symptoms.

Question 1153: Which of the following characteristics does NOT apply to the rash of chickenpox when differentiating it from smallpox?

A. Not centripetal
B. Deep-seated (Correct Answer)
C. Monomorphic
D. Superficial

Explanation: ***Deep-seated*** - The rash of chickenpox is typically **superficial**, affecting the epidermis and upper dermis, leading to vesicles that are easily ruptured [1]. - In contrast, a **deep-seated** rash is characteristic of smallpox, where lesions extend into the deeper dermis, giving them a firm, "shotty" feel upon palpation. *Not centripetal* - This statement is generally true for chickenpox; its rash distribution tends to be **centrifugal**, meaning it is more concentrated on the trunk and extremities, sparing the face and distal limbs [1]. - Smallpox, however, is characterized by a **centripetal distribution**, with lesions most concentrated on the face and extremities. *Monomorphic* - This characteristic does NOT apply to chickenpox. Chickenpox exhibits a **pleomorphic rash**, meaning lesions at various stages of development (macules, papules, vesicles, scabs) are present simultaneously [1]. - A **monomorphic rash**, where all lesions are at the same stage of development, is a hallmark of smallpox. *Superficial* - This characteristic **applies** to chickenpox [1]. The lesions are typically superficial, affecting the epidermal layers and leading to a fragile, easily ruptured vesicle. - Smallpox lesions, in contrast, are **deep-seated**, firm, and umbilicated.

Question 1154: Which of the following is the PRIMARY risk factor most commonly associated with healthcare-associated pneumonia (HCAP)?

A. Acute care hospitalization for at least 2 days in the preceding 90 days (Correct Answer)
B. Home infusion therapy
C. Immunosuppressive disease or immunosuppressive therapy
D. Antibiotic therapy in the preceding 90 days

Explanation: ***Acute care hospitalization for at least 2 days in the preceding 90 days*** - This criterion is a **primary defining factor** for healthcare-associated pneumonia (HCAP) as it indicates recent exposure to healthcare settings where resistant pathogens are prevalent [1]. - Patients recently hospitalized are at higher risk for colonization with **multi-drug resistant organisms (MDROs)**, increasing the likelihood of difficult-to-treat infections [2]. *Home infusion therapy* - While home infusion therapy does involve healthcare contact, it is considered a **minor risk factor** for HCAP compared to recent acute hospitalization. - The level of exposure to resistant pathogens is typically lower in a home setting than in an acute care facility. *Immunosuppressive disease or immunosuppressive therapy* - Immunosuppression significantly increases a patient's **susceptibility to infection** in general, including pneumonia, but it is not the **primary diagnostic criterion** for defining HCAP [3]. - Immunocompromised patients can develop pneumonia from various sources, not exclusively from healthcare exposure. *Antibiotic therapy in the preceding 90 days* - Recent antibiotic therapy is a risk factor for developing pneumonia with **resistant pathogens**, but it is not the primary factor defining HCAP itself. - This factor influences the **choice of empiric antibiotics** due to potential resistance, rather than establishing the healthcare-associated nature of the infection.

Question 1155: Most common mode of spread for genital tuberculosis is?

A. Hematogenous (Correct Answer)
B. Lymphatic
C. Direct
D. Ascending

Explanation: ***Hematogenous*** - **Genital tuberculosis** most commonly spreads via the bloodstream from a primary site of infection, typically the **lungs** [2]. - This mode of spread allows the **Mycobacterium tuberculosis** bacilli to reach diverse pelvic organs, establishing secondary foci [2]. *Lymphatic* - While lymphatic spread can occur in tuberculosis, it is less common for disseminating infection to the genital tract compared to the **hematogenous route** [1]. - Lymphatic spread often leads to regional lymph node involvement rather than widespread dissemination to reproductive organs [1]. *Direct* - **Direct spread** from an adjacent organ infected with tuberculosis is rare for genital involvement. - This mode would involve local extension, which is not the primary mechanism for establishing genital tuberculosis. *Ascending* - **Ascending infection** is typically seen in other sexually transmitted infections or bacterial vaginosis, where pathogens move upwards from the lower genital tract. - This is not the characteristic mode of spread for **Mycobacterium tuberculosis** to cause genital tuberculosis.

Question 1156: 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 1157: Which of the following statements about amoebic liver abscess is false?

A. More common in males than females
B. More common in the right lobe of the liver
C. Metronidazole is the mainstay of treatment
D. Amoebic liver abscess is not treatable with antibiotics (Correct Answer)

Explanation: Amoebic liver abscess is not treatable with antibiotics - This statement is false because **amoebic liver abscess** (ALA) is caused by *Entamoeba histolytica*, a **protozoan parasite**, and is effectively treated with **anti-parasitic drugs**, which are a type of antimicrobial and can be considered antibiotics in a broader sense for non-bacterial infections. - While traditional **antibiotics** (designed for bacteria) are not directly effective against the parasite, **metronidazole** (an antimicrobial) is the **drug of choice** for ALA. The liquid contents of the abscess typically have a characteristic pinkish or chocolate-brown color, often referred to as 'anchovy sauce' [1]. *More common in males than females* - This statement is **true**; amoebic liver abscess is indeed observed more frequently in **males**, particularly those between **20 and 50 years** of age. - The reasons for this disparity are not fully understood but may relate to hormonal factors or exposure differences. *More common in the right lobe of the liver* - This statement is **true**; the **right lobe** of the liver is the most common site for amoebic liver abscess formation. - This is attributed to the **anatomic fact** that the right lobe receives **more blood flow** from the superior mesenteric vein, which drains the colon where *Entamoeba histolytica* typically resides. *Metronidazole is the mainstay of treatment* - This statement is **true**; **metronidazole** is the **drug of choice** for the treatment of amoebic liver abscess [1]. - It is highly effective in eradicating the **trophozoites** of *Entamoeba histolytica* from the liver.

Question 1158: 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 1159: Which of the following is NOT more commonly seen in Klebsiella Pneumonia compared to Pneumococcal Pneumonia?

A. Abscess Formation
B. Pleural Effusion
C. Cavitation
D. Lower lobe involvement (Correct Answer)

Explanation: ***Lower lobe involvement*** - **Pneumococcal pneumonia** classically presents with **lobar pneumonia**, often affecting a single lobe, which can be any lobe but frequently involves the lower lobes. - While Klebsiella pneumonia can involve any lobe, the frequency of lower lobe involvement is not definitively higher than in pneumococcal pneumonia, making it a feature not *more* commonly seen in Klebsiella. *Abscess Formation* - **Klebsiella pneumonia** is notoriously associated with **necrosis** and abscess formation within the lung parenchyma due to its highly virulent polysaccharide capsule. - Abscesses are less common in uncomplicated **pneumococcal pneumonia**, which more typically causes lobar consolidation without significant tissue destruction [1]. *Pleural Effusion* - **Klebsiella pneumonia** is well-known for causing severe inflammation and an increased likelihood of developing a **parapneumonic pleural effusion**, often a complicated or empyematous one. - While pleural effusions can occur in pneumococcal pneumonia, they are generally less frequent and less severe than those seen with Klebsiella. *Cavitation* - **Cavitation** (breakdown of lung tissue forming cavities) is a hallmark of severe **Klebsiella pneumonia**, often observed as a consequence of extensive necrosis [1]. - Cavitation is a rare finding in **pneumococcal pneumonia**, which tends to resolve with consolidation rather than destructive changes.

Question 1160: 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].

Practice by Chapter

Principles of Antimicrobial Therapy

Practice Questions

Fever of Unknown Origin

Practice Questions

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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