Infectious Diseases Practice Questions

Q: Amoebic liver abscess most commonly affects which part of the liver?

Right lobe of liver. ***Right lobe of liver*** - The **right lobe** of the liver [1] is supplied by a larger proportion of blood from the superior mesenteric and splenic veins, making it more susceptible to parasitic emboli from the bowel. - Due to its larger size and more direct blood supply from the **portal vein**, the right lobe is the most common site (approximately 80-90%) for amoebic liver abscess formation [1]. *Left lobe of liver* - While it can be affected, the **left lobe** is less commonly involved in amoebic liver abscesses compared to the right lobe. - Its blood supply directly from the **portal vein** is less direct and abundant for parasitic entry than that of the right lobe. *Portal vein* - The **portal vein** is the route of entry for *Entamoeba histolytica* cysts from the intestines to the liver, but it is not the site where an abscess forms. - Abscesses form in the **liver parenchyma** [1] after the trophozoites travel via the portal venules and elicit an inflammatory response. *Right pleural cavity* - The **right pleural cavity** is a potential site for complications of a ruptured amoebic liver abscess, leading to **pleural effusion** or **empyema**. - However, it is not the primary site where the amoebic liver abscess itself develops, as it is outside the liver.

Q: Penumococcal meningitis is associated with the following cerebrospinal fluid findings.

Pleocytosis with high protein and low sugar. ***Pleocytosis with high protein and low sugar*** - **Bacterial meningitis**, such as that caused by Streptococcus pneumoniae , typically presents with a **neutrophilic pleocytosis** (increased white blood cells, predominantly neutrophils). - The inflammation and bacterial metabolism lead to increased CSF **protein** and decreased CSF **glucose** (sugar). *Pleocytosis with low protein and normal sugar* - This combination is inconsistent with **bacterial meningitis**. Low protein and normal sugar levels would typically rule out a significant inflammatory or infectious process. - While pleocytosis indicates inflammation, the other findings do not align with the characteristic profile of **pneumococcal meningitis**. *Lymphocytosis with low protein and normal sugar* - **Lymphocytosis** (increased lymphocytes) is more characteristic of **viral meningitis** or certain chronic infections, not acute bacterial meningitis. - **Low protein** and normal sugar are also not typical findings for pneumococcal meningitis, which usually causes elevated protein and low sugar. *Lymphocytosis high protein and low sugar* - While **high protein** and **low sugar** can be seen in some forms of meningitis, **lymphocytosis** is not the predominant cell type in acute bacterial meningitis like pneumococcal meningitis. - This profile might be more indicative of **tuberculous meningitis** or certain fungal meningitides, which have a more subacute or chronic course and a mononuclear cell predominance.

Q: Which infection is not common in HIV patients?

Aspergillosis. ***Aspergillosis*** - While *Aspergillus* can cause infection in severely immunocompromised individuals, it is **less common** in HIV patients compared to other opportunistic infections listed, especially in the era of effective antiretroviral therapy (ART). - Its prevalence in HIV patients is significantly lower than in other populations, such as those with **neutropenia** or following **organ transplantation**. *Cryptosporidiosis* - This is a well-known **opportunistic infection** in HIV patients, especially those with low CD4 counts, causing **severe, chronic diarrhea** [1]. - It often leads to significant **malabsorption** and weight loss, representing a characteristic manifestation of advanced HIV disease [1]. *Atypical mycobacterial infection* - Infections by **Mycobacterium avium complex (MAC)** are very common in HIV patients with advanced immunosuppression (CD4 count <50 cells/µL) [1]. - MAC can cause **disseminated disease**, including fever, night sweats, weight loss, and anemia [1]. *Candidiasis* - **Oropharyngeal** and **esophageal candidiasis** are extremely common in HIV patients, often indicating immune suppression [1]. - While generally not life-threatening, it can be a significant cause of **discomfort** and difficulty eating for individuals with HIV [1].

Q: Infective endocarditis is least common in whom?

ASD.. ***ASD*** - Infective endocarditis is **least common** in atrial septal defects (ASDs) because the low-pressure, laminar flow across the defect does not typically create the turbulent jet lesions that predispose to vegetations. - While vegetations can form on damaged endothelium, the **absence of high-pressure gradients** makes it less likely [1]. *Mitral stenosis* - **Mitral stenosis** can increase the risk of infective endocarditis, particularly when associated with **severe valvular calcification** or **rheumatic heart disease**. - The turbulent flow and predisposition to atrial fibrillation can contribute to endothelial damage and vegetation formation [1]. *VSD* - **Ventricular septal defects (VSDs)** are considered a **high-risk congenital heart lesion** for infective endocarditis due to the turbulent blood flow from the left ventricle to the right ventricle [1]. - The high-velocity jet can cause **endothelial injury**, making the area susceptible to bacterial adherence and vegetation formation. *Aortic stenosis* - **Aortic stenosis** is a significant risk factor for infective endocarditis, especially in **bicuspid aortic valves** or those with **degenerative calcification** [1]. - The turbulent flow across the stenotic valve creates a predisposition to valve damage and subsequent bacterial adherence.

Q: Which of the following pathogens is commonly associated with respiratory infections in patients with HIV?

Pneumocystis jirovecii. ***Pneumocystis jirovecii*** - **Pneumocystis pneumonia (PCP)**, caused by *Pneumocystis jirovecii*, is a classic opportunistic infection in patients with **HIV**, especially those with **CD4 counts below 200 cells/µL** [1]. - It presents as a diffuse interstitial pneumonia with symptoms like **fever**, **cough**, and **dyspnea** [1]. *Haemophilus influenzae* - While *Haemophilus influenzae* can cause **respiratory infections** in HIV patients, it is more commonly associated with exacerbations of **chronic obstructive pulmonary disease (COPD)** or **bronchiectasis**. - It does not typically cause the severe, diffuse pneumonia seen with *Pneumocystis jirovecii* in immunocompromised individuals. *Streptococcus pneumoniae* - **Streptococcus pneumoniae** is a common cause of **bacterial pneumonia** in the general population, and its incidence is also increased in HIV-infected individuals due to impaired immune function [1]. - However, it primarily causes **lobar pneumonia** and is not specifically considered an AIDS-defining opportunistic infection like *Pneumocystis jirovecii*. *All of the options* - Although all three pathogens can cause respiratory infections in HIV patients, *Pneumocystis jirovecii* is the most commonly and uniquely associated opportunistic pathogen causing severe pneumonia in immunocompromised individuals, especially those with advanced HIV disease [1]. - The question asks for the pathogen **commonly associated** with respiratory infections, which in the context of HIV, often points to opportunistic infections specific to immune compromise.

Q: A man presents with fever, weight loss, and cough; the Mantoux test reads an induration of 17 x 19 mm, and sputum cytology is negative for acid-fast bacilli. What is the most likely diagnosis?

Pulmonary tuberculosis. ***Pulmonary tuberculosis*** - The combination of **fever**, **weight loss**, and **cough** are classic symptoms of tuberculosis [1]. - A **Mantoux induration of 17x19 mm** indicates a significant cell-mediated immune response to *Mycobacterium tuberculosis*, supporting the diagnosis even with initial negative sputum cytology [2]. *Histoplasmosis* - While it can cause fever, weight loss, and cough, a **positive Mantoux test** is not characteristic of histoplasmosis. - Diagnosis typically involves fungal cultures, serology, or antigen detection, not tuberculin skin testing. *Influenza* - Influenza is an **acute viral infection** presenting with sudden onset of fever, cough, and myalgia, but **chronic weight loss** is not a typical feature. - The **Mantoux test** being positive does not point towards influenza. *Bacterial pneumonia* - This typically presents with an **acute onset** of fever, productive cough, and dyspnea, while **weight loss** and a **positive Mantoux test** are not typical findings. - It rapidly responds to antibiotics, unlike the more chronic presentation suggested here.

Q: Most common cause of lung abscess?

Oral anaerobes. ***Oral anaerobes*** - **Aspiration of oropharyngeal contents** into the lungs is the most common mechanism for lung abscess formation, especially in patients with impaired consciousness or dysphagia. - The aspirated material frequently contains a high concentration of **anaerobic bacteria** from the oral flora, such as *Bacteroides*, *Prevotella*, *Fusobacterium*, and *Peptostreptococcus* species, which thrive in the low-oxygen environment of compromised lung tissue. *Staphylococcus aureus* - While *S. aureus* can cause lung abscesses, particularly in the context of **hematogenous dissemination** (e.g., from endocarditis or intravenous drug use) or in hospitalized patients, it is not the most common causative agent overall. - *S. aureus* infections tend to be more acute and severe, often leading to **necrotizing pneumonia** and multiple small abscesses rather than a single large cavitary lesion. *Klebsiella pneumoniae* - *Klebsiella pneumoniae* is a significant cause of **severe pneumonia** and lung abscess, particularly in individuals with **alcoholism** or **diabetes mellitus**. - It often produces a characteristic **"currant jelly" sputum** due to mucoid capsule production, but it is less common than aspiration-related anaerobic infections. *Mycobacterium tuberculosis* - *Mycobacterium tuberculosis* causes **tuberculosis**, which can lead to cavitary lung lesions, but these are typically **granulomas** with central caseous necrosis rather than true pyogenic abscesses. - While it can present with similar radiographic findings, the pathogenesis and typical clinical course differ significantly from those of a bacterial lung abscess.

Q: Roth spots are specifically associated with which condition?

Infective endocarditis. ***Infective endocarditis*** - **Roth spots** are retinal hemorrhages with a pale center, typically caused by **immune complex deposition** or **embolism** from infective endocarditis. - Their presence is a classic **ophthalmologic sign** associated with this serious infection of the heart valves. *Papilledema* - This condition involves **optic disc swelling** due to increased intracranial pressure, not retinal hemorrhages with pale centers. - It would typically manifest with visual disturbances like transient vision loss, not specific vascular lesions. *Diabetes* - **Diabetic retinopathy** involves microaneurysms, hemorrhages, and exudates, but Roth spots are not a characteristic feature. - Retinal changes in diabetes are primarily due to **microvascular damage** from chronic hyperglycemia. *Hypertension* - **Hypertensive retinopathy** can cause retinal hemorrhages, cotton wool spots, and arteriolar narrowing. - However, the specific appearance of Roth spots with a pale center is not characteristic of hypertensive retinopathy.

Q: In renal transplant recipients, which is the likely organism causing reactivation disease within 1 to 4 months after surgery?

CMV. ***CMV*** - **Cytomegalovirus (CMV)** is the most common viral infection causing significant morbidity and mortality in solid organ transplant recipients, often leading to **reactivation disease** within 1 to 4 months post-transplant due to immunosuppression [1]. - CMV disease can manifest in various forms, including **fever**, **leukopenia**, **gastroenteritis**, and potentially organ-specific involvement, mimicking transplant rejection [3]. *EBV* - **Epstein-Barr Virus (EBV)** reactivation is a concern in transplant recipients but is more strongly associated with the development of **post-transplant lymphoproliferative disorder (PTLD)**, which tends to occur later than the 1-4 month window for typical CMV reactivation [1]. - While EBV can cause a mononucleosis-like syndrome, its timeline and common severe complications differ from the typical CMV reactivation pattern [2]. *HSV* - **Herpes Simplex Virus (HSV)** reactivation is typically seen much earlier in transplant recipients, often within the first few weeks (usually 1-2 weeks) post-transplant [1]. - HSV reactivation typically presents as **mucocutaneous lesions** (e.g., cold sores, genital ulcers) rather than systemic disease in the 1-4 month window [3]. *VZV* - **Varicella-Zoster Virus (VZV)** reactivation (shingles) occurs in transplant recipients, but it generally has a slightly later onset than CMV, often beyond 4 months post-transplant or less commonly within the 1-4 month window [1]. - VZV reactivation typically presents as **dermatomal rash** and pain, which is distinct from the systemic symptoms of CMV disease.

Q: A sewer worker presents with high-grade fever, neck rigidity, and signs of meningismus. Laboratory findings are suggestive of renal failure and elevated liver enzymes. What is the most appropriate drug to be prescribed in this case?

Penicillin. Penicillin - Given the patient's occupation as a sewer worker, clinical presentation (high-grade fever, neck rigidity, meningismus), and laboratory findings (renal failure, elevated liver enzymes), this is severe leptospirosis (Weil's disease) with multiorgan involvement. - Penicillin G (or Ampicillin) is the first-line treatment for severe leptospirosis according to WHO guidelines, Harrison's, and standard Indian medical protocols. - Dosing: Penicillin G 1.5 million units IV every 6 hours for 7 days, or Ceftriaxone 1g IV daily as an equally effective alternative [1]. - Penicillin has excellent activity against Leptospira interrogans and is the most evidence-based choice for severe disease with organ failure. *Azithromycin* - While macrolides have some activity against Leptospira, azithromycin is NOT first-line therapy for severe leptospirosis. - It may be used in mild cases as an alternative to doxycycline, but lacks strong evidence for severe multiorgan disease. - In Weil's disease with renal and hepatic involvement, beta-lactams (Penicillin/Ceftriaxone) are superior [1]. *Ciprofloxacin* - Ciprofloxacin has poor activity against Leptospira species and is not recommended for leptospirosis treatment [2]. - While fluoroquinolones cover many gram-negative bacteria, they are ineffective for spirochetal infections. *Cotrimoxazole* - Cotrimoxazole (trimethoprim-sulfamethoxazole) has no role in leptospirosis treatment. - It is used for UTIs, certain respiratory infections, and Pneumocystis pneumonia, but lacks efficacy against Leptospira [2].

Question 1

Amoebic liver abscess most commonly affects which part of the liver?

Accepted Answer

Right lobe of liver

Answer

Left lobe of liver

Answer

Portal vein

Answer

Right pleural cavity

Question 2

Penumococcal meningitis is associated with the following cerebrospinal fluid findings.

Accepted Answer

Pleocytosis with high protein and low sugar

Answer

Lymphocytosis high protein and low sugar

Answer

Pleocytosis with low protein and normal sugar

Answer

Lymphocytosis with low protein and normal sugar

Question 3

Which infection is not common in HIV patients?

Accepted Answer

Aspergillosis

Answer

Atypical mycobacterial infection

Answer

Candidiasis

Answer

Cryptosporidiosis

Question 4

Infective endocarditis is least common in whom?

Accepted Answer

ASD.

Answer

Mitral stenosis.

Answer

VSD.

Answer

Aortic stenosis.

Question 5

Which of the following pathogens is commonly associated with respiratory infections in patients with HIV?

Accepted Answer

Pneumocystis jirovecii

Answer

Streptococcus pneumoniae

Answer

Haemophilus influenzae

Answer

All of the options

Question 6

A man presents with fever, weight loss, and cough; the Mantoux test reads an induration of 17 x 19 mm, and sputum cytology is negative for acid-fast bacilli. What is the most likely diagnosis?

Accepted Answer

Pulmonary tuberculosis

Answer

Histoplasmosis

Answer

Influenza

Answer

Bacterial pneumonia

Question 7

Most common cause of lung abscess?

Accepted Answer

Oral anaerobes

Answer

Staphylococcus aureus

Answer

Klebsiella pneumoniae

Answer

Mycobacterium tuberculosis

Question 8

Roth spots are specifically associated with which condition?

Accepted Answer

Infective endocarditis

Answer

Papilledema

Answer

Diabetes

Answer

Hypertension

Question 9

In renal transplant recipients, which is the likely organism causing reactivation disease within 1 to 4 months after surgery?

Accepted Answer

CMV

Answer

EBV

Answer

HSV

Answer

VZV

Question 10

A sewer worker presents with high-grade fever, neck rigidity, and signs of meningismus. Laboratory findings are suggestive of renal failure and elevated liver enzymes. What is the most appropriate drug to be prescribed in this case?

Accepted Answer

Penicillin

Answer

Ciprofloxacin

Answer

Cotrimoxazole

Answer

Azithromycin

Infectious Diseases — MCQs

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