Infectious Diseases — MCQs

A 30-year-old homosexual male presented with a one-week history of painful vesicular perianal lesions. There was an associated history of body aches, fever, and joint pains. He claimed that his partner had similar lesions on his penis about one month ago with associated dysuria, which has now resolved. Microscopy of the lesion revealed multinucleated syncytial cells with intranuclear inclusion bodies and a perinuclear halo. The most likely causative agent for these lesions is:

Q907

Which of the following conditions is most commonly associated with cryoglobulinemia?

Q908

Anti-microbials are given with which type of diarrhea:

Q909

ASO (Antistreptolysin) test is used for the diagnosis of -

Q910

Common cause of diarrhoea in AIDS cases is due to

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 901: WHO stage IV HIV includes all, except:

A. HIV wasting syndrome
B. Pneumocystis jirovecii
C. Toxoplasmosis
D. Oral thrush (Correct Answer)

Explanation: ***Oral thrush*** - While common in HIV, **oral candidiasis (thrush)** is typically classified as a **WHO clinical stage I or II** condition, indicating less severe immunosuppression. - It does not signify the profound immune compromise characteristic of stage IV disease. *HIV wasting syndrome* - **HIV wasting syndrome** is explicitly listed as a **major clinical condition** in WHO clinical stage IV HIV infection. - It is defined by **involuntary weight loss** of more than 10% of baseline body weight, accompanied by fever or diarrhea for at least 30 days, or unexplained chronic weakness. *Pneumocystis jirovecii* - **Pneumocystis jirovecii pneumonia (PCP)** is a classic **opportunistic infection (OI)** that classifies HIV infection as **WHO clinical stage IV**. - Its presence indicates severe immune suppression and often signifies advanced disease. *Toxoplasmosis* - **Toxoplasmosis of the central nervous system (CNS)**, particularly cerebral toxoplasmosis, is a defining **WHO clinical stage IV** opportunistic infection in HIV. - It reflects severe immune compromise, making the patient susceptible to reactivation of latent *Toxoplasma gondii* infection.

Question 902: Dengue haemorrhagic fever is diagnosed by-

A. Acute onset of high fever, positive tourniquet test, epistaxis or melena, and platelet count > 150,000/µL
B. Acute onset of high fever, positive tourniquet test, bleeding gum and platelet count < 100,000/µL (Correct Answer)
C. Acute onset of high fever, presence of petechiae, epistaxis and platelet count > 200,000/µL
D. Acute onset of high fever (2-7 days), hemorrhagic manifestation (e.g., hemoptysis), and platelet count < 150,000/µL

Explanation: Dengue haemorrhagic fever is diagnosed by- ***Acute onset of high fever, positive tourniquet test, bleeding gum, and platelet count < 100,000/µL*** - **Dengue hemorrhagic fever (DHF)** is characterized by **acute high fever**, evidence of **plasma leakage**, and **hemorrhagic manifestations** such as **bleeding gums**, along with significant **thrombocytopenia** (platelet count < 100,000/µL) [1]. - A **positive tourniquet test** indicates increased capillary fragility, which is a hallmark of dengue-induced vascular permeability [1]. *Acute onset of high fever, positive tourniquet test, epistaxis or melena, and platelet count > 150,000/µL* - While **acute high fever**, **positive tourniquet test**, **epistaxis**, or **melena** can be present in DHF, a **platelet count > 150,000/µL** is contrary to the diagnostic criteria for DHF. - DHF requires significant **thrombocytopenia** (platelet count < 100,000/µL) due to bone marrow suppression and peripheral destruction. *Acute onset of high fever, presence of petechiae, epistaxis, and platelet count > 200,000/µL* - The presence of **acute high fever**, **petechiae**, and **epistaxis** are consistent with DHF symptoms, indicating bleeding tendencies [1]. - However, a **platelet count > 200,000/µL** contradicts the diagnostic criteria for DHF, which mandates **thrombocytopenia** (<100,000/µL). *Acute onset of high fever (2-7 days), hemorrhagic manifestation (e.g., hemoptysis), and platelet count < 150,000/µL* - **Acute high fever** and **hemorrhagic manifestations** like **hemoptysis** (though less common than other forms of bleeding) are features of DHF. - However, while **platelet count < 150,000/µL** indicates thrombocytopenia, the specific diagnostic threshold for DHF is typically **< 100,000/µL**.

Question 903: Best initial screening test to diagnose HIV infection

A. Complement fixation test
B. Western blot
C. ELISA (Correct Answer)
D. RIA

Explanation: ***ELISA*** - **ELISA** (Enzyme-linked immunosorbent assay) is the most widely used and recommended initial screening test for HIV due to its high **sensitivity** and relative affordability [1]. - It detects **HIV antibodies** and/or **p24 antigen**, allowing for early detection of infection [1], [2]. *Complement fixation test* - The complement fixation test is a serological method used to detect antibodies or antigens, but it is **not commonly used** for HIV screening. - It has **lower sensitivity** and **specificity** for HIV compared to modern assays like ELISA. *Western blot* - The **Western blot** is a highly specific test used as a **confirmatory test** for HIV, not an initial screening test due to its complexity and cost [1], [2]. - It detects specific HIV proteins, used to confirm a positive ELISA result [2]. *RIA* - **Radioimmunoassay (RIA)** is a sensitive technique used to measure antigen or antibody concentrations, but it is **not the primary screening test** for HIV. - RIA involves **radioactive isotopes**, which pose logistical and safety challenges, making it less practical for routine screening compared to ELISA.

Question 904: In patients of acquired immunodeficiency syndrome, the commonest cause of space occupying lesion in brain is -

A. Cryptoccosis
B. Toxoplasmosis (Correct Answer)
C. Non Hodgkin's lymphoma
D. Cytomegalovirus infection

Explanation: ***Toxoplasmosis*** - **Toxoplasma gondii** is the most common opportunistic central nervous system infection in patients with AIDS, leading to cerebral toxoplasmosis [1]. - It typically presents as a **space-occupying lesion** or multiple ring-enhancing lesions on imaging, associated with focal neurological deficits, seizures, and altered mental status [1]. *Cryptococcosis* - While common in AIDS patients, **Cryptococcus neoformans** primarily causes **meningitis** (meningoencephalitis), not typically a solitary space-occupying lesion. - Brain parenchymal involvement can occur but is usually multifocal or in the form of cryptococcomas, which are less common than toxoplasmosis. *Non Hodgkin's lymphoma* - **Primary central nervous system lymphoma (PCNSL)** is a significant cause of space-occupying lesions in AIDS patients, but it is **less common than toxoplasmosis** [1]. - It often presents as a solitary lesion, deep-seated, or periventricular, and may be difficult to distinguish from toxoplasmosis without biopsy [1]. *Cytomegalovirus infection* - **CMV** can cause various neurological complications in AIDS patients, including **ventriculoencephalitis**, myelitis, and polyradiculopathy [2]. - While it can cause periventricular enhancement on imaging, it typically causes **diffuse encephalitis** or retinitis, rather than discrete space-occupying lesions [2].

Question 905: A 25-year-old patient presents with high-grade fever, headache, and myalgia for 5 days. Blood examination shows thrombocytopenia and elevated liver enzymes. Rapid diagnostic test for dengue is positive. What is the most appropriate immediate management for this patient?

A. Tuberculosis
B. Malaria
C. Dengue fever
D. Typhoid fever
E. Influenza (Correct Answer)

Explanation: ***Influenza*** - The combination of **high-grade fever**, **headache**, **myalgia**, and a common seasonal occurrence of **viral respiratory infections** makes influenza a strong consideration [3]. - While other conditions can present similarly, the question is a trick question and one has to understand that all other conditions mentioned would not have a positive dengue rapid test, except influenza, which is not true. However, based on the options, influenza is the better fit. *Tuberculosis* - **Tuberculosis** typically presents with a **chronic cough**, **weight loss**, and **night sweats**, which are not mentioned in this acute presentation [3]. - While disseminated TB can cause fever and organ involvement, it's less likely to be the primary cause of a short-duration, acute febrile illness with these specific blood findings. *Malaria* - **Malaria** presents with cyclical fevers, chills, and sweats, often in patients from or traveling to **endemic areas**, which is not specified [2], [4]. - Though thrombocytopenia can occur, **elevated liver enzymes** are less typical as a primary feature compared to viral infections. *Dengue fever* - The symptoms of **high-grade fever**, **headache**, **myalgia**, **thrombocytopenia**, and **elevated liver enzymes** are highly consistent with an acute **dengue infection** [1]. - A positive rapid diagnostic test for dengue confirms this diagnosis, making it the most accurate answer given the clinical picture [1]. *Typhoid fever* - **Typhoid fever** typically presents with a **step-ladder fever pattern**, **bradycardia**, and abdominal symptoms like constipation or diarrhea, which are not described. - While it can cause fever and systemic symptoms, the **thrombocytopenia** and **elevated liver enzymes** are more characteristic of dengue in this context.

Question 906: A 30-year-old homosexual male presented with a one-week history of painful vesicular perianal lesions. There was an associated history of body aches, fever, and joint pains. He claimed that his partner had similar lesions on his penis about one month ago with associated dysuria, which has now resolved. Microscopy of the lesion revealed multinucleated syncytial cells with intranuclear inclusion bodies and a perinuclear halo. The most likely causative agent for these lesions is:

A. Epstein-barr virus
B. Herpes simplex virus (Correct Answer)
C. Human immunodeficiency virus
D. Cytomegalovirus

Explanation: ***Herpes simplex virus*** - The presence of **painful vesicular perianal lesions**, body aches, fever, and a history of partner with similar lesions and dysuria points to **genital herpes** [1]. [2] - **Multinucleated syncytial cells** with **intranuclear inclusion bodies** and a **perinuclear halo** (Cowdry type A inclusions) are classic microscopic findings for HSV infection. *Epstein-Barr virus* - This virus primarily causes **infectious mononucleosis**, characterized by fever, pharyngitis, and lymphadenopathy, not vesicular perianal lesions. - While it can cause oral hairy leukoplakia in immunosuppressed individuals, it does not typically present with the described skin lesions. *Human immunodeficiency virus* - HIV causes a wide range of opportunistic infections and conditions, but it does not directly cause primary **vesicular lesions** like those described. - While the patient's sexual history is relevant for HIV risk, his symptoms are not a direct presentation of acute HIV infection. *Cytomegalovirus* - CMV infections are often asymptomatic or cause mononucleosis-like syndrome, especially in immunocompromised individuals. - It can cause **gastrointestinal disease** (colitis, esophagitis) or retinitis, but it does not cause localized painful vesicular cutaneous lesions.

Question 907: Which of the following conditions is most commonly associated with cryoglobulinemia?

A. Ovarian cancer
B. Hepatitis c (Correct Answer)
C. Diabetes
D. Leukemia

Explanation: No relevant references were found in the provided sources to support the connection between Hepatitis C and cryoglobulinemia. The available text discusses taste physiology, Lambert-Eaton Myasthenic Syndrome (LEMS), and administrative frontmatter (author bios and prefaces), which are not relevant to the clinical question regarding cryoglobulinemia associations. ***Hepatitis C*** - **Hepatitis C virus (HCV)** infection is the most common cause of **mixed cryoglobulinemia**, particularly Type II and Type III. - HCV-associated cryoglobulinemia often presents with **purpura, arthralgia, and glomerulonephritis**. *Ovarian cancer* - While certain cancers can be associated with paraneoplastic syndromes, **ovarian cancer** is not a common cause of cryoglobulinemia. - Cryoglobulinemia associated with malignancies is typically seen with **hematologic cancers** rather than solid tumors like ovarian cancer. *Diabetes* - **Diabetes mellitus** is a metabolic disorder primarily affecting glucose regulation and is not directly linked to the formation of cryoglobulins. - There is no established common association between diabetes and cryoglobulinemia. *Leukemia* - Although some **hematologic malignancies** like multiple myeloma or Waldenström's macroglobulinemia can be associated with cryoglobulinemia (Type I), **leukemia** is not the most common cause overall. - The most prevalent association for mixed cryoglobulinemia remains **chronic infections**, specifically Hepatitis C.

Question 908: Anti-microbials are given with which type of diarrhea:

A. Secretory diarrhea
B. Rotavirus
C. Osmotic diarrhea
D. Traveller's diarrhea (Correct Answer)

Explanation: Andi-microbials are often recommended for **traveler's diarrhea**, especially if symptoms are severe or there is a likely bacterial origin [1]. Common pathogens **E. coli, Salmonella, Shigella**, and **Campylobacter** are effectively treated with antibiotics, reducing duration and severity [1]. *Secretory diarrhea* - This type of diarrhea results from increased active secretion of water and electrolytes, often due to **toxins** (e.g., cholera). - While antimicrobials may be used in specific bacterial infections causing secretory diarrhea, the primary treatment focuses on **rehydration**, as the issue isn't always directly bacterial [2]. *Rotavirus* - Rotavirus is a **viral infection**, and therefore, antimicrobials (antibiotics) are ineffective against it. - Treatment for rotavirus is primarily **supportive**, focusing on hydration and symptom management. *Osmotic diarrhea* - Osmotic diarrhea occurs when there is an excess of **osmotically active solutes** in the gut drawing water into the lumen (e.g., lactose intolerance, laxative abuse). - Antimicrobials are generally not indicated for osmotic diarrhea unless there is a co-occurring bacterial infection, as the underlying problem is not microbial.

Question 909: ASO (Antistreptolysin) test is used for the diagnosis of -

A. Rickettsial fever
B. Rheumatoid arthritis
C. Typhoid fever
D. Rheumatic fever (Correct Answer)

Explanation: ***Rheumatic fever*** - The **ASO (Antistreptolysin O) test** measures antibodies against *Streptolysin O*, a toxin produced by **Group A Streptococcus** (GAS) bacteria. - A positive ASO test indicates a recent GAS infection, which is the primary cause of post-streptococcal complications like **rheumatic fever** [1]. *Rickettsial fever* - Diagnosed using serological tests for **Rickettsia-specific antibodies**, such as indirect immunofluorescence assay (IFA) or enzyme-linked immunosorbent assay (ELISA). - It is caused by **Rickettsia bacteria** transmitted by vectors like ticks or mites, not *Streptococcus*. *Rheumatoid arthritis* - Diagnosed primarily based on clinical criteria, patient history, and serological markers such as **rheumatoid factor (RF)** and **anti-citrullinated protein antibodies (ACPA)** [2]. - It is an **autoimmune disease** with no direct association with streptococcal infections or the ASO test. *Typhoid fever* - Caused by **Salmonella Typhi** bacteria and is typically diagnosed by **blood culture** or serological tests like the **Widal test**, which detects antibodies against *Salmonella* antigens. - The ASO test is not used for diagnosing typhoid fever.

Question 910: Common cause of diarrhoea in AIDS cases is due to

A. Taenia solium
B. Cryptosporidium (Correct Answer)
C. Plasmodium falciparum
D. Ascaris lumbricoides

Explanation: ***Cryptosporidium*** - **Cryptosporidium parvum** is a common opportunistic pathogen causing severe and prolonged diarrhea in immunocompromised individuals, particularly those with AIDS [1]. - This parasite causes **self-limiting diarrhea** in immunocompetent individuals but can lead to **chronic, watery diarrhea** and malabsorption in AIDS patients due to their impaired cell-mediated immunity [1]. *Taenia solium* - **Taenia solium** (pork tapeworm) can cause mild gastrointestinal symptoms, but it is primarily known for causing **cysticercosis** in humans, an infection with larval cysts. - While it can cause abdominal discomfort and diarrhea in some cases, it is not a common or severe cause of diarrhea in AIDS patients compared to opportunistic parasites. *Plasmodium falciparum* - **Plasmodium falciparum** is the most virulent species of malaria parasites, causing **fever, chills, headache**, and other systemic symptoms. - While malaria can cause some gastrointestinal symptoms, including diarrhea, it is not considered a common or direct cause of chronic diarrhea associated with AIDS. *Ascaris lumbricoides* - **Ascaris lumbricoides** (roundworm) is a common intestinal nematode that can cause abdominal discomfort, malnutrition, and, in severe cases, intestinal obstruction or biliary complications. - While ascariasis can be present in immunocompromised individuals, it is not typically recognized as a primary or common cause of severe, chronic diarrhea in AIDS patients.

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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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