Infectious Diseases Practice Questions

Q: The classic opportunistic infection in acquired immune deficiency syndrome is:

Pneumocystis jirovecii pneumonia. ***Pneumocystis jirovecii pneumonia*** - **Pneumocystis jirovecii pneumonia (PJP)** is a classic and common opportunistic infection in individuals with **AIDS**, especially when the **CD4 count drops below 200 cells/mm³** [1]. - It presents with fever, dyspnea, non-productive cough, and hypoxia, and is a major cause of morbidity and mortality in untreated HIV. *Aphthous stomatitis* - While common in HIV-positive individuals, **aphthous stomatitis** is not typically considered an **opportunistic infection** or an **AIDS-defining illness** [2]. - It represents a painful inflammation of the oral mucosa, often recurring due to local irritants or systemic factors, rather than a pathogen exploiting immunodeficiency. *Tuberculosis* - **Tuberculosis (TB)** is an opportunistic infection and a serious concern in HIV-infected individuals, but the question asks for the **classic** opportunistic infection in AIDS [1]. - While TB incidence is significantly higher in HIV-positive patients, **Pneumocystis jirovecii pneumonia** is historically and clinically more often cited as the classic infection associated with the initial presentation or diagnosis of AIDS. *Herpetic gingivostomatitis* - **Herpes simplex virus (HSV)** infections, including gingivostomatitis, are more frequent and severe in immunocompromised individuals. - However, **herpetic gingivostomatitis** is a specific manifestation that doesn't usually define AIDS as readily as **Pneumocystis jirovecii pneumonia**.

Q: Which of the following statements is true about mumps?

Meningoencephalitis can precede parotitis. ***Meningoencephalitis can precede parotitis*** - While **parotitis** is the most common manifestation of mumps, **meningoencephalitis** can occur as a complication and, in some cases, may appear before the onset of salivary gland swelling. - The mumps virus can directly infect the central nervous system, leading to neurological symptoms independent of or concurrent with glandular involvement [1]. *Mumps orchitis frequently leads to infertility* - While mumps **orchitis** (inflammation of the testes) can occur, especially in adolescent and adult males, it **rarely** leads to complete infertility, and more commonly affects only **one testis** if it impacts fertility at all. - The risk of bilateral testicular atrophy and subsequent infertility is low, occurring in a small percentage of affected individuals. *The patient is not infectious prior to clinical parotid enlargement* - Individuals infected with mumps are **infectious** typically **1-2 days before** the onset of parotid swelling and up to 5 days after, making transmission possible before clinical symptoms are apparent. - The virus is shed in respiratory secretions during this **prodromal period** and early stages of parotitis. *Salivary glands involvement is limited to parotid* - While the **parotid glands** are most commonly affected in mumps, the **submandibular** and **sublingual glands** can also be involved, though less frequently. - Mumps is a systemic viral infection that can affect various glandular tissues, not just the parotid.

Q: A 45 day - old infant developed icterus and two days later symptoms and signs of acute liver failure appeared. Child was found to be positive for Hbs Ag. The mother was also HBs Ag carrier. The mother's hepatitis B serological profile is likely to be ?

HBs Ag and Hbe Ag positivity. ***HBs Ag and HBe Ag positivity*** - The infant developed **acute liver failure** early in life (45 days old) and tested positive for **HBsAg**, suggesting vertical transmission from the mother. [1] - For vertical transmission to lead to **acute, severe infection** in the neonate, the mother must have a high viral load and be highly infectious, which is indicated by **HBeAg positivity**. *Mother infected with mutant HBV* - While mutant HBV can cause severe disease, there's no direct evidence in the scenario to suggest a **mutant strain** over a highly replicative wild-type virus. - **Precore and basal core promoter mutants** are generally associated with HBeAg-negative chronic hepatitis B, not necessarily acute neonatal infection. *HBs Ag positive only* - Being **HBsAg positive only** (without HBeAg) usually indicates a lower level of viral replication and infectivity. [1] - This scenario would make severe vertical transmission leading to **acute liver failure** in an infant less likely. *HBsAg and anti-HBe antibody positivity* - **Anti-HBe antibody positivity** indicates seroconversion from HBeAg, signifying a phase of lower viral replication and reduced infectivity. [1] - This profile would be less likely to result in the acute, severe neonatal infection observed, as the mother's viral load would typically be lower.

Q: True regarding Dengue fever is all, EXCEPT -

Transmitted by Anopheles mosquito. ***Transmitted by Anopheles mosquito*** - Dengue fever is primarily transmitted by the **Aedes aegypti** mosquito, not the Anopheles mosquito. - The **Anopheles mosquito** is the primary vector for **malaria**, not dengue. *Haemorrhagic tendency* - **Haemorrhagic manifestations**, ranging from mild petechiae to severe gastrointestinal bleeding, are a well-known feature of dengue fever, particularly in severe cases [1]. - This tendency results from **platelet dysfunction** and **increased vascular permeability** [1]. *Spontaneous remission* - Most cases of classic dengue fever resolve spontaneously within a week without specific treatment, indicating a tendency for **spontaneous remission**. - Supportive care, including **hydration** and **rest**, is typically sufficient for recovery. *Fever is saddle back type* - The fever pattern in dengue is often described as **biphasic** or "saddle-back," where the fever subsides for a day or two and then returns. - This unique fever curve is a characteristic clinical feature of dengue infection [1].

Q: Which is not associated with community acquired pneumonia

Pseudomonas aeruginosa. ***Pseudomonas aeruginosa*** - **_Pseudomonas aeruginosa_** is most commonly associated with **hospital-acquired pneumonia** (HAP) or pneumonia in individuals with **structural lung disease** (e.g., cystic fibrosis, bronchiectasis) [1] or **immunocompromised states**. - Its presence in community-acquired pneumonia (CAP) is **rare** and usually indicates severe, complicated cases or specific risk factors not typical for CAP. *Pneumococcus* - **_Streptococcus pneumoniae_** (Pneumococcus) is the **most common cause** of typical bacterial community-acquired pneumonia (CAP) [1]. - It presents with **acute onset** of fever, chills, productive cough, and lobar infiltrates on chest X-ray [1]. *Chlamydia* - **_Chlamydia pneumoniae_** is a common cause of **atypical community-acquired pneumonia**, often presenting with a more gradual onset and milder symptoms [1]. - It can cause a **"walking pneumonia"** with symptoms like persistent cough, sore throat, and low-grade fever. *Legionella* - **_Legionella pneumophila_** is a cause of severe **atypical community-acquired pneumonia**, often linked to contaminated water sources [1]. - It can present with systemic symptoms such as **gastrointestinal upset**, **neurological symptoms**, and hyponatremia, in addition to respiratory symptoms.

Q: Rickettsial organisms infect humans worldwide, although geographic locations may be limited for some species and possibly produce some challenges in medical diagnosis. All are obligate intracellular parasites, except C. burnetii, and transmitted by an insect vector. Typhus, spotted fever, and scrub typhus share which of the following manifestations of disease?

Fever and rash. ***Fever and rash*** - **Fever** is a universal response to infection, and **rash** is a common dermatological manifestation due to **vascular damage** caused by rickettsial organisms. [1] - The combination of **fever** and **rash** is a hallmark sign in clinical presentations of **typhus**, **spotted fever group rickettsioses**, and **scrub typhus**. [1] *Arthritis* - While arthritis can occur in some infectious diseases, it is **not a characteristic or common manifestation** across all rickettsial diseases mentioned. - The primary targets for rickettsial organisms are **endothelial cells**, leading to vasculitis, rather than direct joint involvement. *Common vector* - The rickettsial diseases mentioned are transmitted by **different vectors**: typhus by **lice or fleas**, spotted fever by **ticks**, and scrub typhus by **chiggers**. [1] - Therefore, they do **not share a common insect vector**. *Short incubation period (<48 hours)* - Rickettsial diseases typically have an incubation period ranging from **5 to 14 days**, which is considerably longer than 48 hours. [1] - A very short incubation period (<48 hours) is more typical of **bacterial food poisonings** or **viral infections** like influenza.

Q: A 25 yr. old girl admitted as a case of septic abortion with tricuspid valve endocarditis. Vegetation from the valve likely to affect will be

Lung. ***Lung*** - Injected drug users often develop **tricuspid valve endocarditis**, which can lead to septic emboli lodging in the **pulmonary vasculature and causing lung damage** [2]. - Right-sided endocarditis, seen here with tricuspid valve involvement, typically embolizes to the **lungs**, causing symptoms such as **pneumonia, lung abscesses, or pulmonary infarcts** [3]. *Brain* - Emboli to the brain usually originate from the **left side of the heart**, such as the mitral or aortic valves, or from peripheral venous clots that paradoxically cross through a septal defect. - While possible in rare cases of paradoxical emboli, this is not the typical or most likely site for embolization from isolated tricuspid valve endocarditis. *Spleen* - **Splenic emboli** are more commonly associated with **left-sided endocarditis**, where vegetations can dislodge and travel systemically [1]. - While the spleen is part of the systemic circulation, it is not the primary target foremboli originating from the right heart. *Liver* - The liver receives blood from both the hepatic artery (systemic circulation) and the portal vein (gut circulation), but it is not a common site for embolization from **right-sided valvular endocarditis**. - Emboli from the right heart would first pass through the lungs before reaching the systemic circulation that supplies the liver.

Q: 'Malignant pustule' is -

Anthrax ulcer. **Anthrax ulcer** - The term "malignant pustule" is a classic description for the skin lesion observed in **cutaneous anthrax**. - It refers to the characteristic progression of a papule to a vesicle, then a central **necrotic ulcer (eschar)** surrounded by edema. *Malignant melanoma* - This is a **skin cancer** originating from melanocytes, characterized by irregular borders, varying colors, and evolving size (ABCDEs). - It does not present as a pustule and has a different pathological and clinical course. *Marjolin's ulcer* - This is a **squamous cell carcinoma** that arises in chronic wounds, scars, or areas of chronic inflammation, such as burn scars, venous ulcers, or osteomyelitis. - It is a type of cancer, not an infectious pustular lesion. *Proliferating rodent ulcer* - This term is likely a descriptive phrase referring to a rapidly growing or extensive **basal cell carcinoma (rodent ulcer)**. - Basal cell carcinoma is a slow-growing skin cancer that rarely metastasizes and does not typically present as a pustule.

Q: A person with AIDS related complex is most likely suffering from:

Opportunistic infection. ***Opportunistic infection*** - AIDS-related complex (ARC) describes symptoms experienced by individuals with **HIV infection** before the full onset of AIDS, often including systemic symptoms and increased susceptibility to infections. - The immunocompromised state in ARC makes patients highly vulnerable to **opportunistic infections**, which are common presentations during this phase [1]. *Generalized lymphadenopathy* - While **generalized lymphadenopathy** is a common feature of HIV infection and can be part of ARC, it is a symptom or sign, not the primary "suffering" that defines much of the morbidity [1]. - **Persistent generalized lymphadenopathy (PGL)** is characterized by enlarged lymph nodes in two or more extrainguinal sites for over three months, often seen in early HIV infection, but it *doesn't fully encompass* "suffering" as broadly as opportunistic infections do [1]. *Cancer related to AIDS* - **AIDS-defining cancers** (e.g., Kaposi's sarcoma, non-Hodgkin lymphoma) are more characteristic of full-blown AIDS, when the immune system is severely compromised (CD4 count typically < 200 cells/µL). - While the risk of certain cancers increases with HIV, and some may occur in ARC, **opportunistic infections** are a more ubiquitous and defining feature of the "suffering" associated with the ARC stage [1]. *Herpes zoster* - **Herpes zoster**, or shingles, results from reactivation of the varicella-zoster virus and is more prevalent and often more severe in HIV-positive individuals, including those with ARC [1]. - However, it represents *one specific type* of opportunistic infection or condition, and the question asks what the person is "most likely suffering from" in a general sense within ARC, for which opportunistic infections are the overarching category.

Q: Super infection is common in:

Broad spectrum antibiotics. ***Broad spectrum antibiotics*** - **Broad-spectrum antibiotics** disrupt a wide range of normal flora, including beneficial bacteria, which creates an ecological void that opportunistic pathogens can then colonize [1]. - This disruption allows resistant organisms or fungi (e.g., *Clostridium difficile*, *Candida*) to proliferate unchecked, leading to a **superinfection**. *Narrow spectrum antibiotics* - **Narrow-spectrum antibiotics** target a specific type of bacteria, causing less disruption to the overall normal microbial flora [1]. - Due to their selective action, they are less likely to create the ecological imbalance that predisposes to superinfections. *Immuno compromised host* - While **immunocompromised hosts** are certainly prone to various opportunistic infections, superinfection specifically refers to a new infection occurring during or after treatment for a prior infection, often facilitated by antibiotic use [2]. - In this context, the primary cause of superinfection lies with the antibiotic's effect on flora, rather than the host's immune status directly initiating it. *Nutritional deficiency* - **Nutritional deficiencies** can impair immune function and increase susceptibility to infections in general. - However, they do not directly cause or predispose to superinfections in the specific sense of antibiotic-induced changes in microbial flora.

Question 1

The classic opportunistic infection in acquired immune deficiency syndrome is:

Accepted Answer

Pneumocystis jirovecii pneumonia

Answer

Aphthous stomatitis

Answer

Tuberculosis

Answer

Herpetic gingivostomatitis

Question 2

Which of the following statements is true about mumps?

Accepted Answer

Meningoencephalitis can precede parotitis

Answer

Mumps orchitis frequently leads to infertility

Answer

The patient is not infectious prior to clinical parotid enlargement

Answer

Salivary glands involvement is limited to parotid

Question 3

A 45 day - old infant developed icterus and two days later symptoms and signs of acute liver failure appeared. Child was found to be positive for Hbs Ag. The mother was also HBs Ag carrier. The mother's hepatitis B serological profile is likely to be ?

Accepted Answer

HBs Ag and Hbe Ag positivity

Answer

Mother infected with mutant HBV

Answer

HBs Ag positive only

Answer

HBsAg and anti-HBe antibody positivity

Question 4

True regarding Dengue fever is all, EXCEPT -

Accepted Answer

Transmitted by Anopheles mosquito

Answer

Haemorrhagic tendency

Answer

Spontaneous remission

Answer

Fever is saddle back type

Question 5

Which is not associated with community acquired pneumonia

Accepted Answer

Pseudomonas aeruginosa

Answer

Pneumococcus

Answer

Chlamydia

Answer

Legionella

Question 6

Rickettsial organisms infect humans worldwide, although geographic locations may be limited for some species and possibly produce some challenges in medical diagnosis. All are obligate intracellular parasites, except C. burnetii, and transmitted by an insect vector. Typhus, spotted fever, and scrub typhus share which of the following manifestations of disease?

Accepted Answer

Fever and rash

Answer

Arthritis

Answer

Common vector

Answer

Short incubation period (<48 hours)

Question 7

A 25 yr. old girl admitted as a case of septic abortion with tricuspid valve endocarditis. Vegetation from the valve likely to affect will be

Accepted Answer

Lung

Answer

Brain

Answer

Spleen

Answer

Liver

Question 8

'Malignant pustule' is -

Accepted Answer

Anthrax ulcer

Answer

Malignant melanoma

Answer

Marjolin's ulcer

Answer

Proliferating rodent ulcer

Question 9

A person with AIDS related complex is most likely suffering from:

Accepted Answer

Opportunistic infection

Answer

Generalized lymphadenopathy

Answer

Cancer related to AIDS

Answer

Herpes zoster

Question 10

Super infection is common in:

Accepted Answer

Broad spectrum antibiotics

Answer

Narrow spectrum antibiotics

Answer

Immuno compromised host

Answer

Nutritional deficiency

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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