Infectious Diseases Practice Questions

Q: Which one of the following hepatitis viruses has significant perinatal transmission?

Hepatitis B virus. ***Hepatitis B virus*** - **Perinatal transmission** is a major mode of HBV spread, occurring from an infected mother to her baby during birth. - Infants born to HBV-positive mothers have a high risk of developing **chronic HBV infection**, leading to serious liver disease later in life if not properly managed with immunization and immunoglobulin. *Hepatitis E virus* - Primarily transmitted via the **fecal-oral route**, often through contaminated water. - While it can be transmitted vertically, significant **perinatal transmission** leading to chronic outcomes in the infant is not a primary concern compared to HBV. *Hepatitis C virus* - While vertical transmission from mother to child can occur, the rate of **perinatal HCV transmission** is much lower (around 5%) compared to HBV. - It is mainly transmitted through exposure to infected blood, such as via **intravenous drug use** or blood transfusions prior to screening. *Hepatitis A virus* - Transmitted almost exclusively via the **fecal-oral route**, usually through contaminated food or water. - Perinatal transmission is **extremely rare** and does not represent a significant mode of global HAV spread or burden of disease.

Q: Intestinal perforation in typhoid occurs commonly in which part of the intestine?

Ileum. Ileum - The **ileum** is the most common site of typhoid perforation due to the highest concentration of **Peyer's patches** in this region. - Salmonella typhi preferentially invades and proliferates within these lymphoid aggregates, leading to **necrosis** and subsequent perforation. Jejunum - The **jejunum** has fewer Peyer's patches compared to the ileum, making it a much less common site for typhoid-related complications like perforation. - While inflammation can occur, the extensive lymphoid hyperplasia and subsequent ulceration seen in the ileum are less pronounced here. Duodenum - The **duodenum** is rarely affected by typhoid perforation, as it lacks significant Peyer's patches, which are the primary target for Salmonella typhi. - Perforations in the duodenum are generally associated with other causes, such as **peptic ulcer disease**. Cecum - While the **cecum** is part of the large intestine and contains lymphoid tissue, it is not the primary site of attack for Salmonella typhi leading to perforation. - The characteristic pathology of typhoid, involving extensive ulceration of Peyer's patches, is most prominent in the terminal ileum before the ileocecal valve.

Q: A patient presents with clustered, white lesions on the buccal mucosa, typically near the upper molars. These lesions are pathognomonic for measles. What are these lesions called?

Koplik spots. ***Koplik spots*** - These are pathognomonic for **measles (rubeola)** and appear as small, **white or bluish-white lesions** on an erythematous base on the buccal mucosa. - They typically precede the characteristic rash of measles by 1-2 days, making them a crucial early diagnostic sign. *Leukoplakia* - Refers to **thickened, white patches** on the mucous membranes that cannot be scraped off and are often precancerous. - These lesions are usually associated with chronic irritation (e.g., tobacco use) and are not a feature of viral infections like measles. *Kaposi spots* - This term is **not typically used** to describe oral lesions, particularly in the context of measles. - Kaposi sarcoma involves **purple or brown skin lesions** associated with HHV-8 infection, commonly seen in immunocompromised individuals. *None of the options* - This option is incorrect because **Koplik spots** accurately describe the buccal mucosal lesions pathognomonic for measles.

Q: A truck driver, who is HIV-positive, presented with a history of fever since four weeks, and a dry cough, as well as a history of weight loss of about 10 kg. X-ray shows bilateral reticulonodular infiltrates. The most likely diagnosis is:

Pneumocystis pneumonia. ***Pneumocystis pneumonia*** - This patient, an HIV-positive individual with prolonged **fever**, **dry cough**, significant **weight loss**, and **bilateral reticulonodular infiltrates** on X-ray, presents with a classic clinical picture for **Pneumocystis jirovecii pneumonia (PCP)**, which is an opportunistic infection common in immunocompromised individuals [1]. - The **dry cough** and **diffuse bilateral infiltrates** are highly characteristic of PCP, especially in the context of HIV and unexplained weight loss, suggesting advanced HIV disease [1]. *Tuberculosis* - While **tuberculosis (TB)** is common in HIV-positive individuals and can cause fever, weight loss, and cough, the X-ray finding of **bilateral reticulonodular infiltrates** is less typical for primary pulmonary TB, which often presents with cavitary lesions or focal infiltrates [1]. - The **cough** in TB is often productive, whereas in this case, it is described as dry. *Pneumococcal pneumonia* - **Pneumococcal pneumonia** typically presents with an **acute onset** of high fever, productive cough, and pleuritic chest pain, and chest X-rays usually show **lobar consolidation** [1]. - The patient's presentation of a four-week history and dry cough does not align with the typical acute bacterial pneumonia caused by *Streptococcus pneumoniae*. *Interstitial lung disease* - **Interstitial lung disease (ILD)** usually presents with **progressive dyspnea** and a dry cough over a longer period, often without significant fever or rapid weight loss unless it's an acute exacerbation [1]. - While ILD can cause reticulonodular infiltrates, the acute febrile illness and significant weight loss point more towards an infectious etiology, especially in an HIV-positive patient [1].

Q: Pneumothorax could be a complication of what?

Staphylococcal pneumonia. ***Staphylococcal pneumonia*** - *Staphylococcus aureus* is known for causing **necrotizing pneumonia**, forming abscesses and **cavitary lesions** that can rupture into the pleural space. - This rupture leads to a **bronchopleural fistula** and subsequent development of a **pneumothorax** [2]. *Pneumococcal pneumonia* - This is the most common cause of **community-acquired pneumonia** but typically causes **lobar consolidation** [1]. - It is rarely associated with necrotizing changes or significant pleural complications like pneumothorax, though **empyema** can occur [2]. *Klebsiella pneumonia* - Often causes severe, **necrotizing pneumonia**, particularly in debilitated or alcoholic individuals, but is more commonly associated with **abscess formation** within the lung parenchyma [3]. - While lung destruction can occur, pneumothorax is a less frequent direct complication compared to cavitary lesions seen in staphylococcal infections. *Viral pneumonia* - Typically causes **interstitial inflammation** and diffuse involvement of the lung parenchyma [4]. - It does not usually lead to significant tissue necrosis or cavitation that would predispose to a pneumothorax.

Q: What is the diagnostic criterion for sputum-positive tuberculosis (TB)?

At least 1 sputum sample positive for AFB. The definition of sputum-positive TB, particularly in initial diagnosis, generally requires at least one **acid-fast bacilli (AFB) smear-positive** sputum sample [1]. This criterion is crucial for guiding initial treatment strategies and public health interventions for **infectious TB** [1]. While a BACTEC-positive result confirms the presence of **Mycobacterium tuberculosis**, a rapid AFB smear positive result is often the initial criterion for "sputum-positive" classification for immediate management [2]. While some guidelines or clinical contexts might emphasize multiple positive samples for confirmation, the widely accepted minimum for sputum-positive TB is **at least one positive AFB smear** [1].

Q: Kaposi's sarcoma (KS) usually occurs when CD4+ lymphocyte counts are what?

CD4+ lymphocyte counts below 200. ***CD4+ lymphocyte counts below 200*** - **Kaposi's sarcoma (KS)** is an **AIDS-defining illness** and typically appears in individuals with severe immunocompromise [3]. - A CD4 count below **200 cells/µL** indicates a severely compromised immune system, making the patient susceptible to opportunistic infections and cancers like KS [1], [2]. *CD4+ lymphocyte counts above 600* - CD4 counts above **600 cells/µL** generally indicate a relatively healthy immune system [2]. - While HIV infection might be present, the risk of developing KS at this CD4 level is very low. *CD4+ lymphocyte counts between 1000-2000* - Normal CD4 counts in healthy individuals are typically between **500 and 1500 cells/µL** [2]. Counts in the 1000-2000 range are considered normal or even elevated, indicating a robust immune system. - Individuals with such CD4 counts are highly unlikely to develop Kaposi's sarcoma, as this cancer is associated with significant immunodeficiency [1]. *CD4+ lymphocyte counts above 2000* - CD4 counts above **2000 cells/µL** are significantly higher than the normal range and indicate a very strong immune system. - Kaposi's sarcoma is a disease of immunodeficiency, so it would not be expected in individuals with such high CD4 counts [1].

Q: Which of the following is NOT a complication of Typhoid ulcers?

Endocarditis. ### Endocarditis - **Endocarditis** is primarily associated with **bacterial infections** of the heart valves, not typically a direct complication of **Typhoid ulcers** [2]. - While systemic infections can rarely lead to endocarditis, Typhoid ulcers themselves are a localized gastrointestinal pathology. ### Perforation - **Perforation** is a serious complication of deep Typhoid ulcers, particularly in the **ileum**, where the **Peyer's patches** become necrotic [1]. - This leads to the leakage of bowel contents into the peritoneal cavity, causing **peritonitis**. ### Stricture - **Stricture formation** can occur in the intestine as a result of the healing process of deep and extensive Typhoid ulcers. - The fibrotic tissue laid down during repair can narrow the lumen of the bowel, leading to **obstruction**. ### Haemorrhage - **Haemorrhage** is a common and potentially life-threatening complication of typhoid ulcers, occurring when the ulcer erodes into a **blood vessel** [1]. - This can manifest as **melena** or **hematochezia**, indicating gastrointestinal bleeding.

Q: What is the route of administration for the tuberculin test?

Intradermal. ***Intradermal*** - The tuberculin test (also known as the **Mantoux test** or **PPD test**) involves injecting a small amount of **purified protein derivative (PPD)** into the **dermis layer** of the skin [1]. - This route allows for a localized immune response to be observed as an area of **induration** (a palpable, raised, hardened area) if the person has been exposed to *Mycobacterium tuberculosis* [1]. *Intramuscular* - This route involves injecting into a **muscle**, which is used for many vaccines and medications that need to be absorbed into the bloodstream. - It would not allow for the localized skin reaction necessary to interpret the tuberculin test. *Subcutaneous* - This route involves injecting into the **fatty tissue** just under the skin. - While close to the surface, it is not as precise as an intradermal injection for eliciting the specific localized immune response required for tuberculin testing. *None of the options* - This option is incorrect because the intradermal route is a standard and recognized method for administering the tuberculin test.

Q: Risk of HIV transmission is not seen with

Plasma derived hepatitis B vaccine. The original text with [1] citations added (ONLY for relevant references) - **Plasma-derived hepatitis B vaccines** undergo extensive purification and inactivation processes, which effectively eliminate the risk of **HIV transmission** [1]. - The manufacturing process ensures that any potential viral contaminants, including HIV, are **inactivated** or removed, making the vaccine safe [1]. *Whole blood* - **Whole blood** transfusions carry a significant risk of **HIV transmission** if the donor is infected and the blood is not properly screened [2]. - HIV can survive in whole blood, making it a direct conduit for transmission from an infected donor to a recipient [1], [2]. *Platelets* - **Platelets** are derived from whole blood and can contain viable **HIV particles**, posing a risk of transmission during transfusion [2]. - Although the risk might be slightly lower than with whole blood due to processing, it is still a recognized route for HIV transmission [1]. *Leukocytes vaccines* - The term "leukocytes vaccines" is vague, but if it refers to products containing **leukocytes** (white blood cells), these cells are a primary host for **HIV**. - Components directly derived from or containing viable leukocytes from an infected individual would carry a high risk of HIV transmission.

Question 1

Which one of the following hepatitis viruses has significant perinatal transmission?

Accepted Answer

Hepatitis B virus

Answer

Hepatitis E virus

Answer

Hepatitis C virus

Answer

Hepatitis A virus

Question 2

Intestinal perforation in typhoid occurs commonly in which part of the intestine?

Accepted Answer

Ileum

Answer

Jejunum

Answer

Duodenum

Answer

Cecum

Question 3

A patient presents with clustered, white lesions on the buccal mucosa, typically near the upper molars. These lesions are pathognomonic for measles. What are these lesions called?

Accepted Answer

Koplik spots

Answer

Leukoplakia

Answer

Kaposi spots

Answer

None of the options

Question 4

A truck driver, who is HIV-positive, presented with a history of fever since four weeks, and a dry cough, as well as a history of weight loss of about 10 kg. X-ray shows bilateral reticulonodular infiltrates. The most likely diagnosis is:

Accepted Answer

Pneumocystis pneumonia

Answer

Tuberculosis

Answer

Pneumococcal pneumonia

Answer

Interstitial lung disease

Question 5

Pneumothorax could be a complication of what?

Accepted Answer

Staphylococcal pneumonia

Answer

Pneumococcal pneumonia

Answer

Klebsiella pneumonia

Answer

Viral pneumonia

Question 6

What is the diagnostic criterion for sputum-positive tuberculosis (TB)?

Accepted Answer

At least 1 sputum sample positive for AFB

Answer

BACTEC positive

Answer

No positive samples

Answer

2 out of 3 sputum samples positive

Question 7

Kaposi's sarcoma (KS) usually occurs when CD4+ lymphocyte counts are what?

Accepted Answer

CD4+ lymphocyte counts below 200

Answer

CD4+ lymphocyte counts above 600

Answer

CD4+ lymphocyte counts between 1000-2000

Answer

CD4+ lymphocyte counts above 2000

Question 8

Which of the following is NOT a complication of Typhoid ulcers?

Accepted Answer

Endocarditis

Answer

Stricture

Answer

Haemorrhage

Answer

Perforation

Question 9

What is the route of administration for the tuberculin test?

Accepted Answer

Intradermal

Answer

Intramuscular

Answer

Subcutaneous

Answer

None of the options

Question 10

Risk of HIV transmission is not seen with

Accepted Answer

Plasma derived hepatitis B vaccine

Answer

Platelets

Answer

Leukocytes vaccines

Answer

Whole blood

Infectious Diseases — MCQs

Infectious Diseases — MCQs

On this page

Practice by Chapter

Want unlimited practice?