Infectious Diseases Practice Questions

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: A 50-year-old HIV-seropositive male presented to the emergency room with multiple episodes of generalized tonic-clonic seizures. The patient is not on highly active antiretroviral therapy. The CD4 count was 45/μL. On examination, the patient was mildly arousable and disoriented, with no nuchal rigidity or focal neurological deficits. Gadolinium-enhanced magnetic resonance imaging and magnetic resonance spectroscopy were conducted. Which is the most appropriate drug to be given in this condition?

Pyrimethamine + Sulphadiazine. ***Pyrimethamine + Sulphadiazine*** - The patient's presentation with new-onset **generalized tonic-clonic seizures**, severe **immunocompromise (CD4 count 45/μL)**, and characteristic imaging findings (though not fully described, strongly suggestive of toxoplasmosis in this context) points to **cerebral toxoplasmosis**. - **Pyrimethamine combined with sulphadiazine** is the **first-line treatment** for cerebral toxoplasmosis, an opportunistic infection common in HIV patients with advanced immunosuppression. *Caspofungin* - **Caspofungin** is an **echinocandin antifungal agent** primarily used to treat invasive fungal infections, such as candidiasis and aspergillosis. - It has no activity against **Toxoplasma gondii**, which is a protozoan parasite, not a fungus. *Streptokinase* - **Streptokinase** is a **thrombolytic agent** used to dissolve blood clots in conditions like myocardial infarction and pulmonary embolism. - It has no role in the management of neurologic infections or seizures in an HIV-positive patient, as it does not address the underlying **pathogen**. *Voriconazole* - **Voriconazole** is a **broad-spectrum triazole antifungal agent** effective against various fungal infections, including aspergillosis and candidiasis. - While it is an antifungal, it is not indicated for treating **Toxoplasma gondii** infection, which is a parasitic infection.

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: 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: A 63-year-old man with small cell carcinoma of the left mainstem bronchus begins chemotherapy. During the treatment period, he becomes febrile and develops a productive cough. The temperature is 38.7°C (103°F), respirations are 32 per minute, and blood pressure is 125/85 mm Hg. A complete blood count shows leukocytosis (WBC = 18,500/mL). The patient's cough worsens, and he begins expectorating large amounts of foul-smelling sputum. A chest X-ray shows a distinct cavity with an air/fluid level distal to the tumor area. Which of the following is the most likely diagnosis?

Pulmonary abscess. ***Pulmonary abscess*** - The presence of **foul-smelling sputum**, a distinct **cavity with an air/fluid level** on chest X-ray, and a recent history of chemotherapy in an immunocompromised patient are classic signs of a pulmonary abscess, often due to **anaerobic bacteria**. - Small cell carcinoma in the mainstem bronchus can lead to bronchial obstruction, predisposing the distal lung tissue to **post-obstructive pneumonia** and abscess formation. *Atelectasis* - This involves **collapse of lung tissue** and would typically present with diminished breath sounds and dullness to percussion, not necessarily with a cavitary lesion or foul-smelling sputum. - While an obstructing tumor can cause atelectasis, it does not explain the **foul-smelling sputum** or the **air/fluid level** in a cavity. *Bronchiectasis* - Characterized by **irreversible dilation of bronchi**, leading to chronic cough and sputum production, but it typically involves chronic inflammation and does not usually present with an acute cavitary lesion with an air-fluid level. - While it can be associated with chronic infections and sputum, the **acute presentation** with a distinct cavity and air-fluid level after chemotherapy points away from bronchiectasis as the primary diagnosis. *Ghon complex* - This is a feature of **primary tuberculosis**, consisting of a calcified lung lesion and associated hilar lymph node calcification. - It is a **chronic, granulomatous inflammatory process** and does not present acutely with foul-smelling sputum, fever, or a cavitary lesion with an air/fluid level in the context of recent chemotherapy.

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: Which of the following is the most accurate description of thrush?

Is characterized by white patches in the oral cavity. ***Is characterized by white patches in the oral cavity*** - Thrush, or **oral candidiasis**, classically presents as creamy **white patches** on the tongue, inner cheeks, roof of the mouth, and back of the throat. - These patches can often be **scraped off**, revealing reddened and sometimes bleeding tissue underneath. *Occurs in individuals of all ages* - While thrush can occur at any age, it is most common in **infants**, **elderly individuals**, and those with **compromised immune systems**. - It is less common in healthy adults, making this description not the *most* accurate and comprehensive. *Is caused by a fungal infection* - Thrush is indeed caused by the fungus ***Candida albicans***, a type of yeast. - However, simply stating the cause does not fully describe the condition's distinct clinical presentation, which is essential for diagnosis. *Responds to antifungal treatment* - Thrush is typically treated with **antifungal medications** such as nystatin, clotrimazole, or fluconazole. - While true, describing the treatment is not the most direct or accurate description of the condition itself, which focuses on its characteristic features.

Q: Tropical splenomegaly is characterized by all the following, except which one?

Persistent high grade fever. ***Persistent high grade fever*** - **Tropical splenomegaly syndrome (TSS)**, also known as **hyperreactive malarial splenomegaly (HMS)**, typically does not present with **persistent high-grade fever**. - Fever, if present, is usually **low-grade** or intermittent, and the primary symptom is a massively enlarged spleen. *Moderate to massive splenomegaly* - This is a **defining characteristic** of tropical splenomegaly, as the condition is named for this prominent feature. - The spleen can become significantly enlarged, sometimes extending into the pelvis [1]. *Residence in areas endemic for Malaria* - **TSS/HMS** is a condition found in individuals living in or migrating from **malaria-endemic regions**, particularly those with stable, high-level transmission [2]. - It represents an abnormal immune response to chronic or repeated malarial exposure. *Clinical response to antimalarials* - Patients with tropical splenomegaly typically show **clinical improvement** and a reduction in spleen size after a prolonged course of **antimalarial treatment**. - This response helps differentiate it from other causes of splenomegaly.

Q: Manifestation of erythema nodosum leprosum (ENL) include all of the following except:

Pancreatitis. ***Pancreatitis*** - **Erythema nodosum leprosum (ENL)** is a type II **hypersensitivity reaction** in leprosy, which primarily affects the skin, nerves, and internal organs [1], [3]. - While ENL can affect various organs, **pancreatitis** is generally not considered a typical or common manifestation. *Fever* - **Fever** is a very common systemic symptom accompanying ENL, indicating a widespread inflammatory response. - It often acts as a key indicator of the acute phase of an ENL reaction. *Arthritis* - **Arthritis** and **arthralgia** (joint pain) are frequent musculoskeletal manifestations in patients with ENL. - It can affect both large and small joints, leading to pain and swelling [2]. *Lymphadenopathy* - **Lymphadenopathy** (enlarged lymph nodes) is a recognized systemic feature in patients experiencing ENL. - This indicates the involvement of the lymphatic system in the inflammatory process.

Q: Which of the following agents is least likely to cause meningitis in the elderly?

Herpes Simplex Virus - 2 (HSV-2).. Herpes Simplex Virus - 2 (HSV-2) - While HSV-2 can cause meningitis, it is **less common** in the elderly compared to bacterial pathogens, and primarily causes **aseptic meningitis**, often recurrently [1]. - Though immunocompromised elderly can be susceptible, HSV-2 meningitis is generally more prevalent in younger, sexually active individuals. *Listeria Monocytogenes* - This is a significant cause of **bacterial meningitis** in the elderly, particularly those over 60, due to their weakened immune systems. - It's known to affect individuals with **compromised cell-mediated immunity**, which is common in older adults. *Streptococcus pneumoniae* - **Pneumococcal meningitis** is one of the most common and severe forms of bacterial meningitis in all age groups, including the elderly [1]. - Elderly individuals have a higher risk of severe disease and complications from **S. pneumoniae** infections [1]. *Gram Negative bacteria* - **Gram-negative bacilli**, such as *Escherichia coli* and *Klebsiella pneumoniae*, are important causes of meningitis in older adults, especially those with comorbidities or who have undergone neurosurgery. - This risk increases with age due to factors like indwelling catheters, nursing home residence, and weakened immune responses [1].

Question 1

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 2

A 50-year-old HIV-seropositive male presented to the emergency room with multiple episodes of generalized tonic-clonic seizures. The patient is not on highly active antiretroviral therapy. The CD4 count was 45/μL. On examination, the patient was mildly arousable and disoriented, with no nuchal rigidity or focal neurological deficits. Gadolinium-enhanced magnetic resonance imaging and magnetic resonance spectroscopy were conducted. Which is the most appropriate drug to be given in this condition?

Accepted Answer

Pyrimethamine + Sulphadiazine

Answer

Caspofungin

Answer

Streptokinase

Answer

Voriconazole

Question 3

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

Accepted Answer

Ileum

Answer

Jejunum

Answer

Duodenum

Answer

Cecum

Question 4

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 5

A 63-year-old man with small cell carcinoma of the left mainstem bronchus begins chemotherapy. During the treatment period, he becomes febrile and develops a productive cough. The temperature is 38.7°C (103°F), respirations are 32 per minute, and blood pressure is 125/85 mm Hg. A complete blood count shows leukocytosis (WBC = 18,500/mL). The patient's cough worsens, and he begins expectorating large amounts of foul-smelling sputum. A chest X-ray shows a distinct cavity with an air/fluid level distal to the tumor area. Which of the following is the most likely diagnosis?

Accepted Answer

Pulmonary abscess

Answer

Atelectasis

Answer

Bronchiectasis

Answer

Ghon complex

Question 6

What is the route of administration for the tuberculin test?

Accepted Answer

Intradermal

Answer

Intramuscular

Answer

Subcutaneous

Answer

None of the options

Question 7

Which of the following is the most accurate description of thrush?

Accepted Answer

Is characterized by white patches in the oral cavity

Answer

Occurs in individuals of all ages

Answer

Is caused by a fungal infection

Answer

Responds to antifungal treatment

Question 8

Tropical splenomegaly is characterized by all the following, except which one?

Accepted Answer

Persistent high grade fever

Answer

Moderate to massive splenomegaly

Answer

Residence in areas endemic for Malaria

Answer

Clinical response to antimalarials

Question 9

Manifestation of erythema nodosum leprosum (ENL) include all of the following except:

Accepted Answer

Pancreatitis

Answer

Fever

Answer

Arthritis

Answer

Lymphadenopathy

Question 10

Which of the following agents is least likely to cause meningitis in the elderly?

Accepted Answer

Herpes Simplex Virus - 2 (HSV-2).

Answer

Listeria Monocytogenes

Answer

Gram Negative bacteria

Answer

Streptococcus pneumoniae

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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