Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 841: Treatment of choice for sputum positive pulmonary tuberculosis detected in 1st trimester of pregnancy-

A. Sta cat. III immediately
B. Sta cat. II immediately
C. Defer till second trimester
D. Sta cat. I immediately (Correct Answer)

Explanation: ***Sta cat. I immediately*** - All pregnant women with **active tuberculosis (TB)**, regardless of the trimester, should receive treatment immediately to prevent disease progression and transmission [1]. - **Category I treatment** includes a 6-month regimen with **isoniazid (INH), rifampicin (RIF), ethambutol (EMB), and pyrazinamide (PZA)** for the initial phase, which is generally considered safe during pregnancy [1]. *Sta cat. III immediately* - **Category III** refers to treatment for new patients with **smear-negative pulmonary TB** or **extrapulmonary TB** with severe forms, which does not fit the description of sputum-positive pulmonary TB. - While it's important to start treatment immediately, using the incorrect category would lead to an inappropriate drug regimen. *Sta cat. II immediately* - **Category II** is reserved for **retreatment cases** such as relapses, treatment failures, or treatment after default, which is not indicated for a newly diagnosed sputum-positive case. - Starting Category II treatment would involve a different, often more complex, drug regimen not appropriate for a new case. *Defer till second trimester* - **Delaying treatment** for sputum-positive pulmonary TB, even in the first trimester, increases the risk of maternal and fetal complications, including **disease progression**, **maternal mortality**, and congenital TB if the mother transmits the infection to the fetus [1]. - The benefits of immediate treatment outweigh the theoretical risks of medications during the first trimester, as key anti-TB drugs are considered relatively safe. - Pyridoxine should be prescribed in pregnant women to reduce the risk of peripheral neuropathy with isoniazid [1].

Question 842: Most common cause of hemolytic uremic syndrome is –

A. E.coli (Correct Answer)
B. Shigella
C. Pseudomonas
D. Salmonella

Explanation: **E.coli** * The most common cause of **hemolytic uremic syndrome (HUS)** is infection with Shiga toxin-producing **Escherichia coli (STEC)**, particularly **E. coli O157:H7** [1]. * The **Shiga toxin** damages endothelial cells, leading to microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury [1]. * *Shigella* * While **Shigella dysenteriae type 1** can also produce Shiga toxin and cause HUS, it is a less common cause compared to STEC in most regions. * Shigella infections commonly lead to **dysentery**, but HUS is a less frequent complication than with E. coli O157:H7. * *Pseudomonas* * **Pseudomonas aeruginosa** is an opportunistic pathogen that can cause severe infections, particularly in immunocompromised individuals, but it is not directly associated with causing HUS. * Pseudomonas infections are known for causing conditions like **ventilator-associated pneumonia**, **otitis externa**, and skin infections, not HUS. * *Salmonella* * **Salmonella** species are common causes of food poisoning and enteric fever, but they do not produce Shiga toxin and are not a recognized cause of HUS. * Salmonella infections typically manifest as **gastroenteritis**, **typhoid fever**, or bacteremia, without triggering the thrombotic microangiopathy characteristic of HUS.

Question 843: A patient with cough was sputum AFB negative but chest X-ray was suggestive of TB. What should be the next step according to RNTCP?

A. Nucleic acid amplification test (Correct Answer)
B. Tuberculin test
C. Line probe assay
D. Culture

Explanation: Nucleic acid amplification test - According to the and Revised National Tuberculosis Control Program (RNTCP) guidelines, if sputum AFB microscopy is negative but clinical suspicion and chest X-ray point towards TB, NAAT (Nucleic Acid Amplification Test) is recommended as the next confirmatory step [1]. - NAATs like CBNAAT (Cartridge-Based Nucleic Acid Amplification Test) or TrueNat provide rapid detection of Mycobacterium tuberculosis and resistance to Rifampicin, aiding in early diagnosis and appropriate treatment initiation. Tuberculin test - The Tuberculin Skin Test (TST), also known as the Mantoux test, indicates past exposure to TB or latent infection, but it cannot differentiate between active disease, latent infection, or past treated infection [2]. - A positive TST in an adult with a suggestive chest X-ray still requires further investigation for active disease, as it does not confirm active pulmonary TB [2]. Line probe assay - Line Probe Assay (LPA) is a molecular test used for rapid detection of MDR-TB (multi-drug resistant TB) by identifying mutations associated with resistance to Rifampicin and Isoniazid. - While useful for resistance testing, it typically requires a positive culture or direct sputum sample with a higher bacterial load and is not the primary diagnostic test for initial confirmation of TB when sputum AFB is negative. Culture - Mycobacterial culture is the gold standard for TB diagnosis, providing definitive confirmation and enabling drug susceptibility testing (DST) [1]. - However, culture results can take several weeks (typically 3-6 weeks), which delays treatment initiation, making it a less immediate next step compared to rapid molecular tests like NAAT in cases of strong clinical suspicion.

Question 844: Period of onset in tetanus refers to the time between:

A. First spasm to death
B. First injury to spasm
C. Trismus to laryngeal spasm
D. First symptom to spasm (Correct Answer)

Explanation: ***First symptom to spasm*** - The **period of onset** in tetanus specifically refers to the time elapsed from the first noticeable symptom of tetanus to the development of the first generalized **spasm** [1]. - A shorter period of onset is generally associated with a **more severe prognosis** as it indicates rapid progression of toxin effects [1]. *First spasm to death* - This timeframe describes the **duration of illness** following the onset of generalized spasms but does not define the period of onset. - It is more relevant for gauging the overall severity and **outcome** of the disease course. *First injury to spasm* - This interval is known as the **incubation period** for tetanus, which is the time from the injury (when *Clostridium tetani* spores enter the body) to the first symptom [1]. - It reflects the time required for bacterial multiplication and **toxin production** but is distinct from the period of onset [1]. *Trismus to laryngeal spasm* - Both **trismus** (lockjaw) and **laryngeal spasm** are symptoms of tetanus; however, this specific interval does not define the widely accepted "period of onset." - The period of onset refers to the time from the very **first symptom** (which might be trismus) to the *first generalized spasm*, not just between two specific types of spasms.

Question 845: AIDS, secondary infection will be all except

A. Candida
B. Kaposi's sarcoma (Correct Answer)
C. HSV
D. Rubella

Explanation: ***Kaposi's sarcoma*** - Kaposi's sarcoma is a **cancer** caused by human herpesvirus 8 (HHV-8) [2] that is common in patients with AIDS, but it is a **malignancy**, not a secondary infection [2],[3]. - While it arises due to immune suppression, it represents abnormal cell proliferation rather than direct microbial invasion. *Candida* - **Candidiasis** (e.g., oral thrush, esophageal candidiasis) is a common opportunistic fungal infection in AIDS patients due to their **impaired cellular immunity** [1]. - It often presents as **white plaques** on mucous membranes and is a clear example of a secondary infection. *HSV* - **Herpes Simplex Virus (HSV)** infections, including oral and genital herpes, are common and often severe in AIDS patients. - Due to immunocompromise, these infections can be **more widespread**, chronic, or recur frequently, qualifying as secondary infections. *Rubella* - **Rubella (German measles)** is a viral infection that is generally mild and self-limiting in immunocompetent individuals. - It is **not considered an opportunistic infection** or a common secondary infection specifically associated with AIDS; rather, it is listed as a differential diagnosis for the primary HIV infection rash [1].

Question 846: All of the following organs may be involved in Leprosy except -

A. Eye
B. Nasal mucosa
C. Uterus (Correct Answer)
D. Testes

Explanation: ***Uterus*** - The **uterus** is generally considered resistant to infection by *Mycobacterium leprae* due to its internal environment and typical host immune responses. - Leprosy primarily affects tissues with a **lower core body temperature**, and the uterus does not fit this criterion. *Eye* - Ocular involvement in leprosy is common, particularly in **lepromatous leprosy**, and can lead to significant morbidity including blindness. [1] - Complications can include **keratitis**, **iritis**, and lagophthalmos due to facial nerve damage. [1] *Nasal mucosa* - The **nasal mucosa** is a very common site of early involvement in leprosy, often serving as a primary entry point and shedding site for the bacteria. - Chronic nasal obstruction, epistaxis, and ultimately nasal septal perforation and **saddle nose deformity** can occur. [1] *Testes* - The **testes** are frequently affected in lepromatous leprosy, as the cooler temperature of the scrotum creates a favorable environment for *M. leprae*. - Testicular involvement can lead to **atrophy**, infertility, and hypogonadism due to inflammation and destruction of testicular tissue. [1]

Question 847: Pathognomonic of measles?

A. Koplik spot (Correct Answer)
B. Rash
C. Conjunctivitis
D. Fever

Explanation: ***Koplik spot*** - **Koplik spots** are tiny, white spots with a bluish-white center found on the buccal mucosa opposite the molars; they are **pathognomonic** for measles [1]. - The appearance of Koplik spots often precedes the characteristic measles rash by 1-2 days and helps in early diagnosis [1]. *Rash* - While a **maculopapular rash** is a prominent feature of measles [1], it is not pathognomonic as similar rashes can be seen in other viral exanthems. - The measles rash typically starts on the face and behind the ears, spreading downwards, but its presence alone is insufficient for a definitive diagnosis. *Conjunctivitis* - **Conjunctivitis** is a common symptom in measles, contributing to the "3 C's" (cough, coryza, conjunctivitis), but it is a non-specific finding seen in many other viral illnesses. - It presents as red, watery eyes and is part of the prodromal phase but does not uniquely identify measles. *Fever* - **Fever** is a universal symptom of measles, usually high-grade, but it is a general sign of infection and not specific to measles. - Many viral and bacterial infections cause fever, making it a poor diagnostic indicator on its own.

Question 848: Following are the characteristics of vincent’s angina, except:

A. Caused due to malnutrition
B. Caused by Leptospira interrogans (Correct Answer)
C. Ulcerative gingivostomatitis
D. A symbiotic infection

Explanation: ***Caused by Leptospira interrogans*** - Vincent's angina, also known as **necrotizing ulcerative gingivitis (NUG)**, is not caused by *Leptospira interrogans*. - *Leptospira interrogans* is the causative agent of **leptospirosis**, a zoonotic infection. *Caused due to malnutrition* - **Malnutrition**, particularly deficiencies in vitamins B and C, is considered a **predisposing factor** for Vincent's angina, worsening the immune response. - While not the direct cause, it can significantly contribute to the development and severity of the condition. *Ulcerative gingivostomatitis* - Vincent's angina is characterized by **ulcerative lesions** on the gums and oral mucosa, fitting the description of ulcerative gingivostomatitis. - These ulcers are often painful and covered with a grayish pseudomembrane. *A symbiotic infection* - It is caused by a **symbiotic infection** involving an overgrowth of specific oral bacteria, primarily **spirochetes** (e.g., *Treponema denticola*) and **fusobacteria** (e.g., *Fusobacterium nucleatum*). - These bacteria thrive in anaerobic conditions, leading to tissue necrosis and ulceration.

Question 849: Immune reconstitution inflammatory syndrome typically occurs following anti retroviral therapy after a duration of:

A. 6-12 months
B. 2-6 weeks (Correct Answer)
C. 1-2 years
D. 1-2 weeks

Explanation: ***2-6 weeks*** - **Immune reconstitution inflammatory syndrome (IRIS)** typically occurs within the first 2-6 weeks of initiating antiretroviral therapy (ART) in HIV-infected individuals [1]. - This time frame represents the period when the **recovering immune system** begins to mount an inflammatory response against previously subclinical or treated opportunistic infections [1]. *6-12 months* - This duration is generally too long for the typical presentation of IRIS, which is characterized by a rapid immune response shortly after ART initiation. - While immune changes continue over months, the acute inflammatory reactions defining IRIS usually manifest much earlier. *1-2 years* - This period is well beyond the typical window for IRIS onset, as the initial profound immune recovery triggering the syndrome would have already occurred. - At this stage, the immune system is usually much more stable and controlled. *1-2 weeks* - While some very rapid forms of IRIS can occur within this timeframe, the 2-6 week window is more broadly representative of the typical onset [1]. - The immune system often needs a slightly longer period to mount a sufficient inflammatory response to trigger overt IRIS symptoms.

Question 850: False negative Mantoux test is seen in all EXCEPT:

A. Malnourished
B. Measles
C. Immunocompromised
D. Chicken pox (Correct Answer)

Explanation: ***Chicken pox*** - While other viral infections like measles can cause temporary **anergy** leading to a false negative Mantoux, chickenpox (varicella) is less commonly cited as a direct cause of false negative results. - The immunocompromised state or severe illness associated with widespread viral infections is more likely to cause anergy rather than the specific virus itself in immunocompetent individuals. *Measles* - **Measles virus infection** is known to cause a transient suppression of cell-mediated immunity, leading to a state of **anergy** [2]. - This anergy can result in a **false negative Mantoux test** as the body's immune response to tuberculin is temporarily blunted [2]. *Malnourished* - **Severe malnutrition**, especially protein-energy malnutrition, significantly impairs the immune system, including **cell-mediated immunity** [2]. - A compromised immune response due to malnutrition can prevent the proper reaction to tuberculin, leading to a **false negative Mantoux test** [2]. *Immunocompromised* - Individuals who are **immunocompromised** (e.g., HIV infection, organ transplant recipients on immunosuppressants, certain cancers) have a diminished or absent cell-mediated immune response [1]. - This inability to mount an adequate immune reaction to tuberculin results in a **false negative Mantoux test**, even if they have latent tuberculosis [1].

Practice by Chapter

Principles of Antimicrobial Therapy

Practice Questions

Fever of Unknown Origin

Practice Questions

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.)

Practice Questions

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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