Infectious Diseases Practice Questions

Q: 'Bull-neck' is seen in severe cases of which of the following?

Diphtheria. ***Diphtheria*** - The term **'bull-neck'** refers to the severe, diffuse swelling of the neck and **submandibular** and **anterior cervical lymph nodes** seen in advanced laryngeal or pharyngeal diphtheria [1]. - This swelling is due to inflammation and edema caused by the **diphtheria toxin**, giving the neck a characteristic bulky appearance [1]. *Goitre* - A **goitre** is an enlargement of the thyroid gland, which can cause a swelling in the anterior neck. - While it can be large, it typically does not produce the diffuse, inflammatory "bull-neck" appearance associated with severe diphtheria. *Mumps* - **Mumps** primarily causes swelling of the **parotid glands**, which are located in front of and below the ears. - The swelling is usually bilateral and localized to the parotid region, not a diffuse neck swelling like a "bull-neck." *Tubercular lymphadenitis* - This condition involves chronic inflammation and enlargement of **lymph nodes** due to **Mycobacterium tuberculosis** infection. - While it can cause cervical lymph node swelling ("scrofula"), it is typically more localized, often matted, and does not produce the acute, diffuse, and severe "bull-neck" edema seen in diphtheria.

Q: All of the following are major criteria for staphylococcal toxic shock syndrome, except:

Central nervous system abnormalities. ***Central nervous system abnormalities*** * **Central nervous system (CNS) abnormalities** are considered a **minor criterion** for staphylococcal toxic shock syndrome (TSS), not a major one. * While CNS involvement can occur, it's not a defining feature used in the initial classification of major criteria. *Rash* * A **diffuse macular erythroderma (rash)** is a **major criterion** for TSS. * This characteristic rash is a key indicator of the systemic inflammatory response. *Acute fever (Temperature >38.9°C (102°F))* * An **acute fever** with a temperature greater than 38.9°C (102°F) is a **major criterion** for TSS [1]. * This reflects the severe systemic inflammatory response elicited by the bacterial toxins. *Hypotension (Orthostatic, shock, blood pressure below age-appropriate norms)* * **Hypotension**, defined as orthostatic hypotension, shock, or blood pressure below age-appropriate norms, is a **major criterion** for TSS. * This indicates the severe cardiovascular dysfunction caused by the toxins.

Q: Positive tuberculin test signifies -

Prior exposure to tubercle bacilli. ***Prior exposure to tubercle bacilli*** - A positive tuberculin test (also known as a **Mantoux test** or PPD test) indicates that an individual has been **infected with Mycobacterium tuberculosis** at some point, leading to a cell-mediated immune response [1]. - This test detects a delayed-type hypersensitivity reaction to mycobacterial proteins, suggesting the immune system has been sensitized. *Active tuberculous infection* - While prior exposure is necessary, a positive tuberculin test alone **does not confirm active disease**. Additional diagnostic tests like **sputum microscopy, culture**, and chest X-ray are required for active infection [1]. - Many individuals with latent tuberculosis infection (LTBI) will have a positive tuberculin test but are **asymptomatic and not contagious** [1]. *Presence of cavitary lesion in lung* - **Cavitary lesions** are typically associated with **active, progressive pulmonary tuberculosis** and are detected by imaging studies like chest X-ray or CT scans, not by a tuberculin skin test. - A positive tuberculin test only indicates sensitization to the bacteria and does not provide information about the **pathological extent or manifestation** of the disease within the lungs. *Presence of matted pulmonary lymph nodes* - **Matted pulmonary lymph nodes** are a radiographic finding, usually seen in advanced or complicated primary tuberculosis, especially in children, and are identified via **chest imaging**. - A tuberculin test screens for immune response to the bacteria, not for specific anatomical findings within the lymphatic system.

Q: The classic triad of brucellosis include all, except

Meningoencephalitis. ***Meningoencephalitis*** - While neurological complications like **meningoencephalitis** can occur in brucellosis, it is **not considered part of the classic triad**. - Neurological involvement is a less common manifestation, seen in a smaller percentage of patients. *Hepatosplenomegaly* - **Hepatosplenomegaly** is a common finding in brucellosis, reflecting the systemic nature of the infection and involvement of the reticuloendothelial system. - The bacteria can replicate in macrophages within the liver and spleen, leading to their enlargement. *Fever with profuse night sweats* - **Fever**, often undulating or relapsing, is a hallmark symptom of brucellosis, frequently accompanied by **drenching night sweats**. - These symptoms are characteristic of the disease and contribute to its common name, **"undulant fever"**. *Arthralgia* - **Arthralgia** (joint pain) is a very common musculoskeletal manifestation of brucellosis, affecting a significant number of patients. - It often involves large joints and can be a persistent and debilitating symptom.

Q: A 55-year old man presented with a two-day history of headache, fever and generalized weakness. He had received a cadaveric kidney transplant 5 years earlier. His medications included 5 mg of tacrolimus twice a day and 10 mg of prednisone daily. On neurologic examination, he was confused and incoherent. Cranial nerves were normal, but he had a hazy left retina. Magnetic resonance imaging of the brain with the administration of gadolinium showed multiple enhancing lesion in both cerebral hemispheres. The treatment of choice in this condition is -

Trimethoprim-sulfamethoxazole. ***Trimethoprim-sulfamethoxazole*** - The patient's presentation with **headache**, **fever**, **generalized weakness**, **confusion**, **incoherence**, and **multiple enhancing brain lesions** in an immunocompromised transplant recipient on immunosuppressants strongly suggests **cerebral toxoplasmosis**. [1] - **Trimethoprim-sulfamethoxazole (TMP-SMX)** is the primary treatment for cerebral toxoplasmosis and also provides prophylaxis against *Pneumocystis jirovecii* pneumonia, a common opportunistic infection in this population. [1] *Penicillin long acting* - **Penicillin** is primarily used for bacterial infections, such as streptococcal infections or syphilis, and would not be effective against parasitic infections like cerebral toxoplasmosis. - Given the patient's immunosuppressed state and CNS symptoms, a bacterial etiology is less likely the primary cause in this clinical context. *Steroids* - **Steroids** like prednisone are **immunosuppressants**, and the patient is already on them (10 mg prednisone daily), which likely contributed to his immunocompromised state. - While steroids might be used to reduce brain edema in some CNS infections, they are not the primary treatment for the underlying infection and could worsen an opportunistic infection if used without appropriate antimicrobial therapy. *Anti tubercular therapy* - **Anti-tubercular therapy** is used to treat tuberculosis, which can present with CNS lesions but typically has a more chronic course and different epidemiological risk factors. [2] - While CNS tuberculosis can cause enhancing lesions, the rapid onset, retinal findings (hazy left retina potentially suggestive of uveitis or chorioretinitis associated with toxoplasmosis), and immunosuppression point more to toxoplasmosis.

Q: In scrub typhus all are true except:

Icterus. ***Icterus*** - While **scrub typhus** can cause **hepatic dysfunction** and abnormal liver enzymes, **frank icterus** (jaundice) is an uncommon and non-specific finding, making it the least likely "always" true symptom among the options. - Severe liver involvement causing jaundice is rare and usually indicates a **complicated** or severe disease course. *Maculopapular rash* - A **maculopapular rash** is a common dermatological manifestation in **scrub typhus**, often appearing a few days after fever onset. - It results from widespread **vasculitis** caused by the obligate intracellular bacterium *Orientia tsutsugamushi* [1]. *Lymphadenopathy* - **Regional lymphadenopathy** is a very common finding, particularly in the lymphatic drainage area corresponding to the eschar [1]. - This symptom is a direct response to the **local bacterial infection** spreading via the lymphatic system [1]. *Fever* - **Fever** is a hallmark symptom of **scrub typhus**, typically high-grade and persistent [1]. - It is one of the earliest and most consistent clinical signs, indicating a systemic inflammatory response to the infection [1].

Q: A 28 year old man with 3 weeks of fever presented with tricuspid valve vegetation. What is the MOST common cause of Endocarditis in I.V. drug abusers?

Staph.aureus. ***Staph.aureus*** - **_Staphylococcus aureus_** is the most common cause of **infective endocarditis** in intravenous drug abusers due to its prevalence on the skin and ability to adhere to damaged endothelial surfaces [1]. - The organism frequently accesses the bloodstream through contaminated needles, leading to tricuspid valve involvement as it is the first valve encountered by venous blood. *Pseudomonas* - While **_Pseudomonas aeruginosa_** can cause endocarditis, particularly in _IV drug users_ or immunocompromised individuals, it is significantly less common than **_Staphylococcus aureus_**. - Its infections are often associated with more severe, rapidly progressive disease and may be more challenging to treat. *Candida albicans* - **_Candida albicans_** can cause endocarditis, especially in **immunocompromised patients** or those with **indwelling catheters** or prosthetic valves, but it is not the most common cause in intravenous drug abusers [2]. - Fungal endocarditis is generally rarer than bacterial endocarditis and has a higher mortality rate. *Streptococcus viridans* - **_Streptococcus viridans_** group is a common cause of subacute bacterial endocarditis, especially in patients with **pre-existing valvular heart disease** [1]. - However, in the context of intravenous drug abuse, **_Staphylococcus aureus_** is significantly more prevalent than **_Streptococcus viridans_** [1].

Q: What is the recommended drug for treatment of mild leptospirosis?

Tetracycline. ***Tetracycline (Doxycycline)*** - **Doxycycline** (a tetracycline antibiotic) is the **first-line treatment for mild leptospirosis** - It has excellent activity against **spirochetes** including *Leptospira* species - Typically given as **doxycycline 100 mg twice daily for 7 days** - Also effective as **prophylaxis** in high-risk exposures - Alternative oral agents include **amoxicillin** or **ampicillin** for mild cases *Penicillin* - While **penicillin** is highly effective against *Leptospira*, this specifically refers to **IV Penicillin G for severe leptospirosis** - For **severe disease with organ involvement**, IV Penicillin G (1.5 million units every 6 hours) is the drug of choice - Oral penicillins (amoxicillin/ampicillin) can be used for mild cases but doxycycline is generally preferred - The question asks about general treatment, where **doxycycline is the standard first-line choice for mild cases** *Erythromycin* - Erythromycin is **not recommended** as primary treatment for leptospirosis - It has **poor activity** against *Leptospira* compared to tetracyclines and beta-lactams - Not included in standard treatment guidelines for this infection *Azithromycin* - Azithromycin has **limited documented efficacy** in leptospirosis - It is **not a first-line agent** and is not routinely recommended in treatment guidelines - May be considered as an alternative in specific situations with allergies, but tetracyclines or penicillins are strongly preferred

Q: A 25-year-old female presented to the hospital on 3rd day of menstruation with complaints of high fever, vomiting and rash on her trunk and extremities. On investigations she had leukocytosis and negative blood culture. She is diagnosed as:

toxic shock syndrome. ***Toxic shock syndrome*** - The combination of **high fever, vomiting, rash, leukocytosis, and menstruation** (especially tampon use) is highly suggestive of **Toxic Shock Syndrome (TSS)**, which is often caused by *Staphylococcus aureus* exotoxins. - A **negative blood culture** is common in TSS as it is a toxemia, not primarily a bacteremia, though bacteria are present at the local infection site. *Staphylococcal food poisoning* - While caused by *Staphylococcus aureus* toxins, **food poisoning** is typically characterized by rapid onset **gastrointestinal symptoms** (nausea, vomiting, diarrhea) [1] and usually resolves within 24 hours. - It does not typically present with the widespread **exfoliative rash** and systemic features seen in TSS. *Scalded skin syndrome* - **Staphylococcal scalded skin syndrome (SSSS)** is characterized by **blistering and exfoliation of the skin**, primarily affecting young children. - While both involve staphylococcal toxins, SSSS does not typically present with the prominent **fever, vomiting, and menstrual association** seen in this patient. *Varicella zoster infection* - **Varicella zoster infection** (chickenpox or shingles) presents with characteristic **vesicular lesions** in various stages of healing. - The rash described (trunk and extremities without vesicles) and the association with menstruation do not fit the clinical picture of a varicella zoster infection.

Q: True about tuberculin test are all except:

No risk of developing TB, if tuberculin test is negative. ***No risk of developing TB, if tuberculin test is negative*** - A negative tuberculin skin test (TST) does not completely rule out the risk of developing **tuberculosis (TB)**, especially in certain populations. - Individuals may have a **false-negative result** if they are immunocompromised, have recent TB infection (before sensitization occurs), or have overwhelming active TB disease. *Recent conversion in adult is an indication for ATT* - A **recent tuberculin conversion** (a change from negative to positive TST within a 2-year period) in an adult indicates new infection and a high risk of progression to active TB, thus warranting **anti-tuberculosis therapy (ATT)**. [1] - This is a critical indicator for initiating **prophylactic treatment** to prevent active disease. *May be false negative in immunocompromised patients* - **Immunocompromised patients**, such as those with HIV, on immunosuppressive therapy, or with severe malnutrition, may not mount a sufficient immune response to the TST, leading to a **false-negative result**. - This phenomenon is called **anergy** and can be life-threatening if it leads to delayed diagnosis and treatment of active TB. *INH prophylaxis is started, if the test is positive* - A **positive tuberculin test** with no evidence of active TB typically indicates **latent tuberculosis infection (LTBI)**. - In such cases, **isoniazid (INH) prophylaxis** is often recommended, especially for individuals at high risk of developing active disease, to prevent progression from latent to active TB. [1]

Question 1

'Bull-neck' is seen in severe cases of which of the following?

Accepted Answer

Diphtheria

Answer

Goitre

Answer

Mumps

Answer

Tubercular lymphadenitis

Question 2

All of the following are major criteria for staphylococcal toxic shock syndrome, except:

Accepted Answer

Central nervous system abnormalities

Answer

Rash

Answer

Acute fever (Temperature >38.9°C (102°F))

Answer

Hypotension (Orthostatic, shock, blood pressure below age-appropriate norms)

Question 3

Positive tuberculin test signifies -

Accepted Answer

Prior exposure to tubercle bacilli

Answer

Active tuberculous infection

Answer

Presence of cavitary lesion in lung

Answer

Presence of matted pulmonary lymph nodes

Question 4

The classic triad of brucellosis include all, except

Accepted Answer

Meningoencephalitis

Answer

Hepatosplenomegaly

Answer

Fever with profuse night sweats

Answer

Arthralgia

Question 5

A 55-year old man presented with a two-day history of headache, fever and generalized weakness. He had received a cadaveric kidney transplant 5 years earlier. His medications included 5 mg of tacrolimus twice a day and 10 mg of prednisone daily. On neurologic examination, he was confused and incoherent. Cranial nerves were normal, but he had a hazy left retina. Magnetic resonance imaging of the brain with the administration of gadolinium showed multiple enhancing lesion in both cerebral hemispheres. The treatment of choice in this condition is -

Accepted Answer

Trimethoprim-sulfamethoxazole

Answer

Penicillin long acting

Answer

Steroids

Answer

Anti tubercular therapy

Question 6

In scrub typhus all are true except:

Accepted Answer

Icterus

Answer

Maculopapular rash

Answer

Lymphadenopathy

Answer

Fever

Question 7

A 28 year old man with 3 weeks of fever presented with tricuspid valve vegetation. What is the MOST common cause of Endocarditis in I.V. drug abusers?

Accepted Answer

Staph.aureus

Answer

Pseudomonas

Answer

Candida albicans

Answer

Streptococcus viridans

Question 8

What is the recommended drug for treatment of mild leptospirosis?

Accepted Answer

Tetracycline

Answer

Erythromycin

Answer

Penicillin

Answer

Azithromycin

Question 9

A 25-year-old female presented to the hospital on 3rd day of menstruation with complaints of high fever, vomiting and rash on her trunk and extremities. On investigations she had leukocytosis and negative blood culture. She is diagnosed as:

Accepted Answer

toxic shock syndrome

Answer

staphylococcal food poisoning

Answer

scalded skin syndrome

Answer

varicella zoster infection

Question 10

True about tuberculin test are all except:

Accepted Answer

No risk of developing TB, if tuberculin test is negative

Answer

Recent conversion in adult is an indication for ATT

Answer

May be false negative in immunocompromised patients

Answer

INH prophylaxis is started, if the test is positive

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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