Infectious Diseases Practice Questions

Q: Infection caused by which of the following organism may mimic as malignancy?

Echinococcus multilocularis. ***Echinococcus multilocularis*** - This parasite causes **alveolar echinococcosis**, which manifests as a **destructive, infiltrative growth** in organs, primarily the liver. [1] - The lesions can be difficult to differentiate from **malignant tumors** due to their invasive nature and irregular margins, often leading to misdiagnosis. [1] *Echinococcus oliganthus* - This species is known to cause **polycystic echinococcosis**, primarily affecting wild felids and occasionally humans through accidental ingestion of eggs. - While it forms cysts, its growth pattern is generally **cystic** rather than infiltrative, making it less likely to mimic malignancy compared to *E. multilocularis*. *Echinococcus vogeli* - This parasite causes **polycystic hydatid disease** (or polycystic echinococcosis), similar to *E. oliganthus*, but is primarily associated with dholes and causes lesions in humans. - The disease typically presents as **large, multiloculated cysts** in organs, which are distinct from the infiltrative, tumor-like lesions of *E. multilocularis*. *Echinococcus granulosus* - This species is responsible for **cystic echinococcosis** (or hydatid disease), forming slow-growing, unilocular cysts, most commonly in the liver and lungs. [1] - While these cysts can grow large, their **well-defined, encapsulated nature** generally makes them distinguishable from malignant tumors, unlike the invasive lesions of alveolar echinococcosis. [1]

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 statements regarding measles are true, except:

Koplik spot are seen on retina. ***Koplik spot are seen on retina*** - **Koplik spots** are pathognomonic for measles and are typically found on the **buccal mucosa** (inside the cheeks), not on the retina [1]. - These are small, white, or bluish-white lesions with a red halo, appearing before the characteristic rash. *I-P is 10-14 days* - The **incubation period (I-P)** for measles, from exposure to the onset of symptoms, typically ranges from **10 to 14 days**. - This period includes the initial prodromal symptoms before the rash appears. *Long term complication may be seen in form of SSPE* - **Subacute sclerosing panencephalitis (SSPE)** is a rare, but fatal, **late complication** of measles infection [1]. - It results from persistent measles virus infection in the central nervous system, often developing years after the initial infection [1]. *Caused by RNA virus* - Measles is caused by the **measles virus**, which is a **single-stranded RNA virus** belonging to the *Paramyxoviridae* family. - It is an enveloped virus that primarily infects respiratory epithelial cells and replicates in lymphoid tissues. *Rash appears first on face* - The characteristic **maculopapular rash** of measles typically begins on the **face and behind the ears**. - It then spreads downwards to the trunk and extremities, fading in the same order [1].

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: Most common organism causing SBP after E. coli is

Streptococcus. ***Streptococcus*** - After **E. coli**, **Streptococcus species** are the most common pathogens isolated in cases of **spontaneous bacterial peritonitis (SBP)**. - This includes various Streptococcal strains, which can translocate from the gut lumen into the ascetic fluid. *Bacteroids* - **Bacteroides fragilis** and other Bacteroids species are obligate anaerobes and are more commonly associated with **secondary peritonitis** due to bowel perforation, rather than SBP. - While they are abundant in the gut, their recovery in SBP is rare, suggesting a different pathogenic mechanism. *Enterococcus* - **Enterococci** are found in the gut flora and can cause SBP, but they are less common than Streptococcus species as the second leading cause. - Infections with Enterococcus are often seen in patients with **nosocomial infections** or those with prior antibiotic exposure. *Klebsiella* - **Klebsiella pneumoniae** is a common Gram-negative bacterium that can cause SBP, but it is typically the third most common Gram-negative cause after E. coli. - While significant, it does not surpass Streptococcus as the second most common overall cause of SBP following E. coli.

Q: To prevent acute rheumatic fever, acute pharyngitis due to group A streptococci should be treated with antibiotics before:

9 days of illness. ***9 days of illness*** - Treatment of **Group A Streptococcus (GAS)** pharyngitis with appropriate antibiotics within **9 days** of symptom onset effectively prevents subsequent acute rheumatic fever. - This timeframe is crucial because it allows for clearance of the bacteria before the immune response that triggers **rheumatic fever** becomes fully established. *10 days of illness* - This duration is **beyond** the optimal window for preventing acute rheumatic fever, as the immune response may already be sufficient to initiate the disease process. - While still beneficial for symptom resolution, antibiotic treatment initiated at this point is **less effective** in preventing the sequelae of rheumatic fever. *7 days of illness* - Administering antibiotics within **7 days** of illness is highly effective and falls within the appropriate treatment window for preventing acute rheumatic fever [2]. - However, **9 days provides a slightly longer, yet still effective, cutoff**, making prevention of rheumatic fever still possible within this slightly extended period. *8 days of illness* - Antibiotic treatment at **8 days of illness** is still considered within the therapeutic window for preventing acute rheumatic fever [2]. - The goal is to clear the infection and prevent the immune system from mounting the **autoimmune response** that leads to cardiac damage [1].

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: Which of the following is the most common central nervous system parasitic infestation-

Neurocysticercosis. ***Neurocysticercosis*** - **Neurocysticercosis** is caused by the larval stage of the **pork tapeworm**, *Taenia solium*, and is considered the most common parasitic infection of the central nervous system worldwide [1]. - It is a leading cause of **acquired epilepsy** in endemic areas due to the presence of cysts in the brain tissue. *Sparganosis* - **Sparganosis** is a rare parasitic infection caused by larvae of **Spirometra** tapeworms, typically acquired by ingesting contaminated water or undercooked amphibian/reptile meat. - While it can affect the CNS, it is significantly **less common** than neurocysticercosis. *Paragonimiasis* - **Paragonimiasis** is caused by the lung fluke, mainly *Paragonimus westermani*, and is primarily a **pulmonary infection**. - Although it can rarely lead to **cerebral paragonimiasis**, it is not the most common CNS parasitic infestation. *Echinococcosis* - **Echinococcosis**, or hydatid disease, is caused by tapeworms of the genus *Echinococcus*, leading to the formation of **hydatid cysts** [1]. - While it can affect the brain, causing neurohydatidosis, it is **less frequent** than neurocysticercosis and often presents as a space-occupying lesion.

Question 1

Infection caused by which of the following organism may mimic as malignancy?

Accepted Answer

Echinococcus multilocularis

Answer

Echinococcus oliganthus

Answer

Echinococcus vogeli

Answer

Echinococcus granulosus

Question 2

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

Accepted Answer

Diphtheria

Answer

Goitre

Answer

Mumps

Answer

Tubercular lymphadenitis

Question 3

All of the following statements regarding measles are true, except:

Accepted Answer

Koplik spot are seen on retina

Answer

I-P is 10-14 days

Answer

Long term complication may be seen in form of SSPE

Answer

Caused by RNA virus

Answer

Rash appears first on face

Question 4

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 5

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 6

Most common organism causing SBP after E. coli is

Accepted Answer

Streptococcus

Answer

Bacteroids

Answer

Enterococcus

Answer

Klebsiella

Question 7

To prevent acute rheumatic fever, acute pharyngitis due to group A streptococci should be treated with antibiotics before:

Accepted Answer

9 days of illness

Answer

10 days of illness

Answer

7 days of illness

Answer

8 days of illness

Question 8

The classic triad of brucellosis include all, except

Accepted Answer

Meningoencephalitis

Answer

Hepatosplenomegaly

Answer

Fever with profuse night sweats

Answer

Arthralgia

Question 9

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 10

Which of the following is the most common central nervous system parasitic infestation-

Accepted Answer

Neurocysticercosis

Answer

Sparganosis

Answer

Paragonimiasis

Answer

Echinococcosis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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