Infectious Diseases — MCQs

A young lady complains of sore throat for 3 days along with fever and headache. On examination, she was severely dehydrated, her BP was found to be 90/ 50 mm Hg and on the distal aspect of the cuff, small red spots were noted. What could be the most probable etiological agent responsible for causing these symptoms -

Q947

Most common muscle involved in Tropical pyomyositis

Q948

Six days after receiving several flea bites in a rat-infested shed, a homeless 24-year-old man develops fever, chills, and a rash that spreads from his abdomen to cover his extremities. He is seen at the hospital emergency department, where blood is drawn for analysis. Eight days later, the public health department reports the presence of antibody to one of the rickettsial group antigens. Which of the following is the most likely diagnosis?

Q949

Which of the following parasite infections predispose to malignancies? (Select all that apply)

Q950

Negative Mantoux test is when induration is:

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 941: A 34-year-old lady presents with high grade fever with chills and rigors. On examination a firm spleen is felt 3 cm below costal margin with right upper quadrant tenderness. Peripheral smear was prepared. Diagnosis is?

A. Plasmodium vivax
B. Infectious mononucleosis
C. Plasmodium falciparum (Correct Answer)
D. Amoebic liver abscess

Explanation: ***Plasmodium falciparum*** - **High-grade fever with chills and rigors** is a classic presentation of malaria, often more severe with *P. falciparum* [1]. - **Splenomegaly** and **right upper quadrant tenderness** can occur in severe malaria due to liver and spleen involvement, especially with *P. falciparum*'s ability to cause profound organ dysfunction [1]. *Plasmodium vivax* - While *P. vivax* causes fever, chills, and rigors, it typically presents with a **tertian fever pattern** (fever every 48 hours), and severe complications like significant right upper quadrant tenderness are less common than with *P. falciparum* [1]. - **Splenomegaly** can be present, but the overall severity and potential for complications are higher in *P. falciparum* [1]. *Infectious mononucleosis* - Characterized by **fever, fatigue, pharyngitis**, and **lymphadenopathy**, often with splenomegaly. - However, **right upper quadrant tenderness** and the acute, severe presentation with prominent chills and rigors described are less typical of infectious mononucleosis. *Amoebic liver abscess* - This typically presents with **fever** and **right upper quadrant pain**, often with a tender hepatomegaly. - However, **prominent chills and rigors** are less common, and it is usually not associated with a palpable, firm spleen as a primary feature.

Question 942: A microbiology laboratory reports growth of Staphylococcus aureus from pus drained from a breast abscess. What is the most likely condition predisposing the patient to the development of a breast abscess?

A. Endocarditis
B. Menopause
C. Breast feeding (Correct Answer)
D. Inflammatory breast carcinoma

Explanation: ***Breast feeding*** - **Lactation** is the most common predisposing factor for breast abscesses, as **milk stasis** and **cracked nipples** can lead to bacterial entry and infection. - *Staphylococcus aureus* is the most frequent pathogen isolated in **lactational mastitis** and subsequent abscess formation. *Endocarditis* - Endocarditis is an infection of the **heart valves** and, while it can cause septic emboli, it is not a direct predisposing factor for a localized breast abscess. - The primary symptoms of endocarditis are usually systemic, such as fever, new heart murmurs, and embolic phenomena, which are not described here. *Menopause* - Menopause involves hormonal changes that can affect breast tissue but typically does not predispose women to acute bacterial breast abscesses. - Postmenopausal breast infections are less common and often associated with duct ectasia or other benign conditions rather than acute abscesses from *Staphylococcus aureus*. *Inflammatory breast carcinoma* - Inflammatory breast carcinoma can mimic infection with redness and warmth, but it is a **malignancy** and does not directly predispose to a bacterial abscess. - While it can sometimes be superimposed on an infection or cause skin changes that increase infection risk, it is not the most direct predisposing condition for a *Staphylococcus aureus* abscess.

Question 943: Which of the following organisms is commonly implicated in spontaneous bacterial peritonitis in patients of Nephrotic syndrome?

A. Streptococcus pneumoniae (Correct Answer)
B. Salmonella
C. Hemophilus influenza
D. Staphylococcus

Explanation: ***Streptococcus pneumoniae*** - This organism is a common cause of **spontaneous bacterial peritonitis (SBP)** in patients with **nephrotic syndrome**, particularly in children. - Patients with nephrotic syndrome are prone to infections due to impaired immunity (e.g., loss of immunoglobulins in urine) and **ascites**, providing a favorable environment for bacterial growth. *Salmonella* - While Salmonella can cause opportunistic infections, it is **not commonly implicated** in spontaneous bacterial peritonitis in nephrotic syndrome. - Salmonella typically causes **gastroenteritis** and can lead to bacteremia, but peritoneal infection is less common without direct bowel perforation. *Hemophilus influenza* - *Haemophilus influenzae* is a significant pathogen, but it is **not typically a cause** of spontaneous bacterial peritonitis in nephrotic syndrome. - It is more commonly associated with **respiratory infections**, meningitis, and epiglottitis. *Staphylococcus* - **Staphylococcal species** are generally not the primary cause of spontaneous bacterial peritonitis in uncomplicated nephrotic syndrome. - While *Staphylococcus aureus* can cause peritonitis, particularly in patients on **peritoneal dialysis** or with other predisposing factors, it is less common in SBP associated with nephrotic syndrome compared to *Streptococcus pneumoniae*.

Question 944: In bacterial meningitis, CSF has:

A. High glucose
B. High neutrophils
C. High lymphocytes
D. High protein (Correct Answer)

Explanation: High protein - In bacterial meningitis, inflammation and increased permeability of the blood-brain barrier lead to significant leakage of plasma proteins into the cerebrospinal fluid (CSF), resulting in elevated CSF protein levels [1]. - This is a hallmark finding due to the breakdown of normal barrier function and the presence of bacterial exudates [1]. *High glucose* - Bacterial meningitis is characterized by low CSF glucose because bacteria metabolize glucose for their growth and survival. - White blood cells also consume glucose, further decreasing its concentration in the CSF. *High lymphocytes* - While lymphocytes may be present, the predominant cell type in acute bacterial meningitis is neutrophils, indicating an acute inflammatory response [1]. - Lymphocyte predominance is typically seen in viral or chronic meningitis [2]. *High neutrophils* - High neutrophils are indeed characteristic of bacterial meningitis, reflecting the acute inflammatory response to bacterial pathogens [1]. - However, the question asks for a single characteristic, and while neutrophilic pleocytosis is prominent, elevated protein is another consistent and significant finding.

Question 945: True about influenza -

A. Incubation period 2-3 weeks
B. Pandemic is caused by Type-B virus
C. Most infections are subclinical (Correct Answer)
D. Type-A virus causes Reye's syndrome

Explanation: **Most infections are subclinical** - Many individuals infected with influenza virus experience **mild symptoms** or no symptoms at all, making the infection subclinical. - This characteristic contributes significantly to the **spread of the virus**, as asymptomatic carriers can unknowingly transmit it. *Incubation period 2-3 weeks* - The typical incubation period for influenza is much shorter, usually **1 to 4 days**, with an average of 2 days [1]. - An incubation period of 2-3 weeks would be more characteristic of other viral infections, such as **chickenpox** or **measles**. *Pandemic is caused by Type-B virus* - **Influenza A virus** is primarily responsible for pandemics due to its ability to undergo both **antigenic drift** and **antigenic shift**, leading to novel viral strains that can spread globally [1]. - Influenza B viruses primarily cause **seasonal epidemics**, often affecting children more severely, and do not typically cause pandemics. *Type-A virus causes Reye's syndrome* - Reye's syndrome is a rare but severe condition associated with the use of **aspirin** (salicylates) in children recovering from certain viral infections, including **influenza A or B** and **chickenpox**. - It is not directly caused by the influenza virus itself but is a medication-related complication in the context of a viral infection, making aspirin use a contraindication in pediatric viral illnesses.

Question 946: A young lady complains of sore throat for 3 days along with fever and headache. On examination, she was severely dehydrated, her BP was found to be 90/ 50 mm Hg and on the distal aspect of the cuff, small red spots were noted. What could be the most probable etiological agent responsible for causing these symptoms -

A. Brucella suis
B. Neisseria meningitidis (Correct Answer)
C. Brucella abortus
D. Staphylococcus aureus

Explanation: Neisseria meningitidis - The combination of sore throat, fever, headache, severe dehydration, hypotension, and petechiae (small red spots from broken capillaries, often seen with bleeding diathesis) is highly suggestive of meningococcemia [1]. - Neisseria meningitidis can cause fulminant sepsis and meningitis, leading to rapid progression of symptoms including DIC and widespread petechial rashes due to vasculitis [2]. Brucella suis - Brucellosis typically presents as an insidious illness with undulating fever, arthralgia, and organomegaly, not sudden onset severe symptoms with dehydration and petechiae. - While it can be severe, it does not commonly manifest with the acute, dramatic hemorrhagic signs seen in this patient. Brucella abortus - Similar to Brucella suis, Brucella abortus causes brucellosis, which is a chronic or subacute infection. - The clinical picture of acute onset, severe dehydration, hypotension, and petechiae points away from brucellosis. Staphylococcus aureus - Staphylococcus aureus can cause various infections, including sepsis, but a sore throat and the specific presentation of petechiae with hypotension following an apparent upper respiratory tract infection are less characteristic [3]. - While S. aureus can produce toxins leading to toxic shock syndrome, meningococcal sepsis is a more direct fit for the rapid onset and hemorrhagic signs.

Question 947: Most common muscle involved in Tropical pyomyositis

A. Triceps
B. Biceps
C. Quadriceps (Correct Answer)
D. Gluteus

Explanation: ***Quadriceps*** - The **quadriceps femoris muscle** is the most frequently affected muscle group in tropical pyomyositis, being involved in 30-50% of cases. - Its large muscle mass and susceptibility to minor trauma may contribute to its high incidence of involvement. *Triceps* - While other muscles can be affected, the **triceps muscle** is less commonly involved than the large muscles of the thigh in tropical pyomyositis. - Involvement of upper limb muscles is generally less frequent compared to lower limb and trunk muscles. *Biceps* - The **biceps muscle** is an infrequently affected site in tropical pyomyositis. - The disease typically shows a predilection for larger muscle groups in the lower limbs and trunk rather than the upper limbs. *Gluteus* - The **gluteal muscles** can be affected in tropical pyomyositis but are not as commonly involved as the quadriceps. - Involvement of the gluteal region is more likely to occur in disseminated disease or in specific risk groups.

Question 948: Six days after receiving several flea bites in a rat-infested shed, a homeless 24-year-old man develops fever, chills, and a rash that spreads from his abdomen to cover his extremities. He is seen at the hospital emergency department, where blood is drawn for analysis. Eight days later, the public health department reports the presence of antibody to one of the rickettsial group antigens. Which of the following is the most likely diagnosis?

A. Epidemic typhus
B. Endemic typhus (Correct Answer)
C. Q fever
D. Rocky Mountain spotted fever

Explanation: ***Endemic typhus*** - The patient's history of exposure to a rat-infested shed and flea bites, followed by fever, chills, and a rash spreading from the abdomen to the extremities [1], is highly consistent with **endemic (murine) typhus** [1]. - **Endemic typhus** is caused by *Rickettsia typhi* and is transmitted by the **flea vector** with rats as the reservoir [1]. *Epidemic typhus* - **Epidemic typhus** is caused by *Rickettsia prowazekii* and is transmitted by the **human body louse**, typically in conditions of overcrowding and poor hygiene. - While it shares similar symptoms, the **flea bite** and **rat exposure** in this case point away from epidemic typhus. *Q fever* - **Q fever** is caused by *Coxiella burnetii* and is typically acquired through inhalation of **contaminated aerosols** from infected livestock (cattle, sheep, goats). - Symptoms usually include fever, headache, and flu-like illness, but a **rash is uncommon**, and the transmission vector (flea) is inconsistent with the patient's presentation. *Rocky Mountain spotted fever* - **Rocky Mountain spotted fever (RMSF)** is caused by *Rickettsia rickettsii* and is transmitted by **tick bites**. - The rash of RMSF typically starts on the **ankles and wrists** and spreads centrally, often involving the palms and soles, which differs from the described abdominal onset and flea vector.

Question 949: Which of the following parasite infections predispose to malignancies? (Select all that apply)

A. Clonorchiasis
B. Guinea worm infection
C. Paragonimus westermani
D. Schistosomiasis (Correct Answer)

Explanation: Schistosomiasis - Chronic infection with *Schistosoma haematobium* is a major risk factor for developing **squamous cell carcinoma of the bladder**. [1] - The parasite's eggs deposited in the bladder wall induce chronic inflammation, cell proliferation, and ultimately **neoplastic transformation**. *Clonorchiasis* - Caused by *Clonorchis sinensis* (the Chinese liver fluke), which is strongly associated with **cholangiocarcinoma** (bile duct cancer). - Chronic inflammation and mechanical irritation from the flukes in the bile ducts lead to epithelial hyperplasia and, eventually, malignant changes. *Guinea worm infection* - Caused by *Dracunculus medinensis*, which primarily causes painful skin lesions and ulcers as the adult worm emerges. - While it causes significant morbidity, there is **no known association** with an increased risk of malignancy. *Paragonimus westermani* - This lung fluke causes paragonimiasis, leading to chronic inflammation and granuloma formation in the lungs, mimicking tuberculosis. - Although it causes severe pathology, there is **no well-established link** between *Paragonimus westermani* infection and the development of malignancy.

Question 950: Negative Mantoux test is when induration is:

A. <15mm
B. <5mm (Correct Answer)
C. <20mm
D. <10mm

Explanation: **<5mm** - A **Mantoux test** (tuberculin skin test) result of less than 5mm induration is generally considered **negative** in all populations, indicating no evidence of M. tuberculosis infection. - However, interpretation can vary depending on the patient's risk factors; for some, induration <5mm would still be considered positive. For a generally healthy individual with no known risk factors, it is a definitive negative. *<15mm* - An induration of 15mm or more is usually considered a **positive** result in anyone, including those with no known risk factors for TB. - This threshold indicates a high likelihood of M. **tuberculosis infection**. *<20mm* - While an induration over 20mm is definitively positive, specifying "<20mm" as negative would incorrectly classify many positive results (e.g., 5-19mm) as negative. - The standard cut-off for a universally negative result is much lower than 20mm. *<10mm* - An induration between **5mm and 9mm** can be considered positive in certain high-risk groups (e.g., recent contacts of TB patients, immunocompromised individuals) and is not universally negative. - Therefore, a test result of "<10mm" does not solely define a negative test, as it might include positive results for some populations [1].

Practice by Chapter

Principles of Antimicrobial Therapy

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Fever of Unknown Origin

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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.)

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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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