Infectious Diseases Practice Questions

Q: Recrudescences are commonly seen in which type of malaria:

P. falciparum. ***P. falciparum*** - **Recrudescence** refers to the reappearance of malaria symptoms after a period of remission, due to the survival and subsequent increase of asexual parasites in the blood [1]. - This is common in *P. falciparum* due to the high parasite burden and its ability to sequester in deep capillaries, evading splenic clearance and developing drug resistance. *P. vivax* - *P. vivax* is known for **relapses**, which are caused by the activation of dormant liver stages called **hypnozoites**, rather than a recrudescence of blood-stage parasites [1]. - Relapses can occur months or years after the initial infection, even after the blood-stage parasites have been cleared. *P. malariae* - *P. malariae* is uniquely characterized by infections that can persist for many years, even decades, causing symptoms of **recrudescence**, although less frequently than *P. falciparum* [1]. - It has a prolonged erythrocytic cycle, which can lead to chronic low-level parasitemia and sporadic symptomatic episodes. *P. ovale* - Similar to *P. vivax*, *P. ovale* also causes **relapses** due to the presence of **hypnozoites** in the liver [1]. - While it can manifest with symptoms similar to *P. vivax*, it is generally less common and causes milder disease.

Q: Which of the following statements is true regarding amoebic liver abscess?

Mostly involving the right lobe of the liver.. ***Mostly involving the right lobe of the liver*** - The **right lobe** of the liver is the most common site for an amoebic liver abscess due to its larger size and preferential blood flow from the portal venous system, which drains the intestines where *Entamoeba histolytica* resides. - The **superior mesenteric vein**, draining the cecum and ascending colon (common sites for amebiasis), primarily feeds the right hepatic lobe. *May rupture into the pleural cavity* - While rupture can occur, the **peritoneal cavity** is a more common site of rupture for amoebic liver abscesses. - Rupture into the pleural cavity or lung is less frequent but can lead to **empyema** or **bronchopleural fistula** [1]. *For asymptomatic luminal carriers, metronidazole is the drug of choice* - **Metronidazole** is effective against invasive amoebiasis (like liver abscess or dysentery) but is not the drug of choice for asymptomatic luminal carriers. - For **asymptomatic luminal carriers**, **luminal amebicides** such as **paromomycin** or **diloxanide furoate** are used to eradicate cysts from the intestine [1]. *Multiple abscesses is less common than a single abscess* - **A single amoebic liver abscess** is more common than multiple abscesses [1]. - Multiple abscesses are typically seen in disseminated disease or immunocompromised individuals, though even then a solitary lesion is more frequent.

Q: Which of the following statements regarding Pertussis is INCORRECT?

Cerebellar ataxia is a known complication.. ***Cerebellar ataxia is a known complication.*** - **Cerebellar ataxia** is not a typical or known complication of pertussis. Complications usually involve the respiratory, neurological (e.g., seizures, encephalopathy due to hypoxia), and nutritional systems due to severe coughing. - While neurological complications can occur, **ataxia** specifically is not frequently sighted in the context of pertussis. *Some infections may be subclinical.* - Some individuals, especially those partially immunized or older, can experience **subclinical or atypical infections** with pertussis, often presenting as a mild cough. - This characteristic makes it difficult to control the spread of the disease as infected individuals may not be recognized. *The most infective stage is the catarrhal stage.* - The **catarrhal stage**, characterized by non-specific cold-like symptoms, is the most contagious phase because bacterial shedding is highest. - During this stage, symptoms are mild and often indistinguishable from a common cold, leading to widespread transmission before diagnosis. *The drug of choice is Erythromycin.* - **Erythromycin**, or other macrolides like azithromycin or clarithromycin, are the drugs of choice for treating pertussis. - These antibiotics are most effective when administered early in the **catarrhal stage** to reduce disease severity and prevent transmission.

Q: What is the causative agent of trench fever?

Bartonella quintana. ***Bartonella quintana*** - **Trench fever** is a **rickettsial-like illness** primarily transmitted by the human body louse. - The causative agent is the bacterium **Bartonella quintana**, which causes recurrent fever, headache, and body pains. *Q-fever* - Q-fever is caused by the bacterium **Coxiella burnetii** and is typically transmitted through airborne exposure to contaminated aerosols from infected animals. - It presents with fever, headache, and atypical pneumonia, and is not associated with human body lice. *Boutonneuse fever* - This fever is caused by **Rickettsia conorii**, transmitted by the **brown dog tick**. - Characterized by a **maculopapular rash** and an **eschar (tache noire)** at the site of the tick bite. *Indian tick typhus* - This is a form of spotted fever group rickettsiosis caused by **Rickettsia conorii subspecies indica**, transmitted by ticks [1]. - It presents with fever, rash, and an eschar, similar to boutonneuse fever, but is specified for the Indian subcontinent [1].

Q: Most common route of infection in pasteurella cellulitis -

Animal bites or scratches. ***Animal bites or scratches*** - *Pasteurella multocida* is a common commensal bacterium in the oral flora of **cats and dogs**. - **Animal bites or scratches** are the primary mode of transmission for *Pasteurella* infections, particularly cellulitis, due to direct inoculation. *Aerosols or dust* - Transmission via **aerosols or dust** is rare for *Pasteurella* infections, which typically require direct contact or inoculation. - While other bacteria can spread this way, *Pasteurella* cellulitis is not commonly acquired through airborne routes. *Contaminated tissue* - While possible in some contexts, **contaminated tissue** is not the most common route of infection for *Pasteurella* cellulitis. - Direct inoculation from an **animal's oral flora** is far more frequent than contact with contaminated environmental tissues. *Human to human* - *Pasteurella* infections are generally **not transmissible from human to human**. - The organism is primarily associated with animals and their bites or scratches.

Q: What is the most common cause of lung abscess in comatose patients?

Oral anaerobes. Oral anaerobes - **Comatose patients** are at high risk for **aspiration** of oropharyngeal flora, which predominantly consists of anaerobic bacteria. [1] - Aspiration of these organisms, especially in compromised lung tissue, frequently leads to **necrotizing pneumonia** and subsequent abscess formation. [1] *Staph aureus* - While *Staphylococcus aureus* can cause lung abscesses, particularly in the context of **hematogenous spread** (e.g., endocarditis) or nosocomial infections, it is not the most common cause in *comatose patients* who typically aspirate oral flora. [2] - *S. aureus* lung abscesses are often associated with multiple, smaller lesions rather than a single, large abscess from aspiration. *Klebsiella* - *Klebsiella pneumoniae* can cause severe, **rapidly progressive pneumonia** that may lead to abscess formation, especially in individuals with **alcoholism** or **diabetes**. - However, it is less common than oral anaerobes as the primary cause of abscess in the general population of comatose patients, whose main risk factor is aspiration of normal oral flora. [1] *Tuberculosis* - **Mycobacterium tuberculosis** can cause cavitary lung lesions, but these are typically chronic and result from primary or reactivated tuberculosis disease, not acute aspiration. [3] - Lung abscesses caused by tuberculosis are histologically distinct from pyogenic abscesses and are characterized by **granulomatous inflammation** and caseous necrosis.

Q: What is the most common form of leptospirosis?

Anicteric form. ***Anicteric form*** - The **anicteric form** accounts for about 90% of all leptospirosis cases, presenting with milder, flu-like symptoms without jaundice. - Patients typically experience **fever, headache, myalgia**, and conjunctival suffusion during the initial septicemic phase [1], followed by an immune phase that can involve meningitis or uveitis [1]. *Icteric form* - The **icteric form** (Weil's disease) is a severe manifestation, characterized by jaundice, renal failure, and hemorrhage, occurring in a minority of cases (5-10%). - Although more severe and often life-threatening, it is **less common** than the anicteric presentation [1]. *Hepatorenal form* - This term describes the severe complications of leptospirosis, including **liver and kidney dysfunction**, specifically associated with Weil's disease. - While a critical aspect of severe leptospirosis, it is a description of the organ involvement rather than a distinct common form of the disease. *Weil's disease* - **Weil's disease** is the most severe and potentially fatal form of leptospirosis, characterized by **jaundice, renal failure, hemorrhage, and myocarditis**. - It is a severe subset of the icteric form, making it a very serious but **uncommon variant** of the overall disease.

Q: Which of the following statements about gas gangrene is true?

High-dose penicillin is the drug of choice. ***High-dose penicillin is the drug of choice*** - **High-dose penicillin G** is the primary antibiotic therapy for gas gangrene due to the sensitivity of *Clostridium perfringens* to penicillin. - This aggressive antibiotic treatment is crucial in conjunction with surgical debridement to control the rapidly spreading infection. *Most common cause is Staphylococcus aureus* - The most common cause of gas gangrene is **Clostridium perfringens**, not *Staphylococcus aureus*. - *Staphylococcus aureus* is primarily associated with **pyogenic infections**, cellulitis, and abscesses, not gas gangrene. *Causes mild inflammation of muscles* - Gas gangrene causes **severe myonecrosis** (muscle death) and rapid tissue destruction, not mild inflammation. - The infection leads to necrosis, gas formation in tissues, and systemic toxicity. *Clostridium perfringens produces heat-sensitive spores* - *Clostridium perfringens* produces **heat-resistant spores**, which allow it to survive in harsh conditions and contribute to its pervasive nature in the environment. - The spores are resistant to boiling and can survive for extended periods, making sterilization a challenge.

Q: What is the significance of the absence of Vi-antibody in a patient with typhoid fever?

Indicates a favorable prognosis. ***Indicates a favorable prognosis*** - The **Vi (Virulence) antigen** is a **polysaccharide capsule** that helps *Salmonella typhi* evade the immune system and is associated with **virulence** and **carrier state development**. - **Absence of Vi-antibody** indicates infection with a **less virulent strain**, successful **immune clearance**, and **lower likelihood** of developing a chronic carrier state. *Indicates a poor prognosis* - The **absence of Vi-antibody** is actually associated with **better outcomes**, not worse prognosis. - **Poor prognosis** in typhoid fever is typically related to complications like **intestinal perforation** or **septic shock**, not Vi-antibody status [1]. *No impact on prognosis* - **Vi-antibody status** is a **recognized prognostic marker** in typhoid fever and does have clinical significance. - The **presence of Vi-antibodies** may indicate **persistent infection** or **carrier state development**, making it a relevant prognostic indicator. *Suggests a negative response to treatment* - **Absence of Vi-antibody** typically indicates **successful treatment response** and **effective clearance** of the organism. - **Negative treatment response** would be evidenced by **persistent fever**, **positive cultures**, or **clinical deterioration** despite appropriate antibiotic therapy.

Question 1

Recrudescences are commonly seen in which type of malaria:

Accepted Answer

P. falciparum

Answer

P. vivax

Answer

P. malariae

Answer

P. ovale

Question 2

Which of the following statements is true regarding amoebic liver abscess?

Accepted Answer

Mostly involving the right lobe of the liver.

Answer

May rupture into the pleural cavity.

Answer

For asymptomatic luminal carriers, metronidazole is the drug of choice.

Answer

Multiple abscesses is less common than a single abscess.

Question 3

Which of the following statements regarding Pertussis is INCORRECT?

Accepted Answer

Cerebellar ataxia is a known complication.

Answer

The drug of choice is Erythromycin.

Answer

Some infections may be subclinical.

Answer

The most infective stage is the catarrhal stage.

Question 4

What is the causative agent of trench fever?

Accepted Answer

Bartonella quintana

Answer

Q-fever

Answer

Boutonneuse fever

Answer

Indian tick typhus

Question 5

Most common route of infection in pasteurella cellulitis -

Accepted Answer

Animal bites or scratches

Answer

Aerosols or dust

Answer

Contaminated tissue

Answer

Human to human

Question 6

What is the most common cause of lung abscess in comatose patients?

Accepted Answer

Oral anaerobes

Answer

Staph aureus

Answer

Klebsiella

Answer

Tuberculosis

Question 7

What is the most common form of leptospirosis?

Accepted Answer

Anicteric form

Answer

Icteric form

Answer

Hepatorenal form

Answer

Weil's disease

Question 8

Which of the following statements about gas gangrene is true?

Accepted Answer

High-dose penicillin is the drug of choice

Answer

Causes mild inflammation of muscles

Answer

Most common cause is Staphylococcus aureus

Answer

Clostridium perfringens produces heat-sensitive spores

Question 9

What is the significance of the absence of Vi-antibody in a patient with typhoid fever?

Accepted Answer

Indicates a favorable prognosis

Answer

Indicates a poor prognosis

Answer

No impact on prognosis

Answer

Suggests a negative response to treatment

Question 10

Which of the following best defines extensively drug-resistant tuberculosis (XDR TB)?

Accepted Answer

MDR TB with resistance to fluoroquinolone and at least one injectable second-line drug, including Amikacin

Answer

MDR TB with resistance to fluoroquinolone, streptomycin, and at least one injectable second-line drug

Answer

MDR TB with additional resistance to fluoroquinolone and at least one injectable second-line drug

Answer

MDR TB with resistance to fluoroquinolone and Amikacin, but not to other second-line drugs

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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