NEET-PG 2015 Practice Questions

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: Which of the following statements about Legionella is most accurate?

Aerosol inhalation is a common mode of transmission.. ***Aerosol inhalation is a common mode of transmission.*** - **Legionella pneumophila** is primarily transmitted through **inhalation of aerosolized water droplets** containing the bacteria - Common sources include **cooling towers, air conditioning systems, hot tubs, showerheads**, and decorative fountains - This is the **most defining and clinically important characteristic** of Legionella transmission - Understanding aerosol transmission is crucial for **outbreak control and prevention strategies** *There is no human-to-human transmission.* - This statement is **medically accurate** - Legionella does NOT spread from person to person - However, this is a secondary characteristic compared to the primary transmission mode - The question asks for the **most accurate** statement, making aerosol transmission more definitive *Prolonged carriers are common.* - This is **INCORRECT** - Legionella does NOT cause a chronic carrier state in humans - The bacteria **colonizes environmental water systems and amoebae** (like *Acanthamoeba* and *Naegleria*), not human hosts - Humans are accidental hosts through aerosol exposure *All of the options are true* - This is **INCORRECT** because "Prolonged carriers are common" is false - Only two of the three substantive statements are true

Q: Granuloma inguinale is caused by:

Calymmatobacterium granulomatis. ***Calymmatobacterium granulomatis*** - **Granuloma inguinale**, also known as **donovanosis**, is a sexually transmitted infection caused by **_Calymmatobacterium granulomatis_**. - This bacterium is notoriously difficult to culture, so diagnosis is typically made by identifying **Donovan bodies** (macrophages filled with bacteria) in tissue samples. *Haemophilus ducreyi* - **_Haemophilus ducreyi_** is the causative agent of **chancroid**, - Chancroid is characterized by **painful genital ulcers** with a ragged, undermined border, and often accompanied by **tender inguinal lymphadenopathy**. *Chlamydia trachomatis* - **_Chlamydia trachomatis_** is responsible for several conditions, including **chlamydia** (the most common bacterial STI), **lymphogranuloma venereum (LGV)**, and **trachoma**. - LGV presents with a transient, often unnoticed genital lesion followed by painful, suppurative lymphadenopathy, which is distinct from granuloma inguinale. *Treponema pallidum* - **_Treponema pallidum_** is the spirochete that causes **syphilis**, which progresses through several stages. - Primary syphilis manifests as a **painless chancre**, while secondary syphilis can involve a widespread rash, lymphadenopathy, and mucosal lesions.

Q: What is the causative agent of Izumi fever?

Yersinia pseudotuberculosis. ***Yersinia pseudotuberculosis*** - Izumi fever (also called **Far East scarlet-like fever**) is caused by Yersinia pseudotuberculosis, particularly referring to outbreaks that occurred in Japan. - This infection presents with **fever, abdominal pain, and a scarlet fever-like rash**, often mimicking appendicitis due to mesenteric lymphadenitis. - Y. pseudotuberculosis is transmitted through **contaminated food and water**, and the Izumi fever variant is characterized by systemic manifestations including erythema and desquamation. *Yersinia enterocolitica* - While this is a closely related species that also causes **gastroenteritis and mesenteric adenitis**, it is NOT the causative agent of Izumi fever. - Y. enterocolitica typically presents with diarrhea, abdominal pain, and fever, but lacks the distinctive scarlet fever-like rash seen in Izumi fever. *Pseudomonas aeruginosa* - This bacterium is an **opportunistic pathogen** often associated with nosocomial infections, especially in immunocompromised individuals. - It causes **pneumonia**, urinary tract infections, and wound infections, but not Izumi fever. *Pasteurella multocida* - This bacterium is common in the **respiratory tracts of animals**, especially cats and dogs, and is a frequent cause of wound infections from animal bites or scratches. - It typically causes localized cellulitis, abscesses, and occasionally severe infections like meningitis or osteomyelitis, not Izumi fever.

Q: Which of the following statements about the Widal test is true?

The O antigen used in the Widal test is from S. typhi.. ***Correct: The O antigen used in the Widal test is from S. typhi.*** - The Widal test uses **O (somatic) antigens from S. Typhi** to detect anti-O antibodies - It also uses **H (flagellar) antigens from S. Typhi** to detect anti-H antibodies - Additionally, antigens from **S. Paratyphi A and B** are included for comprehensive detection of enteric fever - The statement is correct that O antigen from S. typhi is used (along with antigens from other organisms) *Incorrect: The H-antigen is the most immunogenic.* - The **O antigen** is generally considered more immunogenic than the H antigen in enteric fever - Anti-O antibodies appear earlier and are more specific for acute infection - However, O antibodies disappear faster after recovery *Incorrect: Felix tubes are not used in the Widal test.* - **Dreyer's tubes** (also known as Felix tubes) are traditionally used in the Widal test - These special tubes allow for quantitative antibody titration - They enable observation of agglutination patterns at different serum dilutions *Incorrect: Anti-O antibody persists longer than anti-H antibody.* - This is **backwards** - Anti-H antibodies actually persist longer (can last for years) - **Anti-O antibodies** appear later and disappear relatively quickly after infection resolves - Anti-O antibodies are more indicative of acute/recent infection - Anti-H antibodies are less specific due to their prolonged persistence and possible cross-reactions

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.

Q: What is the clinical significance of the Vi antigen in Salmonella typhi?

Indicates carrier status in individuals. ***Indicates carrier status in individuals*** - The **Vi (Virulence) antigen** is a **capsular polysaccharide** found on *Salmonella typhi* that helps the bacterium evade immune responses - The presence of persistent **anti-Vi antibodies** is the **hallmark of chronic typhoid carriers**, particularly those harboring bacteria in the **gallbladder** - Vi antibody testing is specifically used for **carrier screening** and identification, as carriers maintain high anti-Vi titers even without active symptoms - This is the **primary clinical significance** of the Vi antigen in diagnostic microbiology *Used for diagnosing typhoid fever* - This is **incorrect** - the Vi antigen is NOT used for diagnosing acute typhoid fever - The standard **Widal test** detects antibodies against **O (somatic)** and **H (flagellar)** antigens, NOT Vi antigen - Acute diagnosis relies on **blood culture** and detection of O and H antibodies, not Vi antibodies - Vi antibodies appear later in infection and persist longer, making them markers of **chronic carriage** rather than acute disease *Stimulates an immune response* - While true that Vi antigen stimulates antibody production, this is not its **clinical significance** - All bacterial antigens stimulate immune responses - this doesn't distinguish Vi antigen's specific clinical utility - The key clinical value lies in its use for **carrier detection**, not merely immunogenicity *Not primarily used in Widal test* - This is a **true statement** but not the answer to what the clinical significance IS - The Widal test uses O and H antigens for acute diagnosis - While accurate, this option describes what Vi antigen is NOT used for, rather than its actual clinical significance as a **carrier marker**

Q: Which of the following is a non-motile bacterium?

Clostridium perfringens. ***Clostridium perfringens*** - *Clostridium perfringens* is unique among the *Clostridium* species for being **non-motile**, lacking flagella. - This immotility distinguishes it from other closely related bacteria and is an important characteristic in its identification. *Vibrio* - *Vibrio* species are **highly motile**, possessing a single **polar flagellum** that enables rapid movement in liquid environments. - Their motility is crucial for their survival and pathogenesis, particularly in aquatic habitats and the human intestine. *Legionella* - *Legionella* species, including *Legionella pneumophila*, are **motile** by means of one or more **polar flagella**. - Their motility is important for disseminating within water systems and for infecting macrophages. *Clostridium septicum* - *Clostridium septicum* is a **motile** bacterium, possessing **peritrichous flagella** that allow it to move through tissues. - Its motility contributes to its ability to spread rapidly in infected hosts, often causing severe gas gangrene.

Q: Which of the following is non-motile:

Burkholderia mallei. ***Burkholderia mallei*** - This bacterium is notably **non-motile**, lacking flagella, which is a key characteristic differentiating it from other members of its genus. - It is a **facultative intracellular pathogen** capable of surviving within host cells, primarily causing **glanders** in equids and occasional human infections. - Its immobility is a significant feature in its identification and pathogenesis. *Pseudomonas aeruginosa* - This bacterium is highly **motile** due to the presence of **polar flagella**. - Its motility contributes to its ability to colonize and invade host tissues, common in opportunistic infections. *Burkholderia pseudomallei* - This species is known to be **motile** by means of flagella, which aids its survival and dissemination in diverse environments and within a host. - It is the causative agent of **melioidosis**, a severe infectious disease. *None of the options* - This option is incorrect because **Burkholderia mallei** is indeed non-motile, making it a correct choice among the provided options. - The other specified bacteria, *Pseudomonas aeruginosa* and *Burkholderia pseudomallei*, are motile.

Q: Which tumor is characterized by the presence of cells that resemble tennis rackets?

Langerhans cell histiocytosis. ***Langerhans cell histiocytosis*** - This condition is characterized by **Birbeck granules** within the Langerhans cells, which have a distinctive **tennis racket-like appearance** on electron microscopy. - The cells are also positive for **CD1a** and **S-100** immunohistochemical markers. *Sarcoma botyroides* - This is a subtype of **embryonal rhabdomyosarcoma** typically found in mucosal sites, presenting as a polypoid, grape-like mass. - Its histology shows small, undifferentiated cells with primitive skeletal muscle differentiation, but **not tennis racket-shaped cells**. *Vaginal adenocarcinoma* - This is a rare malignancy of the vagina, often associated with **diethylstilbestrol (DES) exposure** in utero, presenting as glands. - The cells show glandular differentiation and produce mucin, but **lack Birbeck granules**. *Seminoma* - This is a germ cell tumor of the testis characterized by large, uniform cells with clear cytoplasm and prominent nucleoli, divided into lobules by fibrous septa containing lymphocytes. - There are **no tennis racket-shaped cells** or Birbeck granules associated with seminoma.

Question 1

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 2

Which of the following statements about Legionella is most accurate?

Accepted Answer

Aerosol inhalation is a common mode of transmission.

Answer

Prolonged carriers are common.

Answer

There is no human-to-human transmission.

Answer

All of the options are true

Question 3

Granuloma inguinale is caused by:

Accepted Answer

Calymmatobacterium granulomatis

Answer

Haemophilus ducreyi

Answer

Chlamydia trachomatis

Answer

Treponema pallidum

Question 4

What is the causative agent of Izumi fever?

Accepted Answer

Yersinia pseudotuberculosis

Answer

Yersinia enterocolitica

Answer

Pseudomonas aeruginosa

Answer

Pasteurella multocida

Question 5

Which of the following statements about the Widal test is true?

Accepted Answer

The O antigen used in the Widal test is from S. typhi.

Answer

The H-antigen is the most immunogenic.

Answer

Felix tubes are not used in the Widal test.

Answer

Anti-O antibody persists longer than anti-H antibody.

Question 6

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 7

What is the clinical significance of the Vi antigen in Salmonella typhi?

Accepted Answer

Indicates carrier status in individuals

Answer

Stimulates an immune response

Answer

Not primarily used in Widal test

Answer

Used for diagnosing typhoid fever

Question 8

Which of the following is a non-motile bacterium?

Accepted Answer

Clostridium perfringens

Answer

Vibrio

Answer

Legionella

Answer

Clostridium septicum

Question 9

Which of the following is non-motile:

Accepted Answer

Burkholderia mallei

Answer

Pseudomonas aeruginosa

Answer

Burkholderia pseudomallei

Answer

None of the options

Question 10

Which tumor is characterized by the presence of cells that resemble tennis rackets?

Accepted Answer

Langerhans cell histiocytosis

Answer

Seminoma

Answer

Vaginal adenocarcinoma

Answer

Sarcoma botyroides

NEET-PG 2015

Microbiology

Pathology