NEET-PG 2015 - Microbiology Practice Questions

Q: Bartonella quintana causes:

Trench fever. ***Trench fever*** - **Bartonella quintana** is the causative agent of **trench fever**, a louse-borne disease historically common during wartime. - Symptoms include **recurrent fevers**, headache, bone pain (especially in the shins), and rash. *Scrub typhus* - Scrub typhus is caused by **Orientia tsutsugamushi**, a rickettsial bacterium, not Bartonella. - It is transmitted by **chiggers** and characterized by a rash, fever, and eschar at the bite site. *Epidemic typhus* - Epidemic typhus is caused by **Rickettsia prowazekii** and is also louse-borne. - It presents with sudden high fever, severe headache, and a maculopapular rash that spares the face, palms, and soles. *Endemic typhus* - Endemic typhus (murine typhus) is caused by **Rickettsia typhi** and is transmitted by **rat fleas**. - Its symptoms are generally milder than epidemic typhus, including fever, headache, and a truncal rash.

Q: Granulomatosis infantiseptica is caused by:

Listeria. ***Listeria*** - **Granulomatosis infantiseptica** is a severe manifestation of congenital **listeriosis**, caused by *Listeria monocytogenes*. - This condition is characterized by widespread **granulomas** and **microabscesses** in various organs of the infected newborn. *Pseudomonas* - *Pseudomonas aeruginosa* is a common cause of healthcare-associated infections but is not typically associated with **granulomatosis infantiseptica**. - It can cause severe infections in immunocompromised individuals, including **pneumonia**, **sepsis**, and wound infections. *Chlamydia trachomatis* - *Chlamydia trachomatis* is a common cause of **conjunctivitis** and **pneumonia** in neonates, acquired during passage through the birth canal. - It does not cause **granulomatosis infantiseptica**. *Group D streptococci* - While Group D streptococci (e.g., *Enterococcus faecalis*) can cause neonatal infections like **sepsis** and **meningitis**, they are not the causative agents of **granulomatosis infantiseptica**. - This condition is specifically linked to **Listeria**.

Q: Which type of DNase produced by Streptococcus is known to be the most antigenic in humans?

DNase B. ***DNase B*** - **DNase B** is the most **antigenic** of the four DNases (A, B, C, D) produced by *Streptococcus pyogenes*. - Antibodies against DNase B are commonly measured as anti-DNase B titers in the diagnosis of **streptococcal infections** and their sequelae, like **acute rheumatic fever** and **post-streptococcal glomerulonephritis**, especially when ASO titers are negative. *DNase A* - While *Streptococcus pyogenes* produces **DNase A**, it is not considered the most antigenically potent or clinically relevant for antibody testing in humans. - Its antigenicity is generally **lower** than that of DNase B in response to streptococcal infection. *DNase C* - **DNase C** is another deoxyribonuclease produced by *Streptococcus pyogenes*. - Similar to DNase A, it does not elicit as strong or as consistent an **antibody response** in human infections compared to DNase B. *DNase D* - **DNase D** is the fourth type of deoxyribonuclease produced by *Streptococcus pyogenes*. - Its **antigenicity** in humans is less pronounced and less diagnostically significant than that of **DNase B**.

Q: Proteus isolated from a patient of UTI will show which biochemical reaction.

Production of phenylpyruvic acid from phenylalanine. ***Production of phenylpyruvic acid from phenylalanine*** - *Proteus* species possess the enzyme **phenylalanine deaminase**, which deaminates phenylalanine to **phenylpyruvic acid**. - This reaction is a **key biochemical test** used to identify *Proteus*, *Providencia*, and *Morganella* species. *Hydrolysis of esculin in bile* - This reaction is characteristic of **Group D streptococci** and **enterococci**, not *Proteus* species. - The organism hydrolyzes **esculin** in the presence of bile, turning the agar black. *Sensitivity to colchicine* - **Colchicine** is an anti-inflammatory drug, not part of standard **biochemical identification tests** for bacteria. - This is not a recognized biochemical reaction used to identify *Proteus* or any bacterial species. *Sensitivity to bacitracin* - **Bacitracin sensitivity** is primarily used to differentiate **Group A streptococci** (e.g., *Streptococcus pyogenes*) from other beta-hemolytic streptococci. - It is an **antibiotic susceptibility test**, not a biochemical reaction characteristic of *Proteus* species.

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: What is the most sensitive test for diagnosing syphilis?

FTA-ABS. ***FTA-ABS*** - The **fluorescent treponemal antibody absorption (FTA-ABS)** test is a treponemal test that is highly sensitive (>95%) and specific for detecting antibodies to *Treponema pallidum*. - It was traditionally considered the gold standard confirmatory test and is often used to confirm positive screening results. - It detects antibodies early in infection and remains positive for life, even after successful treatment. - **Note:** Modern treponemal tests like TP-PA have comparable sensitivity, but FTA-ABS remains widely recognized in clinical practice. *VDRL* - The **Venereal Disease Research Laboratory (VDRL)** test is a non-treponemal test that measures antibodies to cardiolipin, a lipid released from damaged host cells and *T. pallidum*. - While useful for screening and monitoring treatment response (titers decrease with successful treatment), it is less sensitive than treponemal tests, especially in early primary and late/tertiary syphilis. - Can yield false positives in various conditions (pregnancy, autoimmune diseases, infections). *TP-PA* - The **Treponema pallidum particle agglutination (TP-PA)** test is a highly sensitive and specific treponemal test that detects antibodies to *T. pallidum*. - It has sensitivity comparable to FTA-ABS (>95%) and is increasingly preferred in modern laboratories due to easier performance and objective reading. - Like other treponemal tests, it remains positive for life. *RPR* - The **rapid plasma reagin (RPR)** test is a non-treponemal test similar to VDRL, detecting antibodies to cardiolipin. - It is commonly used for screening due to ease of use and ability to monitor treatment response through quantitative titers. - Like VDRL, it has lower sensitivity compared to treponemal tests and can produce false positives.

Q: Most common site for Staphylococcus carriage?

Nose. ***Nose*** - The **anterior nares** are the most common site for **Staphylococcus aureus** colonization in healthy individuals. - Nasal carriage is a significant risk factor for subsequent **Staphylococcus aureus infections**, both self-acquired and transmitted to others. *Skin* - While Staphylococcus aureus can colonize the skin, especially in areas like the axillae and groin, it is **less common** as a primary carrier site compared to the nose. - Skin colonization often occurs due to spread from **nasal carriage**. *Oropharynx* - The oropharynx can be colonized by various bacteria, but it is **not the primary or most common site** for Staphylococcus aureus carriage. - Other bacteria like **Streptococcus species** are more prevalent colonizers of the oropharynx. *Perineum* - The perineum can harbor Staphylococcus aureus, particularly in specific populations or in individuals with certain skin conditions, but it is **not the most common or primary site** of colonization. - Colonization here is often **secondary** to nasal carriage or contact with contaminated surfaces.

Q: All are true about anaerobic infections except:

Exudates and swabs are ideal for culture. ***Exudates and swabs are ideal for culture.*** - **Swabs exposed to air** are generally **not ideal** for anaerobic culture because oxygen exposure can kill obligate anaerobes, leading to false-negative results. - Optimal anaerobic specimen collection requires techniques that **minimize oxygen exposure**, such as aspirates or tissue biopsies placed in anaerobic transport media. *Most infections are endogenous* - Anaerobic infections commonly arise from **one's own commensal flora**, which becomes pathogenic under specific conditions like tissue damage or impaired blood supply. - These bacteria are part of the normal microbiota of various body sites, including the gastrointestinal tract, oral cavity, and skin. *Specimen for UTI is suprapubic aspiration* - For **suspected anaerobic urinary tract infections (UTIs)**, suprapubic aspiration is considered the gold standard for specimen collection. - This method bypasses potential contamination from urethral flora and ensures a sterile, oxygen-free sample for accurate anaerobic culture. *They are found normally on skin and GIT* - **Anaerobic bacteria** are a significant component of the normal flora of the **skin and gastrointestinal tract (GIT)**, as well as the oral cavity and genitourinary tract. - Their presence in these sites is crucial for maintaining normal physiological functions and preventing the overgrowth of pathogens.

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

Question 1

Bartonella quintana causes:

Accepted Answer

Trench fever

Answer

Scrub typhus

Answer

Epidemic typhus

Answer

Endemic typhus

Question 2

Granulomatosis infantiseptica is caused by:

Accepted Answer

Listeria

Answer

Pseudomonas

Answer

Chlamydia trachomatis

Answer

Group D streptococci

Question 3

Which type of DNase produced by Streptococcus is known to be the most antigenic in humans?

Accepted Answer

DNase B

Answer

DNase C

Answer

DNase D

Answer

DNase A

Question 4

Proteus isolated from a patient of UTI will show which biochemical reaction.

Accepted Answer

Production of phenylpyruvic acid from phenylalanine

Answer

Hydrolysis of esculin in bile

Answer

Sensitivity to colchicine

Answer

Sensitivity to bacitracin

Question 5

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 6

What is the most sensitive test for diagnosing syphilis?

Accepted Answer

FTA-ABS

Answer

VDRL

Answer

RPR

Answer

TP-PA

Question 7

Most common site for Staphylococcus carriage?

Accepted Answer

Nose

Answer

Skin

Answer

Oropharynx

Answer

Perineum

Question 8

All are true about anaerobic infections except:

Accepted Answer

Exudates and swabs are ideal for culture

Answer

Specimen for UTI is suprapubic aspiration

Answer

They are found normally on skin and GIT

Answer

Most infections are endogenous

Question 9

What is the causative agent of Izumi fever?

Accepted Answer

Yersinia pseudotuberculosis

Answer

Yersinia enterocolitica

Answer

Pseudomonas aeruginosa

Answer

Pasteurella multocida

Question 10

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.

NEET-PG 2015 — Microbiology