NEET-PG 2013 - Microbiology Practice Questions

Q: An adult male presents with chronic atrophic gastritis. Growth on Skirrow's medium and a positive rapid urease test were observed. What is the most likely diagnosis?

H. pylori. ***H pylori*** - The combination of **chronic atrophic gastritis**, growth on **Skirrow's medium**, and a **positive rapid urease test** is highly characteristic of *Helicobacter pylori* infection. - *H. pylori* is a known cause of **gastritis**, peptic ulcers, and is the only bacterium that produces large amounts of **urease**, which is detected by the rapid urease test. *H. influenzae* - This bacterium is primarily associated with **respiratory tract infections**, meningitis, and otitis media, not gastric conditions. - It does not typically grow on Skirrow's medium and is not known to produce significant urease for a positive rapid urease test. *K. pneumoniae* - *Klebsiella pneumoniae* is a common cause of **pneumonia**, urinary tract infections, and sepsis, with no direct involvement in chronic atrophic gastritis or urease production in the stomach. - It does not typically grow on selective media like Skirrow's, which is designed for microaerophilic organisms. *V. cholerae* - *Vibrio cholerae* is the causative agent of **cholera**, characterized by severe watery diarrhea, and is not associated with gastric inflammation or positive urease tests in this context. - It grows on specific media like TCBS agar and does not cause chronic atrophic gastritis.

Q: What is the most common cause of a peritonsillar abscess?

Group A beta-hemolytic streptococcus. ***Group A beta-hemolytic streptococcus*** - This bacterium, also known as **_Streptococcus pyogenes_**, is the most common cause of **streptococcal pharyngitis**, which is the precursor to most peritonsillar abscesses. - Peritonsillar abscesses are typically a complication of untreated or inadequately treated **tonsillitis**. *Streptococcus pneumoniae* - While **_Streptococcus pneumoniae_** can cause upper respiratory infections like sinusitis and otitis media, it is not the primary cause of peritonsillar abscesses. - Its infections are more commonly associated with **pneumonia** and **meningitis**. *Staphylococcus aureus* - **_Staphylococcus aureus_** is a common cause of skin and soft tissue infections, but it is less frequently isolated as the primary pathogen in peritonsillar abscesses. - It can be involved in **polymicrobial infections** or as a secondary invader. *H. influenzae* - **_Haemophilus influenzae_** can cause various infections, particularly in children, such as otitis media and epiglottitis. - However, it is not considered the most common cause of **peritonsillar abscesses**.

Q: Which organism causes puerperal sepsis?

Group A beta hemolytic streptococci. ***Group A beta hemolytic streptococci*** - **Group A Streptococcus (GAS)**, specifically *Streptococcus pyogenes*, is the **classic and most important cause of puerperal sepsis** (puerperal fever). - Historically, GAS was responsible for devastating epidemics of puerperal fever in maternity wards before the introduction of antiseptic practices by Ignaz Semmelweis. - GAS causes severe, rapidly progressive postpartum infections with **high morbidity and mortality** if untreated. - Clinically presents with fever, severe uterine tenderness, and can progress to **toxic shock syndrome** and septicemia. *Group B beta hemolytic streptococci* - **Group B Streptococcus (GBS)**, *Streptococcus agalactiae*, can cause postpartum endometritis and maternal infections. - However, GBS is **more commonly associated with neonatal sepsis** rather than being the primary cause of classic puerperal sepsis. - While it can colonize the genital tract and cause infection, it is not the historical or most severe cause of puerperal fever. *CMV* - **Cytomegalovirus (CMV)** is a viral infection that causes congenital infections when transmitted in utero. - It is not a bacterial cause of **puerperal sepsis**, which is primarily a bacterial postpartum infection. *Toxoplasma gondii* - **Toxoplasma gondii** is a parasite causing toxoplasmosis, which can lead to congenital abnormalities. - It is not associated with **puerperal sepsis**, which is a bacterial infection of the postpartum period.

Q: A young sexually active female presents with intense pruritus and watery discharge. What is the most likely causative organism?

Trichomonas vaginalis. ***Trichomonas vaginalis*** - **Trichomoniasis** commonly presents with **intense vulvovaginal pruritus**, a **frothy, greenish-yellow discharge**, and sometimes a **strawberry cervix**. - It is a **sexually transmitted infection (STI)** caused by a flagellated protozoan. *Candida vaginitis* - Typically causes severe **pruritus**, **dysuria**, and a **thick, white, curd-like discharge**, often without the watery characteristic. - Known as a **yeast infection**, it is caused by an overgrowth of *Candida* species. *Gardnerella vaginalis* - Associated with **bacterial vaginosis**, which presents with a **thin, grayish-white discharge** and a **fishy odor**, especially after intercourse, but usually less intense pruritus. - It's characterized by an imbalance of vaginal flora rather than being a true STI in the same sense as trichomoniasis. *Chlamydia trachomatis* - Often causes **asymptomatic infections** or symptoms such as **mucopurulent discharge**, **dysuria**, or **post-coital bleeding**, but usually **not intense pruritus** or watery discharge. - It is a **bacterial STI** known for causing cervicitis and pelvic inflammatory disease.

Q: Dermatophytes affect -

Keratin. ***Keratin*** - **Dermatophytes** are a group of fungi that have a unique ability to digest **keratin**, a protein found in **skin, hair, and nails**. - This characteristic allows them to colonize and thrive in these superficial tissues, causing infections like **tinea corporis** (ringworm) or **tinea pedis** (athlete's foot). *Dermis of skin* - The **dermis** is the layer of skin beneath the epidermis, rich in **collagen, elastin, blood vessels, and nerves**. - Dermatophytes do not typically invade the dermis; their infections are generally limited to the **stratum corneum** and other keratinized structures. *Stratum spongiosum* - **Stratum spongiosum** is a term sometimes used to describe an edematous (swollen) epidermis, often seen in **eczema** and **dermatitis**. - Dermatophytes do not target this specific architectural change in the epidermis but rather feed on the keratin present in the more superficial layers. *Stratum basal* - The **stratum basale** (also called stratum germinativum) is the deepest layer of the **epidermis**, responsible for cell division and producing new skin cells. - Dermatophytes primarily infect the **dead keratinized cells** of the stratum corneum rather than the metabolically active cells of the stratum basale.

Q: Rash is absent in ?

Q. fever. ***Q. fever*** - Q fever, caused by **Coxiella burnetii**, is characterized by **flu-like symptoms**, pneumonia, and hepatitis, but **does not typically present with a rash**. - This differentiates it from other rickettsial infections that commonly involve skin manifestations. *Endemic typhus* - Endemic (murine) typhus, caused by **Rickettsia typhi**, is transmitted by **fleas** and commonly presents with a **maculopapular rash** on the trunk and extremities [2]. - The rash usually appears several days after fever onset [2]. *Epidemic typhus* - Epidemic typhus, caused by **Rickettsia prowazekii** and transmitted by the **human body louse**, classically presents with a **centrifugal rash** that spares the face, palms, and soles [2]. - The rash typically starts on the trunk and spreads outwards [2]. *Scrub typhus* - Scrub typhus, caused by **Orientia tsutsugamushi**, is transmitted by **chiggers** and often features an **eschar** (a necrotic lesion at the bite site) along with a **maculopapular rash** [1]. - The rash may be transient or absent in some cases, but an eschar is a highly characteristic finding [1].

Q: Inactivated SA 14-14-2 vaccine is an example of which type of vaccine?

Live attenuated vaccine. ***Live attenuated vaccine*** - The **SA 14-14-2 vaccine** is a **live attenuated Japanese Encephalitis (JE) vaccine** developed through serial passage and attenuation of the wild-type SA 14 strain. - The designation "14-14-2" refers to the specific **attenuated strain** after multiple passages, not to an inactivation process. - This vaccine uses **weakened (attenuated) virus** that can replicate minimally, providing robust and long-lasting immunity similar to natural infection. - It is widely used in **China, India, and other Asian countries** in national immunization programs. *Inactivated vaccine* - While there is also an **inactivated version** of the SA 14-14-2 strain (vero cell-derived inactivated JE vaccine), the term "SA 14-14-2 vaccine" by itself typically refers to the **live attenuated formulation**. - Inactivated vaccines contain killed viral particles that cannot replicate. *Toxoid vaccine* - **Toxoid vaccines** are based on inactivated bacterial toxins (toxoids), not viral antigens. - Examples include vaccines for **tetanus** and **diphtheria**, which target toxins produced by bacteria. - This type does not apply to viral vaccines like Japanese Encephalitis. *Subunit vaccine* - **Subunit vaccines** contain only specific purified antigenic components (proteins, polysaccharides) rather than whole organisms. - Examples include **Hepatitis B vaccine** (HBsAg) and **HPV vaccine**. - The SA 14-14-2 vaccine uses the whole attenuated virus, not subunits.

Q: The difference between contamination and infection is that in infection

Infectious agent is in the body of human. ***Infectious agent is in the body of human*** - **Infection** implies that microorganisms have successfully **invaded the host tissues** and are replicating within the body, potentially causing a host response or disease. - The presence of the pathogen *inside* the body, beyond just surface adherence, is the defining characteristic of infection. *Arthropods on the body surface* - This describes an **infestation** (e.g., lice, mites), where the arthropods are physically present on the body surface but may not have *invaded* tissues in the same way bacteria or viruses do during an infection. - While some arthropods can transmit infectious agents, their mere presence on the surface is not synonymous with an internal infection. *Infectious agent is on body surface or on non-human objects* - This scenario describes **contamination**, where microorganisms are present on surfaces (either human skin or inanimate objects) but have not yet penetrated or established themselves within host tissues. - Contamination is a potential precursor to infection but is not an infection itself. *Infectious agents on clothes* - This is a clear example of **fomite contamination**, where infectious agents are present on inanimate objects like clothing. - The microorganisms are external to the body and are not causing an infection in the person wearing the clothes unless they are transferred and subsequently invade the host.

Question 1

An adult male presents with chronic atrophic gastritis. Growth on Skirrow's medium and a positive rapid urease test were observed. What is the most likely diagnosis?

Accepted Answer

H. pylori

Answer

V. cholerae

Answer

H. influenzae

Answer

K. pneumoniae

Question 2

What is the most common cause of a peritonsillar abscess?

Accepted Answer

Group A beta-hemolytic streptococcus

Answer

Streptococcus pneumoniae

Answer

Staphylococcus aureus

Answer

H. influenzae

Question 3

Which organism causes puerperal sepsis?

Accepted Answer

Group A beta hemolytic streptococci

Answer

CMV

Answer

Toxoplasma gondii

Answer

Group B beta hemolytic streptococci

Question 4

A young sexually active female presents with intense pruritus and watery discharge. What is the most likely causative organism?

Accepted Answer

Trichomonas vaginalis

Answer

Chlamydia trachomatis

Answer

Candida albicans

Answer

Gardnerella vaginalis

Question 5

Dermatophytes affect -

Accepted Answer

Keratin

Answer

Dermis of skin

Answer

Stratum spongiosum

Answer

Stratum basale

Question 6

Rash is absent in ?

Accepted Answer

Q. fever

Answer

Endemic typhus

Answer

Epidemic typhus

Answer

Scrub typhus

Question 7

Inactivated SA 14-14-2 vaccine is an example of which type of vaccine?

Accepted Answer

Live attenuated vaccine

Answer

Toxoid vaccine

Answer

Inactivated vaccine

Answer

Subunit vaccine

Question 8

The difference between contamination and infection is that in infection

Accepted Answer

Infectious agent is in the body of human

Answer

Infectious agent is on body surface (arthropods)

Answer

Infectious agent is on body surface or on non-human objects

Answer

Infectious agent is on clothes

NEET-PG 2013 — Microbiology