NEET-PG 2021 - Microbiology Practice Questions

Q: A male patient presents with white discharge from the urethra, as shown in the image. What is the most probable causative organism?

Neisseria gonorrhoeae. ***Neisseria gonorrhoeae*** - Among the given options, *Neisseria gonorrhoeae* is the **most probable causative organism** for **urethral discharge** in males. - Gonorrhea is a common sexually transmitted infection (STI) presenting with **purulent urethritis**, typically with thick, yellow-green discharge, though appearance can vary. - **Clinical note:** While classic gonococcal discharge is purulent and yellow-green, the clinical presentation can vary. None of the other organisms listed cause urethritis with discharge. *Haemophilus ducreyi* - This bacterium causes **chancroid**, a sexually transmitted infection characterized by **painful genital ulcers (chancres)** and **inguinal lymphadenopathy**, not urethral discharge. - Presents with ulcerative lesions, not discharge. *Klebsiella granulomatis* - This organism is responsible for **donovanosis** (granuloma inguinale), which manifests as **painless, progressive ulcerative lesions** on the genitals. - It does not cause urethral discharge; presents with beefy red granulomatous lesions. *Treponema pallidum* - This spirochete causes **syphilis**, which presents with **painless chancres** in the primary stage, **maculopapular rash** in the secondary stage, and gummas or neurological symptoms in later stages. - Urethral discharge is not a typical symptom of syphilis; primary lesions are ulcerative.

Q: A hair perforation test was performed on a yeast isolate, and the result was positive. Which of the following organisms is associated with a positive hair perforation test?

Candida albicans. ***Candida albicans*** - The **hair perforation test** is a classic diagnostic test specifically used to identify *Candida albicans*, which characteristically produces **conical projections** when incubated with sterilized blonde hair in water at room temperature. - This test has historically been used as a simple, rapid method for **presumptive identification** of *C. albicans* from other Candida species, indicating the organism's ability to produce **keratinolytic enzymes**. *Candida tropicalis* - *Candida tropicalis* gives a **negative hair perforation test** and does not produce the characteristic hair perforations seen with *C. albicans*. - While it can form **pseudohyphae** and true hyphae, it can be differentiated from *C. albicans* using this test among others. *Candida glabrata* - *Candida glabrata* does **NOT** produce a positive hair perforation test and typically remains in **yeast form**. - It is distinguished from other Candida species by its **smaller cell size** and inability to form germ tubes or hair perforations. *Candida parapsilosis* - *Candida parapsilosis* also gives a **negative hair perforation test** and does not produce hair perforations. - This species can form **pseudohyphae** but the hair perforation test helps distinguish it from *C. albicans*.

Question 1

A male patient presents with white discharge from the urethra, as shown in the image. What is the most probable causative organism?

Accepted Answer

Neisseria gonorrhoeae

Answer

Haemophilus ducreyi

Answer

Klebsiella granulomatis

Answer

Treponema pallidum

Question 2

A hair perforation test was performed on a yeast isolate, and the result was positive. Which of the following organisms is associated with a positive hair perforation test?

Accepted Answer

Candida albicans

Answer

Candida tropicalis

Answer

Candida glabrata

Answer

Candida parapsilosis

NEET-PG 2021 — Microbiology