UPSC-CMS 2025 - Microbiology PYQs Practice Questions

Q: Which one of the following is the causative organism of Erythrasma, a mild, localized and superficial skin infection?

Corynebacterium minutissimum. ***Corynebacterium minutissimum*** - This bacterium is the **primary causative agent** of erythrasma, a superficial skin infection. - It produces **porphyrins**, which fluoresce with a characteristic **coral-red color** under a Wood's lamp, aiding in diagnosis. *Corynebacterium matruchotii* - This species is typically found in the **oral cavity** and is associated with dental plaque and periodontal diseases. - It is **not known** to cause erythrasma or superficial skin infections. *Corynebacterium pseudotuberculosis* - This bacterium is a significant pathogen in **animals**, particularly livestock, causing conditions like caseous lymphadenitis. - While it can *rarely* cause infections in humans (e.g., lymphadenitis), it is **not associated** with erythrasma. *Corynebacterium diphtheriae* - This is the causative agent of **diphtheria**, a severe respiratory illness characterized by a pseudomembrane in the throat. - It causes systemic toxemia and is **not responsible** for localized, superficial skin infections like erythrasma. [Practice more Microbiology PYQs on OnCourse]

Q: Which one among the following vectors transmits the filaria *Loa loa*?

Chrysops. ***Chrysops*** - **Deer flies** of the genus *Chrysops* are the **intermediate hosts** for *Loa loa*, transmitting the microfilariae when they bite. - These flies are typically found in the **humid rainforests of West and Central Africa**, where loiasis is endemic. *Cyclops* - *Cyclops* (copepods) are the **intermediate hosts** for **Dracunculus medinensis** (guinea worm) and **Diphyllobothrium latum** (fish tapeworm). - They are **freshwater crustaceans** and not involved in the transmission of filarial worms like *Loa loa*. *Simulium* - *Simulium* (blackflies) are the **vectors** for **Onchocerca volvulus**, which causes **onchocerciasis** (river blindness). - These flies breed in **fast-flowing rivers** and are known for their painful bites. *Culicoides* - *Culicoides* (biting midges) are the **vectors** for **Mansonella perstans** and **Mansonella streptocerca** filarial worms, as well as some viral diseases. - They are distinct from the *Chrysops* flies that transmit *Loa loa*. [Practice more Microbiology PYQs on OnCourse]

Q: Which of the following are the primary organisms involved in PID ? I. N. gonorrhoeae II. Chlamydia III. Mycoplasma hominis IV. Candida albicans Select the correct answer using the code given below :

I, II and III. ***I, II and III*** - **Neisseria gonorrhoeae** and **Chlamydia trachomatis** are the two most common and well-established primary bacterial causes of PID, responsible for the majority of sexually transmitted cases that ascend from the cervix to the upper genital tract. - **Mycoplasma hominis** is frequently isolated in PID cases and is recognized as a significant pathogen contributing to the polymicrobial nature of PID, particularly in cases not solely due to gonorrhea or chlamydia. - These three organisms together represent the primary causative pathogens in acute PID. *II, III and IV* - This option incorrectly omits **Neisseria gonorrhoeae**, which is one of the two most important primary causes of PID. - **Candida albicans** causes vulvovaginal candidiasis but is **not a primary causative agent of PID**, which involves ascending bacterial infection of the upper reproductive tract (endometrium, fallopian tubes, ovaries, and pelvic peritoneum). *I, II and IV* - While **Neisseria gonorrhoeae** and **Chlamydia trachomatis** are correctly identified as major primary causes, **Candida albicans** is not typically involved in PID pathogenesis. - This option incorrectly excludes **Mycoplasma hominis**, which is a recognized pathogen in PID. *I, III and IV* - This option correctly identifies **Neisseria gonorrhoeae** and **Mycoplasma hominis** but incorrectly includes **Candida albicans**, which is not a PID pathogen. - Critically, this omits **Chlamydia trachomatis**, the single most common cause of PID and a leading cause of tubal factor infertility. [Practice more Microbiology PYQs on OnCourse]

Question 1

Which one of the following statements is correct in the diagnosis of Giardiasis?

Accepted Answer

Stool sample at 2-3 days interval should be examined for cysts

Answer

String test is done to find out cysts of Giardia lamblia

Answer

Jejunal biopsy samples can show presence of larvae of Giardia lamblia

Answer

Cystic form of Giardia lamblia remains viable in water upto 1 week only

Question 2

Which one of the following is the causative organism of Erythrasma, a mild, localized and superficial skin infection?

Accepted Answer

Corynebacterium minutissimum

Answer

Corynebacterium matruchotii

Answer

Corynebacterium pseudotuberculosis

Answer

Corynebacterium diphtheriae

Question 3

Which one among the following vectors transmits the filaria *Loa loa*?

Accepted Answer

Chrysops

Answer

Cyclops

Answer

Simulium

Answer

Culicoides

Question 4

Which of the following are the primary organisms involved in PID ?
I. N. gonorrhoeae
II. Chlamydia
III. Mycoplasma hominis
IV. Candida albicans

Select the correct answer using the code given below :

Accepted Answer

I, II and III

Answer

II, III and IV

Answer

I, II and IV

Answer

I, III and IV

UPSC-CMS 2025 — Microbiology