NEET-PG 2019 - Microbiology Practice Questions

Q: Identify the parasite shown in the image.

Sarcoptes scabiei. ***Sarcoptes scabiei*** - The image displayed is a characteristic microscopic view of **_Sarcoptes scabiei_**, the mite responsible for scabies. Key features include its **round to oval body** shape and the presence of **spines and setae** on its dorsal surface, which are visible. - The short, stubby legs with prominent suckers are consistent with the morphology used for burrowing into the skin. *Pediculus humanus capitis* - This parasite, the **head louse**, has a more **elongated body** shape and distinct legs with claws adapted for gripping hair shafts, which is not what is seen in the image. - Head lice are typically found on the scalp and attach nits (eggs) to hair, unlike the burrowing nature of the organism shown. *Pthirus Pubis* - **_Pthirus pubis_**, or the **pubic louse** (crab louse), has a distinctly **crab-like appearance** with broad bodies and large, clawed legs, especially the second and third pairs, which is not consistent with the image. - These lice typically infest coarse body hair, such as pubic hair, eyelashes, and eyebrows. *Dermatobia hominis* - **_Dermatobia hominis_** is the **human botfly**, and its larval stage (maggot) causes **cutaneous myiasis**. The image does not show a maggot-like larva but rather a microscopic mite. - The morphology of a botfly larva is worm-like and segmented, featuring prominent spines for anchoring within the host's skin.

Q: The following culture medium is used for the isolation of: (NEET Pattern 2019)

Legionella. ***Legionella*** - The image displays growth on **buffered charcoal yeast extract (BCYE) agar**, which is the selective medium for the isolation of *Legionella* species. - *Legionella* requires **L-cysteine** and **iron salts** for growth, which are provided in BCYE agar, making it distinctively well-suited for its isolation. *Listeria* - *Listeria* species are typically isolated on selective media such as Oxford agar or PALCAM agar, which contain **antibiotics** and **chromogenic substrates** to differentiate them from other bacteria. - While *Listeria* can grow on general purpose media, BCYE agar is not the primary selective medium for its isolation. *Escherichia* - **Escherichia coli** is a common fecal coliform that grows readily on various non-selective media like blood agar and selective/differential media such as MacConkey agar (lactose fermenter with pink colonies) or eosin methylene blue (EMB) agar (green metallic sheen colonies). - BCYE agar is not a standard medium for *Escherichia* isolation, as it lacks the necessary components for its optimal differentiation and growth. *Campylobacter* - **Campylobacter** species are **microaerophilic** and require specialized selective media like **Campy-BAP (Campylobacter Blood Agar Plate)**, Skirrow's medium, or CCDA (cefoperazone charcoal deoxycholate agar). - These media contain antibiotics to inhibit normal flora and are incubated in a microaerophilic atmosphere; BCYE agar is not used for *Campylobacter* isolation.

Q: CSF gram stain of a child suffering with meningitis is shown below. What is the causative agent? (NEET Pattern 2019)

H. influenzae. ***H. Influenzae*** - The image shows **Gram-negative rods or coccobacillary forms**, which are characteristic of *Haemophilus influenzae*. - *H. influenzae* is a common cause of **bacterial meningitis** in children, particularly before the widespread use of vaccines. *Streptococcus pneumoniae* - This bacterium would appear as **Gram-positive cocci** in pairs or short chains, which is not consistent with the image. - *Streptococcus pneumoniae* is also a common cause of meningitis but has a distinct morphological appearance. *Klebsiella pneumonia* - While *Klebsiella pneumoniae* is a Gram-negative rod, it is typically a larger, more plump rod, and less commonly a cause of **pediatric meningitis** compared to *H. influenzae*. - The morphology in the image, particularly the coccobacillary appearance, is more typical of *Haemophilus*. *Staphylococcus aureus* - This bacterium would appear as **Gram-positive cocci** in grape-like clusters, which clearly differs from the Gram-negative rods/coccobacillary forms seen in the image. - *Staphylococcus aureus* can cause meningitis, especially in cases of head trauma or neurosurgery, but its morphology is distinct.

Question 1

Identify the parasite shown in the image.

Accepted Answer

Sarcoptes scabiei

Answer

Pediculus humanus capitis

Answer

Pthirus pubis

Answer

Dermatobia hominis

Question 2

The following culture medium is used for the isolation of: (NEET Pattern 2019)

Accepted Answer

Legionella

Answer

Listeria

Answer

Escherichia

Answer

Campylobacter

Question 3

CSF gram stain of a child suffering with meningitis is shown below. What is the causative agent? (NEET Pattern 2019)

Accepted Answer

H. influenzae

Answer

Streptococcus pneumoniae

Answer

Klebsiella pneumoniae

Answer

Staphylococcus aureus

NEET-PG 2019 — Microbiology