NEET-PG 2017 - Microbiology PYQs Practice Questions

Q: All are true about Helicobacter pylori on special stain preparation of stomach except:

S shaped non-flagellated bacteria. ***S shaped non-flagellated bacteria*** - *H. pylori* are generally **spiral-shaped** or **curved rods**, not typically S-shaped, and are characterized by their **polar flagella** which are essential for their motility in the viscous gastric mucus. - The presence of flagella is a key feature distinguishing *H. pylori* and enabling its survival in the stomach environment. *Steiner stain preparation* - The **Steiner silver stain** is commonly used to visualize *H. pylori* in gastric biopsies, demonstrating them as dark, helical organisms. - While effective, other stains like Giemsa or Warthin-Starry are also used, but Steiner stain is a valid method for detection. *Dormant stage is coccoid form* - Under stressful conditions, such as antibiotic exposure or prolonged culture, *H. pylori* can transform into a **coccoid form**. - This coccoid form is considered a **viable but non-culturable** dormant stage, potentially contributing to persistence and recurrence of infection. *Attaches but does not invade the cells* - *H. pylori* colonizes the **mucus layer** and attaches to the apical surface of gastric epithelial cells but generally **does not invade** the cells. - Its effects are mediated by toxins and enzymes released into the extracellular space, leading to inflammation and cellular damage without direct intracellular invasion. [Practice more Microbiology PYQs on OnCourse]

Q: All are true about bacteria shown in the smear of pus below, except:

Most strains are inhibited in presence of 5 % NaCl. The image shows **Gram-positive cocci** arranged in clusters, which is characteristic of *Staphylococcus aureus*. Many pus cells (neutrophils) are also seen, indicating an inflammatory response, consistent with a bacterial infection. ***Most strains are inhibited in presence of 5 % NaCl*** - *Staphylococcus aureus* is known to be **halophilic**, meaning it **grows well** in the presence of high salt concentrations (e.g., 7.5% NaCl), which distinguishes it from many other bacteria. - Therefore, the statement that it is 'inhibited in the presence of 5% NaCl' is **incorrect**. *Produce black colonies on potassium tellurite blood agar* - *Staphylococcus aureus* **reduces tellurite** to metallic tellurium, resulting in the production of **black colonies** on potassium tellurite blood agar. - This is a characteristic feature used in the identification of *Staphylococcus aureus*, particularly on media like Baird-Parker agar. *Liquefy gelatin* - *Staphylococcus aureus* produces the enzyme **gelatinase**, which **hydrolyzes gelatin**, causing it to liquefy. - This is a biochemical characteristic used to differentiate *Staphylococcus aureus* from certain other staphylococcal species. *Seen in Job syndrome* - **Job syndrome** (Hyper-IgE syndrome) is characterized by recurrent severe **Staphylococcal infections** of the skin and lungs. - Patients with Job syndrome have impaired neutrophil chemotaxis and elevated IgE levels, making them highly susceptible to *Staphylococcus aureus* infections. [Practice more Microbiology PYQs on OnCourse]

Q: All are true about the bacteria shown in the figure except:

Urease positive. ***Urease positive*** - The image depicts **Corynebacterium diphtheriae**, characterized by **metachromatic granules** and its bacillary (rod) shape, often showing V or L formations. - *Corynebacterium diphtheriae* is **urease negative**, not positive, making this statement false and the correct answer to this "except" question. *Pyrazinamidase test positive* - *Corynebacterium diphtheriae* is **pyrazinamidase positive**, an important biochemical characteristic used in its identification. - This enzyme activity distinguishes it from other *Corynebacterium* species like *C. pseudodiphtheriticum* and *C. ulcerans*. *C. gravis has daisy head colony* - The **mitis** and **gravis** biotypes are distinct strains of *Corynebacterium diphtheriae*, with *C. gravis* characterized by its distinctive **"daisy head" colony morphology** on tellurite medium. - This irregular growth pattern is a known characteristic feature of *C. diphtheriae* biotype gravis. *Heat labile toxin has affinity for myocardium* - The **diphtheria toxin** produced by *C. diphtheriae* is indeed **heat-labile** and has strong affinity for various tissues, particularly the **myocardium** and nerve cells. - This tissue affinity leads to serious complications such as **myocarditis** and neurological deficits in diphtheria patients. [Practice more Microbiology PYQs on OnCourse]

Q: All of the following are caused by the organism shown except:

Meningitis. ***Meningitis*** - The image shows **Gram-positive rods** with **spores**, characteristic of *Clostridium perfringens*. - *Clostridium perfringens* is **not a recognized cause of meningitis** in standard clinical practice. - While clostridial infections can occur in various body sites, meningitis is not among the typical clinical presentations of *C. perfringens*. - CNS infections by anaerobes typically involve other organisms like *Bacteroides* species or *Clostridium* species other than *C. perfringens*. *Hemorrhagic diarrhea* - *Clostridium perfringens* Type C causes **necrotizing enteritis (pigbel disease)** characterized by **hemorrhagic diarrhea**, particularly in areas with poor sanitation. - *C. perfringens* Type A causes **food poisoning** with watery diarrhea and abdominal cramps. - Enteritis necroticans presents with severe abdominal pain, bloody diarrhea, and can be fatal. *Pneumonia* - *Clostridium perfringens* can rarely cause **necrotizing pneumonia**, usually following aspiration or in immunocompromised patients. - This presents with rapid tissue destruction and gas formation in lung tissue. *Myonecrosis* - *Clostridium perfringens* is the **most common cause** of **gas gangrene** or **clostridial myonecrosis**. - Characterized by rapid muscle destruction due to **alpha-toxin** (lecithinase), producing gas in tissues and causing severe systemic toxicity. [Practice more Microbiology PYQs on OnCourse]

Q: What is the drug of choice for organism producing the following colonies?

Ciprofloxacin. ***Ciprofloxacin*** - The image displays characteristic **"Medusa head" colonies**, which are pathognomonic for *Bacillus anthracis* (anthrax). - **Ciprofloxacin** is a fluoroquinolone and is the **first-line drug of choice** for *Bacillus anthracis* infections (treatment and prophylaxis). - Other first-line options include **doxycycline**, and combination therapy is often used for systemic/inhalational anthrax. - Early antibiotic therapy significantly reduces mortality, though delayed treatment in inhalational anthrax carries high mortality risk. *Erythromycin* - Erythromycin is a **macrolide antibiotic** that is **not recommended** for *Bacillus anthracis* infections. - It has lower efficacy and is not considered effective against anthrax, especially in severe systemic forms. *Ceftriaxone* - Ceftriaxone is a **third-generation cephalosporin** that is **not recommended** for anthrax. - *Bacillus anthracis* produces **beta-lactamase enzymes** that confer resistance to many beta-lactam antibiotics. - Therefore, ceftriaxone would be ineffective as monotherapy. *No treatment with approx. 100% mortality* - This is **incorrect** as a treatment option since effective antibiotics are available. - While untreated inhalational anthrax has very high mortality (approaching 90-100%), **treatment exists and is effective**, especially when initiated early. - The drug of choice for anthrax is ciprofloxacin (or doxycycline), not "no treatment." [Practice more Microbiology PYQs on OnCourse]

Question 1

All are true about Helicobacter pylori on special stain preparation of stomach except:

Accepted Answer

S shaped non-flagellated bacteria

Answer

Steiner stain preparation

Answer

Dormant stage is coccoid form

Answer

Attaches but does not invade the cells

Question 2

All are true about bacteria shown in the smear of pus below, except:

Accepted Answer

Most strains are inhibited in presence of 5 % NaCl

Answer

Produce black colonies on potassium tellurite blood agar

Answer

Liquefy gelatin

Answer

Seen in Job syndrome

Question 3

All are true about the bacteria shown in the figure except:

Accepted Answer

Urease positive

Answer

Pyrazinamidase test positive

Answer

C. gravis has daisy head colony

Answer

Heat labile toxin has affinity for myocardium

Question 4

All of the following are caused by the organism shown except:

Accepted Answer

Meningitis

Answer

Pneumonia

Answer

Hemorrhagic diarrhea

Answer

Myonecrosis

Question 5

What is the drug of choice for organism producing the following colonies?

Accepted Answer

Ciprofloxacin

Answer

Erythromycin

Answer

Ceftriaxone

Answer

No treatment with approx. 100% mortality

Question 6

What is the following pattern seen with *Clostridium perfringens* called?

Accepted Answer

Nagler's reaction

Answer

Reverse CAMP test

Answer

Stormy clot reaction

Answer

CAMP test

Question 7

Which of the bacteria is shown in this culture plate of nutrient agar? (Recent NEET Pattern 2016-17)

Accepted Answer

Pseudomonas

Answer

Plesiomonas

Answer

Burkholderia

Answer

Pasteurella

Question 8

The following plate shows *H. influenzae* colonies. Which of the following is responsible for the phenomenon shown? (Recent NEET Pattern 2016-17)

Accepted Answer

V factor

Answer

X factor

Answer

All of the above

Answer

PRP antigen

Question 9

All are true about the organism whose colonies are shown below except:

Accepted Answer

Warm agglutinin production

Answer

Mulberry shaped colony

Answer

Lack cell wall

Answer

Divide by binary fission

Question 10

A 35-year-old patient presents to the OPD 24 hours after a fight with a stranger in which he was bitten. GCS is 15/15 and following injury is noted on left forearm. He complains of extreme pain and tenderness in the injury. Swab from the injury was plated in chocolate agar and incubated in 10% carbon dioxide for 48 hours. Small colonies with pitting appearance were noted. Which of the following organism is responsible?

Accepted Answer

Eikenella corrodens

Answer

Flavobacterium meningosepticum

Answer

Capnocytophaga gingivalis

Answer

Streptobacillus moniliformis

NEET-PG 2017 — Microbiology