Bacteriology Practice Questions

Q: Waterhouse-Friderichsen syndrome is seen in:

Neisseria meningitidis. ***Neisseria meningitidis*** - **Waterhouse-Friderichsen syndrome** is a severe complication of **meningococcal sepsis**, predominantly caused by *Neisseria meningitidis* [1]. - It is characterized by **adrenal gland hemorrhage**, leading to acute adrenal insufficiency, hemorrhagic skin rash, and shock [1]. *Pseudomonas* - While *Pseudomonas aeruginosa* can cause severe infections, including sepsis, it is **not typically associated** with Waterhouse-Friderichsen syndrome. - *Pseudomonas* infections often lead to **ecthyma gangrenosum** in immunocompromised patients, a different dermatological manifestation. *Yersinia* - *Yersinia* species can cause various infections, such as **yersiniosis** (gastroenteritis) and **plague** (*Yersinia pestis*). - These infections do not commonly present with the distinct features of **adrenal hemorrhage** and **fulminant sepsis** seen in Waterhouse-Friderichsen syndrome. *Pneumococci* - *Streptococcus pneumoniae* (**pneumococci**) is a common cause of **meningitis** and **sepsis**, especially in children and the elderly. - Although it can lead to severe bloodstream infections, it is **rarely specifically linked** to the adrenal hemorrhage syndrome known as Waterhouse-Friderichsen syndrome.

Q: What is the most common cause of Hemolytic Uremic Syndrome (HUS) in children?

E. coli O157:H7. ***E. coli O157:H7*** - This **Shiga toxin-producing E. coli (STEC)** strain is the predominant cause of **diarrhea-associated HUS** in children. - The Shiga toxin damages endothelial cells, leading to **thrombotic microangiopathy**, red blood cell fragmentation, and acute kidney injury. - Accounts for approximately **90% of typical HUS cases** in children. *Salmonella typhi* - This bacterium is primarily responsible for causing **typhoid fever**, a systemic illness characterized by prolonged fever, abdominal pain, and sometimes rash. - While it can cause gastrointestinal symptoms, it is **not a cause of HUS**. *Shigella dysenteriae* - This bacterium causes **shigellosis**, an acute inflammatory colitis characterized by bloody diarrhea. - Although *Shigella dysenteriae* type 1 produces **Shiga toxin** and can cause HUS, it is a **less common cause in most developed countries** compared to *E. coli O157:H7*. - More commonly associated with HUS in developing countries with poor sanitation.

Q: Which of the following is called Preisz-Nocard bacillus?

C. pseudotuberculosis. ***C. pseudotuberculosis*** - This bacterium is historically known as the **Preisz-Nocard bacillus**, named after its discoverers. - It is an important pathogen in animals, causing conditions like **caseous lymphadenitis** in sheep and goats. *C. diphtheriae* - This bacterium causes **diphtheria** and is known for producing a potent **exotoxin** that can lead to systemic complications. - It forms a characteristic **pseudomembrane** in the throat and is not associated with the Preisz-Nocard designation. *M. tuberculosis* - This is the causative agent of **tuberculosis** in humans, primarily affecting the lungs. - It is known for its **acid-fast staining** property and a complex pathogenesis involving granuloma formation. *Mycoplasma* - This genus includes bacteria that lack a **cell wall**, making them resistant to many common antibiotics. - They are known for causing various infections, including **atypical pneumonia** and genitourinary tract infections, but are not referred to as the Preisz-Nocard bacillus.

Q: Which of the following Chlamydia species is primarily associated with respiratory infections?

C pneumoniae. ***C pneumoniae*** - *C. pneumoniae* is the **primary Chlamydia species** associated with **respiratory infections** in humans - It is a common cause of **community-acquired pneumonia** (5-10% of cases), **atypical pneumonia**, **bronchitis**, **pharyngitis**, and **sinusitis** - Transmission occurs via **respiratory droplets** from person to person - Causes both **acute and chronic respiratory infections** and has been linked to exacerbations of asthma and COPD - It is the most frequently encountered Chlamydia species in respiratory tract infections *C psittaci* - Causes **psittacosis** (ornithosis), a specific type of **atypical pneumonia** transmitted from **birds** (parrots, pigeons, poultry) - While it does cause respiratory infection, it is much **less common** than C. pneumoniae and is associated with **occupational or recreational bird exposure** - Not the primary Chlamydia species for general respiratory infections *C trachomatis* - Primarily causes **genital tract infections** (urethritis, cervicitis, PID) and **ocular infections** (trachoma, inclusion conjunctivitis) - Can cause **neonatal pneumonia** in infants exposed during birth, presenting at 1-3 months of age with a staccato cough - NOT a primary respiratory pathogen in adults *None of the options* - This is incorrect because **C. pneumoniae** is definitively the Chlamydia species primarily associated with respiratory infections

Q: Darting motility which occurs in V.cholerae, also found in -

Campylobacter jejuni. ***Campylobacter jejuni*** - *Campylobacter jejuni* is well-known for its **rapid, corkscrew-like motility**, often described as **darting motility**, which is a key characteristic for its identification. - This characteristic movement is due to its **polar flagella** and helps the bacterium penetrate the intestinal mucosa. *Shigella* - *Shigella* species are notable for being **non-motile**, a crucial feature distinguishing them from other enterobacteriaceae. - Their lack of flagella and motility prevents them from exhibiting darting or any other form of self-propulsion. *Bacillus anthracis* - *Bacillus anthracis* is typically described as **non-motile** in its vegetative form. - While other *Bacillus* species can be motile, *B. anthracis* lacks the flagella necessary for darting motility. *Pneumococcus* - *Pneumococcus* (Streptococcus pneumoniae) is a **non-motile** bacterium. - It does not possess flagella and therefore cannot exhibit darting or any other type of active movement.

Q: Which of the following bacteria does not exhibit bipolar staining?

Haemophilus influenzae. ***Haemophilus influenzae*** - *Haemophilus influenzae* is a **pleomorphic coccobacillus** that typically stains uniformly and does not exhibit characteristic **bipolar staining**. - Its presence is often identified by Gram stain showing small, Gram-negative rods, but without the distinctive safety pin appearance. *Calymmatobacterium granulomatis* - *Calymmatobacterium granulomatis* (now *Klebsiella granulomatis*) is known to exhibit **bipolar staining**, often described as a **"safety pin" appearance**, especially in tissue smears from granuloma inguinale lesions. - This characteristic staining is due to the concentration of stain at the ends of the rod-shaped bacteria. *Yersinia pestis* - *Yersinia pestis*, the causative agent of plague, is classically described as having **bipolar staining**, giving it a distinctive **"safety pin" appearance** under a microscope. - This finding is a key diagnostic feature, particularly when observed in Gram-stained smears of clinical samples. *Francisella tularensis* - *Francisella tularensis* is a small, Gram-negative coccobacillus that is known to exhibit **bipolar staining**, though it may be less prominent than in *Yersinia pestis*. - This characteristic can assist in the microscopic identification of the bacterium, which causes tularemia.

Q: Inclusion body containing glycogen is seen in which of the following organisms?

Chlamydia trachomatis. ***Chlamydia trachomatis*** - This species is known to form **intracytoplasmic inclusion bodies** that contain **glycogen**. - The presence of this glycogen allows these inclusions to be stained by **iodine**, aiding in laboratory identification. *Chlamydia pneumoniae* - Inclusion bodies of *Chlamydia pneumoniae* are typically **round or pear-shaped** and **do not contain glycogen**. - They are often **vacuolated** and stain poorly with iodine, unlike those of *C. trachomatis*. *Chlamydia psittaci* - The inclusion bodies of *Chlamydia psittaci* are usually **dense and pleiomorphic**, but they **do not contain glycogen**. - They tend to be **larger** and are often found near the host cell nucleus. *None of the options* - This option is incorrect because *Chlamydia trachomatis* specifically forms **glycogen-containing inclusion bodies**. - The presence of glycogen within inclusions is a key distinguishing feature of this species.

Q: Which is the most common bacterial organism causing bacterial upper respiratory tract infections (including sinusitis, otitis media, and pharyngitis) in adults?

Streptococcus pneumoniae. ***Streptococcus pneumoniae*** - *Streptococcus pneumoniae* is the **most common bacterial pathogen** causing upper respiratory tract infections overall, including **bacterial sinusitis**, **otitis media**, and **community-acquired pneumonia**. - It is a frequent colonizer of the nasopharynx and leads to infection when host immunity is compromised. - Accounts for the highest burden of bacterial URTIs when considering all anatomical sites. *Haemophilus influenzae* - *Haemophilus influenzae* (particularly non-typeable strains) is the **second most common** cause of bacterial sinusitis and otitis media in adults. - While significant, it is less prevalent overall than *S. pneumoniae* across all URTI types. *Staphylococcus aureus* - *Staphylococcus aureus* primarily causes **skin and soft tissue infections** and device-related infections. - It is **not a common primary pathogen** in typical acute bacterial URTIs, though it may cause secondary infections or colonize the anterior nares. *Streptococcus pyogenes* - *Streptococcus pyogenes* (Group A Streptococcus) is the **most common cause of bacterial pharyngitis** (strep throat) in adults. - However, when considering the **full spectrum of bacterial URTIs** (pharyngitis, sinusitis, otitis media), *S. pneumoniae* has a broader overall impact and higher prevalence across multiple sites.

Q: Which of the following is a saccharolytic species of Clostridium?

Clostridium septicum. ***Clostridium septicum*** - *Clostridium septicum* is a **saccharolytic** species, meaning it ferments carbohydrates to produce gas, which contributes to the rapid tissue destruction seen in **gas gangrene**. - Its ability to rapidly consume sugars in tissues fuels its invasive growth and toxin production, which is characteristic of its pathogenic mechanism. *Clostridium tetani* - *Clostridium tetani* is a **proteolytic** species, primarily deriving its energy from **protein degradation**. - It does not ferment carbohydrates, and its pathogenicity is mainly due to the production of **tetanospasmin**, a neurotoxin. *Clostridium cochlearium* - *Clostridium cochlearium* is a **proteolytic** species that metabolizes proteins and amino acids. - It is not known for significant saccharolytic activity and is typically found in environments rich in protein. *None of the options* - This option is incorrect because *Clostridium septicum* is indeed a saccharolytic species, as detailed above.

Q: Which of the following stimulate adenylate cyclase with G-protein coupled action ?

Cholera toxin. ***Cholera toxin*** - Cholera toxin is a **G-protein-activating toxin** that irreversibly activates **adenylate cyclase**. - This leads to increased intracellular levels of **cAMP**, causing excessive fluid secretion into the intestinal lumen and severe diarrhea. *Shiga toxin* - Shiga toxin acts by inactivating the **60S ribosomal subunit**, thereby inhibiting protein synthesis in eukaryotic cells. - Its primary effect is **cytotoxicity**, not direct stimulation of adenylate cyclase. *Diphtheria toxin* - Diphtheria toxin inhibits **protein synthesis** by inactivating **elongation factor-2 (EF-2)** through ADP-ribosylation. - This toxin specifically targets host cells, leading to cellular death and tissue damage. *Pseudomonas toxin* - **Exotoxin A** produced by *Pseudomonas aeruginosa* also inhibits **protein synthesis** by ADP-ribosylating and inactivating **EF-2**, similar to diphtheria toxin. - It does not directly affect adenylate cyclase activity.

Question 1

Waterhouse-Friderichsen syndrome is seen in:

Accepted Answer

Neisseria meningitidis

Answer

Yersinia

Answer

Pseudomonas

Answer

Pneumococci

Question 2

What is the most common cause of Hemolytic Uremic Syndrome (HUS) in children?

Accepted Answer

E. coli O157:H7

Answer

Salmonella typhi

Answer

Shigella dysenteriae

Question 3

Which of the following is called Preisz-Nocard bacillus?

Accepted Answer

C. pseudotuberculosis

Answer

C. diphtheriae

Answer

M. tuberculosis

Answer

Mycoplasma

Question 4

Which of the following Chlamydia species is primarily associated with respiratory infections?

Accepted Answer

C pneumoniae

Answer

C psittaci

Answer

C trachomatis

Answer

None of the options

Question 5

Darting motility which occurs in V.cholerae, also found in -

Accepted Answer

Campylobacter jejuni

Answer

Bacillus anthracis

Answer

Shigella

Answer

Pneumococcus

Question 6

Which of the following bacteria does not exhibit bipolar staining?

Accepted Answer

Haemophilus influenzae

Answer

Yersinia pestis

Answer

Calymmatobacterium granulomatis

Answer

Francisella tularensis

Question 7

Inclusion body containing glycogen is seen in which of the following organisms?

Accepted Answer

Chlamydia trachomatis

Answer

Chlamydia pneumoniae

Answer

Chlamydia psittaci

Answer

None of the options

Question 8

Which is the most common bacterial organism causing bacterial upper respiratory tract infections (including sinusitis, otitis media, and pharyngitis) in adults?

Accepted Answer

Streptococcus pneumoniae

Answer

Staphylococcus aureus

Answer

Haemophilus influenzae

Answer

Streptococcus pyogenes

Question 9

Which of the following is a saccharolytic species of Clostridium?

Accepted Answer

Clostridium septicum

Answer

Clostridium tetani

Answer

Clostridium cochlearium

Answer

None of the options

Question 10

Which of the following stimulate adenylate cyclase with G-protein coupled action ?

Accepted Answer

Cholera toxin

Answer

Shiga toxin

Answer

Diphtheria toxin

Answer

Pseudomonas toxin

Bacteriology — MCQs

Bacteriology — MCQs

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