Bacteriology Practice Questions

Q: A 35 year old man presents to an emergency department with an exquisitely tender prostate gland. An acute bacterial infection is suspected. Which of the following organisms is the most common pathogen in this setting?

Escherichia. ***Escherichia*** - **_Escherichia coli_** is the most common Gram-negative bacillus responsible for both acute and chronic bacterial prostatitis due to its prevalence in the normal gut flora and its ability to ascend the urinary tract. - It accounts for approximately **80% of all acute bacterial prostatitis cases** because of its uropathogenic factors like fimbriae that allow adherence to urinary epithelial cells. *Enterobacter* - While **_Enterobacter_ species** can cause urinary tract infections and prostatitis, they are significantly less common than _E. coli_. - Prostatitis due to _Enterobacter_ often occurs in **hospitalized patients** or those with complicated UTIs, not typically in a healthy 35-year-old in the community. *Klebsiella* - **_Klebsiella pneumoniae_** is another Gram-negative rod that can cause prostatitis, frequently in patients with **urinary tract abnormalities** or catheterization. - It is less common than _E. coli_ in community-acquired acute bacterial prostatitis and is often associated with more severe disease or resistance patterns. *Proteus* - **_Proteus mirabilis_** is known for its ability to produce **urease**, which can lead to struvite stone formation in the urinary tract, and can cause UTIs. - While it can cause prostatitis, it is much **less frequent than _E. coli_** and often associated with urinary calculi or long-term catheter use.

Q: BPF (Brazilian purpuric fever) is caused by:

H.influenzae biotype aegyptius. ***H.influenzae biotype aegyptius*** - **Brazilian purpuric fever (BPF)** is a severe, acute pediatric disease characterized by **fever, purpura, vascular collapse, and high mortality**, specifically caused by this distinct strain of *Haemophilus influenzae biotype aegyptius*. - The infection typically starts as a **conjunctivitis** caused by the same organism, which then disseminates, leading to the systemic symptoms of BPF. *Salmonella* - *Salmonella* species are typically associated with **gastroenteritis**, **typhoid fever**, or other systemic infections, but not Brazilian purpuric fever. - While *Salmonella* can cause severe infections in children, its clinical presentation and typical symptoms (e.g., diarrhea, enteric fever) differ significantly from BPF. *V. cholerae* - *Vibrio cholerae* is the causative agent of **cholera**, an acute diarrheal illness characterized by severe watery diarrhea and dehydration. - It does not cause the purpuric rash, vasculitis, or the specific sudden onset and high mortality seen in Brazilian purpuric fever. *None of the options* - This option is incorrect because *H.influenzae biotype aegyptius* is the established and specific cause of Brazilian purpuric fever. - The disease is well-defined with a particular etiology, making "none of the options" an invalid choice.

Q: Most common causative organism for bacterial meningitis beyond 3 years of age is -

Pneumococcus. ***Pneumococcus*** - *Streptococcus pneumoniae* (Pneumococcus) is currently the most common cause of **bacterial meningitis** in individuals older than 3 years, particularly after the widespread use of the HiB vaccine. - It frequently causes severe disease with **high mortality and morbidity** due to its ability to colonize the nasopharynx and invade the bloodstream and meninges. *H. influenzae Type b* - Before the introduction of the **HiB vaccine**, *Haemophilus influenzae* type b was the leading cause of bacterial meningitis in children under 5 years of age. - Due to **routine vaccination**, its incidence has dramatically decreased, making it less common now in children beyond 3 years. *Meningococcus* - *Neisseria meningitidis* (Meningococcus) is a significant cause of bacterial meningitis, particularly in **epidemics** and in young adults and adolescents. - While it causes outbreaks and serious disease, it is generally less common than pneumococcal meningitis beyond childhood in areas with high vaccination coverage. *Staphylococcus aureus* - *Staphylococcus aureus* can cause bacterial meningitis but is more often associated with **neurosurgical procedures**, head trauma, or indwelling medical devices, rather than being a primary community-acquired pathogen for meningitis in immunocompetent individuals. - It is not the most common causative organism for community-acquired bacterial meningitis in the general population beyond 3 years of age.

Q: Most common organism that can contaminate crowded army camps is?

Neisseria meningitidis. ***Neisseria meningitidis*** - This bacterium is a common cause of **meningitis** and can spread rapidly in crowded environments like army camps due to close contact. - Transmission occurs through **respiratory droplets**, making confined spaces ideal for its dissemination. *Klebsiella* - While *Klebsiella* can cause various infections, including pneumonia and UTIs, it is not typically associated with widespread outbreaks in crowded settings like meningococcal disease. - It usually acts as an **opportunistic pathogen**, often affecting individuals with weakened immune systems or those in healthcare settings. *Staphylococcus* - *Staphylococcus* species, particularly *S. aureus*, are common causes of skin infections, bloodstream infections, and food poisoning. - However, they are not the most frequent cause of highly transmissible, community-wide outbreaks in crowded camps, unlike meningococcus. *E. coli* - *E. coli* is a common cause of **urinary tract infections** and **gastroenteritis**, often associated with contaminated food or water. - It is not typically responsible for widespread respiratory outbreaks in crowded, healthy populations like *Neisseria meningitidis*.

Q: Main site of action of tetanus toxin:

Presynaptic terminal of spinal cord. ***Presynaptic terminal of spinal cord*** - The **tetanus toxin** (tetanospasmin) travels via **retrograde axonal transport** to the **presynaptic terminals** of inhibitory interneurons in the spinal cord. - It then cleaves **synaptobrevin**, a protein essential for the release of inhibitory neurotransmitters **GABA** and **glycine**, leading to uncontrolled muscle spasms. *Neuromuscular junction* - While it can be transported through the motor neurons supplying the neuromuscular junction, its primary site of action for systemic effects is not directly at the junction itself. - Toxins like **botulinum toxin** primarily act at the neuromuscular junction to inhibit acetylcholine release. *Muscle fibers* - Tetanus toxin does not directly act on muscle fibers to cause contraction or paralysis. - Muscle hyperexcitability is an indirect result of disinhibited motor neurons. *Postsynaptic terminal of spinal cord* - Tetanus toxin does not directly bind to or act on the postsynaptic receptors of the spinal cord neurons. - Its mechanism involves preventing the release of neurotransmitters from the **presynaptic terminal**.

Q: Patient presenting with abdominal pain, diarrhea taking clindamycin for 5 days. Treated with metronidazole symptoms subsided. What is the causative agent -

Clostridium difficile. ***Clostridium difficile*** - **Clindamycin** is a common antibiotic associated with **Clostridium difficile** infection, which causes **antibiotic-associated diarrhea** and **colitis**. - The successful treatment with **metronidazole** further supports the diagnosis of *C. difficile* infection. *Clostridium welchii* (also known as *Clostridium perfringens*) - Primarily causes **gas gangrene** and **food poisoning**, with symptoms more acute and severe than described. - Not typically associated with antibiotic-induced diarrhea but rather **contaminated food** or **wound infections**. *Clostridium perfringens* - This bacterium is a common cause of **food poisoning** (type A) featuring **abdominal cramps** and **diarrhea**, and **gas gangrene** (type C) due to deep tissue infections. - While it can cause diarrhea, it's not the classic cause of **antibiotic-associated diarrhea** like *C. difficile*. *Clostridium botulinum* - Produces a **neurotoxin** that causes **flaccid paralysis**, not abdominal pain and diarrhea due to antibiotic use. - The infection is typically acquired through **improperly canned food** or **wound contamination**.

Q: Donovanosis is caused by

Calymmatobacter granulomatis. ***Calymmatobacter granulomatis*** - **Donovanosis**, also known as granuloma inguinale, is a sexually transmitted infection primarily caused by the bacterium ***Calymmatobacterium granulomatis*** (now reclassified as *Klebsiella granulomatis*). - The disease is characterized by chronic, progressive ulcerative lesions of the **genitalia** and **perianal area**. *H. ducreyi* - ***Haemophilus ducreyi*** is the causative agent of **chancroid**, another sexually transmitted infection. - Chancroid typically presents as painful **genital ulcers** with associated **inguinal lymphadenopathy** (buboes). *Chlamydia trachomatis* - ***Chlamydia trachomatis*** is a common cause of several sexually transmitted infections, including **chlamydia**, **lymphogranuloma venereum (LGV)**, and **trachoma**. - Its clinical manifestations can range from **urethritis** and **cervicitis** to more severe systemic disease like LGV with invasive lymphadenopathy. *Treponema pallidum* - ***Treponema pallidum*** subspecies *pallidum* is the bacterium responsible for **syphilis**. - Syphilis progresses through distinct stages: **primary (chancre)**, secondary (rash, mucocutaneous lesions), and tertiary (neurosyphilis, cardiovascular syphilis, gummas).

Q: Most common cause of Acute epiglottitis in the pre-vaccine era was

Haemophilus influenzae B. ***Haemophilus influenzae B*** - **Historically**, *Haemophilus influenzae type B* (Hib) was the **most common bacterial cause of acute epiglottitis**, especially in children, accounting for >90% of cases in the pre-vaccine era. - The introduction of the **Hib vaccine** (starting in the 1990s) has **dramatically reduced the incidence** of Hib-related epiglottitis by >95%. - **Currently**, in the post-vaccine era, other pathogens like *Streptococcus pyogenes*, *S. pneumoniae*, and *S. aureus* are more common causes, though Hib may still occur in unvaccinated individuals. *Haemophilus influenzae A* - *Haemophilus influenzae type A* is occasionally associated with invasive infections but was **not the predominant cause** of acute epiglottitis even historically. - It lacks the same epidemiological significance as type B in causing epiglottitis. *Respiratory Syncytial Virus* - **Respiratory Syncytial Virus (RSV)** is a primary cause of **bronchiolitis and pneumonia** in young children. - It is **not associated with epiglottitis**, which is a distinct condition involving supraglottic inflammation. *Parainfluenza virus* - **Parainfluenza viruses** are a common cause of **croup (laryngotracheobronchitis)**, characterized by subglottic inflammation and a "barking" cough. - While it affects the upper airway, it **does not cause epiglottitis**, which involves the supraglottic structures.

Q: Which of the following is NOT transmitted sexually?

T. pertenue. ***T. pertenue*** - *T. pertenue* causes **yaws**, a chronic infection primarily affecting the skin, bones, and joints. - Yaws is transmitted through **direct skin-to-skin contact** with infectious lesions (non-sexual contact), making it distinctly **not a sexually transmitted infection**. - It is endemic in tropical regions and primarily affects children. *Gonorrhoea* - **Gonorrhoea** is a common **sexually transmitted infection (STI)** caused by the bacterium *Neisseria gonorrhoeae*. - It primarily affects the genitals, rectum, and throat, and is transmitted through **sexual contact**. *Syphilis* - **Syphilis** is a sexually transmitted infection caused by the bacterium *Treponema pallidum subspecies pallidum*. - It is transmitted through **direct contact with a syphilitic sore** (chancre) during sexual activity. *Candida* - While **vulvovaginal candidiasis** is often due to overgrowth of normal flora (influenced by hormonal changes, antibiotic use, or immunosuppression), *Candida* species **can be transmitted through sexual contact**. - Candida is recognized as a **sexually transmissible infection**, though it has multiple modes of transmission beyond sexual activity.

Question 1

A 35 year old man presents to an emergency department with an exquisitely tender prostate gland. An acute bacterial infection is suspected. Which of the following organisms is the most common pathogen in this setting?

Accepted Answer

Escherichia

Answer

Enterobacter

Answer

Klebsiella

Answer

Proteus

Question 2

BPF (Brazilian purpuric fever) is caused by:

Accepted Answer

H.influenzae biotype aegyptius

Answer

Salmonella

Answer

V. cholerae

Answer

None of the options

Question 3

Most common causative organism for bacterial meningitis beyond 3 years of age is -

Accepted Answer

Pneumococcus

Answer

H. influenzae Type b

Answer

Meningococcus

Answer

Staphylococcus aureus

Question 4

A major step in the pathogenesis of listeriosis is?

Accepted Answer

The survival and multiplication of L. monocytogenes within mononuclear phagocytes and host epithelial cells

Answer

The antiphagocytic activity of the L. monocytogenes capsule

Answer

The release of hyaluronidase by L. monocytogenes, which contributes to its dissemination from local sites

Answer

The formation of antigen-antibody complexes with resultant complement activation and tissue damage

Question 5

Most common organism that can contaminate crowded army camps is?

Accepted Answer

Neisseria meningitidis

Answer

Klebsiella

Answer

Staphylococcus

Answer

E. coli

Question 6

Main site of action of tetanus toxin:

Accepted Answer

Presynaptic terminal of spinal cord

Answer

Neuromuscular junction

Answer

Muscle fibers

Answer

Postsynaptic terminal of spinal cord

Question 7

Patient presenting with abdominal pain, diarrhea taking clindamycin for 5 days. Treated with metronidazole symptoms subsided. What is the causative agent -

Accepted Answer

Clostridium difficile

Answer

Clostridium welchii

Answer

Clostridium perfringens

Answer

Clostridium botulinum

Question 8

Donovanosis is caused by

Accepted Answer

Calymmatobacter granulomatis

Answer

H. ducreyi

Answer

Chlamydia trachomatis

Answer

Treponema pallidum

Question 9

Most common cause of Acute epiglottitis in the pre-vaccine era was

Accepted Answer

Haemophilus influenzae B

Answer

Haemophilus influenzae A

Answer

Respiratory Syncytial Virus

Answer

Parainfluenza virus

Question 10

Which of the following is NOT transmitted sexually?

Accepted Answer

T. pertenue

Answer

Gonorrhoea

Answer

Syphilis

Answer

Candida

Bacteriology — MCQs

Bacteriology — MCQs

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