Bacteriology Practice Questions

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.

Q: A patient with colorectal cancer develops septicemia complicated by endocarditis. You would expect the blood cultures to grow?

Streptococcus bovis. ***Streptococcus bovis*** - **Streptococcus bovis** (now often referred to as *Streptococcus gallolyticus subsp. gallolyticus*) is strongly associated with **colorectal cancer** and can cause **bacteremia** and **infective endocarditis**. - Its presence in blood cultures, particularly in cases of endocarditis, should prompt a workup for underlying colorectal malignancy. *Streptococcus agalactiae* - This organism, also known as **Group B Streptococcus (GBS)**, is a common cause of **neonatal sepsis** and meningitis, and can cause infections in immunocompromised adults, but it does not have a specific association with colorectal cancer. - While it can cause endocarditis, it is not the most likely causative agent in a patient with colorectal cancer. *Streptococcus pyogenes* - **Streptococcus pyogenes** (Group A Streptococcus or **GAS**) is known for causing **pharyngitis** ("strep throat"), **scarlet fever**, **rheumatic fever**, and **necrotizing fasciitis**. - It is not typically associated with chronic conditions like colorectal cancer or with endocarditis in this specific context. *Streptococcus pneumoniae* - **Streptococcus pneumoniae** is a leading cause of **pneumonia**, **otitis media**, **meningitis**, and **sepsis**, particularly in young children and the elderly. - While it can cause endocarditis, there is no direct link between *S. pneumoniae* infection and underlying colorectal cancer.

Q: Carrion's disease is caused by:

Bartonella bacilliformis. ***Bartonella bacilliformis*** - **Carrion's disease**, also known as **Bartonellosis**, is exclusively caused by the bacterium **Bartonella bacilliformis**. - This disease manifests in two distinct stages: an acute phase (**Oroya fever**) characterized by severe anemia, and a chronic eruptive phase (**verruga peruana**) with skin lesions. *Bartonella henselae* - This bacterium is primarily responsible for **Cat-scratch disease** and can also cause **bacillary angiomatosis**, endocarditis, and trench fever-like syndrome. - It is typically transmitted to humans through scratches or bites from infected cats. *Bartonella quintana* - This species is the causative agent of **trench fever**, a louse-borne illness, and can also lead to **bacillary angiomatosis**. - Trench fever is characterized by recurrent fevers, headache, body aches, and sometimes a rash. *Bartonella washoensis* - **Bartonella washoensis** is a less common species primarily associated with **myocarditis** and endocarditis in humans. - Infections with this bacterium are often linked to exposure to rodents, particularly ground squirrels.

Q: A child after consuming food in a party complains of diarrhea within 1-5 hours. The diagnosis is:

S. aureus. ***S. aureus*** - **_Staphylococcus aureus_** food poisoning has a rapid onset (**1-6 hours**) because symptoms are caused by preformed **exotoxins** ingested with contaminated food, not by bacterial growth in the host. - Common sources include foods handled extensively and left at **room temperature**, allowing the bacteria to multiply and produce heat-stable toxins. *Clostridium perfringens* - **_Clostridium perfringens_** food poisoning typically has a longer incubation period (**6-24 hours**), as symptoms are caused by toxins produced by bacteria replicating in the host intestine. - It often results from eating large quantities of contaminated meat or poultry that has been improperly cooked or stored. *Streptococcus* - **_Streptococcus_** species are not primary causes of acute **foodborne diarrheal illness** with such a rapid onset. - While some strains can cause infections, their role in common food poisoning with preformed toxins is negligible compared to _S. aureus_. *Clostridium botulinum* - **_Clostridium botulinum_** causes **botulism**, a severe neuroparalytic illness, not primarily diarrhea, and typically has a longer incubation period (**12-36 hours**). - Symptoms are due to neurotoxins affecting the nervous system, leading to **flaccid paralysis**, not acute gastroenteritis.

Q: Subdural empyema is most commonly caused by:

Streptococcus pneumoniae. ***Streptococcus pneumoniae*** - **_Streptococcus species_**, including **_S. pneumoniae_**, aerobic and anaerobic streptococci, and S. milleri group, are the **most common causative organisms** of **subdural empyema**, accounting for **60-70% of cases**. - **Subdural empyema** most frequently arises from **paranasal sinusitis** (50-80% of cases) or **otitis media/mastoiditis**, infections typically caused by **streptococcal species**. - The polymicrobial nature of sinus and ear infections explains why **streptococci** predominate in subdural empyema. *Staphylococcus aureus* - **_Staphylococcus aureus_** is an important cause of **subdural empyema**, particularly in **post-neurosurgical cases** and following **penetrating head trauma**. - It accounts for approximately **10-20% of cases** but is **not the most common** overall pathogen. - When subdural empyema follows **surgery** or **direct inoculation**, S. aureus becomes more likely than in community-acquired cases. *H. influenzae* - **_Haemophilus influenzae_** was historically significant before widespread **Hib vaccination**. - Currently uncommon as a cause of **subdural empyema**, especially in vaccinated populations. - May still be seen in unvaccinated individuals or those with underlying immunodeficiency. *E. coli* - **_E. coli_** is a rare cause of **subdural empyema** in adults. - More relevant in **neonatal meningitis** and infections in **immunocompromised hosts**. - Gram-negative bacilli are generally uncommon in subdural empyema compared to gram-positive cocci.

Question 1

Most common organism that can contaminate crowded army camps is?

Accepted Answer

Neisseria meningitidis

Answer

Klebsiella

Answer

Staphylococcus

Answer

E. coli

Question 2

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 3

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 4

Donovanosis is caused by

Accepted Answer

Calymmatobacter granulomatis

Answer

H. ducreyi

Answer

Chlamydia trachomatis

Answer

Treponema pallidum

Question 5

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 6

Which of the following is NOT transmitted sexually?

Accepted Answer

T. pertenue

Answer

Gonorrhoea

Answer

Syphilis

Answer

Candida

Question 7

A patient with colorectal cancer develops septicemia complicated by endocarditis. You would expect the blood cultures to grow?

Accepted Answer

Streptococcus bovis

Answer

Streptococcus agalactiae

Answer

Streptococcus pyogenes

Answer

Streptococcus pneumoniae

Question 8

Carrion's disease is caused by:

Accepted Answer

Bartonella bacilliformis

Answer

Bartonella henselae

Answer

Bartonella quintana

Answer

Bartonella washoensis

Question 9

A child after consuming food in a party complains of diarrhea within 1-5 hours. The diagnosis is:

Accepted Answer

S. aureus

Answer

Clostridium perfringens

Answer

Streptococcus

Answer

Clostridium botulinum

Question 10

Subdural empyema is most commonly caused by:

Accepted Answer

Streptococcus pneumoniae

Answer

Staphylococcus aureus

Answer

H. influenzae

Answer

E. coli

Bacteriology — MCQs

Bacteriology — MCQs

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