Bacteriology Practice Questions

Q: Which organism is the most common cause of acute bacterial prostatitis?

E.coli. ***E.coli*** - **E.coli** is the most common cause of **acute bacterial prostatitis**, accounting for a significant majority of cases. - It is a **gram-negative rod** commonly found in the gastrointestinal tract and can ascend into the urinary tract and prostate. *Enterococcus* - While **Enterococcus species** can cause urinary tract infections and, less commonly, prostatitis, they are a distant second to E.coli in frequency. - They are **gram-positive cocci** and are often associated with catheter-associated infections or healthcare-acquired infections. *Streptococcus viridans* - **Streptococcus viridans** group bacteria are typically commensals of the oral cavity and are more known for causing **endocarditis** or dental infections. - They are not a common cause of acute bacterial prostatitis. *Peptostreptococcus* - **Peptostreptococcus** is a genus of **anaerobic gram-positive cocci** commonly found in the normal flora of the mouth, gastrointestinal tract, and vagina. - They are typically involved in **polymicrobial anaerobic infections** but are not a primary or common cause of acute bacterial prostatitis.

Q: Which of the following vectors is known to transmit a disease that can be identified by the presence of spirochetes under dark-field microscopy?

Ixodes scapularis ticks. ***Ixodes scapularis ticks*** - *Ixodes scapularis* ticks are the primary vectors for **Lyme disease**, caused by the spirochete *Borrelia burgdorferi*. - **Spirochetes** can be identified in tissue samples or cultures using **dark-field microscopy** or silver staining techniques. - Direct visualization from patient samples is uncommon; diagnosis typically relies on serology and clinical presentation. *Louse* - Lice (e.g., *Pediculus humanus corporis*) transmit **relapsing fever** (*Borrelia recurrentis*) and epidemic typhus (*Rickettsia prowazekii*). - *Borrelia recurrentis* spirochetes are readily visible in **peripheral blood smears** using Wright or Giemsa stain during febrile episodes. - While this is also a spirochete disease, the question specifically refers to dark-field microscopy, which is classically associated with Lyme disease spirochete identification. *Anopheles* - The *Anopheles* mosquito is the vector for **malaria**, caused by *Plasmodium* parasites, not spirochetes. - Malaria is diagnosed by identifying ring forms, trophozoites, and schizonts within red blood cells on blood smears. *Rat flea* - The rat flea (*Xenopsylla cheopis*) is the primary vector for **bubonic plague** (*Yersinia pestis*) and murine typhus (*Rickettsia typhi*). - *Yersinia pestis* is a gram-negative coccobacillus, not a spirochete.

Q: Which anaerobic organism is known to cause multiple abscesses with discharging sinuses and demonstrates sulfur granules in pus?

Actinomyces. ***Actinomyces*** - *Actinomyces* species are classic causes of **actinomycosis**, characterized by chronic, suppurative infections with **multiple abscesses**, draining sinuses, and the presence of **sulfur granules** in pus. - They are **anaerobic or microaerophilic gram-positive bacteria** that are part of the normal flora of the mouth and gastrointestinal tract, causing infection when mucosal barriers are disrupted. *Nocardia asteroides* - *Nocardia asteroides* causes **nocardiosis**, which can also present with abscesses, but it is an **aerobic bacterium** and typically does not produce sulfur granules. - Nocardial infections often involve the lungs, skin, or central nervous system, particularly in **immunocompromised individuals**. *Salmonella enterica* - *Salmonella enterica* is a facultative anaerobic Gram-negative bacterium known for causing **gastroenteritis**, typhoid fever, and bacteremia. - It is not associated with the formation of multiple abscesses with draining sinuses or sulfur granules. *Francisella tularensis* - *Francisella tularensis* causes **tularemia**, a zoonotic disease characterized by ulceroglandular lesions, fever, and lymphadenopathy. - It does not typically cause multiple abscesses with draining sinuses or produce sulfur granules.

Q: Which microorganism is the most common cause of pyogenic osteomyelitis?

S. aureus. ***Staph aureus*** - **_Staphylococcus aureus_** is the most frequent cause of **pyogenic osteomyelitis** across all age groups and routes of infection. - Its ability to adhere to bone, form biofilms, and produce toxins contributes to its prevalence in bone infections. *Streptococcus spp.* - While various **_Streptococcus_** species can cause infections, they are less common causes of pyogenic osteomyelitis compared to **_Staphylococcus aureus_**. - **Group A _Streptococcus_** can cause severe invasive infections but rarely involves primary bone infection. *Corynebacterium spp.* - **_Corynebacterium_** species, particularly **_Corynebacterium striatum_**, are increasingly recognized as opportunistic pathogens, especially in immunocompromised individuals or those with foreign bodies. - However, they are not the most common cause of osteomyelitis in the general population. *Neisseria gonorrhoeae (gonococcus)* - **_Neisseria gonorrhoeae_** can cause **disseminated gonococcal infection (DGI)**, which may include joint involvement (**septic arthritis**). - While it can lead to bone pain and swelling, it primarily affects joints and is a less common cause of direct **pyogenic osteomyelitis** than **_S. aureus_**.

Q: Bartonella quintana causes:

Trench fever. ***Trench fever*** - **Bartonella quintana** is the causative agent of **trench fever**, a louse-borne disease historically common during wartime. - Symptoms include **recurrent fevers**, headache, bone pain (especially in the shins), and rash. *Scrub typhus* - Scrub typhus is caused by **Orientia tsutsugamushi**, a rickettsial bacterium, not Bartonella. - It is transmitted by **chiggers** and characterized by a rash, fever, and eschar at the bite site. *Epidemic typhus* - Epidemic typhus is caused by **Rickettsia prowazekii** and is also louse-borne. - It presents with sudden high fever, severe headache, and a maculopapular rash that spares the face, palms, and soles. *Endemic typhus* - Endemic typhus (murine typhus) is caused by **Rickettsia typhi** and is transmitted by **rat fleas**. - Its symptoms are generally milder than epidemic typhus, including fever, headache, and a truncal rash.

Q: All are true about anaerobic infections except:

Exudates and swabs are ideal for culture. ***Exudates and swabs are ideal for culture.*** - **Swabs exposed to air** are generally **not ideal** for anaerobic culture because oxygen exposure can kill obligate anaerobes, leading to false-negative results. - Optimal anaerobic specimen collection requires techniques that **minimize oxygen exposure**, such as aspirates or tissue biopsies placed in anaerobic transport media. *Most infections are endogenous* - Anaerobic infections commonly arise from **one's own commensal flora**, which becomes pathogenic under specific conditions like tissue damage or impaired blood supply. - These bacteria are part of the normal microbiota of various body sites, including the gastrointestinal tract, oral cavity, and skin. *Specimen for UTI is suprapubic aspiration* - For **suspected anaerobic urinary tract infections (UTIs)**, suprapubic aspiration is considered the gold standard for specimen collection. - This method bypasses potential contamination from urethral flora and ensures a sterile, oxygen-free sample for accurate anaerobic culture. *They are found normally on skin and GIT* - **Anaerobic bacteria** are a significant component of the normal flora of the **skin and gastrointestinal tract (GIT)**, as well as the oral cavity and genitourinary tract. - Their presence in these sites is crucial for maintaining normal physiological functions and preventing the overgrowth of pathogens.

Q: Anaplasma phagocytophilum mainly affects -

Neutrophils (white blood cells). ***Neutrophils (white blood cells)*** - *Anaplasma phagocytophilum* specifically infects and replicates within **neutrophils**, leading to the characteristic morulae observed inside these cells. - This infection causes **human granulocytic anaplasmosis (HGA)**, primarily affecting white blood cells. *Red Blood Cells (RBCs)* - While other tick-borne diseases like **babesiosis** infect RBCs, *Anaplasma phagocytophilum* does not target red blood cells. - RBCs are responsible for oxygen transport and lack the necessary cellular machinery for *Anaplasma* replication. *Macrophages (immune cells)* - Macrophages are significant immune cells but are not the primary target cell for *Anaplasma phagocytophilum*. - Infections that primarily target macrophages include some **bacterial** and **parasitic infections** like *Leishmania*. *Platelets (thrombocytes)* - Platelets are crucial for **blood clotting** and are not directly infected by *Anaplasma phagocytophilum*. - Although **thrombocytopenia** (low platelet count) is a common finding in anaplasmosis, it is an indirect effect of the infection, not due to direct platelet invasion.

Q: Which of the following statements about Listeria is false?

Characteristic tumbling motility at 37°C. ***Characteristic tumbling motility at 37°C*** - *Listeria monocytogenes* exhibits **"tumbling motility" at 20-25°C**, but it is non-motile at 37°C. - This temperature-dependent motility is a key diagnostic feature, and the statement claiming motility at 37°C is incorrect. *Gram positive* - *Listeria monocytogenes* is indeed a **gram-positive bacillus**, a key characteristic aiding in its initial identification. - Its gram stain reaction distinguishes it from gram-negative bacteria, guiding appropriate treatment. *PALCAM agar is used for isolation* - **PALCAM (Polymyxin Acriflavin Lithium Chloride Ceftazidime Esculin Mannitol) agar** is a selective and differential medium specifically designed for the isolation and detection of *Listeria monocytogenes*. - It utilizes esculin hydrolysis and mannitol fermentation to differentiate *Listeria* species. *Umbrella shaped growth* - When cultured in a semi-solid medium, *Listeria monocytogenes* typically displays a characteristic **umbrella-shaped pattern of growth** at reduced temperatures (e.g., 20-25°C) due to its motility. - This macroscopic appearance is a classic identifier for *Listeria*.

Q: What is the causative agent of Rhinoscleroma?

Klebsiella rhinoscleromatis. ***Klebsiella rhinoscleromatis*** - This bacterium is the **specific causative agent** of rhinoscleroma, a chronic progressive granulomatous disease affecting the upper respiratory tract. - It is a sub-species of *Klebsiella pneumoniae*. *Staphylococcus aureus* - *Staphylococcus aureus* is a common cause of various **skin infections**, **abscesses**, and systemic infections like **sepsis** and **endocarditis**. - It is not associated with rhinoscleroma. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* is an **opportunistic pathogen** often associated with hospital-acquired infections, particularly in immunocompromised individuals. - It can cause **pneumonia**, urinary tract infections, and infections in burn patients, but not rhinoscleroma. *Corynebacterium diphtheriae* - *Corynebacterium diphtheriae* is the causative agent of **diphtheria**, characterized by the formation of a **pseudomembrane** in the throat and toxin-mediated systemic effects. - Its clinical presentation is distinct from rhinoscleroma.

Q: Granuloma inguinale is caused by:

Calymmatobacterium granulomatis. ***Calymmatobacterium granulomatis*** - **Granuloma inguinale**, also known as **donovanosis**, is a sexually transmitted infection caused by **_Calymmatobacterium granulomatis_**. - This bacterium is notoriously difficult to culture, so diagnosis is typically made by identifying **Donovan bodies** (macrophages filled with bacteria) in tissue samples. *Haemophilus ducreyi* - **_Haemophilus ducreyi_** is the causative agent of **chancroid**, - Chancroid is characterized by **painful genital ulcers** with a ragged, undermined border, and often accompanied by **tender inguinal lymphadenopathy**. *Chlamydia trachomatis* - **_Chlamydia trachomatis_** is responsible for several conditions, including **chlamydia** (the most common bacterial STI), **lymphogranuloma venereum (LGV)**, and **trachoma**. - LGV presents with a transient, often unnoticed genital lesion followed by painful, suppurative lymphadenopathy, which is distinct from granuloma inguinale. *Treponema pallidum* - **_Treponema pallidum_** is the spirochete that causes **syphilis**, which progresses through several stages. - Primary syphilis manifests as a **painless chancre**, while secondary syphilis can involve a widespread rash, lymphadenopathy, and mucosal lesions.

Question 1

Which organism is the most common cause of acute bacterial prostatitis?

Accepted Answer

E.coli

Answer

Enterococcus

Answer

Streptococcus viridans

Answer

Peptostreptococcus

Question 2

Which of the following vectors is known to transmit a disease that can be identified by the presence of spirochetes under dark-field microscopy?

Accepted Answer

Ixodes scapularis ticks

Answer

Anopheles

Answer

Louse

Answer

Rat flea

Question 3

Which anaerobic organism is known to cause multiple abscesses with discharging sinuses and demonstrates sulfur granules in pus?

Accepted Answer

Actinomyces

Answer

Nocardia asteroides

Answer

Salmonella enterica

Answer

Francisella tularensis

Question 4

Which microorganism is the most common cause of pyogenic osteomyelitis?

Accepted Answer

S. aureus

Answer

Streptococcus spp.

Answer

Corynebacterium spp.

Answer

Neisseria gonorrhoeae (gonococcus)

Question 5

Bartonella quintana causes:

Accepted Answer

Trench fever

Answer

Scrub typhus

Answer

Epidemic typhus

Answer

Endemic typhus

Question 6

All are true about anaerobic infections except:

Accepted Answer

Exudates and swabs are ideal for culture

Answer

Specimen for UTI is suprapubic aspiration

Answer

They are found normally on skin and GIT

Answer

Most infections are endogenous

Question 7

Anaplasma phagocytophilum mainly affects -

Accepted Answer

Neutrophils (white blood cells)

Answer

Red Blood Cells (RBCs)

Answer

Macrophages (immune cells)

Answer

Platelets (thrombocytes)

Question 8

Which of the following statements about Listeria is false?

Accepted Answer

Characteristic tumbling motility at 37°C

Answer

PALCAM agar is used for isolation

Answer

Gram positive

Answer

Umbrella shaped growth

Question 9

What is the causative agent of Rhinoscleroma?

Accepted Answer

Klebsiella rhinoscleromatis

Answer

Staphylococcus aureus

Answer

Pseudomonas aeruginosa

Answer

Corynebacterium diphtheriae

Question 10

Granuloma inguinale is caused by:

Accepted Answer

Calymmatobacterium granulomatis

Answer

Haemophilus ducreyi

Answer

Chlamydia trachomatis

Answer

Treponema pallidum

Bacteriology — MCQs

Bacteriology — MCQs

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