Bacteriology Practice Questions

Q: Hemorrhagic meningitis is caused by

Bacillus anthracis. ***Bacillus anthracis*** - *Bacillus anthracis* causes **anthrax meningitis**, which is characteristically **hemorrhagic** and rapidly fatal - Characterized by extensive **meningeal and brain parenchymal bleeding** with hemorrhagic CSF - This form of meningitis is specifically known for its **hemorrhagic nature** due to the toxins produced by the bacteria, leading to vascular damage and edema - Often presents as "cardinal's cap" appearance due to severe hemorrhagic involvement *Streptococcus pneumoniae* - *Streptococcus pneumoniae* is the most common cause of **bacterial meningitis** in adults - Typically causes **purulent meningitis** with neutrophilic infiltration, not hemorrhagic meningitis - While severe cases can have complications with vascular involvement, it is not characterized by hemorrhagic meningitis *Neisseria meningitidis* - *Neisseria meningitidis* is a common cause of **bacterial meningitis**, often presenting with petechial rash due to **vasculitis** - Can lead to **disseminated intravascular coagulation (DIC)** and purpura fulminans with hemorrhagic skin lesions - However, the meningitis itself is typically **purulent**, not grossly hemorrhagic *Haemophilus influenzae* - *Haemophilus influenzae* type b (Hib) was a major cause of **bacterial meningitis** before vaccination - Causes **purulent meningitis** with inflammation and pus formation, rather than significant hemorrhage within the meninges - Now rare due to effective vaccination programs

Q: Causative organism for ANUG is:

Fusospirochetal complex. ***Fusospirochetal complex*** - **Acute Necrotizing Ulcerative Gingivitis (ANUG)**, also known as Vincent's angina or trench mouth, is caused by a synergistic polymicrobial infection involving **Fusobacterium species** (particularly F. nucleatum) and **oral spirochetes** (Borrelia vincentii and Treponema species). - This fusospirochetal complex creates a destructive, ulcerative inflammation of the gingiva, presenting with **painful, bleeding gums, punched-out papillae, pseudomembrane formation**, and characteristic **fetid breath**. - The condition typically occurs in patients with **poor oral hygiene, stress, immunosuppression**, or **malnutrition**. *Streptococcus sanguis* - This bacterium is a common commensal of the oral cavity and plays a role in **dental plaque formation** and initial colonization of tooth surfaces. - While present in the mouth, it is **not the causative agent** for the necrotizing lesions characteristic of ANUG. *Treponema pallidum and spirochetes* - **Treponema pallidum** specifically causes **syphilis**, a sexually transmitted infection, not ANUG. - While **oral spirochetes** (other Treponema and Borrelia species) are indeed critical components of ANUG, they work synergistically with **Fusobacterium**, hence the term "fusospirochetal complex." - This option is partially correct but incomplete and includes T. pallidum which is incorrect. *Staphylococcus epidermidis* - **Staphylococcus epidermidis** is a skin commensal organism implicated in **nosocomial infections** and biofilm formation on medical devices. - It has **no role** in the pathogenesis of ANUG.

Q: Epiglottitis is mainly caused by:

Haemophilus. ***Haemophilus*** - **_Haemophilus influenzae_ type b (Hib)** was historically the leading cause of epiglottitis, especially in children, prior to widespread vaccination. - While other bacteria can cause epiglottitis, **_Haemophilus influenzae_** remains one of the most significant causative agents, particularly in unvaccinated populations or in adults. *Streptococcus* - Various species of **_Streptococcus_**, such as **_Streptococcus pneumoniae_** and **Group A _Streptococcus_ (GAS)**, can cause other upper respiratory tract infections like pharyngitis or pneumonia. - While they can occasionally be isolated in epiglottitis, they are **not the main cause** compared to Haemophilus. *Staphylococcus* - **_Staphylococcus aureus_** is a common cause of skin infections, abscesses, and some respiratory infections, such as pneumonia. - It is **rarely the primary pathogen** responsible for acute epiglottitis. *Mycoplasma* - **_Mycoplasma pneumoniae_** is a common cause of atypical pneumonia, often presenting with a more gradual onset and milder symptoms compared to bacterial epiglottitis. - It is a **bacterium lacking a cell wall** and does not typically cause the acute, life-threatening inflammation characteristic of epiglottitis.

Q: Pseudomembranous colitis is caused by:

Cl. difficile. ***Clostridium difficile*** - **Pseudomembranous colitis** is a severe inflammation of the colon, most commonly caused by an overgrowth of **Clostridium difficile** bacteria in the gut. - This overgrowth often occurs after antibiotic use, which disrupts the normal gut flora, allowing **C. difficile** to produce toxins that damage the colon lining. *Pseudomonas* - **Pseudomonas aeruginosa** is a common opportunistic pathogen but is not associated with causing **pseudomembranous colitis**. - It is more commonly linked to infections such as hospital-acquired pneumonia, urinary tract infections, and wound infections. *Clostridium welchii* - **Clostridium welchii** is an older name for **Clostridium perfringens**, and it is not the causative agent of **pseudomembranous colitis**. - **Clostridium perfringens** is primarily known for causing **gas gangrene** and a type of **food poisoning**. *Clostridium perfringens* - **Clostridium perfringens** primarily causes **gas gangrene** (a severe soft tissue infection) and certain types of **food poisoning** due to its toxin production. - Unlike **Clostridium difficile**, it does not typically cause **pseudomembranous colitis** following antibiotic use.

Q: Sulfur granules in pus are seen in

Actinomyces israelii. ***Actinomyces israelii*** - **Sulfur granules** are characteristic macroscopic aggregates of filamentous bacteria found in pus from infections caused by *Actinomyces israelii*. - These granules are yellow, gritty, and represent colonies of the organism embedded in a calcium phosphate matrix, indicating an **actinomycosis infection**. *Candida albicans* - *Candida albicans* is a **yeast** that typically causes infections like thrush or candidiasis, which produce creamy white plaques or a curd-like discharge, but not sulfur granules. - It is a **fungus**, not a filamentous bacterium, and its microscopic appearance involves budding yeast cells and pseudohyphae. *Nocardia brasiliensis* - *Nocardia brasiliensis* can cause **nocardiosis**, which may involve cutaneous or pulmonary infections. While it can form granules (mycetoma-like lesions), these are not typically referred to as "sulfur granules" in the same way as *Actinomyces*. - Nocardial infections often present with abscesses and draining sinuses, and its granules are usually smaller and have a different microscopic appearance than those of *Actinomyces*. *Histoplasma capsulatum* - *Histoplasma capsulatum* is a **dimorphic fungus** that causes histoplasmosis, primarily affecting the lungs. - It exists as a mold in the environment and as yeast cells within macrophages in the host; it does not form sulfur granules in pus.

Q: Causative agents of "Vincent's angina"

Borrelia vincenti and Fusobacterium nucleatum. ***Borrelia vincenti and Fusobacterium nucleatum*** - **Vincent's angina**, also known as **acute necrotizing ulcerative gingivitis (ANUG)**, is polymicrobial and characteristically involves a synergistic infection of **spirochetes** (like *Borrelia vincenti*, now classified as *Treponema vincentii*) and **fusobacteria** (like *Fusobacterium nucleatum*). - These organisms thrive in an anaerobic environment, leading to the characteristic ulcerative and necrotic lesions of the gingiva and oral mucosa. - This synergistic infection produces the classic "fusospirochaetal" complex seen on microscopy. *Borrelia burgdorferi and Lactobacillus* - *Borrelia burgdorferi* is the causative agent of **Lyme disease**, a tick-borne illness causing systemic symptoms, not Vincent's angina. - *Lactobacillus* species are common commensal bacteria found in the oral cavity, gut, and vagina, and are not pathogenic in the context of Vincent's angina. *Leptospira and Treponema pallidum* - *Leptospira* species cause **leptospirosis**, a zoonotic disease with symptoms like fever, headache, and muscle aches, often affecting the kidneys and liver. - *Treponema pallidum* is the causative agent of **syphilis**, a sexually transmitted infection, which presents with different oral lesions (e.g., chancre, mucous patches) that are distinct from Vincent's angina. *Borrelia recurrentis and Bacteroides* - *Borrelia recurrentis* causes **relapsing fever**, characterized by recurrent episodes of fever and other systemic symptoms, transmitted by lice or ticks. - While *Bacteroides* are common anaerobic bacteria in the oral flora, they are not the primary synergistic pair specifically associated with the distinct clinical presentation of Vincent's angina, as are the spirochetes and fusobacteria.

Q: A person returns to Delhi from Bangladesh after 2 days and has diarrhea. Stool examination shows RBC's in stool. The likely organism causing is ?

Shigella dysenteriae. ***Shigella dysenteriae*** - This organism causes **bacillary dysentery**, characterized by fever, abdominal cramps, and frequent, small-volume stools containing **blood and mucus (RBCs)**, which fits the clinical picture of a traveler experiencing diarrhea with RBCs in stool. - The rapid onset (within 2 days of return) and the presence of **RBCs in stool** are highly suggestive of an invasive bacterial pathogen like *Shigella*. *Enteropathogenic E. Coli* - **EPEC** typically causes **watery diarrhea**, particularly in infants, by disrupting intestinal microvilli. - It does **not usually cause bloody stools** or significant red blood cells in the stool. *Salmonella typhi* - While *Salmonella typhi* causes **typhoid fever**, its initial presentation is typically with fever, headache, and constipation, followed by a **pea-soup diarrhea** in later stages, which is usually not bloody. - The rapid onset of bloody diarrhea within 2 days is less characteristic of typhoid fever, which has a longer incubation period. *Enterotoxigenic E. Coli* - **ETEC** is a common cause of **traveler's diarrhea**, but it produces toxins that lead to **watery, non-bloody diarrhea**. - The presence of **RBCs in the stool** makes ETEC an unlikely cause in this scenario.

Q: All of the following cause Fournier's gangrene except:

Clostridium. ***Clostridium*** - While *Clostridium* species (especially *C. perfringens*) **CAN be isolated** from Fournier's gangrene cases and contribute to gas formation and tissue necrosis, they are **less commonly identified as primary pathogens** compared to other organisms. - In the context of this question, *Clostridium* is considered the "except" option because it is **relatively less frequently implicated** in Fournier's gangrene compared to the other listed organisms, though it is NOT entirely excluded from the microbiology of this condition. - *Clostridium* species are more classically associated with **gas gangrene (clostridial myonecrosis)** in traumatic wounds and deep muscle tissue. *Bacteroides* - ***Bacteroides fragilis*** and other **anaerobic gram-negative bacilli** are among the **most commonly isolated organisms** in Fournier's gangrene. - They produce enzymes that facilitate tissue destruction and contribute significantly to the **polymicrobial synergistic necrotizing infection**. - Essential component of the typical microbial flora in perianal and genital infections. *Streptococcus* - ***Streptococcus pyogenes*** (Group A Streptococcus) and other streptococcal species are **frequently isolated** from Fournier's gangrene. - They produce toxins and enzymes causing **rapid necrotizing fasciitis** with systemic toxicity. - Major contributor to the aggressive nature and rapid progression of the infection. *Staphylococcus* - ***Staphylococcus aureus*** (including MRSA) is **commonly found** in polymicrobial Fournier's gangrene infections. - Contributes to local tissue destruction through toxin production and enzyme activity. - Often isolated from perianal and genital skin flora, facilitating its involvement in these infections.

Q: Causative organism of "glanders" is:

Burkholderia mallei. ***Burkholderia mallei*** - **_Burkholderia mallei_** is the bacterial species responsible for causing **glanders**, a contagious disease primarily affecting horses, donkeys, and mules. - Humans can contract glanders through direct contact with infected animals or contaminated materials, with respiratory and cutaneous forms of the disease being common. *Pseudomonas pseudomallei* - **_Pseudomonas pseudomallei_** (`_Burkholderia pseudomallei_`) is the causative agent of **melioidosis**, a severe infection with a wide range of clinical manifestations. - While it's closely related to _Burkholderia mallei_, melioidosis is distinct from glanders and typically found in tropical and subtropical regions. *Leptospira* - **_Leptospira_** is a spirochete bacterium responsible for **leptospirosis**, a zoonotic disease that affects both animals and humans. - It is typically transmitted through contact with water or soil contaminated with the urine of infected animals, presenting with fever, headache, body aches, and sometimes severe organ damage. *Chlamydia* - **_Chlamydia_** is a genus of intracellular bacteria known for causing a variety of infections in humans, including sexually transmitted infections (STIs), eye infections (`_trachoma_`), and respiratory infections. - It is not associated with glanders, which is caused by a distinct bacterial species with a different mode of transmission and host range.

Question 1

Hemorrhagic meningitis is caused by

Accepted Answer

Bacillus anthracis

Answer

Neisseria meningitidis

Answer

Haemophilus influenzae

Answer

Streptococcus pneumoniae

Question 2

Causative organism for ANUG is:

Accepted Answer

Fusospirochetal complex

Answer

Streptococcus sanguis

Answer

Treponema pallidum and spirochetes

Answer

Staphylococcus epidermidis

Question 3

Epiglottitis is mainly caused by:

Accepted Answer

Haemophilus

Answer

Streptococcus

Answer

Staphylococcus

Answer

Mycoplasma

Question 4

Residual auditory defect is a common complication in meningitis caused by

Accepted Answer

Haemophilus influenzae

Answer

Staphylococcus

Answer

Meningococcus

Answer

Escherichia coli

Question 5

Pseudomembranous colitis is caused by:

Accepted Answer

Cl. difficile

Answer

Pseudomonas

Answer

Cl. welchii

Answer

Cl. perfringens

Question 6

Sulfur granules in pus are seen in

Accepted Answer

Actinomyces israelii

Answer

Candida albicans

Answer

Nocardia brasiliensis

Answer

Histoplasma capsulatum

Question 7

Causative agents of "Vincent's angina"

Accepted Answer

Borrelia vincenti and Fusobacterium nucleatum

Answer

Borrelia burgdorferi and Lactobacillus

Answer

Leptospira and Treponema pallidum

Answer

Borrelia recurrentis and Bacteroides

Question 8

A person returns to Delhi from Bangladesh after 2 days and has diarrhea. Stool examination shows RBC's in stool. The likely organism causing is ?

Accepted Answer

Shigella dysenteriae

Answer

Enteropathogenic E. Coli

Answer

Salmonella typhi

Answer

Enterotoxigenic E. Coli

Question 9

All of the following cause Fournier's gangrene except:

Accepted Answer

Clostridium

Answer

Bacteroides

Answer

Streptococcus

Answer

Staphylococcus

Question 10

Causative organism of "glanders" is:

Accepted Answer

Burkholderia mallei

Answer

Pseudomonas pseudomallei

Answer

Leptospira

Answer

Chlamydia

Bacteriology — MCQs

Bacteriology — MCQs

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