Bacteriology Practice Questions

Q: A microbiologist wants to develop a vaccine for prevention of attachment of diarrhoeagenic E.coli to the specific receptors in the gastro-intestinal tract. All of the following fimbrial adhesions would be appropriate vaccine candidates except -

P1-Pili. ***P1-Pili*** - **P1-pili** (also known as P-fimbriae or Pap-pili) are primarily associated with **uropathogenic *E. coli*** causing **urinary tract infections**, not diarrhoeagenic *E. coli* in the gastrointestinal tract. - A vaccine targeting P1-pili would therefore not be relevant for preventing gastrointestinal attachment. *K 88* - **K88 fimbriae** are well-known **adhesins** found in certain strains of **enterotoxigenic *E. coli*** (ETEC) that colonize the gut and cause diarrhoea, especially in piglets. - Targeting K88 would be an appropriate strategy for a vaccine against diarrhoeagenic *E. coli*. *CFA-1* - **Colonization Factor Antigen I (CFA/I)** is a major **fimbrial adhesin** expressed by human **enterotoxigenic *E. coli*** (ETEC) strains. - CFA/I mediates bacterial attachment to intestinal epithelial cells and is a critical virulence factor, making it a suitable vaccine candidate. *CS-2* - **Colonization Factor Antigen II (CFA/II)**, which includes subunits like **CS-2** (CS for "coli surface"), is another important **fimbrial adhesin** found in human **enterotoxigenic *E. coli*** (ETEC). - CS-2 contributes significantly to ETEC's ability to colonize the small intestine and cause diarrhoea, making it a strong vaccine candidate.

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: A 24-year-old man had been treated for gonorrhea 2 months previously. He developed an ulcerative lesion in the glands of the penis that is noted to be condylomata lata. The etiology of condylomata lata is which of the following?

Treponema pallidum. ***Treponema pallidum*** - **Condylomata lata** are characteristic lesions of **secondary syphilis**, caused by *Treponema pallidum* [1]. - They are typically broad, flat, moist, wart-like lesions that occur in warm, moist areas such as the anogenital region [1]. *Herpesvirus hominis, type II* - Herpesvirus hominis, type II (HSV-2) causes **genital herpes**, which manifests as painful vesicles that ulcerate [1]. - The lesions caused by HSV-2 are typically clustered, vesicular, and very painful, which is distinct from the hypertrophic, non-painful nature of condylomata lata [1]. *Hemophilus ducreyi* - *Hemophilus ducreyi* is the causative agent of **chancroid**, which presents as painful, soft ulcers with ragged, undermined borders, often accompanied by painful inguinal lymphadenopathy. - Chancroid lesions are typically destructive and highly painful, contrasting with the proliferative and less painful nature of condylomata lata. *Mixture of organisms* - While some sexually transmitted infections can involve coinfection, **condylomata lata** specifically point to a single etiological agent: *Treponema pallidum* [1]. - Attributing condylomata lata to a "mixture of organisms" is too vague and inaccurate given the specific morphology and strong association with syphilis [1].

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: Kallu, a 22 year old male had an outing with his friends and developed fever of 38.50C, diarrhoea, and vomiting following eating chicken salad, 24 hours back. Two of his friends developed the same symptoms. The diagnosis is -

Salmonella enteritis. ***Salmonella enteritis*** - The onset of **fever**, **diarrhea**, and **vomiting** 24 hours after eating potentially contaminated chicken salad, affecting multiple individuals, is highly characteristic of **Salmonella food poisoning** [2], [4]. - **Salmonella enteritidis** is a common cause of foodborne illness associated with poultry and eggs, and causes an **invasive infection** leading to systemic symptoms like fever [2]. *Vibrio cholerae* - **Vibrio cholerae** typically causes profuse, watery diarrhea ("rice-water stools") with severe dehydration, a much shorter incubation period (hours), and less pronounced fever, if any [3]. - It is usually associated with contaminated water sources in endemic areas and not typically isolated cases from common food items like chicken salad. *Bacillus cereus* - **Bacillus cereus** can cause two types of food poisoning: diarrheal (onset 6-15 hours) and emetic (onset 1-6 hours), usually associated with **reheated rice** [1]. - While it causes vomiting and diarrhea, the 24-hour incubation period for the symptoms described makes it less likely, and fever is less prominent than with Salmonella [1], [4]. *S. aureus* - **Staphylococcus aureus** food poisoning typically has a very rapid onset (1-6 hours) after consuming food contaminated with preformed toxins [2], [4]. - Symptoms are predominantly **nausea**, **vomiting**, and abdominal cramps, with diarrhea sometimes present, but fever is uncommon or mild due to the toxin-mediated nature rather than an invasive infection [2].

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.

Question 1

A microbiologist wants to develop a vaccine for prevention of attachment of diarrhoeagenic E.coli to the specific receptors in the gastro-intestinal tract. All of the following fimbrial adhesions would be appropriate vaccine candidates except -

Accepted Answer

P1-Pili

Answer

K 88

Answer

CFA-1

Answer

CS-2

Question 2

Hemorrhagic meningitis is caused by

Accepted Answer

Bacillus anthracis

Answer

Neisseria meningitidis

Answer

Haemophilus influenzae

Answer

Streptococcus pneumoniae

Question 3

Causative organism for ANUG is:

Accepted Answer

Fusospirochetal complex

Answer

Streptococcus sanguis

Answer

Treponema pallidum and spirochetes

Answer

Staphylococcus epidermidis

Question 4

A 24-year-old man had been treated for gonorrhea 2 months previously. He developed an ulcerative lesion in the glands of the penis that is noted to be condylomata lata. The etiology of condylomata lata is which of the following?

Accepted Answer

Treponema pallidum

Answer

Herpesvirus hominis, type II

Answer

Hemophilus ducreyi

Answer

Mixture of organisms

Question 5

Epiglottitis is mainly caused by:

Accepted Answer

Haemophilus

Answer

Streptococcus

Answer

Staphylococcus

Answer

Mycoplasma

Question 6

Residual auditory defect is a common complication in meningitis caused by

Accepted Answer

Haemophilus influenzae

Answer

Staphylococcus

Answer

Meningococcus

Answer

Escherichia coli

Question 7

Pseudomembranous colitis is caused by:

Accepted Answer

Cl. difficile

Answer

Pseudomonas

Answer

Cl. welchii

Answer

Cl. perfringens

Question 8

Sulfur granules in pus are seen in

Accepted Answer

Actinomyces israelii

Answer

Candida albicans

Answer

Nocardia brasiliensis

Answer

Histoplasma capsulatum

Question 9

Kallu, a 22 year old male had an outing with his friends and developed fever of 38.50C, diarrhoea, and vomiting following eating chicken salad, 24 hours back. Two of his friends developed the same symptoms. The diagnosis is -

Accepted Answer

Salmonella enteritis

Answer

Vibrio cholerae

Answer

Bacillus cereus

Answer

S. aureus

Question 10

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

Bacteriology — MCQs

Bacteriology — MCQs

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