Bacteriology Practice Questions

Q: Cerebrospinal fever is due to

Neisseria meningitidis. ***Neisseria meningitidis*** - **Cerebrospinal fever** is another name for **meningococcal meningitis**, which is primarily caused by *Neisseria meningitidis*. - This bacterium is highly transmissible and can cause severe inflammation of the meninges, the membranes surrounding the brain and spinal cord. *Streptococcus pyogenes* - *Streptococcus pyogenes* is known for causing **strep throat**, **scarlet fever**, and **rheumatic fever**. - While it can cause severe infections, it is not the primary cause of cerebrospinal fever or meningococcal meningitis. *Staphylococcus aureus* - *Staphylococcus aureus* is a common cause of **skin infections**, **pneumonia**, and **sepsis**. - While it can cause meningitis, it is typically seen in specific contexts (e.g., healthcare-associated infections) and not primarily associated with the term "cerebrospinal fever." *None of the options* - This option is incorrect because *Neisseria meningitidis* is a well-established cause of cerebrospinal fever.

Q: Which of the following statements is TRUE about tetanus (Clostridium tetani)?

Produces tetanolysin and tetanospasmin. ***Produces tetanolysin and tetanospasmin*** - *Clostridium tetani* produces two exotoxins: **tetanospasmin** (a neurotoxin responsible for muscle spasms) and **tetanolysin** (a hemolysin whose role in pathogenesis is less clear but may contribute to tissue damage). - **Tetanospasmin** blocks the release of inhibitory neurotransmitters, leading to unopposed muscle excitation. *Trismus and neck stiffness are early sign* - While **trismus** (lockjaw) and **neck stiffness** are indeed characteristic early signs of tetanus, this statement is not the *most complete* or *fundamental* truth about the *mechanism* of the disease, which is toxin production. - Early symptoms also include difficulty swallowing and muscle spasms localized to the wound area before becoming generalized. *Gram -ve spore forming organism* - *Clostridium tetani* is a **Gram-positive**, not Gram-negative, bacterium. - It is an **anaerobic**, spore-forming rod, and its spores are highly resistant to heat and disinfectants. *Generalized tonic-clonic seizure occurs on hyperstimulation* - Tetanus causes **generalized tonic spasms** and **convulsions**, especially in response to sensory stimuli (hyperstimulation). - These are typically sustained, painful muscle contractions rather than classic generalized tonic-clonic seizures, though severe cases can resemble seizures.

Q: Tuberculin positivity means:

Infection with mycobacterium. ***Infection with mycobacterium*** - Tuberculin positivity, detected by a **positive tuberculin skin test (TST)** or **interferon-gamma release assay (IGRA)**, indicates that an individual has been exposed to and infected with **Mycobacterium tuberculosis** [1]. - This response reflects a **delayed-type hypersensitivity reaction** to tuberculin proteins, signifying the presence of cell-mediated immunity against the pathogen. *Resistance to tubercular protein* - Tuberculin positivity does not signify **resistance**; rather, it indicates prior exposure and the development of an immune response. - While prior infection can offer some protection, it doesn't equate to complete resistance, and individuals can still develop active disease. *Immunodeficiency* - Immunodeficiency would typically lead to a **false-negative** tuberculin test due to an inability to mount an adequate immune response, rather than a positive result. - A positive tuberculin test generally implies a functioning immune system capable of reacting to the bacterial antigens. *Patient suffering from disease* - A positive tuberculin test indicates **infection** with Mycobacterium tuberculosis, but it does **not differentiate** between latent TB infection (LTBI) and active TB disease [2]. - Further diagnostic tests, such as chest X-rays, sputum cultures, and clinical evaluation, are required to establish a diagnosis of active disease.

Q: Most common cause of UTI in young females is?

E. coli. ***E. coli*** - **Uropathogenic *E. coli*** (*UPEC*) is the most prevalent bacterium responsible for uncomplicated UTIs in otherwise healthy young women. - Its virulence factors, such as **P-fimbriae** (adhesins), allow it to attach to uroepithelial cells and colonize the urinary tract effectively. *Klebsiella* - While *Klebsiella pneumoniae*: can cause UTIs, it is more commonly associated with **hospital-acquired infections** or UTIs in patients with **comorbidities** or instrumentation. - It ranks significantly lower than *E. coli* as a cause of community-acquired UTIs in young females. *Proteus* - *Proteus mirabilis* is known for causing UTIs, especially those associated with **struvite kidney stones** due to its **urease activity**. - However, its incidence as a cause of UTI in young females is much less frequent compared to *E. coli*. *Staph saprophyticus* - **Staphylococcus saprophyticus** is a common cause of UTIs in young, sexually active women, accounting for a significant percentage [1]. - While it is a notable cause, **it is still less common than *E. coli***, which is overwhelmingly the leading pathogen in this demographic.

Q: Most common organism responsible for pseudomembranous colitis is:

Clostridium difficile. ***Clostridium difficile*** - **_Clostridium difficile_** is the most common causative organism for **pseudomembranous colitis**, an inflammation of the colon characterized by the formation of pseudomembranes. - This condition often develops after **antibiotic use** that disrupts the normal gut flora, allowing **_C. difficile_** to proliferate and produce toxins. *Clostridium botulinum* - **_Clostridium botulinum_** is responsible for **botulism**, a severe neuroparalytic illness caused by its potent toxins. - It does not cause pseudomembranous colitis, and its primary mode of action is through **neuromuscular blockade**, not intestinal inflammation. *Clostridium butyricum* - **_Clostridium butyricum_** is primarily known for producing **butyric acid** and is sometimes used as a probiotic. - It is not associated with causing pseudomembranous colitis or other significant human infections in healthy individuals. *Clostridium histolyticum* - **_Clostridium histolyticum_** is involved in **gas gangrene** and other soft tissue infections, producing powerful enzymes that break down tissues. - It is not implicated in the pathogenesis of pseudomembranous colitis.

Q: The most frequent cause of scalded skin syndrome is?

Staphylococci. ***Staphylococci*** - **Staphylococcus aureus** produces an **exotoxin (exfoliatin)** that targets desmosomes, leading to epidermal cleavage and the characteristic blistering seen in **staphylococcal scalded skin syndrome (SSSS)**. - SSSS is primarily seen in **infants and young children** due to their immature renal clearance of the exfoliatin toxin and lack of protective antibodies. *Meningococci* - **Neisseria meningitidis** is known to cause **meningitis** and **meningococcemia**, which can present with a **purpuric rash** but not typically widespread blistering characteristic of scalded skin syndrome. - The skin manifestations of meningococcal disease are usually due to **vasculitis** and **coagulopathy**, not exotoxin-mediated epidermal separation. *Pneumococci* - **Streptococcus pneumoniae** is a common cause of **pneumonia**, **otitis media**, and **meningitis**. - It does not produce exotoxins that cause the characteristic skin peeling seen in scalded skin syndrome. *Enterococci* - **Enterococci** are opportunistic pathogens primarily associated with **urinary tract infections**, **bacteremia**, and **nosocomial infections**. - They are not known to produce toxins that cause epidermolysis or scalded skin syndrome.

Q: Toxic shock syndrome is due to the following virulence factor:

Pyrogenic exotoxin. ***Pyrogenic exotoxin*** - **Pyrogenic exotoxins**, specifically **Toxic Shock Syndrome Toxin-1 (TSST-1)** and other streptococcal pyrogenic exotoxins (SPEs), are **superantigens** responsible for the symptoms of **toxic shock syndrome**. - These superantigens bind directly to **MHC class II** and **T-cell receptors**, leading to a massive, non-specific release of **cytokines** that cause severe systemic inflammation and organ failure. *M protein* - **M protein** is a major virulence factor of **Streptococcus pyogenes**, contributing to its antiphagocytic properties and adherence. - While important for streptococcal infections, it is not the primary mediator of the **toxic shock syndrome** associated with *Staphylococcus aureus* or *Streptococcus pyogenes*. *Carbohydrate cell wall* - The **carbohydrate cell wall** is a structural component of bacteria, particularly Gram-positive bacteria, and can have some immunogenic properties. - However, it does not directly act as a specific virulence factor like a superantigen to cause the severe systemic symptoms characteristic of **toxic shock syndrome**. *Streptolysin O* - **Streptolysin O** is an **exotoxin produced by Streptococcus pyogenes** that causes **hemolysis** and is cardiotoxic and cytolytic. - While it contributes to tissue damage and can be involved in severe streptococcal infections, it is not the main superantigen responsible for the widespread systemic effects of **toxic shock syndrome**.

Q: Which of the following statements about tetanus is true?

Caused by C. Tetani. ***Caused by C. Tetani*** - Tetanus is definitively caused by the bacterium **Clostridium tetani**, which is known for producing the potent neurotoxin **tetanospasmin**. - This neurotoxin is responsible for the characteristic **muscle spasms** and rigidity seen in tetanus. *Anaerobic infection* - While *Clostridium tetani* is an **anaerobic bacterium**, stating that tetanus is an "anaerobic infection" is a description of the causative agent, not the most definitive or unique statement about the disease itself. - The unique aspect of tetanus lies in the **neurotoxin production** by this specific anaerobe. *Cannot be prevented* - Tetanus is highly **preventable** through vaccination with the **tetanus toxoid**, which provides active immunity. - Public health efforts globally focus on widespread **immunization** to reduce the incidence of tetanus. *Forms terminal spores* - *Clostridium tetani* forms **spores**, but these are typically **subterminal** or terminal, depending on the strain, which is a characteristic of the bacterium, not the most defining statement about the disease process. - The spores are resilient and allow the bacterium to survive in harsh conditions until they find an **anaerobic environment** to germinate.

Q: Which one of the following statements best characterizes lympho-granuloma venereum (LGV)?

The causative agent is C. trachomatis. **The causative agent is *C. trachomatis*** - **Lymphogranuloma venereum (LGV)** is a sexually transmitted infection caused by specific serovars (**L1, L2, L2a, L2b, L3**) of *Chlamydia trachomatis*. [1] - These serovars are **invasive** and replicate in **mononuclear phagocytes** of lymphatic tissue, leading to the characteristic lymphadenopathy. [1] *It is most common in temperate regions* - LGV is **most common in tropical and subtropical regions**, particularly in parts of Africa, Southeast Asia, South America, and the Caribbean. - Its prevalence is much lower in temperate regions, though outbreaks can occur, especially in specific *high-risk populations*. *In the United States, it is more common among women* - In developed countries like the United States, LGV primarily affects **men who have sex with men (MSM)**, particularly those who are HIV-positive. [1] - While it can occur in women, its incidence is **significantly lower** in this population. *Penicillin is effective in early treatment* - LGV is caused by *Chlamydia trachomatis*, which is a **bacterium that lacks a peptidoglycan cell wall**, making it inherently resistant to penicillin. - The recommended treatments for LGV are **doxycycline** or **erythromycin**, not penicillin.

Q: 45 yrs old Ramlal has intra-abdominal sepsis. The causative organism was found to be vancomycin, gentamicin and ampicillin resistant. It grows well in presence of 6.5% NaCl and arginine. Bile esculin hydrolysis is positive. Which of the following is the organism? -

Enterococcus fecalis. ***Enterococcus fecalis*** - *Enterococcus fecalis* is commonly associated with **intra-abdominal sepsis** and can exhibit resistance to **vancomycin, gentamicin, and ampicillin**. - Its ability to grow in **6.5% NaCl**, hydrolyze **bile esculin**, and utilize **arginine** are classic biochemical characteristics distinguishing it from streptococci. *Streptococcus bovis* - While *Streptococcus bovis* can hydrolyze **bile esculin**, it typically **does not grow in 6.5% NaCl** and is usually susceptible to **ampicillin**. - It is more commonly associated with **bacteremia in patients with colon cancer** or endocarditis, rather than multi-drug resistant intra-abdominal sepsis. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* is known for causing pneumonia and meningitis but **does not grow in 6.5% NaCl** and has a **negative bile esculin test**. - It is also typically **penicillin-sensitive** (though resistance exists) and does not exhibit the multi-drug resistance profile described. *Streptococcus agalactiae* - *Streptococcus agalactiae* (Group B Strep) is known for causing neonatal sepsis and meningitis, but it **does not grow in 6.5% NaCl** and is **bile esculin negative**. - It is generally susceptible to **ampicillin** and does not fit the described multi-drug resistance pattern or biochemical profile.

Question 1

Cerebrospinal fever is due to

Accepted Answer

Neisseria meningitidis

Answer

Streptococcus pyogenes

Answer

Staphylococcus aureus

Answer

None of the options

Question 2

Which of the following statements is TRUE about tetanus (Clostridium tetani)?

Accepted Answer

Produces tetanolysin and tetanospasmin

Answer

Trismus and neck stiffness are early signs

Answer

Gram -ve spore forming organism

Answer

Generalized tonic-clonic seizure occurs on hyperstimulation

Question 3

Tuberculin positivity means:

Accepted Answer

Infection with mycobacterium

Answer

Resistance to tubercular protein

Answer

Immunodeficiency

Answer

Patient suffering from disease

Question 4

Most common cause of UTI in young females is?

Accepted Answer

E. coli

Answer

Klebsiella

Answer

Proteus

Answer

Staph saprophyticus

Question 5

Most common organism responsible for pseudomembranous colitis is:

Accepted Answer

Clostridium difficile

Answer

Clostridium botulinum

Answer

Clostridium butyricum

Answer

Clostridium histolyticum

Question 6

The most frequent cause of scalded skin syndrome is?

Accepted Answer

Staphylococci

Answer

Meningococci

Answer

Pneumococci

Answer

Enterococci

Question 7

Toxic shock syndrome is due to the following virulence factor:

Accepted Answer

Pyrogenic exotoxin

Answer

M protein

Answer

Carbohydrate cell wall

Answer

Streptolysin O

Question 8

Which of the following statements about tetanus is true?

Accepted Answer

Caused by C. Tetani

Answer

Anaerobic infection

Answer

Cannot be prevented

Answer

Forms terminal spores

Question 9

Which one of the following statements best characterizes lympho-granuloma venereum (LGV)?

Accepted Answer

The causative agent is C. trachomatis

Answer

It is most common in temperate regions

Answer

In the United States, it is more common among women

Answer

Penicillin is effective in early treatment

Question 10

45 yrs old Ramlal has intra-abdominal sepsis. The causative organism was found to be vancomycin, gentamicin and ampicillin resistant. It grows well in presence of 6.5% NaCl and arginine. Bile esculin hydrolysis is positive. Which of the following is the organism? -

Accepted Answer

Enterococcus fecalis

Answer

Streptococcus bovis

Answer

Streptococcus pneumoniae

Answer

Streptococcus agalactiae

Bacteriology — MCQs

Bacteriology — MCQs

On this page

Practice by Chapter

Want unlimited practice?