Bacteriology Practice Questions

Q: Which one of the following organisms is not associated with synergistic gangrene?

Escherichia. ***Escherichia*** - ***Escherichia coli* is NOT associated with classic synergistic gangrene** (Meleney's gangrene). - While *E. coli* causes many infections (UTIs, peritonitis, wound infections), it is **not a typical organism** in the polymicrobial synergistic gangrene described by Meleney. - Synergistic gangrene specifically involves **aerobic and microaerophilic organisms** working in combination, which is not the typical pattern for *E. coli* infections. *Staphylococcus* - ***Staphylococcus aureus* is a classic component of synergistic gangrene** (Meleney's gangrene). - Typically works in synergy with **microaerophilic streptococci** to cause progressive necrotizing infection. - *S. aureus* creates conditions that allow **anaerobic and microaerophilic organisms** to proliferate. *Clostridium* - ***Clostridium* species are associated with necrotizing soft tissue infections**, particularly gas gangrene (*C. perfringens*). - While gas gangrene differs from classic Meleney's synergistic gangrene, clostridial infections can occur in **polymicrobial settings** with synergistic tissue destruction. - They produce powerful **exotoxins** (alpha toxin, collagenase) causing rapid necrosis and gas formation. *Peptostreptococcus* - ***Peptostreptococcus* species are frequently isolated from synergistic gangrene**. - These **anaerobic gram-positive cocci** are key components of polymicrobial necrotizing infections. - They create an **anaerobic environment** that promotes tissue necrosis and allows other organisms to thrive.

Q: Donovan bodies are associated with :

Granuloma inguinale. ***Granuloma inguinale*** - **Donovan bodies** are characteristic intracellular inclusions found within macrophages in tissue samples from patients with **granuloma inguinale**, also known as **donovanosis**. - These bodies are the causative organism, *Klebsiella granulomatis*, encapsulated within phagosomes, and appear as safety pin-shaped structures. *Gonorrhoea* - This sexually transmitted infection is caused by **Neisseria gonorrhoeae**, a Gram-negative diplococcus. - Diagnosis is typically based on identifying the organism in smears or cultures, not by Donovan bodies. *Chlamydia trachomatis infection* - **Chlamydia trachomatis** is an obligate intracellular bacterium that causes various infections, including cervicitis, urethritis, and lymphogranuloma venereum. - While it causes inclusion bodies within host cells, these are distinct from Donovan bodies and are known as **chlamydial inclusion bodies**. *Herpes genitalis* - This is a viral infection caused by the **herpes simplex virus (HSV)** type 1 or 2. - Diagnosis involves viral culture, PCR, or the identification of **Tzanck cells** (multinucleated giant cells) in vesicular fluid, not Donovan bodies.

Q: The pathogenic organism responsible for the causation of Donovaniasis is

Klebsiella granulomatis. ***Klebsiella granulomatis*** - This bacterium is the causative agent of **granuloma inguinale**, also known as **donovaniasis**. - It infects macrophages and causes chronic, progressive **genital ulcers** with a characteristic beefy-red appearance. *Herpes simplex virus* - This virus causes **genital herpes**, characterized by painful **vesicular or ulcerative lesions** that tend to recur. *Haemophilus ducreyi* - This bacterium causes **chancroid**, characterized by painful, soft chancres with **ragged, undermined borders**. *Chlamydia trachomatis* - This bacterium is responsible for several sexually transmitted infections, including **lymphogranuloma venereum (LGV)**, which presents with transient genital lesions followed by painful, suppurative lymphadenopathy, and **genital chlamydial infections** which often cause urethritis or cervicitis.

Q: All of the following organisms are involved in post-splenectomy sepsis except

Staphylococcus aureus. ***Staphylococcus aureus*** - While *Staphylococcus aureus* can cause various infections, it is **not typically considered a primary encapsulated organism** for which the spleen's filtering function is critical, and therefore, it is **less commonly implicated in overwhelming post-splenectomy infection (OPSI)** compared to encapsulated bacteria. - The risk of OPSI is significantly higher with **encapsulated bacteria** due to the spleen's role in clearing these pathogens. *Neisseria meningitidis* - *Neisseria meningitidis* is an **encapsulated bacterium** and a well-known cause of **meningitis and sepsis**, particularly in individuals with **asplenia**. - The **spleen plays a crucial role in filtering encapsulated organisms** from the bloodstream, making asplenic individuals highly susceptible. *Haemophilus influenzae* - **Encapsulated strains** of *Haemophilus influenzae* (especially type b) are a significant cause of invasive infections in asplenic patients, including **meningitis and epiglottitis**. - The **lack of splenic immune function** impairs the body's ability to clear these bacteria. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* is the **most common cause of OPSI** (overwhelming post-splenectomy infection) due to its **polysaccharide capsule**. - The spleen is essential for **opsonization and phagocytosis** of encapsulated bacteria, a function lost post-splenectomy.

Q: The causative organism of Chancroid is

Haemophilus ducreyi. ***Haemophilus ducreyi*** - **Chancroid** is a sexually transmitted infection characterized by painful genital ulcers and regional lymphadenopathy, caused by the bacterium **Haemophilus ducreyi**. - This bacterium is a **Gram-negative coccobacillus** that requires specific culture media for isolation. *Chlamydia trachomatis* - **Chlamydia trachomatis** is responsible for **chlamydia**, a common STI, and can also cause **lymphogranuloma venereum (LGV)**, which presents with lymphadenopathy and sometimes genital ulcers but not typically the soft, painful ulcers seen in chancroid. - Infections with *Chlamydia trachomatis* are often **asymptomatic** or cause symptoms like urethritis, cervicitis, or proctitis. *Klebsiella granulomatis* - **Klebsiella granulomatis** (formerly *Calymmatobacterium granulomatis*) is the causative agent of **granuloma inguinale** (also known as donovanosis). - **Granuloma inguinale** presents with painless, beefy red, friable ulcerative lesions, which clinically differ from the painful ulcers of chancroid. *Psittacosis lymphogranuloma group* - This option incorrectly groups **psittacosis** (caused by *Chlamydia psittaci*) with **lymphogranuloma venereum (LGV)**, which is caused by specific serovars of *Chlamydia trachomatis*. - **Psittacosis** is primarily a pulmonary infection transmitted by birds, while **LGV** is a sexually transmitted infection distinct from chancroid.

Q: Which of the following cause/causes bacterial vaginosis? 1. Gardnerella 2. Mycoplasma hominis 3. Ureaplasma urealyticum Select the correct answer using the code given below:

1, 2 and 3. ***1, 2 and 3*** - Bacterial vaginosis is a polymicrobial syndrome resulting from an imbalance in the vaginal flora, often characterized by a decrease in **Lactobacilli** and an overgrowth of various anaerobic bacteria. - **Gardnerella vaginalis** is the most commonly associated bacterium, but **Mycoplasma hominis** and **Ureaplasma urealyticum** are also frequently isolated and contribute to the pathogenesis of the condition. *1 and 3 only* - This option incorrectly excludes **Mycoplasma hominis**, which is a recognized contributor to the polymicrobial nature of bacterial vaginosis. - While *Gardnerella* and *Ureaplasma* are significant, the disease involves multiple species. *2 and 3 only* - This option incorrectly excludes **Gardnerella vaginalis**, which is considered the hallmark organism and a primary diagnostic indicator for bacterial vaginosis. - Omitting *Gardnerella* would misrepresent the key infectious agents involved. *1 only* - This option incorrectly suggests that **Gardnerella vaginalis** is the sole causative agent, overlooking the polymicrobial nature of bacterial vaginosis. - The condition is characterized by a shift in the entire vaginal microenvironment, involving multiple types of bacteria.

Q: A surgeon told the patient’s attendant that his patient has “flesh eating bug” which is the cause of such severe infection in his dirty wound on his lower limb. Which organism was the surgeon referring to?

Streptococcus pyogenes. ***Streptococcus pyogenes*** - *Streptococcus pyogenes* (Group A Streptococcus) is the **primary and most common cause** of **necrotizing fasciitis**, which is classically referred to as the "flesh-eating bug" due to its rapid and extensive tissue destruction. - It produces powerful **exotoxins (streptolysins O and S) and enzymes (streptokinase, hyaluronidase)** that lead to widespread tissue necrosis, systemic toxicity, and a severe inflammatory response. - The term **"flesh-eating bug"** specifically refers to this organism in medical parlance. *Clostridium difficile* - *Clostridium difficile* primarily causes **pseudomembranous colitis**, an infection of the colon typically associated with antibiotic use and disruption of normal gut flora. - While it can be life-threatening, it does not cause necrotizing soft tissue infections in open wounds on limbs. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* is a common cause of wound infections, especially in **burn patients**, immunocompromised individuals, and nosocomial settings, characterized by **blue-green pus** and a **fruity/grape-like odor**. - While it can cause severe wound infections, it is not typically referred to as the "flesh-eating bug" and causes a different clinical picture than the rapidly spreading necrotizing fasciitis caused by *S. pyogenes*. *Staphylococcus aureus* - *Staphylococcus aureus* (including MRSA) causes various skin and soft tissue infections including cellulitis, abscesses, and surgical site infections. - While it can occasionally cause necrotizing fasciitis (especially in polymicrobial infections), the colloquial term **"flesh-eating bug"** specifically refers to *Streptococcus pyogenes*, which is the most common single pathogen causing this condition.

Q: Throat swab positive and Schick test negative indicate that the person is:

Immune to diphtheria. ***Immune to diphtheria*** - A **negative Schick test** indicates the presence of sufficient **antitoxin antibodies** in the individual's blood, conferring **immunity** against diphtheria toxin. - A positive throat swab combined with a negative Schick test indicates the person is a **healthy carrier** (or **immune carrier**) – harboring *Corynebacterium diphtheriae* but protected from developing disease due to existing immunity. - Such carriers pose a **public health concern** as they can transmit the organism to susceptible individuals, despite being personally protected. *Hypersensitive to diphtheria* - **Hypersensitivity** to diphtheria is not assessed by the Schick test; a negative result indicates protective immunity, not an allergic or hypersensitivity reaction. - The Schick test specifically measures the ability to neutralize diphtheria toxin through antitoxin antibodies, not immune hypersensitivity. *Susceptible to diphtheria* - **Susceptibility to diphtheria** would be indicated by a **positive Schick test**, meaning there is insufficient antitoxin to neutralize the injected toxin, resulting in a local inflammatory reaction at the test site. - The given scenario states a **negative Schick test**, which definitively rules out susceptibility. *Suffering from diphtheria* - While a **positive throat swab** indicates the presence of *Corynebacterium diphtheriae*, a **negative Schick test** means the individual has protective immunity and is **not suffering from clinical disease**. - Active diphtheria presents with characteristic symptoms (pseudomembrane, bull neck, etc.), which would not occur in an immune individual despite bacterial colonization.

Q: The most common organism causing Acute Otitis media in children is:

Streptococcus pneumoniae. ***Streptococcus pneumoniae*** - **_Streptococcus pneumoniae_** is the most frequent bacterial cause of **acute otitis media (AOM)** in children, accounting for a significant percentage of cases. - Its presence often leads to **inflammation** and **fluid accumulation** in the middle ear, characteristic of AOM. *Staphylococcus epidermidis* - While **_Staphylococcus epidermidis_** is a common **skin commensal** and a frequent cause of device-related infections, it is rarely implicated in acute otitis media. - Its role in AOM is usually limited to **contaminant cultures** rather than true infection. *Klebsiella pneumoniae* - **_Klebsiella pneumoniae_** is more commonly associated with **pneumonia**, **urinary tract infections**, and **healthcare-associated infections**, particularly in immunocompromised individuals. - It is an **uncommon cause** of typical acute otitis media in healthy children. *Escherichia coli* - **_Escherichia coli_** is a common cause of **urinary tract infections** and **gastrointestinal infections**. - It is **rarely a primary cause** of acute otitis media, especially in otherwise healthy children, unless there are underlying risk factors or specific infection pathways.

Q: A 27-year-old man presents with clear urethral discharge and dysuria for 3 days. Gram stain shows numerous polymorphonuclear leukocytes without intracellular diplococci. What is the most likely pathogen?

Chlamydia trachomatis. ***Chlamydia trachomatis*** - The presentation of **clear urethral discharge** and **dysuria** in a sexually active young man, coupled with polymorphonuclear leukocytes on Gram stain but **no intracellular diplococci**, is highly characteristic of **chlamydial urethritis**. - *Chlamydia trachomatis* causes **non-gonococcal urethritis** and is a common cause of sexually transmitted infections (STIs). *Neisseria gonorrhoeae* - This pathogen typically causes **purulent urethral discharge** and would show **intracellular Gram-negative diplococci** on microscopy, which were absent in this case. - Gonococcal urethritis is usually associated with more severe symptoms and a different Gram stain finding. *Trichomonas vaginalis* - While *Trichomonas vaginalis* can cause urethritis in men, it is less common than in women and typically presents with a **foamy, greenish discharge** and may be associated with **pruritus**. - *Trichomonas* is not visible on Gram stain; diagnosis requires **wet mount microscopy** showing motile trophozoites, making this less likely given the laboratory findings. *Ureaplasma urealyticum* - *Ureaplasma urealyticum* can cause **non-gonococcal urethritis**, but it is generally associated with **milder symptoms** or can even be asymptomatic. - While it's a possibility, *Chlamydia trachomatis* is a more common and prominent cause of the described clinical picture.

Question 1

Which one of the following organisms is not associated with synergistic gangrene?

Accepted Answer

Escherichia

Answer

Staphylococcus

Answer

Clostridium

Answer

Peptostreptococcus

Question 2

Donovan bodies are associated with :

Accepted Answer

Granuloma inguinale

Answer

Gonorrhoea

Answer

Chlamydia trachomatis infection

Answer

Herpes genitalis

Question 3

The pathogenic organism responsible for the causation of Donovaniasis is

Accepted Answer

Klebsiella granulomatis

Answer

Herpes simplex virus

Answer

Haemophilus ducreyi

Answer

Chlamydia trachomatis

Question 4

All of the following organisms are involved in post-splenectomy sepsis except

Accepted Answer

Staphylococcus aureus

Answer

Neisseria meningitidis

Answer

Haemophilus influenzae

Answer

Streptococcus pneumoniae

Question 5

The causative organism of Chancroid is

Accepted Answer

Haemophilus ducreyi

Answer

Chlamydia trachomatis

Answer

Klebsiella granulomatis

Answer

Psittacosis lymphogranuloma group

Question 6

Which of the following cause/causes bacterial vaginosis?

1. Gardnerella
2. Mycoplasma hominis
3. Ureaplasma urealyticum

Select the correct answer using the code given below:

Accepted Answer

1, 2 and 3

Answer

1 and 3 only

Answer

2 and 3 only

Answer

1 only

Question 7

A surgeon told the patient’s attendant that his patient has “flesh eating bug” which is the cause of such severe infection in his dirty wound on his lower limb. Which organism was the surgeon referring to?

Accepted Answer

Streptococcus pyogenes

Answer

Clostridium difficile

Answer

Pseudomonas aeruginosa

Answer

Staphylococcus aureus

Question 8

Throat swab positive and Schick test negative indicate that the person is:

Accepted Answer

Immune to diphtheria

Answer

Hypersensitive to diphtheria

Answer

Susceptible to diphtheria

Answer

Suffering from diphtheria

Question 9

The most common organism causing Acute Otitis media in children is:

Accepted Answer

Streptococcus pneumoniae

Answer

Staphylococcus epidermidis

Answer

Klebsiella pneumoniae

Answer

Escherichia coli

Question 10

A 27-year-old man presents with clear urethral discharge and dysuria for 3 days. Gram stain shows numerous polymorphonuclear leukocytes without intracellular diplococci. What is the most likely pathogen?

Accepted Answer

Chlamydia trachomatis

Answer

Neisseria gonorrhoeae

Answer

Trichomonas vaginalis

Answer

Ureaplasma urealyticum

Bacteriology — MCQs

Bacteriology — MCQs

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