Bacteriology Practice Questions

Q: What is not true about yersiniosis -

Caused by Y pestis. ***Caused by Y pestis*** - This statement is **not true** about yersiniosis as it typically refers to infections caused by *Yersinia enterocolitica* or *Yersinia pseudotuberculosis*. - *Yersinia pestis* is the causative agent of the **plague**, a distinct and often more severe disease. *Zoonosis* - Yersiniosis is a **zoonotic disease**, meaning it is transmitted from animals to humans, typically through contaminated food or water. - The primary animal reservoirs include **pigs** for *Y. enterocolitica* and wild rodents for *Y. pseudotuberculosis*. *By yersinia enterocolitica* - **Yersinia enterocolitica** is one of the main species responsible for yersiniosis, causing gastrointestinal symptoms. - It is a common cause of **acute enteritis** and can mimic appendicitis. *By yersinia pseudotuberculosis* - **Yersinia pseudotuberculosis** is another species that causes yersiniosis, often presenting with mesenteric lymphadenitis. - While less common than *Y. enterocolitica*, it can also cause **gastrointestinal symptoms** and erythema nodosum.

Q: Scarlet fever is caused by?

Streptococci. ***Streptococci*** - **Scarlet fever** is caused by **Group A Streptococcus (GAS)**, specifically *Streptococcus pyogenes*. - This bacterium produces **pyrogenic exotoxins** (also known as streptococcal superantigens) that are responsible for the characteristic rash and other systemic symptoms of scarlet fever. *Proteus* - *Proteus* species are commonly associated with **urinary tract infections** and wound infections, not scarlet fever. - They are known for their characteristic "swarming" motility on agar. *Klebsiella* - *Klebsiella* species, particularly *Klebsiella pneumoniae*, are important causes of **pneumonia**, **urinary tract infections**, and **sepsis**. - They are encapsulated, gram-negative rods, distinct from the gram-positive cocci that cause scarlet fever. *Staphylococcus* - **Staphylococci**, such as *Staphylococcus aureus*, cause a variety of infections, including **skin infections** (e.g., impetigo, folliculitis), **food poisoning**, and **toxic shock syndrome**. - While they can produce toxins, the clinical presentation and specific toxins responsible for scarlet fever are distinct and caused by streptococci.

Q: What is the causative agent of angular conjunctivitis?

Moraxella lacunata. ***Moraxella Lacunata*** - **_Moraxella lacunata_** is well-known as the primary cause of **angular conjunctivitis**, characterized by inflammation and maceration of the skin at the outer canthus of the eye. - This bacterium produces **proteolytic enzymes** that contribute to the tissue damage seen in the corners of the eye. *Gonococcus* - **_Neisseria gonorrhoeae_** typically causes **hyperacute purulent conjunctivitis**, often with severe discharge and rapid onset. - It is not commonly associated with angular conjunctivitis. *Moraxella catarrhalis* - **_Moraxella catarrhalis_** is a common cause of **otitis media** and **bronchitis**, and sometimes conjunctivitis, but it does not specifically cause angular conjunctivitis. - While a Moraxella species, it lacks the specific enzymes that cause the characteristic angular lesion. *Meningococcus* - **_Neisseria meningitidis_** can cause **meningitis** and, less commonly, severe **conjunctivitis**, which is usually purulent and acute. - It is rarely implicated in cases of angular conjunctivitis.

Q: Chlamydia trachomatis serovars D-K cause-

Urethritis. ***Urethritis*** - **Chlamydia trachomatis serovars D-K** are the most common cause of **nongonococcal urethritis** in males and cervicitis in females. - These serovars infect the **epithelial cells** of the genital tract, leading to inflammation and symptoms such as dysuria and discharge. *Lymphogranuloma venereum* - This condition is caused by **Chlamydia trachomatis serovars L1, L2, and L3**, not serovars D-K. - LGV is characterized by invasive infection involving the **regional lymph nodes**, leading to painful lymphadenopathy, proctitis, or genital ulcers. *Trachoma* - **Trachoma** is caused by **Chlamydia trachomatis serovars A, B, Ba, and C**, not the D-K serovars. - It is a chronic follicular conjunctivitis that can lead to scarring and blindness, primarily affecting the eyes. *Arteriosclerosis* - **Arteriosclerosis** is a condition involving the hardening and narrowing of arteries, primarily linked to factors like **dyslipidemia, hypertension, and diabetes**. - There is currently no direct evidence to suggest that Chlamydia trachomatis, particularly serovars D-K, is a primary or significant cause of arteriosclerosis.

Q: Trench fever is caused by which of the following organisms?

Bartonella quintana. ***Bartonella quintana*** - **Trench fever**, also known as **Wolhynian fever** or quintan fever, is caused by *Bartonella quintana* (formerly *Rickettsia quintana*). - It is a **louse-borne illness** characterized by recurrent fevers, headache, and bone pain, especially in the shins. - The organism was reclassified from Rickettsia to Bartonella based on molecular and phylogenetic studies. *Borrelia recurrentis* - This bacterium is the causative agent of **epidemic relapsing fever**, also transmitted by body lice. - While it causes relapsing fevers, its clinical presentation and causative organism are distinct from trench fever. *Tunga penetrans* - This is a species of **flea** commonly known as the **jigger flea** or sand flea. - It causes a parasitic skin infection called **tungiasis**, characterized by intense itching and inflammation, and is not associated with trench fever. *Rickettsia prowazekii* - This bacterium is the etiologic agent of **epidemic typhus**, also a louse-borne disease. - While *Rickettsia prowazekii* causes a severe febrile illness, it presents differently from trench fever with symptoms like a characteristic rash and neurological complications.

Q: Patient having gastroenteritis after eating contaminated food. Microscopy showed gram-positive bacillus with subterminal spore. The bacteria is

Clostridium perfringens. ***Clostridium perfringens*** - This bacterium is a **Gram-positive, anaerobic bacillus** known for forming **subterminal spores**, matching the microscopy description. - It is a common cause of **food poisoning (gastroenteritis)** after consumption of contaminated meat or poultry. - The clinical presentation and microscopic findings are characteristic of *C. perfringens* infection. *Clostridium tetani* - While also a **Gram-positive bacillus**, *C. tetani* produces **terminal spores** (drumstick appearance), **not subterminal spores** as seen in this case. - It causes **tetanus**, not gastroenteritis, producing a neurotoxin that leads to muscle spasms and paralysis. *Corynebacterium* - Bacteria in this genus are **Gram-positive rods** but are **non-spore forming**, so they do not match the microscopy findings. - *Corynebacterium diphtheriae* causes diphtheria, an upper respiratory tract infection, not gastroenteritis. *Staphylococcus* - This is a genus of **Gram-positive cocci** (spherical bacteria), **not bacilli** (rods), and they do not form spores. - *Staphylococcus aureus* can cause food poisoning, but it would not appear as a Gram-positive bacillus with spores on microscopy.

Q: Osteomyelitis of spine is caused by the most common organism?

Staphylococcus aureus. ***Staphylococcus aureus*** - **_Staphylococcus aureus_** is the most common causative organism for **hematogenous osteomyelitis** in adults, including osteomyelitis of the spine. - It frequently gains access to bone through the bloodstream, leading to infection of the vertebral bodies. *Streptococcus* - While various species of **_Streptococcus_** can cause bone infections, they are **less common** than **_Staphylococcus aureus_** in vertebral osteomyelitis. - **Group A Streptococcus** primarily causes soft tissue infections, and **_S. pneumoniae_** is more associated with pneumonia and meningitis. *Pseudomonas* - **_Pseudomonas aeruginosa_** is a common cause of osteomyelitis, particularly in specific risk groups such as intravenous drug users, patients with puncture wounds (especially through footwear), or those with implanted medical devices. - It is **not the most common** overall cause of general osteomyelitis of the spine. *Mycobacterium tuberculosis* - **_Mycobacterium tuberculosis_** causes tuberculous spondylitis **(Pott's disease)**, which commonly affects the spine, leading to characteristic vertebral destruction and kyphosis. - While significant globally, it is **not the most common bacterial cause** of acute pyogenic vertebral osteomyelitis.

Q: All of the following species of Borrelia are associated with tick-borne relapsing fever, except:

Borrelia recurrentis. ***Borrelia recurrentis*** - This species is primarily associated with **louse-borne relapsing fever**, not tick-borne. - *Borrelia recurrentis* is transmitted by the human body louse (*Pediculus humanus humanus*). - It causes **epidemic relapsing fever**, particularly in conditions of overcrowding and poor hygiene. *Borrelia hermsii* - This is a well-known species that causes **tick-borne relapsing fever** in North America, transmitted by *Ornithodoros* ticks. - It is associated with **endemic outbreaks** of relapsing fever in specific geographic regions. *Borrelia turicatae* - This species is also a cause of **tick-borne relapsing fever** in North America, endemic to the southern United States. - It is transmitted by the soft tick *Ornithodoros turicata*. *Borrelia duttoni* - This species is a primary cause of **tick-borne relapsing fever** in Africa, primarily transmitted by *Ornithodoros moubata*. - It leads to cycles of fever and remission characteristic of relapsing fever.

Q: True about typhoid is -

Vi polysaccharide of bacterial cell used for vaccination. ***Vi polysaccharide of bacterial cell used for vaccination*** - The **Vi antigen** (capsular polysaccharide) from *Salmonella typhi* is used in **subunit vaccines** to induce protective immunity against typhoid fever. - This vaccine is effective and is recommended for travelers to endemic areas and high-risk individuals. *Chronic carrier is 10-15%* - The percentage of individuals who become **chronic carriers** after acute typhoid fever is much lower, typically around **1-5%**. - Chronic carriage is defined as shedding *Salmonella typhi* in stool or urine for more than one year. *Widal test is specific* - The **Widal test** detects antibodies against O and H antigens of *Salmonella typhi*, but it is **not specific** due to cross-reactions with other infections and prior vaccination. - Its utility is limited by low sensitivity and specificity, especially in endemic areas, making culture or PCR more reliable. *Incubation period 3-6 weeks* - The typical **incubation period** for typhoid fever is much shorter, usually ranging from **6 to 30 days**, with an average of 1-3 weeks. - A 3-6 week incubation period would be uncharacteristically long for typhoid fever.

Q: Most common organism causing SBP after E. coli is

Streptococcus. ***Streptococcus*** - After **E. coli**, **Streptococcus species** are the most common pathogens isolated in cases of **spontaneous bacterial peritonitis (SBP)**. - This includes various Streptococcal strains, which can translocate from the gut lumen into the ascetic fluid. *Bacteroids* - **Bacteroides fragilis** and other Bacteroids species are obligate anaerobes and are more commonly associated with **secondary peritonitis** due to bowel perforation, rather than SBP. - While they are abundant in the gut, their recovery in SBP is rare, suggesting a different pathogenic mechanism. *Enterococcus* - **Enterococci** are found in the gut flora and can cause SBP, but they are less common than Streptococcus species as the second leading cause. - Infections with Enterococcus are often seen in patients with **nosocomial infections** or those with prior antibiotic exposure. *Klebsiella* - **Klebsiella pneumoniae** is a common Gram-negative bacterium that can cause SBP, but it is typically the third most common Gram-negative cause after E. coli. - While significant, it does not surpass Streptococcus as the second most common overall cause of SBP following E. coli.

Question 1

What is not true about yersiniosis -

Accepted Answer

Caused by Y pestis

Answer

Zoonosis

Answer

By yersinia enterocolitica

Answer

By yersinia pseudotuberculosis

Question 2

Scarlet fever is caused by?

Accepted Answer

Streptococci

Answer

Proteus

Answer

Klebsiella

Answer

Staphylococcus

Question 3

What is the causative agent of angular conjunctivitis?

Accepted Answer

Moraxella lacunata

Answer

Gonococcus

Answer

Moraxella catarrhalis

Answer

Meningococcus

Question 4

Chlamydia trachomatis serovars D-K cause-

Accepted Answer

Urethritis

Answer

Lymphogranuloma venereum

Answer

Trachoma

Answer

Arteriosclerosis

Question 5

Trench fever is caused by which of the following organisms?

Accepted Answer

Bartonella quintana

Answer

Borrelia recurrentis

Answer

Tunga penetrans

Answer

Rickettsia prowazekii

Question 6

Patient having gastroenteritis after eating contaminated food. Microscopy showed gram-positive bacillus with subterminal spore. The bacteria is

Accepted Answer

Clostridium perfringens

Answer

Clostridium tetani

Answer

Corynebacterium

Answer

Staphylococcus

Question 7

Osteomyelitis of spine is caused by the most common organism?

Accepted Answer

Staphylococcus aureus

Answer

Streptococcus

Answer

Pseudomonas

Answer

Mycobacterium tuberculosis

Question 8

All of the following species of Borrelia are associated with tick-borne relapsing fever, except:

Accepted Answer

Borrelia recurrentis

Answer

Borrelia hermsii

Answer

Borrelia turicatae

Answer

Borrelia duttoni

Question 9

True about typhoid is -

Accepted Answer

Vi polysaccharide of bacterial cell used for vaccination

Answer

Chronic carrier is 10-15%

Answer

Widal test is specific

Answer

Incubation period 3-6 weeks

Question 10

Most common organism causing SBP after E. coli is

Accepted Answer

Streptococcus

Answer

Bacteroids

Answer

Enterococcus

Answer

Klebsiella

Bacteriology — MCQs

Bacteriology — MCQs

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