Bacteriology Practice Questions

Q: Traveller’s diarrhoea is most commonly caused by

ETEC. ***ETEC*** - **Enterotoxigenic Escherichia coli (ETEC)** is the most frequent cause of traveler's diarrhoea worldwide. - It produces toxins that cause **fluid secretion** in the intestine, leading to watery diarrhoea. *Salmonella* - While a common cause of food poisoning, **Salmonella** typically presents with more severe symptoms like fever, abdominal cramps, and sometimes bloody stool, and is not the most common cause of traveler's diarrhoea. - Salmonella infections are often associated with consumption of contaminated poultry, eggs, or dairy products. *EPEC* - **Enteropathogenic Escherichia coli (EPEC)** causes diarrhoea primarily in infants and young children, leading to destruction of intestinal microvilli. - It is not a common cause of traveler's diarrhoea in adults. *S. dysenteriae* - **Shigella dysenteriae** is known for causing bacillary dysentery, characterized by severe, often bloody diarrhoea, high fever, and abdominal cramps. - While it can cause severe illness, it is not the most common cause of the more general traveller's diarrhoea.

Q: Most common cause of hemolytic uremic syndrome is –

E.coli. **E.coli** * The most common cause of **hemolytic uremic syndrome (HUS)** is infection with Shiga toxin-producing **Escherichia coli (STEC)**, particularly **E. coli O157:H7** [1]. * The **Shiga toxin** damages endothelial cells, leading to microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury [1]. * *Shigella* * While **Shigella dysenteriae type 1** can also produce Shiga toxin and cause HUS, it is a less common cause compared to STEC in most regions. * Shigella infections commonly lead to **dysentery**, but HUS is a less frequent complication than with E. coli O157:H7. * *Pseudomonas* * **Pseudomonas aeruginosa** is an opportunistic pathogen that can cause severe infections, particularly in immunocompromised individuals, but it is not directly associated with causing HUS. * Pseudomonas infections are known for causing conditions like **ventilator-associated pneumonia**, **otitis externa**, and skin infections, not HUS. * *Salmonella* * **Salmonella** species are common causes of food poisoning and enteric fever, but they do not produce Shiga toxin and are not a recognized cause of HUS. * Salmonella infections typically manifest as **gastroenteritis**, **typhoid fever**, or bacteremia, without triggering the thrombotic microangiopathy characteristic of HUS.

Q: Two of 3 family members have dinner at a local restaurant and, within 48 hours, start experiencing double vision, difficulty in swallowing and speaking, and breathing problems. These symptoms are consistent with which of the following?

Ingestion of a neurotoxin. ***Ingestion of a neurotoxin*** - The symptoms of **double vision**, **difficulty swallowing (dysphagia)**, **difficulty speaking (dysarthria)**, and **breathing problems** are classic manifestations of **botulism**, a severe form of food poisoning caused by the **botulinum neurotoxin** [1, 2]. - The rapid onset (within 48 hours) and association with a shared meal at a restaurant strongly suggest exposure to a preformed toxin, which is characteristic of foodborne botulism [2]. *Activation of cyclic AMP* - This mechanism is characteristic of toxins like **cholera toxin** or **E. coli enterotoxin**, which cause **secretory diarrhea** by increasing fluid and electrolyte secretion in the gut. - It does not explain the neurological symptoms observed, such as double vision, dysphagia, or breathing difficulties [2]. *Invasion of the gut epithelium by an organism* - This mechanism is typical of diseases caused by invasive bacteria like *Salmonella*, *Shigella*, or some strains of *E. coli*, leading primarily to symptoms like **inflammatory diarrhea**, fever, and abdominal pain [2]. - It does not account for the specific neurological signs of cranial nerve dysfunction and paralysis. *Endotoxin shock* - **Endotoxin shock**, also known as septic shock, is caused by the release of **lipopolysaccharide (LPS)** from gram-negative bacteria, leading to a systemic inflammatory response. - Symptoms include **fever**, **hypotension**, **tachycardia**, and **multiorgan dysfunction**, not the specific neurological symptoms described here.

Q: Botryomycosis is a ___ disease

Bacterial. ***Bacterial*** - **Botryomycosis** is primarily a **bacterial infection**, commonly caused by *Staphylococcus aureus* or, less frequently, by gram-negative bacteria like *Pseudomonas aeruginosa*. - It presents as chronic suppurative granulomatous inflammation characterized by the presence of **"grains" or "granules"** composed of bacterial microcolonies surrounded by hyaline material. *Viral* - **Viral infections** are caused by viruses and are typically characterized by intracellular replication and various cytopathic effects. - Botryomycosis does not involve viral pathogens; its pathogenesis is entirely distinct from viral diseases. *Parasitic* - **Parasitic diseases** are caused by parasites such as protozoa, helminths, or ectoparasites. - The clinical and pathological features of botryomycosis, including the distinct bacterial grains, do not align with parasitic infections. *Fungal* - Although it can superficially resemble **mycetoma (a fungal infection)** due to the presence of "grains," botryomycosis is not caused by fungi. - Mycetoma involves fungal organisms like *Madurella mycetomatis* or *Actinomadura madura*, which are distinctly different from the bacterial agents of botryomycosis.

Q: A college student is surprised one morning by painful urination and a cream-colored exudate. Any person who acquires the gram-negative microbe that causes this infection is most likely to have acquired it via which of the following?

Genitourinary tract. ***Genitourinary tract*** - The symptoms of **painful urination (dysuria)** and a **cream-colored purulent exudate** are pathognomonic for **urethral gonorrhea**, caused by *Neisseria gonorrhoeae*, a gram-negative diplococcus. - *Neisseria gonorrhoeae* is **exclusively acquired through direct sexual contact** (vaginal, anal, or oral) with an infected individual, making the **genitourinary tract the primary route of acquisition and site of infection**. - The organism has a predilection for **columnar epithelium** of the urethra, endocervix, rectum, pharynx, and conjunctiva. *Nasal tract* - The nasal tract is **not a route of acquisition** for *N. gonorrhoeae*. - Pathogens acquired via the nasal route include **respiratory viruses** (influenza, rhinovirus) and some causes of bacterial meningitis (e.g., *N. meningitidis*), which present with **respiratory or CNS symptoms**, not genitourinary symptoms. *GI tract* - The gastrointestinal tract is the entry point for **foodborne and waterborne pathogens** causing gastroenteritis (e.g., *Salmonella*, *Shigella*, *E. coli*). - While pharyngeal gonorrhea can occur from oral sexual contact, the **GI tract is not the primary acquisition route** for the urethral infection described, and gonorrhea does not cause primary GI symptoms. *Respiratory tract* - The respiratory tract is the acquisition route for infections like **tuberculosis** (*Mycobacterium tuberculosis*), **pneumonia** (*Streptococcus pneumoniae*), and **influenza**. - These infections present with **cough, dyspnea, fever, and respiratory distress**, not the genitourinary symptoms described in this case.

Q: Traveller's diarrhoea is caused by:

E. coli. ***E. coli*** - **Enterotoxigenic E. coli (ETEC)** is the most common cause of **traveler's diarrhea**, producing toxins that lead to watery stools. - The disease is typically acquired through ingestion of **contaminated food or water**, particularly in regions with poor sanitation. *E. histolytica* - This parasite causes **amoebiasis**, which can lead to **dysentery** (bloody diarrhea) or liver abscesses. - While it can cause diarrhea in travelers, it is not the most frequent pathogen associated with typical traveler's diarrhea. *Giardia lamblia* - **Giardiasis** typically results in **chronic, greasy, foul-smelling stools**, bloating, and malabsorption rather than acute watery diarrhea. - It's a common cause of **protracted diarrhea** in travelers but not the most frequent cause of acute onset. *Shigella* - This bacterium causes **shigellosis**, characterized by **dysentery (bloody, mucoid stools)**, fever, and abdominal cramps. - While a cause of bacterial diarrhea in travelers, it is less common than ETEC and presents with a more severe, invasive illness.

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.

Question 1

Traveller’s diarrhoea is most commonly caused by

Accepted Answer

ETEC

Answer

Salmonella

Answer

EPEC

Answer

S. dysenteriae

Question 2

Most common cause of hemolytic uremic syndrome is –

Accepted Answer

E.coli

Answer

Shigella

Answer

Pseudomonas

Answer

Salmonella

Question 3

Two of 3 family members have dinner at a local restaurant and, within 48 hours, start experiencing double vision, difficulty in swallowing and speaking, and breathing problems. These symptoms are consistent with which of the following?

Accepted Answer

Ingestion of a neurotoxin

Answer

Activation of cyclic AMP

Answer

Invasion of the gut epithelium by an organism

Answer

Endotoxin shock

Question 4

Botryomycosis is a ___ disease

Accepted Answer

Bacterial

Answer

Viral

Answer

Parasitic

Answer

Fungal

Question 5

A college student is surprised one morning by painful urination and a cream-colored exudate. Any person who acquires the gram-negative microbe that causes this infection is most likely to have acquired it via which of the following?

Accepted Answer

Genitourinary tract

Answer

Nasal tract

Answer

GI tract

Answer

Respiratory tract

Question 6

Traveller's diarrhoea is caused by:

Accepted Answer

E. coli

Answer

E. histolytica

Answer

Giardia lamblia

Answer

Shigella

Question 7

What is not true about yersiniosis -

Accepted Answer

Caused by Y pestis

Answer

Zoonosis

Answer

By yersinia enterocolitica

Answer

By yersinia pseudotuberculosis

Question 8

Scarlet fever is caused by?

Accepted Answer

Streptococci

Answer

Proteus

Answer

Klebsiella

Answer

Staphylococcus

Question 9

What is the causative agent of angular conjunctivitis?

Accepted Answer

Moraxella lacunata

Answer

Gonococcus

Answer

Moraxella catarrhalis

Answer

Meningococcus

Question 10

Chlamydia trachomatis serovars D-K cause-

Accepted Answer

Urethritis

Answer

Lymphogranuloma venereum

Answer

Trachoma

Answer

Arteriosclerosis

Bacteriology — MCQs

Bacteriology — MCQs

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