Bacteriology Practice Questions

Q: A 34-year-old woman is at a family picnic where she has a ham sandwich and potato salad. Three hours after the meal, she feels nauseous and throws up.For the above patient with foodborne illness, select the most likely pathogen.

Staphylococcus aureus. ***Staphylococcus aureus*** - This pathogen produces **exotoxins** that cause rapid onset (1-6 hours) of severe nausea, vomiting, and abdominal cramps after ingesting contaminated food, consistent with the patient's symptoms. - Common sources include **creamy salads** (like potato salad) and **processed meats** (like ham), which are often left at room temperature, allowing toxin production. *C perfringens* - While *C. perfringens* can cause foodborne illness, its onset is typically longer (8-16 hours) and often presents with more pronounced **diarrhea** than vomiting. - It is often associated with **reheated meat dishes** and gravies. *Vibrio parahaemolyticus* - This bacterium is primarily associated with the consumption of **raw or undercooked seafood**, which is not mentioned in the patient's meal. - Symptoms usually include **watery diarrhea** with abdominal cramps, and the incubation period can range from 4 to 96 hours. *Shigella* - *Shigella* causes **dysentery**, characterized by fever, severe abdominal cramps, and bloody diarrhea, and typically has a longer incubation period (1-3 days). - Its transmission often involves the fecal-oral route, usually through contaminated water or food handled by infected individuals, and the clinical picture does not match the rapid onset and vomiting described.

Q: In cholangitis, the organism mostly responsible is ?

E.Coli. ***E.Coli*** - **_E. coli_** is the most common Gram-negative bacterium causing cholangitis due to its prevalence in the gut and ability to ascend the biliary tree. - Its presence is often linked to **biliary obstruction**, creating an environment conducive to bacterial proliferation. *Streptococcus* - While *Streptococcus spp.* can cause infections, they are **less common** as primary causes of cholangitis compared to **Gram-negative bacilli**. - **Enterococci**, a type of streptococcus, can be significant in **healthcare-associated cholangitis** or in recurrent cases. *Klebsiella* - **_Klebsiella_** species are **Gram-negative bacteria** that are the **second most common cause** of acute cholangitis after E. coli. - They are particularly associated with **healthcare-associated biliary infections** and **recurrent cholangitis**. - Like E. coli, they originate from the **gastrointestinal tract** and can ascend the biliary tree. *Clostridium* - **_Clostridium_** species are **anaerobic bacteria** and are generally **not primary pathogens in acute cholangitis** unless there is severe tissue damage or specific conditions. - While some species can cause **gas gangrene** or **colitis**, they are **rarely the sole cause** of acute cholangitis.

Q: Typhoid carriers harbor bacteria in

Gallbladder. ***Gallbladder*** - The **gallbladder** is the primary site where **Salmonella Typhi** bacteria can persist in chronic carriers, leading to asymptomatic shedding and potential transmission. - The bacteria form **biofilms** on gallstones or the gallbladder mucosa, making eradication difficult. *Spleen* - The spleen can be involved during the **acute phase** of typhoid fever, leading to **splenomegaly**, but it is not the primary site for chronic carriage. - While bacteria may transiently reside here, it does not typically harbor the persistent, high bacterial loads seen in chronic carriers. *Pancreas* - The pancreas is generally **not a site for chronic carriage** of Salmonella Typhi. - Pancreatic involvement in typhoid fever is rare and typically presents as **acute pancreatitis**, not persistent bacterial shedding. *Urinary bladder* - While **urinary carriage** of Salmonella Typhi can occur, it is **less common** than fecal carriage and usually associated with underlying urinary tract abnormalities. - The urine is not the primary body fluid through which chronic carriers typically transmit the infection.

Q: The causative agent of louse-borne relapsing fever is:

B recurrentis. ***B recurrentis*** - **_Borrelia recurrentis_** is the specific spirochete responsible for **louse-borne relapsing fever (LBRF)**, which is transmitted by the human body louse, _Pediculus humanus humanus_. - This infection is characterized by recurrent episodes of **fever**, **headache**, and **myalgia**, due to antigenic variation of the bacterium. *B parkeri* - **_Borrelia parkeri_** causes **tick-borne relapsing fever (TBRF)** and is primarily transmitted by soft-bodied ticks, not lice. - Its geographical distribution and clinical presentation, while similar to other relapsing fevers, are associated with tick exposure. *B burgdorferi* - **_Borrelia burgdorferi_** is the causative agent of **Lyme disease**, a distinct tick-borne illness, not relapsing fever. - Lyme disease is characterized by an **erythema migrans** rash, arthritis, and neurological symptoms, and typically does not present with recurrent fevers in the same manner as relapsing fever. *B duttoni* - **_Borrelia duttoni_** is another species that causes **tick-borne relapsing fever (TBRF)**, prevalent in parts of Africa, transmitted by soft ticks of the genus _Ornithodoros_ - It is not associated with louse transmission, differentiating it from louse-borne relapsing fever.

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.

Question 1

A 34-year-old woman is at a family picnic where she has a ham sandwich and potato salad. Three hours after the meal, she feels nauseous and throws up.For the above patient with foodborne illness, select the most likely pathogen.

Accepted Answer

Staphylococcus aureus

Answer

C perfringens

Answer

Vibrio parahaemolyticus

Answer

Shigella

Question 2

In cholangitis, the organism mostly responsible is ?

Accepted Answer

E.Coli

Answer

Streptococcus

Answer

Klebsiella

Answer

Clostridium

Question 3

Typhoid carriers harbor bacteria in

Accepted Answer

Gallbladder

Answer

Spleen

Answer

Pancreas

Answer

Urinary bladder

Question 4

The causative agent of louse-borne relapsing fever is:

Accepted Answer

B recurrentis

Answer

B parkeri

Answer

B burgdorferi

Answer

B duttoni

Question 5

Traveller’s diarrhoea is most commonly caused by

Accepted Answer

ETEC

Answer

Salmonella

Answer

EPEC

Answer

S. dysenteriae

Question 6

Most common cause of hemolytic uremic syndrome is –

Accepted Answer

E.coli

Answer

Shigella

Answer

Pseudomonas

Answer

Salmonella

Question 7

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 8

Botryomycosis is a ___ disease

Accepted Answer

Bacterial

Answer

Viral

Answer

Parasitic

Answer

Fungal

Question 9

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 10

Traveller's diarrhoea is caused by:

Accepted Answer

E. coli

Answer

E. histolytica

Answer

Giardia lamblia

Answer

Shigella

Bacteriology — MCQs

Bacteriology — MCQs

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