Gastrointestinal Infections — MCQs

10 questions

A child with fever with abdominal cramps & pus in stools, causative organism is ?

A tourist with a travel history to India presents with complaints of abdominal pain and multiple episodes of watery diarrhea. He reports having food at a local restaurant the previous night. Which of the following antidiarrheal agents is used in this condition?

A 17 year old adolescent, presented with fever since one week which is step-ladder in pattern. He also has loose stools which are "pea-soup" in consistency. Rose spots are seen on his body. He is most probably infected with:

The most common causative organism for traveler's diarrhea is which of the following?

A 7-year-old girl passed 15 stools in the last 24 hours and vomited thrice in the last 4 hours. She is irritable but drinking fluids. What is the optimal therapy?

All of the following cause hemolytic uremic syndrome except

Traveller's diarrhea is caused by:

Patient presenting with abdominal pain, diarrhea taking clindamycin for 5 days. Treated with metronidazole symptoms subsided. What is the causative agent -

Traveller's diarrhoea is caused by:

Q10

All of the following statements are true regarding central nervous system infections, except:

Gastrointestinal Infections Indian Medical PG Practice Questions and MCQs

Question 1: A child with fever with abdominal cramps & pus in stools, causative organism is ?

A. EHEC
B. ETEC
C. EAEC (Correct Answer)
D. EPEC

Explanation: ***EAEC (Enteroaggregative E. coli)*** - Among the E. coli strains listed, EAEC is the answer for this question, though **this is an atypical presentation**. - EAEC classically causes **persistent watery diarrhea** (>14 days) in children, often with **low-grade fever** and **abdominal pain**. - While EAEC primarily causes non-bloody diarrhea, it can occasionally produce **mucoid stools** with inflammatory cells due to mucosal inflammation from biofilm formation. - **Note:** The classic organism for fever + cramps + pus in stools would be **Shigella**, **Campylobacter**, or **EIEC (Enteroinvasive E. coli)** - not listed here. *EHEC (Enterohemorrhagic E. coli)* - EHEC (O157:H7) causes **hemorrhagic colitis** with bloody diarrhea due to **Shiga toxins**. - Can lead to **hemolytic uremic syndrome (HUS)** in children. - Characterized by **blood** rather than pus in stools, distinguishing it from typical dysentery. *ETEC (Enterotoxigenic E. coli)* - Most common cause of **traveler's diarrhea** and watery diarrhea in developing countries. - Produces **heat-labile (LT)** and **heat-stable (ST)** enterotoxins causing secretory diarrhea. - Results in profuse **watery stools without inflammation, blood, or pus**. *EPEC (Enteropathogenic E. coli)* - Leading cause of infantile diarrhea in developing countries. - Causes **attaching and effacing** lesions on intestinal mucosa. - Results in **watery diarrhea without significant inflammatory cells or pus** in stools.

Question 2: A tourist with a travel history to India presents with complaints of abdominal pain and multiple episodes of watery diarrhea. He reports having food at a local restaurant the previous night. Which of the following antidiarrheal agents is used in this condition?

A. Bismuth subsalicylate
B. Octreotide
C. Loperamide
D. Rifaximin (Correct Answer)
E. Ciprofloxacin

Explanation: ***Rifaximin*** - This patient's symptoms, including **abdominal pain**, **watery diarrhea**, and a recent **travel history to India** coupled with eating at a local restaurant, strongly suggest **traveler's diarrhea**, often caused by bacterial pathogens. - **Rifaximin** is a non-absorbable antibiotic specifically approved for treating non-invasive traveler's diarrhea, as it targets causative bacteria in the gut lumen with minimal systemic absorption. - Rifaximin is preferred due to its **excellent safety profile**, minimal systemic effects, and targeted action against enteric pathogens. *Ciprofloxacin* - **Ciprofloxacin** is a fluoroquinolone antibiotic that can be effective for traveler's diarrhea and has been used historically for this indication. - However, rifaximin is now preferred over ciprofloxacin due to increasing **fluoroquinolone resistance** among enteric pathogens, systemic absorption leading to more side effects, and FDA warnings about serious adverse effects associated with fluoroquinolones. - Ciprofloxacin may be reserved for more severe or invasive diarrhea cases. *Bismuth subsalicylate* - While **bismuth subsalicylate** can be used for symptomatic relief in traveler's diarrhea due to its anti-secretory and anti-inflammatory properties, it is not an antimicrobial agent. - It works by reducing fluid secretion and inflammation but does not directly address the underlying bacterial infection to the same extent as rifaximin. *Octreotide* - **Octreotide** is a somatostatin analog primarily used to treat severe, refractory diarrhea associated with conditions like neuroendocrine tumors or chemotherapy, not typical bacterial traveler's diarrhea. - Its mechanism involves inhibiting gastrointestinal hormone secretion and reducing intestinal motility, which is too potent for this common, self-limiting condition. *Loperamide* - **Loperamide** is an opioid-receptor agonist that acts as an anti-motility agent, reducing the frequency of bowel movements. - It is generally contraindicated as a primary treatment for traveler's diarrhea when an invasive bacterial infection is suspected, as it can prolong the retention of toxins and pathogens in the gut.

Question 3: A 17 year old adolescent, presented with fever since one week which is step-ladder in pattern. He also has loose stools which are "pea-soup" in consistency. Rose spots are seen on his body. He is most probably infected with:

A. Salmonella typhi (Correct Answer)
B. Adenovirus
C. Rotavirus
D. Vibrio cholerae

Explanation: ***Salmonella typhi*** - The combination of **step-ladder fever**, **"pea-soup" diarrhea**, and **rose spots** is a classic presentation of **typhoid fever**, caused by *Salmonella typhi* [1]. - This bacterial infection predominantly affects the gastrointestinal tract and can lead to systemic symptoms [1]. *Adenovirus* - **Adenovirus** typically causes **respiratory tract infections**, **conjunctivitis**, or **gastroenteritis**, but not with the specific symptom profile of step-ladder fever or rose spots. - While it can cause diarrhea, it's usually not described as "pea-soup" and lacks the other systemic features. *Rotavirus* - **Rotavirus** is a common cause of **severe gastroenteritis** in infants and young children, characterized by **watery diarrhea** and vomiting. - It does not present with step-ladder fever or rose spots, which are pathognomonic for typhoid. *Vibrio cholerae* - **Vibrio cholerae** causes **cholera**, an acute diarrheal illness characterized by **profuse watery diarrhea** (often described as "rice-water stools") and rapid dehydration. - It does not typically cause step-ladder fever or skin manifestations like rose spots.

Question 4: The most common causative organism for traveler's diarrhea is which of the following?

A. E. coli (Correct Answer)
B. Shigella
C. Norwalk virus
D. Rotavirus

Explanation: ***Correct: E. coli*** - **Enterotoxigenic Escherichia coli (ETEC)** is the most frequent cause of **traveler's diarrhea** worldwide, accounting for **30-40% of cases**. - It produces heat-labile (LT) and heat-stable (ST) enterotoxins that lead to **watery diarrhea** without significant fever or bloody stools. - Particularly common in travelers to **developing countries** in Latin America, Africa, and South Asia. *Incorrect: Shigella* - While it can cause severe diarrheal illness (dysentery) characterized by **bloody stools**, it accounts for only **5-10% of traveler's diarrhea cases**. - **Shigella infection** is more often associated with person-to-person spread and outbreaks in crowded settings. *Incorrect: Norwalk virus* - Also known as **Norovirus**, it is a very common cause of **gastroenteritis** globally, affecting people of all ages. - However, it is primarily responsible for widespread outbreaks, often in cruise ships or institutions, rather than being the predominant cause of individual traveler's diarrhea cases. *Incorrect: Rotavirus* - This virus is a major cause of **severe dehydrating diarrhea** in **infants and young children** worldwide. - While it can affect travelers, it is less common in adults and generally not considered the predominant cause of traveler's diarrhea in the general traveling population.

Question 5: A 7-year-old girl passed 15 stools in the last 24 hours and vomited thrice in the last 4 hours. She is irritable but drinking fluids. What is the optimal therapy?

A. IV fluids
B. IV fluids followed by ORS
C. ORS (Correct Answer)
D. Home fluids

Explanation: ***Correct: ORS (Oral Rehydration Solution)*** - The child has **some dehydration** (15 stools/24h, irritable, recent vomiting) - **Key feature: She is able to drink fluids** - this is the critical determinant for ORS therapy - According to **WHO Plan B** and **IAP guidelines**, children with some dehydration who can drink should receive ORS - ORS should be given at **75 mL/kg over 4 hours** for some dehydration - This is the **optimal first-line therapy** for this dehydration level *Incorrect: IV fluids* - Too aggressive for a child who can drink fluids - Reserved for **severe dehydration** or inability to tolerate oral intake - Unnecessary invasive intervention with associated risks *Incorrect: IV fluids followed by ORS* - IV therapy is not indicated as first-line when child can drink - This approach is used when IV rehydration is needed initially but child improves - Overtreatment for this clinical scenario *Incorrect: Home fluids* - Insufficient for documented dehydration with high stool frequency - Does not provide the **balanced electrolyte composition** of ORS - Home fluids (water, juices) may worsen electrolyte imbalance

Question 6: All of the following cause hemolytic uremic syndrome except

A. Vibrio cholera (Correct Answer)
B. EHEC
C. Campylobacter
D. Shigella

Explanation: ***Vibrio cholera*** - *Vibrio cholerae* causes **cholera**, characterized by severe watery diarrhea, dehydration, and electrolyte imbalance, but does not typically produce **Shiga toxin** or cause microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury characteristic of HUS. - While it can lead to acute kidney injury due to severe dehydration, it does not directly cause the **microangiopathic hemolytic anemia** and thrombocytopenia seen in HUS. *EHEC* - **Enterohemorrhagic *E. coli* (EHEC)**, particularly serotype O157:H7, is the most common cause of **Shiga toxin-producing E. coli (STEC)-HUS** [2]. - The **Shiga toxin** produced by EHEC damages endothelial cells, leading to platelet aggregation, hemolysis, and renal damage [2]. *Campylobacter* - **Campylobacter jejuni** infections can sometimes precede the development of **HUS**, particularly in children. - While less common than EHEC, *Campylobacter* can produce a **cytolethal distending toxin** which has been implicated in endothelial damage and HUS. *Shigella* - Certain species of **Shigella**, especially *Shigella dysenteriae type 1*, produce **Shiga toxin** and are a known cause of **HUS**. - Similar to EHEC, the Shiga toxin from *Shigella* leads to widespread endothelial damage, resulting in microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury [1].

Question 7: Traveller's diarrhea is caused by:

A. EPEC
B. EIEC
C. ETEC (Correct Answer)
D. EHEC

Explanation: ***ETEC*** - **Enterotoxigenic E. coli (ETEC)** is the most common cause of **traveler's diarrhea**, primarily through the production of **heat-labile (LT)** and **heat-stable (ST)** toxins. - These toxins stimulate **fluid and electrolyte secretion** in the small intestine, leading to watery diarrhea. *EPEC* - **Enteropathogenic E. coli (EPEC)** causes diarrhea, particularly in infants, by forming characteristic **attaching and effacing (A/E) lesions** on intestinal epithelial cells. - EPEC does not produce the toxins typically associated with traveler's diarrhea. *EIEC* - **Enteroinvasive E. coli (EIEC)** causes a form of dysentery by invading and destroying the colonic epithelium, similar to Shigella. - Its clinical presentation involves fever, abdominal cramps, and bloody diarrhea, which is distinct from the watery diarrhea of traveler's diarrhea. *EHEC* - **Enterohemorrhagic E. coli (EHEC)**, especially O157:H7, is known for causing **hemorrhagic colitis** and **hemolytic uremic syndrome (HUS)**, through the production of **Shiga toxins**. - While it causes severe gastrointestinal disease, it is not the primary cause of typical traveler's diarrhea.

Question 8: Patient presenting with abdominal pain, diarrhea taking clindamycin for 5 days. Treated with metronidazole symptoms subsided. What is the causative agent -

A. Clostridium difficile (Correct Answer)
B. Clostridium welchii
C. Clostridium perfringens
D. Clostridium botulinum

Explanation: ***Clostridium difficile*** - **Clindamycin** is a common antibiotic associated with **Clostridium difficile** infection, which causes **antibiotic-associated diarrhea** and **colitis**. - The successful treatment with **metronidazole** further supports the diagnosis of *C. difficile* infection. *Clostridium welchii* (also known as *Clostridium perfringens*) - Primarily causes **gas gangrene** and **food poisoning**, with symptoms more acute and severe than described. - Not typically associated with antibiotic-induced diarrhea but rather **contaminated food** or **wound infections**. *Clostridium perfringens* - This bacterium is a common cause of **food poisoning** (type A) featuring **abdominal cramps** and **diarrhea**, and **gas gangrene** (type C) due to deep tissue infections. - While it can cause diarrhea, it's not the classic cause of **antibiotic-associated diarrhea** like *C. difficile*. *Clostridium botulinum* - Produces a **neurotoxin** that causes **flaccid paralysis**, not abdominal pain and diarrhea due to antibiotic use. - The infection is typically acquired through **improperly canned food** or **wound contamination**.

Question 9: Traveller's diarrhoea is caused by:

A. E. histolytica
B. E. coli (Correct Answer)
C. Giardia lamblia
D. Shigella

Explanation: ***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 10: All of the following statements are true regarding central nervous system infections, except:

A. Prions infection causes spongiform encephalopathy
B. JC virus is causative agent for progressive multifocal leucoencephalopathy
C. Cytomegalovirus is a common cause of bilateral temporal lobe hemorrhagic infarction (Correct Answer)
D. Measles virus is the causative agent for subacute sclerosing pan encephalitis (SSPE)

Explanation: ***Cytomegalovirus is a common cause of bilateral temporal lobe hemorrhagic infarction.*** - **Cytomegalovirus (CMV)** typically causes **ventriculoencephalitis or periventricular necrosis** and microglial nodules in immunocompromised patients, not bilateral temporal lobe hemorrhagic infarction. - **Herpes simplex virus type 1 (HSV-1)** is the classic infectious cause of **bilateral temporal lobe hemorrhagic infarction (necrotizing encephalitis)**. *Prions infection causes spongiform encephalopathy* - **Prions** are misfolded proteins that cause transmissible spongiform encephalopathies (TSEs), such as Creutzfeldt-Jakob disease, characterized by **neuronal loss** and vacuolation (spongiform changes). - These diseases are invariably fatal and lead to rapid neurological deterioration. *JC virus is causative agent for progressive multifocal leucoencephalopathy* - The **JC virus** specifically targets and destroys **oligodendrocytes**, the myelin-producing cells of the central nervous system. - This leads to **demyelination** in multiple areas of the brain, causing the characteristic lesions seen in progressive multifocal leukoencephalopathy (PML). *Measles virus is the causative agent for subacute sclerosing pan encephalitis (SSPE).* - **Subacute sclerosing panencephalitis (SSPE)** is a rare, fatal, progressive neurodegenerative disease caused by a persistent and defective **measles virus infection** in the brain. - It occurs years after the initial measles infection, leading to cognitive decline, seizures, and motor dysfunction.

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