Clostridium difficile Infection — MCQs
A 40-year old woman presented to the surgical OPD with features suggestive of colitis. She was on prolonged treatment with clindamycin. Fecal sample was positive for toxin produced by this agent. Her condition improved on treatment with metronidazole. The clinical condition is associated with -
What is the therapy of choice for pseudomembranous enterocolitis?
Sudha, a 20-year-old female, developed antibiotic-associated pseudomembranous colitis caused by Clostridium difficile. Among the following drugs, which is most likely to be effective in the treatment of this disease?
The organism causing pseudomembranous colitis:
A woman with recurrent diarrhea is prescribed a broad-spectrum antibiotic. Which of the following statements is not true regarding Clostridium difficile infection?
Patient presenting with abdominal pain, diarrhea taking clindamycin for 5 days. Treated with metronidazole symptoms subsided. What is the causative agent -
Diagnosis of C. difficile infection is made by which of the following methods?
A 40-year-old patient presents with frequent watery diarrhea after a recent course of antibiotics. Stool toxin assay is positive for Clostridium difficile. What is the most appropriate treatment?
An otherwise healthy patient who has just received a prosthetic aortic valve develops postoperative fever. Blood cultures are done and she is placed on broad-spectrum antibiotics. Two days later she is still febrile and clinically deteriorating. Which of the following organisms is the most probable etiologic agent?
Which infection commonly spreads to newborns through caregivers?
Clostridium difficile Infection Indian Medical PG Practice Questions and MCQs
Question 1: A 40-year old woman presented to the surgical OPD with features suggestive of colitis. She was on prolonged treatment with clindamycin. Fecal sample was positive for toxin produced by this agent. Her condition improved on treatment with metronidazole. The clinical condition is associated with -
- A. Listeria monocytogenes
- B. Bacillus anthracis
- C. Clostridium difficile (Correct Answer)
- D. Acinetobacter baumannii
Explanation: ***Clostridium difficile*** - The history of **clindamycin use**, followed by **colitis symptoms**, a **positive fecal toxin test**, and improvement with **metronidazole**, are classic indicators of *Clostridium difficile* infection (CDI) [1]. - *C. difficile* produces toxins (Toxin A and Toxin B) that cause **pseudomembranous colitis**, often after antibiotic disruption of normal gut flora [1]. *Listeria monocytogenes* - This bacterium is primarily a cause of **foodborne illness**, leading to febrile gastroenteritis, meningitis, or sepsis, particularly in immunocompromised individuals, pregnant women, and neonates. - It is not typically associated with **antibiotic-associated colitis** or treated with metronidazole as a primary agent for bowel infection. *Bacillus anthracis* - This is the causative agent of **anthrax**, which can manifest as cutaneous, inhalational, or gastrointestinal forms. - **Gastrointestinal anthrax** causes severe abdominal pain, vomiting, bloody diarrhea, and fever, but it is rare and not linked to antibiotic use or toxin detection in stool in the context described. *Acinetobacter baumannii* - *Acinetobacter baumannii* is an important **opportunistic pathogen** often associated with hospital-acquired infections, such as pneumonia, urinary tract infections, and bloodstream infections, particularly in critically ill patients. - It is not a known cause of **antibiotic-associated colitis** due to toxin production, nor is metronidazole the primary treatment.
Question 2: What is the therapy of choice for pseudomembranous enterocolitis?
- A. Penicillin
- B. Ampicillin
- C. Erythromycin
- D. Vancomycin (Correct Answer)
Explanation: ***Vancomycin*** - **Oral vancomycin** is indicated for pseudomembranous enterocolitis, particularly for severe or recurrent cases, as it achieves high luminal concentrations in the colon to target *C. difficile* [1]. - Vancomycin works by inhibiting **bacterial cell wall synthesis**, effectively eradicating the toxigenic *C. difficile* strains responsible for the condition [1]. *Penicillin* - **Penicillin** is ineffective against *C. difficile* because *C. difficile* is a Gram-positive anaerobic bacterium producing toxins, and penicillin does not have the appropriate spectrum of activity. - In fact, many cases of pseudomembranous enterocolitis are triggered by prior **antibiotic use**, including penicillins, which disrupt the normal gut flora [2]. *Ampicillin* - Similar to penicillin, **ampicillin** is a broad-spectrum penicillin derivative and is not considered a treatment for *C. difficile* infection [3]. - Ampicillin can commonly be one of the **antibiotics that precipitates** the development of pseudomembranous enterocolitis by altering the normal gut microbiota [2]. *Erythromycin* - **Erythromycin**, a macrolide antibiotic, is not effective against *C. difficile* and is not used in the treatment of pseudomembranous enterocolitis. - Like other broad-spectrum antibiotics, erythromycin can **disrupt the normal gut flora**, potentially contributing to the overgrowth of *C. difficile* [2].
Question 3: Sudha, a 20-year-old female, developed antibiotic-associated pseudomembranous colitis caused by Clostridium difficile. Among the following drugs, which is most likely to be effective in the treatment of this disease?
- A. Metronidazole (Correct Answer)
- B. Ampicillin
- C. Clindamycin
- D. Chloramphenicol
Explanation: ***Metronidazole*** - Among the options listed, **Metronidazole** is the most effective for treating **Clostridioides difficile infection (CDI)**. - It works by disrupting bacterial DNA synthesis and is highly effective against **anaerobic bacteria** like *C. difficile*. - **Note:** Current guidelines (IDSA/SHEA 2021) recommend **oral vancomycin or fidaxomicin as first-line therapy**, with metronidazole reserved for situations where preferred agents are unavailable. However, among the drugs listed here, metronidazole remains the correct choice. *Ampicillin* - **Ampicillin** is a penicillin-class antibiotic and is **ineffective** against *Clostridioides difficile*. - It is one of the antibiotics that can **trigger** antibiotic-associated pseudomembranous colitis by disrupting normal gut flora and promoting *C. difficile* overgrowth. *Clindamycin* - **Clindamycin** is notorious for being a common cause of **antibiotic-associated pseudomembranous colitis** due to *Clostridioides difficile*. - It would **exacerbate** rather than treat the condition, making it an inappropriate choice. *Chloramphenicol* - **Chloramphenicol** is a broad-spectrum antibiotic that is **not effective** for treating *Clostridioides difficile* infection. - Its use is limited due to significant side effects, including **bone marrow suppression** (aplastic anemia), and it is not a recommended treatment for CDI.
Question 4: The organism causing pseudomembranous colitis:
- A. Clostridium difficile (Correct Answer)
- B. Clostridium botulinum
- C. Clostridium tetani
- D. Clostridium perfringens
Explanation: ***Clostridium difficile*** - This bacterium is the primary cause of **pseudomembranous colitis**, an inflammation of the colon characterized by the formation of membranes on the mucosal surface. - It produces **toxins A and B** which damage the intestinal lining, leading to severe diarrhea, abdominal pain, and fever. *Clostridium botulinum* - This organism is responsible for **botulism**, a severe form of food poisoning or wound infection. - It produces a potent **neurotoxin** that causes flaccid paralysis by blocking acetylcholine release at neuromuscular junctions. *Clostridium tetani* - This bacterium causes **tetanus**, characterized by muscle spasms and rigidity. - It produces the **tetanospasmin neurotoxin** which inhibits inhibitory neurotransmitters in the spinal cord. *Clostridium perfringens* - Primarily known for causing **gas gangrene** (myonecrosis) and certain types of food poisoning. - It produces various **toxins**, including alpha-toxin, which contribute to tissue destruction and gas formation.
Question 5: A woman with recurrent diarrhea is prescribed a broad-spectrum antibiotic. Which of the following statements is not true regarding Clostridium difficile infection?
- A. Pseudomembrane is a layer of inflammatory debris
- B. Oral fidaxomicin is used for treatment
- C. It is toxin mediated
- D. IgM assay is used to confirm the diagnosis of Clostridium difficile infection. (Correct Answer)
Explanation: ***IgM assay is used to confirm the diagnosis of Clostridium difficile infection*** - An **IgM assay** is **not** the standard or recommended method for diagnosing *Clostridium difficile* infection (CDI). - Diagnosis typically relies on detecting **toxins (A and B)** in stool samples through antigen-based tests, PCR, or enzyme immunoassays [1]. *Oral fidaxomicin is used for treatment* - **Fidaxomicin** is an **oral macrolide antibiotic** specifically approved and highly effective for treating *C. difficile* infection, especially recurrent cases. - It works by inhibiting bacterial RNA polymerase, leading to bactericidal activity against *C. difficile* with minimal systemic absorption. *It is toxin mediated* - The pathogenicity of *C. difficile* is primarily mediated by its **exotoxins, Toxin A (enterotoxin)** and **Toxin B (cytotoxin)** [1]. - These toxins cause mucosal inflammation, increased permeability, and cell death in the colon, leading to the characteristic symptoms of CDI. *Pseudomembrane is a layer of inflammatory debris* - **Pseudomembranes** are a hallmark pathological feature of severe *C. difficile* colitis, visible during colonoscopy [1]. - They consist of an inflammatory exudate composed of **necrotic epithelial cells, fibrin, neutrophils, and mucus**, forming raised yellow-white plaques on the colonic mucosa.
Question 6: 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 7: Diagnosis of C. difficile infection is made by which of the following methods?
- A. Stool microscopy for pseudomembranes
- B. Culture
- C. Toxin gene detection by polymerase chain reaction (PCR) (Correct Answer)
- D. Enzyme-linked immunosorbent assay (ELISA)
Explanation: ***Toxin gene detection by polymerase chain reaction (PCR)*** - **PCR for toxin genes (tcdA and tcdB)** is the most sensitive and specific method for diagnosing **Clostridioides difficile infection (CDI)**, directly detecting the genetic material responsible for the pathology. - This method is superior because it identifies the presence of toxigenic C. difficile, which is crucial for determining clinical significance and guiding treatment. *Stool microscopy for pseudomembranes* - While **pseudomembranes** are a hallmark of severe CDI, their detection requires **endoscopy** and is not a direct diagnostic test for the pathogen itself. - Furthermore, their absence does not rule out CDI, as pseudomembranes may not form in all cases, especially milder ones. *Culture* - **Culture for C. difficile** can identify the presence of the organism, but it does not differentiate between toxigenic and non-toxigenic strains. - Many individuals can be **colonized with non-toxigenic C. difficile** without having an active infection, leading to false positives if culture alone is used for diagnosis. *Enzyme - linked immunosorbent assay (ELISA)* - ELISA tests primarily detect **C. difficile toxins A and B** or **glutamate dehydrogenase (GDH)** antigen in stool. - While rapid, ELISA for toxins A/B has **lower sensitivity** than PCR, potentially missing cases, and GDH detection alone only indicates the presence of C. difficile (toxigenic or non-toxigenic), requiring further toxin testing for confirmation.
Question 8: A 40-year-old patient presents with frequent watery diarrhea after a recent course of antibiotics. Stool toxin assay is positive for Clostridium difficile. What is the most appropriate treatment?
- A. IV metronidazole
- B. Oral vancomycin (Correct Answer)
- C. IV ciprofloxacin
- D. Oral doxycycline
Explanation: ***Oral vancomycin*** - **Oral vancomycin** is the **first-line treatment** for *Clostridium difficile* infection (CDI) due to its high efficacy against *C. difficile* and its inability to be absorbed systemically, allowing high concentrations to remain in the gut lumen [1]. - It directly targets the bacteria in the gastrointestinal tract, making it superior to IV antibiotics for localized gut infections. *IV metronidazole* - While **IV metronidazole** was previously used for severe CDI, its efficacy is inferior to oral vancomycin, especially in severe cases, because it does not achieve high enough luminal concentrations. - It is often reserved for circumstances where oral administration is not possible or in combination with oral vancomycin for critically ill patients. *IV ciprofloxacin* - **IV ciprofloxacin** is a fluoroquinolone antibiotic and is **not effective** against *C. difficile*; in fact, fluoroquinolones are a common risk factor for developing CDI [1]. - Using ciprofloxacin would exacerbate the infection rather than treat it. *Oral doxycycline* - **Oral doxycycline** is a tetracycline antibiotic and has **no established efficacy** against *Clostridium difficile* infection. - It would not be an appropriate treatment and could potentially worsen the patient's condition by disrupting the gut microbiome further.
Question 9: An otherwise healthy patient who has just received a prosthetic aortic valve develops postoperative fever. Blood cultures are done and she is placed on broad-spectrum antibiotics. Two days later she is still febrile and clinically deteriorating. Which of the following organisms is the most probable etiologic agent?
- A. Nocardia asteroides
- B. Actinomyces israelii
- C. Histoplasma capsulatum
- D. Candida albicans (Correct Answer)
Explanation: ***Candida albicans*** - *Candida albicans* is a common cause of **early prosthetic valve endocarditis**, especially in patients with prolonged hospitalization, broad-spectrum antibiotic use, or central venous catheters [1]. - The patient's clinical deterioration despite broad-spectrum antibacterial antibiotics suggests a **fungal etiology**, as bacteria are typically covered by such therapy [2]. *Nocardia asteroides* - *Nocardia asteroides* typically causes **pulmonary or cutaneous infections** in immunocompromised individuals, less commonly endocarditis. - It would usually respond to specific antibiotics like **trimethoprim-sulfamethoxazole**, and its presentation as prosthetic valve endocarditis is rare. *Actinomyces israelii* - *Actinomyces israelii* causes **actinomycosis**, characterized by chronic, slowly progressive infections with abscesses and draining sinuses, often following oral or abdominal trauma. - While it can cause endocarditis, it is less common in the context of acute prosthetic valve infection and would likely present with a more indolent course. *Histoplasma capsulatum* - *Histoplasma capsulatum* is a **dimorphic fungus** endemic to the Ohio and Mississippi River valleys, primarily causing pulmonary infections. - Disseminated histoplasmosis with endocarditis is rare and typically occurs in immunocompromised patients, not usually in an otherwise healthy individual post-surgery.
Question 10: Which infection commonly spreads to newborns through caregivers?
- A. Candida parapsilosis (Correct Answer)
- B. Candida albicans
- C. Candida tropicalis
- D. Candida glabrata
Explanation: ***Candida parapsilosis*** - This species is a well-known cause of **nosocomial bloodstream infections** in neonates, particularly in **premature infants** and those with central venous catheters. It is often spread via the hands of **healthcare workers**. - Its ability to form **biofilms on medical devices** (like catheters) further facilitates its transmission and makes it a significant infectious agent in neonatal intensive care units (NICUs). *Candida albicans* - While *Candida albicans* is the **most common Candida species** causing infections in humans, including superficial and invasive candidiasis in neonates, its transmission is less frequently linked to direct caregiver spread in the context of outbreaks compared to *C. parapsilosis*. - Neonatal *C. albicans* infections are often acquired **vertically from the mother** or through endogenous gut colonization. *Candida tropicalis* - *Candida tropicalis* can cause **invasive candidiasis**, especially in immunocompromised patients, but it is less frequently implicated in **outbreaks** attributed to hand-to-patient transmission by caregivers in NICUs than *C. parapsilosis*. - It is often associated with **neutropenia** and broad-spectrum antibiotic use. *Candida glabrata* - *Candida glabrata* is a significant pathogen, particularly in adults and immunocompromised individuals, known for its **fluconazole resistance**. - While it can cause bloodstream infections, it is not typically recognized as a primary cause of **caregiver-spread outbreaks** in newborns to the same extent as *C. parapsilosis*.
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