Healthcare-Associated Infections — MCQs

10 questions

Commonest cause of nosocomial infection is

What is the best way to control the MRSA infection in the ward?

A patient in the ICU with a central venous catheter (CVC) develops an infection. Microscopy reveals ovoid budding yeast cells. What is the most likely organism?

Most common catheter-related bloodstream infection is due to:

A woman with recurrent diarrhea is prescribed a broad-spectrum antibiotic. Which of the following statements is not true regarding Clostridium difficile infection?

Most common mode of transmission of nosocomial infection is -

What is the most common extra-intestinal complication of Shigellosis?

In a surgical post-op ward, a patient developed wound infection. Subsequently 3 other patients developed similar infections in the ward. What is the most effective way of preventing the spread of infection?

In postoperative intensive care unit, five patients developed postoperative wound infection on the same day. The best method to prevent cross infection occurring in other patients in the same ward is to:

Q10

Xanthogranulomatous infection is caused by:

Healthcare-Associated Infections Indian Medical PG Practice Questions and MCQs

Question 1: Commonest cause of nosocomial infection is

A. Staphylococci (Correct Answer)
B. Klebsiella
C. Enterobacteriaceae
D. Pseudomonas

Explanation: ***Staphylococci*** - **Staphylococci**, particularly *Staphylococcus aureus* (including MRSA) and coagulase-negative staphylococci, are the **most common cause** of nosocomial infections according to current surveillance data from CDC, WHO, and Indian hospital studies. - They are the leading cause of **surgical site infections**, **catheter-related bloodstream infections**, **ventilator-associated pneumonia**, and **skin and soft tissue infections** in hospital settings. - Their ability to form biofilms on medical devices, antibiotic resistance (especially MRSA), and widespread colonization of healthcare workers and patients make them the predominant nosocomial pathogen. *Enterobacteriaceae* - The family **Enterobacteriaceae** (including *E. coli*, *Klebsiella*, *Enterobacter*) represents a major group of gram-negative nosocomial pathogens. - They are very common causes of **urinary tract infections**, **pneumonia**, and **bloodstream infections**, particularly associated with indwelling catheters and ventilators. - While collectively representing a large proportion of nosocomial infections, they are the **second most common** group after Staphylococci in most contemporary studies. *Pseudomonas* - *Pseudomonas aeruginosa* is an important nosocomial pathogen, particularly in **ventilator-associated pneumonia**, **burn infections**, and infections in immunocompromised patients. - It accounts for approximately 10-15% of nosocomial infections and is especially problematic due to its intrinsic antibiotic resistance. *Klebsiella* - **Klebsiella** (particularly *K. pneumoniae*) is a member of the Enterobacteriaceae family and an important individual pathogen causing **pneumonia** and **urinary tract infections** in healthcare settings. - While a common pathogen, it represents only a subset of both the Enterobacteriaceae family and overall nosocomial infections, making it less common than the entire Staphylococci group.

Question 2: What is the best way to control the MRSA infection in the ward?

A. Fumigation of ward frequently
B. Washing hand before and after attending patients (Correct Answer)
C. Wearing masks during invasive procedures in ICU
D. Vancomycin given empirically to all the patients

Explanation: **Washing hand before and after attending patients** - **Hand hygiene** is the single most effective measure in preventing the transmission of **healthcare-associated infections**, including **MRSA**. - **Healthcare workers' hands** are the primary vehicle for spreading pathogens from one patient to another. *Fumigation of ward frequently* - **Fumigation** is generally not recommended for routine infection control and has limited efficacy against resistant organisms like **MRSA** in this context. - It does not address the primary mode of transmission, which is direct contact via **contaminated hands** or surfaces. *Wearing masks during invasive procedures in ICU is important.* - While important for preventing infections during **invasive procedures** and protecting against **aerosolized pathogens**, masks are not the primary strategy for controlling the spread of **MRSA** in routine ward settings. - **MRSA transmission** is predominantly contact-based, not airborne. *Vancomycin given empirically to all the patients* - **Empirical broad-spectrum antibiotic use** for all patients is a significant driver of **antibiotic resistance**, including **MRSA**. - It should be reserved for patients with suspected or confirmed **MRSA infections** based on clinical criteria and culture results, not as a general preventive measure.

Question 3: A patient in the ICU with a central venous catheter (CVC) develops an infection. Microscopy reveals ovoid budding yeast cells. What is the most likely organism?

A. Candida (Correct Answer)
B. Staphylococcus epidermidis
C. Escherichia coli
D. Staphylococcus aureus

Explanation: ***Candida*** - **Gram-positive ovoid budding organisms** are characteristic findings for yeast, with **Candida** species being the most common cause of CVC-related fungal infections in ICU patients. - Patients with CVCs are at high risk for candidemia due to compromised skin barriers and often receiving broad-spectrum antibiotics, which can disrupt the normal flora. *Staphylococcus epidermidis* - This is a **Gram-positive coccus** that grows in clusters and is a common cause of CVC-related **bacterial infections**, developing **biofilms** on catheters. - It does not present as an ovoid budding organism on microscopy. *Escherichia coli* - This is a **Gram-negative rod**, typically associated with **urinary tract infections** and sepsis from an abdominal source. - It would not appear as a Gram-positive ovoid budding organism and is not a common cause of primary CVC-related bloodstream infections unless there's an associated abdominal source. *Staphylococcus aureus* - This is a **Gram-positive coccus** that grows in grape-like clusters and can cause severe CVC-related bloodstream infections, often leading to **endocarditis** or widespread dissemination. - Like *S. epidermidis*, it is a bacterium and does not exhibit ovoid budding.

Question 4: Most common catheter-related bloodstream infection is due to:

A. Coagulase-negative Staphylococci (CoNS) (Correct Answer)
B. Candida species
C. Gram-negative bacilli
D. Staphylococcus aureus (S. aureus)

Explanation: ***Coagulase-negative Staphylococci (CoNS)*** - **Coagulase-negative Staphylococci (CoNS)**, particularly *Staphylococcus epidermidis*, are the most common cause of **catheter-related bloodstream infections (CRBSIs)** due to their ability to form **biofilms** on catheter surfaces. - Their ubiquity on the skin, combined with their capacity for **adherence** and **biofilm production**, facilitates their entry and proliferation within the catheter lumen. *Candida species* - While *Candida species* (e.g., *Candida albicans*) are significant causes of CRBSIs, especially in **immunocompromised** patients or those on **broad-spectrum antibiotics**, they are less common overall than CoNS. - Risk factors for *Candida* CRBSIs include prolonged hospitalization, total parenteral nutrition, and **central venous catheters**. *Gram-negative bacilli* - **Gram-negative bacilli** (e.g., *Klebsiella pneumoniae*, *Escherichia coli*, *Pseudomonas aeruginosa*) are important pathogens in CRBSIs, often associated with **severe sepsis** and higher mortality rates. - However, their overall incidence in catheter-induced infections is lower than that of CoNS, though they are more prevalent in certain hospital units like **ICUs**. *Staphylococcus aureus (S. aureus)* - **Staphylococcus aureus** causes clinically significant CRBSIs, often leading to more severe infections, including **endocarditis** and **septic emboli**, than CoNS. - While *S. aureus* infections are serious, CoNS remain the most frequently isolated organism in all CRBSI cases, partly due to the high carriage rate of *S. epidermidis* on human skin.

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: Most common mode of transmission of nosocomial infection is -

A. Hand contact (Correct Answer)
B. Droplet infection
C. Blood and blood products
D. Contaminated water

Explanation: ***Hand contact*** - **Direct contact** with healthcare workers' contaminated hands is the primary way pathogens are transferred between patients in a healthcare setting. - Failure to perform adequate **hand hygiene** between patient contacts is the single most important factor contributing to nosocomial infection transmission. *Droplet infection* - While droplet transmission can cause nosocomial infections, especially for respiratory viruses, it is not the most common mode of transmission for the overall burden of healthcare-associated infections. - **Droplets** usually travel short distances and deposit on mucous membranes of the nose, mouth, or eyes of a susceptible host. *Blood and blood products* - Transmission through **blood and blood products** is a significant concern for specific infections (e.g., HIV, hepatitis B/C), but the incidence is relatively low due to stringent screening and safety protocols. - This mode accounts for a small fraction of overall nosocomial infections compared to contact transmission. *Contaminated water* - **Contaminated water** can lead to outbreaks (e.g., *Legionella*, *Pseudomonas*), especially in immunocompromised patients, but it is not the most frequent mode of transmission on a day-to-day basis across all types of nosocomial infections. - Healthcare facilities implement measures to ensure water safety, limiting this as the primary route.

Question 7: What is the most common extra-intestinal complication of Shigellosis?

A. Pneumonia
B. Meningitis
C. HUS
D. Reactive arthritis (Correct Answer)

Explanation: ***Reactive arthritis*** - **Reactive arthritis** is triggered by a prior infection, such as *Shigellosis*, and is the most common extra-intestinal complication, especially in HLA-B27 positive individuals [1]. - It typically presents with a triad of **arthritis**, **urethritis**, and **conjunctivitis**, though not all symptoms may be present [1]. *Pneumonia* - While pneumonia can occur in severely ill patients, it is not a common nor specific extra-intestinal complication directly linked to the pathogenesis of *Shigellosis*. - Respiratory complications are rare in uncomplicated cases of shigellosis. *Meningitis* - **Meningitis** is a rare and severe complication, primarily seen in young children or immunocompromised individuals, and is not the most common extra-intestinal manifestataion. - It suggests systemic spread of the bacteria beyond the gastrointestinal tract, which is uncommon. *HUS* - **Hemolytic Uremic Syndrome (HUS)** is a well-known complication of *E. coli* O157:H7 (Shiga toxin-producing E. coli, STEC), rather than *Shigella* species. - While some *Shigella* strains produce Shiga toxin, HUS is far less common in *Shigellosis* compared to STEC infections.

Question 8: In a surgical post-op ward, a patient developed wound infection. Subsequently 3 other patients developed similar infections in the ward. What is the most effective way of preventing the spread of infection?

A. Fumigation of the ward
B. Wash OT instruments with 1% perchlorate
C. Proper hand washing of all ward personnel (Correct Answer)
D. Give IV antibiotics to all patients in the ward

Explanation: ***Proper hand washing of all ward personnel*** - **Hand hygiene** is the single most important and effective measure to prevent the spread of **healthcare-associated infections (HAIs)**, especially in a ward where multiple patients are affected. - It directly reduces the transmission of microorganisms from healthcare workers to patients and between patients. *Fumigation of the ward* - **Fumigation** is typically used for **terminal disinfection** or in situations involving highly resistant organisms or outbreaks, but it is not a routine or primary method for preventing day-to-day infection spread. - Its effectiveness is limited, and it can pose **health risks** to personnel and patients if not performed correctly, often requiring the ward to be vacated. *Wash OT instruments with 1% perchlorate* - This option focuses on the **sterilization of operating theater (OT) instruments**, which is crucial for surgical procedures but **irrelevant** to preventing the spread of wound infection within a general ward setting. - The problem describes a ward-based infection spread, not issues with surgical instrument sterility. *Give IV antibiotics to all patients in the ward* - **Prophylactic antibiotics** for all patients in a ward is generally **not recommended** as it can lead to **antibiotic resistance**, mask underlying infections, and cause adverse drug reactions. - Antibiotics should be prescribed judiciously based on specific indications and confirmed infections, not as a general preventive measure.

Question 9: In postoperative intensive care unit, five patients developed postoperative wound infection on the same day. The best method to prevent cross infection occurring in other patients in the same ward is to:

A. Practice proper hand washing (Correct Answer)
B. Disinfect the ward with sodium hypochlorite
C. Fumigate the ward
D. Give antibiotics to all other patients in the ward

Explanation: ***Correct: Practice proper hand washing*** - **Proper hand hygiene** is the **single most effective method** for preventing the transmission of **healthcare-associated infections (HAIs)**, including surgical site infections - It physically removes or inactivates **transient microorganisms** from the hands of healthcare workers, thereby stopping their spread between patients - This is the **gold standard** recommended by **WHO, CDC**, and all major infection control guidelines for preventing **cross-infection** in healthcare settings *Incorrect: Disinfect the ward with sodium hypochlorite* - While disinfection with **sodium hypochlorite** is important for **environmental cleaning**, it is **less effective than hand hygiene** in preventing direct patient-to-patient transmission - Environmental disinfection alone **cannot interrupt the main routes of transmission**, which often involve **direct contact** or contaminated hands of healthcare personnel - This is a **secondary measure**, not the primary prevention strategy *Incorrect: Fumigate the ward* - **Fumigation** is typically used for **terminal disinfection** in specific situations, such as after highly contagious outbreaks, and is **not a routine** or primary method for preventing cross-infection in an active ward - Its effectiveness in preventing day-to-day cross-infection is **limited compared to immediate infection control practices** like hand hygiene - This practice is largely **outdated** in modern infection control protocols *Incorrect: Give antibiotics to all other patients in the ward* - **Prophylactic antibiotic use** in all other patients is **discouraged** due to the risk of **antimicrobial resistance (AMR)** and potential adverse effects - It does **not address the source of infection** or the transmission pathways, and can lead to wider public health issues - This is an **inappropriate primary prevention strategy** that violates antimicrobial stewardship principles

Question 10: Xanthogranulomatous infection is caused by:

A. Nephrolithiasis
B. Proteus Mirabilis
C. All of the options (Correct Answer)
D. Urinary obstruction

Explanation: ***All of the options*** - **Xanthogranulomatous pyelonephritis (XGP)** is a severe, chronic infectious process of the kidney, often associated with a combination of factors including **urinary tract obstruction**, specific bacterial infections, and the presence of kidney stones (nephrolithiasis) [1]. - **Proteus mirabilis** is a common cause of XGP due to its ability to produce urease, which hydrolyzes urea into ammonia, increasing urinary pH and promoting the formation of struvite stones, thus acting in concert with obstruction and stones [1]. *Nephrolithiasis* - While **kidney stones** are a major predisposing factor for XGP, they do not solely cause the infection; they primarily create an environment conducive to bacterial colonization and obstruction. - The presence of stones, particularly **struvite stones**, can lead to persistent infection and the characteristic inflammatory response seen in XGP. *Proteus Mirabilis* - **Proteus mirabilis** is frequently isolated in cases of XGP, but it typically acts in conjunction with urinary obstruction and/or nephrolithiasis [1]. - This bacterium contributes significantly to the pathophysiology by promoting stone formation and maintaining a chronic infectious state, but it is not the sole cause. *Urinary obstruction* - **Urinary tract obstruction** is a key predisposing factor that prevents proper drainage, leading to stasis and increasing susceptibility to infection [1]. - While essential for the development of XGP, obstruction alone does not directly cause the characteristic xanthogranulomatous inflammation without the presence of bacteria and often stones. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 939-940.

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