Hospital Acquired Infections Practice Questions

Q: A patient in the postoperative ICU with an intravenous catheter developed spikes of fever. What is the most likely causative organism?

Coagulase-negative staphylococci. **Explanation:** The clinical scenario describes a **Catheter-Related Bloodstream Infection (CRBSI)**, a common hospital-acquired infection (HAI) in ICU settings. **Why Coagulase-negative staphylococci (CoNS) is correct:** CoNS, specifically ***Staphylococcus epidermidis***, is the most common cause of infections associated with indwelling medical devices (intravenous catheters, prosthetic valves, shunts). These organisms are normal skin flora that gain entry during catheter insertion or manipulation. Their primary virulence factor is the ability to produce a **biofilm (slime layer)**, which allows them to adhere to plastic surfaces and protects them from both the host immune system and antibiotics. **Analysis of Incorrect Options:** * **A. E. coli:** While a leading cause of HAIs, it is most commonly associated with **Urinary Tract Infections (UTIs)** secondary to catheterization, not primary IV line infections. * **C. Pseudomonas:** A common cause of **Ventilator-Associated Pneumonia (VAP)** and burn wound infections in the ICU, but less frequent than CoNS for routine IV catheter-related spikes of fever. * **D. Streptococcus agalactiae (GBS):** Primarily associated with neonatal sepsis and meningitis; it is not a common cause of catheter-related HAIs in adults. **NEET-PG High-Yield Pearls:** * **Most common organism in CRBSI:** CoNS (Staph. epidermidis). * **Most common organism in Surgical Site Infections (SSI):** *Staphylococcus aureus*. * **Most common organism in Catheter-Associated UTI (CAUTI):** *E. coli*. * **Diagnosis of CRBSI:** Established when the same organism grows from both a percutaneous blood culture and the catheter tip (using **Maki’s semi-quantitative technique** showing >15 CFU).

Q: What is the most common cause of nosocomial urinary tract infection?

E. coli. **Explanation:** **1. Why E. coli is the correct answer:** *Escherichia coli* (E. coli) is the most common cause of both community-acquired and **nosocomial (hospital-acquired) urinary tract infections (UTIs)**. In the hospital setting, UTIs are predominantly associated with indwelling urinary catheters (CAUTI). E. coli, a member of the *Enterobacteriaceae* family, is part of the normal colonic flora. It possesses specific virulence factors, such as **P-pili (adhesins)**, which allow it to adhere to the uroepithelium and ascend the urinary tract, even in the presence of a foreign body like a catheter. **2. Why other options are incorrect:** * **Streptococcus:** While Group B Streptococcus can cause UTIs (especially in neonates or pregnant women) and Enterococci are significant nosocomial pathogens, they are less frequent than Gram-negative bacilli. * **Salmonella:** This is primarily a gastrointestinal pathogen. While it can cause bacteriuria during systemic enteric fever, it is an extremely rare cause of primary nosocomial UTI. * **Staphylococcus:** *Staphylococcus saprophyticus* is a common cause of UTI in young, sexually active females (community-acquired), and *S. aureus* may cause UTI via hematogenous spread, but they do not surpass E. coli in frequency. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common nosocomial infection overall:** UTI (followed by Surgical Site Infections and Pneumonia). * **Most common organism in CAUTI:** E. coli. * **Biofilm formation:** Pathogens like *Pseudomonas aeruginosa* and *Proteus mirabilis* are also significant in chronic catheterization due to biofilm production and urease activity (leading to struvite stones). * **Fungal cause:** *Candida albicans* is the most common fungal cause of nosocomial UTI, especially in ICU patients on broad-spectrum antibiotics.

Q: What is true about hand hygiene?

Alcohol-based preparations are used.. **Explanation:** Hand hygiene is the single most important measure to prevent healthcare-associated infections (HAIs). According to WHO guidelines, **alcohol-based hand rubs (ABHR)** are the preferred method for routine hand hygiene in clinical settings when hands are not visibly soiled. **Why Option B is Correct:** Alcohol-based preparations (containing 60–80% ethanol or isopropanol) are the gold standard because they are rapidly germicidal, have a broad spectrum of activity (including most bacteria, fungi, and enveloped viruses), and are more accessible at the point of care compared to traditional sinks. They act by **denaturing proteins** of microorganisms. **Analysis of Incorrect Options:** * **Option A:** While Povidone-iodine (Betadine) can cause skin irritation or allergic contact dermatitis, it is primarily used as a surgical scrub or skin antiseptic for procedures, not for routine hand hygiene. * **Option C:** Hot water should be avoided. It increases the risk of dermatitis by removing protective skin oils and does not enhance microbial killing. Lukewarm or cold water is recommended for handwashing. * **Option D:** Glutaraldehyde (e.g., Cidex) is a high-level disinfectant used for **cold sterilization** of heat-sensitive instruments like endoscopes. It is highly toxic to tissues and should never be used on human skin. **High-Yield NEET-PG Pearls:** * **WHO’s "5 Moments for Hand Hygiene":** 1. Before touching a patient, 2. Before clean/aseptic procedures, 3. After body fluid exposure, 4. After touching a patient, 5. After touching patient surroundings. * **Hand Rub vs. Hand Wash:** Use soap and water (Hand Wash) specifically when hands are **visibly soiled** or when dealing with spore-forming pathogens like ***Clostridium difficile*** (alcohol does not kill spores). * **Duration:** Hand rub (20–30 seconds); Hand wash (40–60 seconds).

Q: What is the most common species of Pseudomonas causing intravenous catheter-related infections?

P. cepacia. **Explanation:** The correct answer is **P. cepacia** (now reclassified as *Burkholderia cepacia*). **1. Why P. cepacia is correct:** While *Pseudomonas aeruginosa* is the most common species of the genus causing general hospital-acquired infections (like VAP or UTIs), **P. cepacia** has a unique predilection for **intravenous catheter-related infections** and contaminated medical devices. This is due to its ability to survive in nutrient-poor environments and its resistance to many common disinfectants (like povidone-iodine and chlorhexidine). It often causes outbreaks in hospitals through contaminated IV fluids, irrigation solutions, or pressure transducers. **2. Why other options are incorrect:** * **P. aeruginosa:** Although it is the most common *Pseudomonas* species isolated in clinical settings overall, it is less specifically associated with IV catheter outbreaks compared to the niche occupied by *P. cepacia*. * **P. maltophilia (now *Stenotrophomonas maltophilia*):** This is an opportunistic pathogen often associated with respiratory infections in cystic fibrosis or ICU patients on carbapenems, but it is not the primary species for IV catheter infections. * **P. pseudomallei (now *Burkholderia pseudomallei*):** This is the causative agent of **Melioidosis**. It is a soil-dwelling saprophyte found in Southeast Asia and Northern Australia, not a common cause of catheter-related bloodstream infections. **High-Yield Clinical Pearls for NEET-PG:** * **B. cepacia Complex:** Highly significant in **Cystic Fibrosis** patients, leading to "Cepacia syndrome" (rapid necrotizing pneumonia). * **Disinfectant Resistance:** *B. cepacia* can actually grow in **quaternary ammonium compounds** (e.g., benzalkonium chloride). * **Drug of Choice:** Unlike *P. aeruginosa*, *B. cepacia* is inherently resistant to aminoglycosides. The treatment of choice is usually **Trimethoprim-sulfamethoxazole (TMP-SMX)**.

Q: Which organism is most likely associated with Ventilator-Associated Pneumonia (VAP)?

Pseudomonas. **Explanation:** **Ventilator-Associated Pneumonia (VAP)** is a subtype of Hospital-Acquired Pneumonia (HAP) occurring more than 48–72 hours after endotracheal intubation. **Why Pseudomonas is the correct answer:** *Pseudomonas aeruginosa* is the most common aerobic Gram-negative bacillus associated with VAP, especially in late-onset cases (occurring after 5 days of hospitalization). It thrives in moist environments (like ventilator tubing and humidifiers) and is notorious for forming biofilms on endotracheal tubes, making it highly resistant to host defenses and antibiotics. **Analysis of Incorrect Options:** * **B. Klebsiella:** While *Klebsiella pneumoniae* is a significant cause of HAP and VAP, it is generally ranked second to *Pseudomonas* in frequency. It is more classically associated with "Friedlander’s pneumonia" (currant jelly sputum) in chronic alcoholics. * **C. Clostridium:** *Clostridium difficile* is the primary cause of antibiotic-associated diarrhea and pseudomembranous colitis. It is an anaerobe and does not typically cause pneumonia. * **D. Mycobacterium TB:** TB is a community-acquired or reactivation infection. While it can occur in hospitalized patients, it is not a standard causative agent of acute VAP. **High-Yield Clinical Pearls for NEET-PG:** 1. **Early-onset VAP ( 5 days):** Predominantly caused by Multidrug-Resistant (MDR) pathogens like *Pseudomonas*, MRSA, and *Acinetobacter*. 3. **Prevention:** The "Ventilator Bundle" is key—includes head-of-bed elevation (30-45°), daily "sedation vacations," and subglottic secretion drainage. 4. **Diagnosis:** Requires a new or progressive infiltrate on CXR plus clinical signs (fever, purulent secretions, or leukocytosis).

Q: All of the following are important precautions to prevent infections associated with arterial catheterizations except?

Use of femoral artery more than radial artery. ### Explanation The primary goal in managing arterial catheters is to minimize the risk of **Catheter-Related Bloodstream Infections (CRBSI)** and local site infections. **Why Option D is the Correct Answer:** The choice of insertion site is a critical determinant of infection risk. The **radial artery** is the preferred site for arterial catheterization because it is associated with the lowest risk of infection and vascular complications. In contrast, the **femoral artery** carries a significantly higher risk of contamination due to its proximity to the perineum and the difficulty in maintaining a sterile dressing in that area. Therefore, using the femoral artery more than the radial artery is a **violation** of standard infection control protocols. **Analysis of Incorrect Options:** * **A. Education of health personnel:** This is the cornerstone of infection control. Proper training in aseptic techniques and catheter maintenance significantly reduces the incidence of CRBSI. * **B. Hand hygiene:** This is the single most important measure to prevent the transmission of nosocomial pathogens during catheter insertion and manipulation. * **C. Use sterile semi-permeable dressing:** Transparent, semi-permeable dressings are recommended as they allow continuous visualization of the site for signs of infection (redness, discharge) while providing a sterile barrier against external contaminants. **High-Yield Clinical Pearls for NEET-PG:** * **Preferred Sites:** Radial > Brachial > Dorsalis pedis > Femoral (Highest risk). * **Skin Antisepsis:** **Chlorhexidine (>0.5%)** with alcohol is superior to povidone-iodine for site preparation. * **Replacement:** Arterial catheters should not be replaced at routine intervals; they should be removed as soon as they are no longer clinically indicated. * **Transducer Safety:** Use disposable rather than reusable transducer assemblies to prevent outbreaks.

Q: A 60-year-old male patient admitted to the ICU develops fever and productive cough 48 hours after hospital admission. Which of the following is the most common causative organism?

Pseudomonas. ### Explanation **Concept: Hospital-Acquired Pneumonia (HAP)** Hospital-Acquired Pneumonia is defined as pneumonia occurring **48 hours or more** after hospital admission, which was not incubating at the time of admission. In the ICU setting, especially among patients who are debilitated or on mechanical ventilation, Gram-negative bacilli are the most frequent culprits. **Why Pseudomonas is Correct:** * **Pseudomonas aeruginosa** is the most common cause of HAP and Ventilator-Associated Pneumonia (VAP) in the ICU. * It thrives in moist hospital environments (sinks, respiratory equipment) and is notorious for its multi-drug resistance. * Other common Gram-negative causes include *Klebsiella pneumoniae* and *Escherichia coli*. **Analysis of Incorrect Options:** * **A. Mycoplasma:** This is a classic cause of **Community-Acquired Pneumonia (CAP)**, specifically "Atypical Pneumonia," usually seen in younger populations. * **C. Staphylococcus:** While *Staphylococcus aureus* (especially MRSA) is a significant cause of HAP, it ranks second to Gram-negative bacilli like *Pseudomonas* in most epidemiological studies. * **D. Haemophilus influenzae:** This is a common cause of CAP, particularly in patients with underlying COPD, but is not the primary driver of late-onset hospital infections. **High-Yield Clinical Pearls for NEET-PG:** * **Timeframe:** If symptoms appear 48 hours, it is HAP. * **VAP:** A subtype of HAP occurring >48–72 hours after endotracheal intubation. * **Most Common Organism (Overall HAP/VAP):** *Pseudomonas aeruginosa*. * **Most Common Gram-Positive Organism (HAP):** *Staphylococcus aureus*. * **Empiric Treatment:** Usually requires "double coverage" for *Pseudomonas* (e.g., Piperacillin-Tazobactam + Amikacin/Ciprofloxacin).

Question 1

A patient in the postoperative ICU with an intravenous catheter developed spikes of fever. What is the most likely causative organism?

Accepted Answer

Coagulase-negative staphylococci

Answer

E. Coli

Answer

Pseudomonas

Answer

Streptococcus agalactiae

Question 2

What is the most cost-effective method of infection control?

Accepted Answer

Hand washing

Answer

Repeated disinfectant use

Answer

Alcohol-based hand rub

Answer

Prophylactic antibiotic therapy

Question 3

What is the most common cause of nosocomial urinary tract infection?

Accepted Answer

E. coli

Answer

Streptococcus

Answer

Salmonella

Answer

Staphylococcus

Question 4

What is true about hand hygiene?

Accepted Answer

Alcohol-based preparations are used.

Answer

Betadine can cause irritation.

Answer

Hot water is best.

Answer

Gluteraldehyde is used.

Question 5

A hospital has identified a significant outbreak of Methicillin-resistant Staphylococcus aureus (MRSA). What is the immediate priority to prevent further spread of the infection?

Accepted Answer

Ensure all healthcare staff practice thorough and frequent hand hygiene.

Answer

Close the hospital for a month to decontaminate.

Answer

Isolate identified MRSA-positive patients and collect nasal swabs to screen for carriers.

Answer

Conduct a thorough cleaning of all hospital surfaces using a chlorhexidine-based disinfectant.

Question 6

What is the most common species of Pseudomonas causing intravenous catheter-related infections?

Accepted Answer

P. cepacia

Answer

P. aeruginosa

Answer

P. maltophilia

Answer

P. pseudomallei

Question 7

Which organism is most likely associated with Ventilator-Associated Pneumonia (VAP)?

Accepted Answer

Pseudomonas

Answer

Klebsiella

Answer

Clostridium

Answer

Mycobacterium TB

Question 8

All of the following are important precautions to prevent infections associated with arterial catheterizations except?

Accepted Answer

Use of femoral artery more than radial artery

Answer

Education of health personnel

Answer

Hand hygiene

Answer

Use sterile semi-permeable dressing

Question 9

A 60-year-old male patient admitted to the ICU develops fever and productive cough 48 hours after hospital admission. Which of the following is the most common causative organism?

Accepted Answer

Pseudomonas

Answer

Mycoplasma

Answer

Staphylococcus

Answer

Haemophilus influenzae

Question 10

Which of the following is NOT a diagnostic criterion for bloodstream infection from a central venous catheter?

Accepted Answer

Apparent source of bloodstream infection present.

Answer

Colony count from catheter culture is 5 times more than peripheral blood culture.

Answer

Blood culture from catheter shows colony formation at least 2 hours before the peripheral blood culture.

Answer

Quantitative catheter tip culture showing >10^3 CFU/catheter segment whereby the same organism is isolated from the catheter segment and a peripheral blood sample.

Hospital Acquired Infections — MCQs

Hospital Acquired Infections — MCQs

On this page

Practice by Chapter

Want unlimited practice?