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Question 1. Which organism is the most common cause of community-acquired pneumonia in adults? A) Streptococcus pneumoniae B) Haemophilus influenzae C) Mycoplasma pneumoniae D) Staphylococcus aureus Answer: A Explanation: Streptococcus pneumoniae accounts for >50 % of adult CAP cases. Question 2. A Gram-negative rod that is oxidase-positive, non-lactose fermenting, and produces a distinctive fruity odor on MacConkey agar most likely is: A) Escherichia coli B) Pseudomonas aeruginosa C) Klebsiella pneumoniae D) Proteus mirabilis Answer: B Explanation: Pseudomonas aeruginosa has these classic laboratory features. Question 3. In interpreting a sputum Gram stain, which finding best indicates a high-quality specimen? A) <10 squamous epithelial cells per low-power field B) >25 polymorphonuclear leukocytes per low-power field C) Presence of Gram-positive cocci in clusters D) Mixed flora with many Gram-negative rods Answer: A Explanation: Few epithelial cells suggest the specimen is from lower respiratory tract rather than oral contamination. Question 4. Which of the following is a multidrug-resistant organism that produces a carbapenemase? A) MRSA B) VRE C) CRE D) ESBL-producing E. coli Answer: C
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Explanation: Carbapenem-resistant Enterobacteriaceae (CRE) harbor carbapenemases. Question 5. A patient with a central line develops fever, chills, and a positive blood culture for coagulase-negative staphylococci. The most likely interpretation is: A) Contamination B) True bacteremia C) Colonization D) Pseudo-infection Answer: B Explanation: Coagulase-negative staphylococci are common CLABSI pathogens; clinical signs support true infection. Question 6. Which viral pathogen is the leading cause of nosocomial respiratory infections in transplant units? A) Influenza virus B) Respiratory syncytial virus C) Adenovirus D) Parainfluenza virus Answer: B Explanation: RSV spreads easily in immunocompromised patients and causes severe lower-respiratory disease. Question 7. Which of the following best describes the difference between prophylactic and empiric antibiotic use? A) Prophylaxis treats established infection; empiric therapy prevents infection B) Prophylaxis is given before exposure; empiric therapy is started before pathogen identification C) Both are given after culture results D) Empiric therapy is always narrow-spectrum Answer: B Explanation: Prophylaxis is administered to prevent infection, whereas empiric therapy is started when infection is suspected but the organism is unknown.
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Answer: A Explanation: SIR compares observed to predicted infections; values > indicate more infections than expected. Question 12. Which statistical measure is most appropriate for comparing median lengths of stay between two groups? A) Student’s t-test B) Chi-square test C) Mann-Whitney U test D) ANOVA Answer: C Explanation: The Mann-Whitney U test compares medians of non-parametric data. Question 13. The first step in verifying an outbreak is: A) Conducting a case-control study B) Developing a line list C) Establishing a case definition D) Performing environmental sampling Answer: C Explanation: A clear case definition is essential to identify which patients belong to the outbreak. Question 14. An epidemic curve that shows a steep rise and gradual decline suggests: A) Point source exposure B) Continuous common source C) Propagated (person-to-person) D) Mixed source Answer: A Explanation: A classic point-source outbreak produces a sharp increase followed by a slow decline. Question 15. Which precaution is required for a patient with confirmed varicella-zoster infection? A) Contact precautions only B) Droplet precautions only C) Airborne and contact precautions D) Standard precautions only
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Answer: C Explanation: VZV is transmitted by airborne droplets and direct contact with lesions. Question 16. Hand hygiene using alcohol-based hand rub is contraindicated when: A) Hands are visibly soiled B) The patient has a C. difficile infection C) The provider is wearing gloves D) The setting is an operating room Answer: A Explanation: Alcohol rubs are ineffective on visibly dirty hands; washing with soap and water is required. Question 17. The appropriate PPE for a patient on droplet precautions for influenza includes: A) N95 respirator B) Surgical mask C) Face shield only D) Gown and gloves only Answer: B Explanation: A surgical mask protects against large respiratory droplets typical of influenza. Question 18. Which of the following best describes a “bundle” in infection control? A) A collection of unrelated policies B) A set of evidence-based practices implemented together C) A single intervention applied repeatedly D) A list of medications for prophylaxis Answer: B Explanation: Bundles combine multiple interventions to improve compliance and outcomes.
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Question 23. During construction, the infection control risk assessment (ICRA) is performed to: A) Estimate construction costs B) Identify potential infection hazards C) Schedule work crews D) Determine HVAC upgrades Answer: B Explanation: ICRA evaluates infection risks associated with construction activities. Question 24. HEPA filtration is required during which of the following situations? A) Routine patient rooms B) Operating rooms C) Construction of new ICU wings D) Negative-pressure isolation rooms Answer: C Explanation: HEPA filters protect vulnerable areas from construction-generated dust and spores. Question 25. According to the Spaulding classification, endoscopes require: A) Sterilization B) High-level disinfection C) Intermediate-level disinfection D) Low-level disinfection Answer: B Explanation: Endoscopes are semi-critical devices that contact mucous membranes and need high-level disinfection. Question 26. Which chemical indicator is used to confirm steam sterilization? A) Bowie-Dick test B) Geobacillus stearothermophilus spore strip C) Hydrogen peroxide indicator D) Phenol red paper Answer: B Explanation: Geobacillus spore strips are the standard biological indicator for steam sterilization.
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Question 27. The most appropriate action when a sterile processing technician observes a broken instrument tray during sterilization is: A) Continue the cycle B) Document in the logbook only C) Stop the cycle, investigate, and reprocess D) Ignore if the tray appears clean Answer: C Explanation: Broken equipment compromises sterility; the cycle must be halted and the issue addressed. Question 28. A root-cause analysis (RCA) is primarily used to: A) Assign blame B) Identify system failures that led to an event C) Calculate infection rates D) Develop new antibiotics Answer: B Explanation: RCA focuses on underlying system factors rather than individual fault. Question 29. In a Plan-Do-Study-Act (PDSA) cycle, the “Study” phase involves: A) Implementing the change B) Measuring outcomes and comparing to predictions C) Planning the next intervention D) Training staff Answer: B Explanation: The “Study” step evaluates data to determine if the change produced the desired effect. Question 30. Which adult-learning principle states that learners retain information best when they see relevance to their own work? A) Reinforcement B) Motivation C) Self-directed learning D) Experiential learning Answer: D
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Explanation: An increase of ≥10 mm from a prior negative test is considered conversion. Question 35. Which of the following is NOT a standard precaution? A) Hand hygiene B) Use of gloves when touching blood C) Wearing a gown for all patient contacts D) Respiratory hygiene/cough etiquette Answer: C Explanation: Gowns are used based on anticipated exposure, not for every patient contact. Question 36. The primary purpose of a “line list” during an outbreak investigation is to: A) Summarize laboratory methods B) Document each case’s details C) List all possible sources D) Record environmental sampling results Answer: B Explanation: A line list captures demographic, clinical, and exposure data for each case. Question 37. The incidence rate of a device-associated infection is calculated as: A) (Number of infections ÷ total device days) × 1000 B) (Number of infections ÷ total admissions) × 100 C) (Number of infections ÷ total patient days) × 1000 D) (Number of infections ÷ total procedures) × 100 Answer: A Explanation: Incidence density uses infections per 1,000 device days. Question 38. Which of the following best describes “colonization”? A) Presence of microorganisms causing tissue damage B) Presence of microorganisms without host response C) Transient contamination that is quickly cleared D) Infection that has resolved
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Answer: B Explanation: Colonization is the presence of organisms without signs of infection. Question 39. A patient with a urinary catheter develops fever, flank pain, and a urine culture growing >10⁵ CFU/mL of Enterococcus faecalis. The most likely diagnosis is: A) Asymptomatic bacteriuria B) Catheter-associated urinary tract infection C) Contamination D) Pseudo-infection Answer: B Explanation: Clinical symptoms plus a high-count culture meet CAUTI criteria. Question 40. The most appropriate method to decontaminate a spill of blood on a non-porous surface is: A) Dry cleaning B) Bleach solution (1:10) C) Alcohol wipes D) UV light Answer: B Explanation: A 1:10 bleach solution is the recommended disinfectant for blood spills. Question 41. Which of the following organisms is intrinsically resistant to vancomycin? A) MRSA B) Enterococcus faecalis C) Enterococcus faecium D) Staphylococcus epidermidis Answer: C Explanation: Vancomycin-resistant Enterococcus (VRE) includes E. faecium with intrinsic resistance. Question 42. The CDC recommends that N95 respirators be fit-tested: A) Every 5 years B) Annually C) Only after a change in model D) When a leak is suspected
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Answer: C Explanation: Point-source outbreaks involve a single exposure event affecting many individuals rapidly. Question 47. A hospital’s water system is sampled and grows >10³ CFU/L of Legionella pneumophila. The immediate action should be: A) No action needed B) Initiate hyperchlorination C) Replace all water filters D) Increase temperature to 60 °C only Answer: B Explanation: Hyperchlorination is the rapid remediation method for Legionella contamination. Question 48. Which of the following best defines “environmental surveillance” in infection control? A) Monitoring staff hand-hygiene rates B) Sampling surfaces and air for pathogens C) Tracking patient admissions D) Auditing antibiotic usage Answer: B Explanation: Environmental surveillance involves testing surfaces, water, and air for microbial contamination. Question 49. A patient receiving chemotherapy develops a fever and a neutrophil count of 0.2 × 10⁹/L. The most appropriate initial antimicrobial therapy is: A) Vancomycin alone B) Piperacillin-tazobactam alone C) Combination of an anti-pseudomonal β-lactam plus vancomycin D) Fluconazole alone Answer: C Explanation: Broad-spectrum anti-pseudomonal coverage plus MRSA coverage is standard for febrile neutropenia.
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Question 50. The most common cause of surgical site infection (SSI) after colorectal surgery is: A) Staphylococcus aureus B) Enterococcus faecalis C) Escherichia coli D) Pseudomonas aeruginosa Answer: C Explanation: Gram-negative enteric organisms, especially E. coli, dominate post-colorectal SSIs. Question 51. Which of the following is the recommended duration of contact precautions for a patient colonized with MRSA? A) 24 hours B) Until discharge C) 48 hours after last positive culture D) Indefinitely Answer: B Explanation: Colonized patients remain on contact precautions for the duration of their hospital stay. Question 52. The most appropriate method to assess the effectiveness of a new hand-hygiene program is: A) Pre- and post-intervention compliance audits B) Staff satisfaction surveys C) Number of soap dispensers installed D) Cost analysis of sanitizer purchase Answer: A Explanation: Direct compliance measurement before and after the intervention objectively evaluates impact. Question 53. Which of the following pathogens is classified as a “Tier 1” bioterrorism agent? A) Bacillus anthracis B) Salmonella typhi C) Streptococcus pneumoniae D) Candida auris Answer: A Explanation: Bacillus anthracis (anthrax) is a high-priority bioterrorism agent.
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Explanation: Proper sequence starts with hand hygiene, then gown, mask, eye protection, and gloves. Question 58. A staff member experiences a needlestick injury from a patient known to be HBsAg-positive and anti-HBs-negative. The appropriate post-exposure action is: A) No action needed B) Hepatitis B immune globulin (HBIG) + vaccine series C) Start antiretroviral therapy D) Observe only Answer: B Explanation: HBIG plus initiation of the hepatitis B vaccine series provides passive and active immunity. Question 59. The most common cause of catheter-related bloodstream infection (CRBSI) in adult ICUs is: A) Staphylococcus epidermidis B) Candida albicans C) Pseudomonas aeruginosa D) Enterococcus faecalis Answer: A Explanation: Coagulase-negative staphylococci, especially S. epidermidis, are the leading CRBSI pathogens. Question 60. Which of the following statements about antimicrobial stewardship is FALSE? A) It aims to optimize patient outcomes B) It reduces antimicrobial resistance C) It encourages unrestricted broad-spectrum use D) It promotes appropriate dosing Answer: C Explanation: Stewardship discourages unnecessary broad-spectrum antibiotic use. Question 61. The most appropriate environmental cleaning method after discharge of a patient with C. difficile is: A) Standard detergent cleaning B) UV-C light disinfection C) Sporicidal agent (bleach) D) Steam cleaning only
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Answer: C Explanation: Sporicidal agents are required to eradicate C. difficile spores. Question 62. In a health-care setting, “standard precautions” are based on the assumption that: A) All patients are sterile B) All patients could be infectious C) Only symptomatic patients transmit disease D) Only bloodborne pathogens are a concern Answer: B Explanation: Standard precautions treat every patient as potentially infectious. Question 63. Which of the following is the most sensitive method for detecting Mycobacterium tuberculosis in respiratory specimens? A) Acid-fast stain B) Culture on Lowenstein-Jensen medium C) Nucleic acid amplification test (NAAT) D) Chest X-ray Answer: C Explanation: NAAT provides rapid and highly sensitive detection of MTB DNA. Question 64. The primary reason for using a “bundle” approach to central line-associated bloodstream infection (CLABSI) prevention is: A) To reduce costs B) To simplify documentation C) To ensure all evidence-based practices are applied together D) To increase staff workload Answer: C Explanation: Bundles increase adherence by combining multiple proven interventions. Question 65. Which of the following PPE is required for handling a patient with suspected meningococcal meningitis? A) N95 respirator only B) Gown
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Question 69. Which of the following organisms is most likely to cause a surgical site infection after cardiac surgery? A) Staphylococcus aureus B) Enterococcus faecalis C) Pseudomonas aeruginosa D) Candida albicans Answer: A Explanation: S. aureus is the predominant pathogen in cardiac SSI. Question 70. The appropriate isolation precaution for a patient with confirmed measles is: A) Contact only B) Droplet only C) Airborne only D) Contact and droplet Answer: C Explanation: Measles is transmitted via aerosolized particles; airborne precautions are required. Question 71. Which of the following is the most common route of transmission for hepatitis C in health-care settings? A) Airborne droplets B) Percutaneous needle sticks C) Fecal-oral route D) Direct contact with skin Answer: B Explanation: Bloodborne transmission via needle stick injuries is the primary route. Question 72. The best indicator of compliance with central line insertion bundle is: A) Number of lines inserted B) Observation of each bundle component C) Staff satisfaction surveys D) Cost of insertion kits Answer: B Explanation: Direct observation ensures each bundle element is performed correctly.
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Question 73. Which of the following is an example of a “high-level disinfectant”? A) 70 % ethanol B) Glutaraldehyde 2 % C) Quaternary ammonium D) Soap and water Answer: B Explanation: Glutaraldehyde at 2 % achieves high-level disinfection suitable for semi-critical devices. Question 74. In a patient with suspected meningitis, the most appropriate initial CSF test is: A) Gram stain B) Culture C) PCR for viral pathogens D) Opening pressure measurement Answer: A Explanation: Gram stain provides rapid preliminary identification of bacterial pathogens. Question 75. Which of the following statements about “hand hygiene compliance monitoring” is TRUE? A) Anonymous observation reduces the Hawthorne effect B) Video recording is prohibited C) Self-reporting is the most accurate method D) Compliance rates are typically >95 % without intervention Answer: A Explanation: Anonymous observers are less likely to influence staff behavior, providing more accurate data. Question 76. The most common cause of ventilator-associated pneumonia (VAP) in the ICU is: A) Staphylococcus aureus B) Pseudomonas aeruginosa C) Acinetobacter baumannii D) Klebsiella pneumoniae Answer: B Explanation: P. aeruginosa is frequently isolated from VAP cases.
