Infection Control & Prevention Flashcards

A healthcare worker sustains a needlestick injury from a patient known to be HIV-positive with a viral load of <50 copies/mL on antiretroviral therapy. What is the most accurate statement regarding post-exposure prophylaxis (PEP) in this scenario?

Answer: PEP should be started immediately and the decision to continue can be reassessed with infectious disease consultation

Even with an undetectable viral load ('U=U' — Undetectable = Untransmittable), current occupational exposure guidelines still recommend initiating PEP promptly after high-risk needlestick injuries and then reassessing with infectious disease consultation. Residual risk, however minimal, and the need for individualized clinical judgment justify starting PEP while expert review occurs. Option A understates occupational guidelines; option B overstates the mandate ignoring clinical nuance; option D is incorrect because PEP can be discontinued after expert review if risk is deemed negligible.

During a carbapenem-resistant Klebsiella pneumoniae (CRKP) outbreak in an ICU, surveillance cultures from environmental surfaces reveal persistent colonization of a specific sink drain. Which intervention is MOST supported by evidence to interrupt this reservoir?

Answer: Replacing the sink drain assembly entirely and reviewing sink design to prevent splash zones

Sink drains are a well-documented environmental reservoir for carbapenem-resistant organisms (CROs). Chemical disinfection of drains is insufficient because biofilm re-establishes rapidly. Evidence supports physical replacement of drain assemblies combined with redesigning sink placement to eliminate splash zones that can aerosolize organisms onto nearby patients or equipment. Hand hygiene and contact precautions address person-to-person transmission but do not eliminate the environmental reservoir driving the outbreak.

A hospital is reviewing its sterilization processes. An arthroscope processed by low-temperature hydrogen peroxide gas plasma sterilization is found to have a lumen diameter of 1 mm and a length of 31 cm. What is the correct interpretation?

Answer: The scope exceeds the lumen geometry limitations of hydrogen peroxide gas plasma sterilization and requires an alternative method such as ethylene oxide

Hydrogen peroxide gas plasma sterilization has defined lumen geometry limitations. For most systems (e.g., STERRAD), lumens must meet specific length-to-diameter ratio thresholds — lumens that are too long or too narrow prevent adequate hydrogen peroxide diffusion, resulting in sterilization failure. A 1 mm × 31 cm lumen exceeds these parameters. Ethylene oxide (EtO) is the validated alternative for such challenging lumen geometries. A booster cycle does not overcome fundamental diffusion physics for extreme geometries. Arthroscopes require sterilization (not just high-level disinfection) as they penetrate sterile body cavities.

In the context of the 'chain of infection,' a hospital implements ultraviolet-C (UV-C) terminal room disinfection after every patient discharge. Which link in the chain of infection does this intervention PRIMARILY target?

Answer: Reservoir

UV-C terminal room disinfection decontaminates environmental surfaces left behind after a patient vacates the room, eliminating or reducing the microbial burden in the physical environment. This directly targets the 'reservoir' — the environment where pathogens persist and from which subsequent patients could be exposed. While some might argue it affects the 'mode of transmission' (indirect contact), UV-C acts on the source of organisms (the contaminated environment/reservoir) rather than the transmission pathway itself. This distinction is important for correctly mapping infection control interventions to the chain of infection model.

A nurse prepares to perform wound care on a patient in contact precautions for MRSA. She dons gloves and a gown, performs the procedure, then removes her PPE. Before leaving the room, she applies alcohol-based hand rub (ABHR) thoroughly. Later, it is discovered the patient also had undiagnosed Clostridioides difficile. What is the critical error in infection control practice?

Answer: ABHR is ineffective against C. difficile spores; soap and water handwashing was required after glove removal

Clostridioides difficile produces spores that are resistant to alcohol-based hand rubs. ABHR is highly effective against most pathogens but does NOT eliminate C. difficile spores. CDC and WHO guidelines specifically mandate soap-and-water handwashing when C. difficile is known or suspected, because the mechanical friction and rinsing action physically removes spores that alcohol cannot inactivate. This is a critical and frequently tested distinction in advanced infection control. While option D reflects good general practice (hand hygiene before donning PPE), it was not the critical failure in this scenario involving C. difficile.

A 58-year-old immunocompromised patient develops a pulmonary infection with Aspergillus fumigatus three weeks after admission to a newly renovated ward. The infection control team investigates. Which finding would MOST strongly implicate the hospital environment as the source?

Answer: Aspergillus fumigatus was isolated from ceiling tiles and HVAC ductwork in the patient's ward using environmental sampling

Definitive environmental linkage in a healthcare-associated Aspergillus outbreak requires microbiological evidence connecting the environmental source to the patient cases. Isolation of Aspergillus fumigatus from HVAC ductwork and ceiling tiles — the classic reservoir disrupted during construction — directly implicates the hospital environment. Ideally, molecular typing (microsatellite or whole-genome sequencing) would confirm strain matching. Elevated particulate counts (option B) suggest disruption but do not confirm Aspergillus specifically. Cluster occurrence (option D) is epidemiologically suggestive but not definitive source evidence. A clean pre-admission CT (option A) supports hospital acquisition but doesn't identify the source.