Peripherally inserted central catheter (PICC)-associated bloodstream infections (BSIs) are a significant concern in healthcare settings, and identifying factors contributing to their increase is critical for infection prevention. The Certification Board of Infection Control and Epidemiology (CBIC) emphasizes the "Surveillance and Epidemiologic Investigation" and "Prevention and Control of Infectious Diseases" domains, which align with the Centers for Disease Control and Prevention (CDC) guidelines for preventing intravascular catheter-related infections. The question asks for the intervention most likely to have contributed to the rise in PICC-associated BSIs over four months, requiring an evaluation of each option based on evidence-based practices.

Option C, "Replacement of the intravenous administration sets every 72 hours," is the most likely contributor to the increase. The CDC’s "Guidelines for the Prevention of Intravascular Catheter-Related Infections" (2017) recommend that intravenous administration sets (e.g., tubing for fluids or medications) be replaced no more frequently than every 72-96 hours unless clinically indicated (e.g., contamination or specific therapy requirements). Frequent replacement, such as every 72 hours as a routine practice, can introduce opportunities for contamination during the change process, especially if aseptic technique is not strictly followed. Studies cited in the CDC guidelines, including those by O’Grady et al. (2011), indicate that unnecessary manipulation of catheter systems increases the risk of introducing pathogens, potentially leading to BSIs. A change to a 72-hour replacement schedule, if not previously standard, could explain the observed increase over the past four months.

Option A, "Use of chlorhexidine skin antisepsis during insertion of the PICC," is a recommended practice to reduce BSIs. Chlorhexidine, particularly in a 2% chlorhexidine gluconate with 70% alcohol solution, is the preferred skin antiseptic for catheter insertion due to its broad-spectrum activity and residual effect, as supported by the CDC (2017). This intervention should decrease, not increase, infection rates, making it an unlikely contributor. Option B, "Daily bathing adult intensive care unit patients with chlorhexidine," is another evidence-based strategy to reduce healthcare-associated infections, including BSIs, by decolonizing the skin of pathogens like Staphylococcus aureus. The CDC and SHEA (Society for Healthcare Epidemiology of America) guidelines (2014) endorse chlorhexidine bathing in intensive care units, suggesting it should lower, not raise, BSI rates. Option D, "Use of a positive pressure device on the PICC," aims to prevent catheter occlusion and reduce the need for frequent flushing, which could theoretically decrease infection risk by minimizing manipulation. However, there is no strong evidence linking positive pressure devices to increased BSIs; if improperly used or maintained, they might contribute marginally, but this is less likely than the impact of frequent tubing changes.

The CBIC Practice Analysis (2022) and CDC guidelines highlight that deviations from optimal catheter maintenance practices, such as overly frequent administration set replacements, can increase infection risk. Given the four-month timeframe and the focus on an intervention’s potential negative impact, Option C stands out as the most plausible contributor due to the increased manipulation and contamination risk associated with routine 72-hour replacements.