Veterans Health Administration Methicillin-Resistant Staphylococcus aureus Prevention Initiative is also Reducing Nosocomial Gram-Negative Rod Bacteremia: An Interrupted Time-Series Analysis

Background: The Veterans Health Administration (VHA) introduced a methicillin-resistant Staphylococcus aureus (MRSA) Prevention Initiative in March 2007, which included active screening and isolation for MRSA, institutional culture changes, and increased infection prevention resources. Although this Initiative has largely been seen as a vertical intervention focusing on MRSA, it also included horizontal components, such as a focus on hand hygiene and resources to hire prevention coordinators. We aimed to assess the effect of this Initiative on nosocomial Gram-negative rod (GNR) bacteremia by interrupted time-series analysis.

Methods: This retrospective cohort included all patients who had nosocomial bacteremia (first positive blood culture >=48 hours after admission) due to Escherichia coli, Klebsiella spp., or Pseudomonas aeruginosa at 115 VHA facilities from 1/2003 to 12/2013. Monthly incidence rates were denominated by patient-days. The significances of changes in slope over time were assessed using autoregressive integrated moving average (ARIMA) models, incorporating seasonality and time before and after the introduction of the Initiative.

Results: 12,073 patients experienced nosocomial GNR bacteremia (E. coli: 4,010, Klebsiella spp.: 4,897, P. aeruginosa: 3,166) during study period. The overall incidence rate for any nosocomial GNR bacteremia was 4.02 per 10,000 patient-days (E. coli: 1.34, Klebsiella spp.: 1.63, P. aeruginosa: 1.05, per 10,000 patient-days respectively). There was a significant decrease in slope before [+0.015/month (95% CI: +0.004;+0.027)] compared to after [-0.024/month (95% CI: -0.029;-0.019)] the initiative (p<0.001), as well as for Klebsiella spp. [+0.011/month to -0.011/month (p<0.001)] and P. aeruginosa [+0.005/month to -0.009/month (p<0.001)]. The slope declined for E. coli (-0.002/month to -0.032/month), but this was not statistically significant (p =0.096).

Conclusion: At VHA, there was a sustained decline seen in nosocomial GNR bacteremia incidence rates after the introduction of MRSA Prevention Initiative. Since these organisms were not specifically targeted, it is likely that elements including a focus on hand hygiene or hiring coordinators contributed to this decline.