Factors contributing to vancomycin-resistant Enterococcus spp. horizontal transmission events: exploration of the role of antibacterial consumption

Background The relationship between antibiotic consumption and resistance is relatively well defined at the population/ecologic level. Increases in antimicrobial consumption correlate with increased antibiotic resistance for clinical and surveillance isolates. However, the impact of antimicrobial consumption on nosocomial transmission of resistant bacteria is less well defined. This study explores the association between antimicrobial consumption, hand hygiene, and horizontal resistant organism transmission. Methods A retrospective cohort pilot study was conducted. Vancomycin-resistant Enterococcus spp. (VRE) horizontal transmission events during a 2-year period were identified. VRE transmission events were defined as isolation of genetically similar VRE strain-types (determined using pulsed field gel electrophoresis) from patients who were temporally and geographically co-localized within our hospital. The Centers for Disease Control and Prevention Antimicrobial Use and Resistance Module was utilized to collect antibacterial consumption data of commonly utilized agents. Hand hygiene was quantified using floor-by-floor peer audit data. Regression techniques were employed to assess population-level relationships between study variables and transmission events. Results One hundred nineteen transmission events were identified. Hand hygiene estimates were homogeneous and did not correlate with VRE transmission rates. Stepwise-multivariate linear regression revealed that aztreonam consumption was associated with a lower rate of transmissions in the medical intensive care unit (P = 0.031), and carbapenem consumption was associated with a higher rate of VRE transmission events on one of two oncology floors (P = 0.033). Discussion/Conclusion Consumption of aztreonam and carbapenems was associated with VRE horizontal transmission rates. Further studies are necessary to identify other associations and elucidate the full clinical significance of this finding.