Differential impact of infection control strategies on rates of resistant hospital-acquired pathogens in critically ill surgical patients

Background: There were two major outbreaks of multi-drug resistant Acinetobacter baumannii (MDRA) in our general surgery and trauma intensive care units (ICUs) in 2004 and 2011. Both required aggressive multi-faceted interventions to control. We hypothesized that the infection control response may have had a secondary benefit of reducing rates of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), and Clostridium difficile (C. diff). Methods: We analyzed data retrospectively from a prospective infection control database at a major university hospital and calculated the incidence rates of nosocomial MRSA, VRE, and C. diff before and after the two MDRA outbreaks (2004 and 2011) in the general surgery and trauma ICUs, and two unaffected control ICUs: thoracic surgery ICU and medical ICU. We tracked incidence rates in 6 mos segments for 24 mos per outbreak and created a composite variable of "any resistant pathogen" for comparison. Results: The incidence rates of "any resistant pathogen" were significantly lower in the general surgery ICU after both outbreaks (24 to 11 cases per 1000 patient days in 2004, p=0.045 and 7.7 ->4.0 cases per 1000 patient days in 2011, p=0.04). This did not persist after 6 mos. The trauma ICU's rate of "any resistant pathogen" did not change after either outbreak (16 ->16.5 cases per 1000 patient days in 2004, p=0.44 and 4.6 ->1.9 cases per 1000 patient days in 2011, p=0.41). The rates in the control ICUs were unchanged during the study periods. Conclusions: Rates of resistant pathogens were lower in the general surgery ICU after response to MDRA outbreaks in both 2004 and 2011 although the rates increased again with time. There were no changes in rates of resistant pathogens in the trauma ICU after MDRA outbreaks in 2004 and 2011. Outbreak responses may have a differential impact in general surgery ICU versus trauma ICUs.