Trends in Multidrug Resistant Bacteria and Clostridium difficile in an Integrated Healthcare Network, 2008-2015

Background:

Multidrug resistant bacterial (MDRO) and Clostridium difficile infections are threats to patient safety. The objective of our study was to describe the burden of MDROs and Clostridium difficile and to depict changing trends over time in an integrated healthcare network.

Methods:

We abstracted electronic data from patients seen at any of Intermountain Healthcare’s 22 hospitals and affiliated clinics between January 1, 2008 and December 31, 2015 who had clinical cultures positive for antibiotic resistant Gram-positive or Gram-negative bacteria and/or a laboratory tests positive for toxigenic C. difficile. MDRO was defined as resistance to ≥3 antibiotic classes, pan-resistance as resistance to all antibiotics tested. Carbapenem resistant Enterobacteriaceae (CRE) was defined according to CDC definitions.  Specimens collected after > 48h (for C. difficile ≥72h) from time of admission were classified as hospital acquired.

Results:

A total of 62,480 cultures collected from 39,158 patients yielded an organism of interest from 4,019,150 total patient encounters. The prevalence of all studied organisms was 155 per 10,000 patient encounters and incidence of 82 per 10,000 patient encounters. Of the 900,000 hospital admissions during the study period, 12,905 (1.4%) were from patients positive for an MDRO and/or C. difficile. Methicillin resistant Staphylococcus aureus, C. difficile and ESBL harboring Gram-negative rods were the most common organisms (Figure A). We observed a 222% increase in the prevalence of C. difficile and a 322% increase in ESBL positive organisms from 2008 to 2015 whereas the prevalence of MRSA decreased by 32% (Figure B). All other organisms occurred at a roughly constant rate over time. MRSA, ESBL E. coli and CRE E.coli were less frequently acquired in the hospital; however, vancomycin resistant E. faecium, MDRO P. aeruginosa and other CRE were more frequently acquired in hospitals (Figure C).

Conclusion:

We describe changing epidemiology of MDROs over the study period. While MRSA continues to be the most common antibiotic resistant bacteria, rates have been declining. In contrast, ESBL and C. difficile rates continue to increase. The rate of acquiring an MDRO in acute care facilities varies by bacterial species. Understanding these trends helps focus limited infection control resources.