Date of Award

11-1-2017

Embargo Period

1-1-2020

Document Type

Thesis

Department

Microbiology and Immunology

College

College of Graduate Studies

First Advisor

Michael G. Schmidt

Second Advisor

Lisa L. Steed

Third Advisor

Laura M. Kasman

Fourth Advisor

Harold D. May

Abstract

Background: Carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a significant cause of healthcare associated infections (HAI) resulting in significant morbidity and mortality. Identification of CRE colonized and/or infected patients early during care enables implementation of comprehensive infection control measures that limit spread and likely reduces the risk of CRE mediated HAI. Hospitals in areas where CRE is endemic have instituted universal surveillance programs to limit risk, typically employing perianal/perirectal swabs or stool. In our facility, CRE isolation from clinical specimens is so infrequent that a universal surveillance program would not be cost effective. Consequently, in facilities with low CRE prevalence, a targeted approach may be more effective at developing an understanding of the CRE colonization pressure and thus spread represents to hospitalized patients. Prior antibiotic receipt is among the most prevalent predictors of CRE carriage and/or infection. Thus, the use of remnant Clostridium difficile diarrhea specimens to assess CRE carriage may be more effective than a universal surveillance program in assessing the risk of CRE to hospitalized patients. Methods: Remnant diarrhea specimens submitted for C difficile toxin PCR (n=600) were compared with remnant perianal swabs collected for vancomycin-resistant Enterococcus (VRE) surveillance (n=600) to determine the superiority of one specimen type over the other for CRE carriage. Specimens were analyzed using the two laboratory protocols recommended by CDC: the direct ertapenem disk method and selective enrichment broth method. Carbapenem resistance was confirmed by disk diffusion testing. Confirmed carbapenem resistant isolates were identified by Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI- TOF). Results: Using samples collected from patients under care in VRE high-risk units, the CRE colonization rate was 1.8 % (11/600). Samples collected from patients presenting with symptoms associated with antibiotic associated diarrhea, the targeted surveillance arm, were found to have a CRE colonization rate of 6.2% (37/600). The colonization rate difference observed between the two arms was significant (p value of < 0.0002, Fisher Exact Test). Conclusions: The use of targeted specimens was superior in the ability to identify CRE colonized individuals from facilities with low a clinical incidence of these microbes.

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