1786. The Burden and Relative Risk of Carbapenem-resistant Pathogens and Correlations with Antibiotic Usage in a National Managed Care System
Session: Poster Abstract Session: Resistant Gram-Negative Infections: CRE Epidemiology
Saturday, October 10, 2015
Room: Poster Hall
Background: Carbapenem-resistant bacteria (CRB) pose urgent public health threats. International travel increases the risk of acquiring antibiotic resistant organisms, but whether travel increases risk for CRB acquisition is not clear. We sought to determine: 1) the burden of CRB in the large and geographically diverse national health care system of the U.S. Military Health System, 2) if antibiotic use correlated with incidences of CRB,  and 3) if overseas locations are associated with an increased risk of acquiring CRB.

Methods: Electronic laboratory records of all beneficiaries were queried for antibiotic prescriptions and all cultures that grew a target organism (Enterobacteriaceae (fermenters) and Acinetobacter baumannii, Acinetobacter calcoaceticus-baumannii complex, and Pseudomonas aeruginosa (non-fermenters)) from 2005 through 2014. De-duplication and incidence definitions were based on the Clinical Laboratory Standards Institute (CLSI) M39-A2 guideline for antibiogram reporting.  Carbapenem resistance was defined as being resistant to ertapenem, doripenem, meropenem, or imipenem according to U.S. Food and Drug Administration and/or CLSI susceptibility breakpoints.

Results: From over 90 million patient-years of surveillance and 14,725,478 clinical cultures, 366,075 grew a target organism.  From these, 0.15% of the fermenters and 11.30% of the non-fermenters were carbapenem-resistant.  Among the non-fermenters, 27.70% of Acinetobacter spp and 8.72% of P. aeruginosa were carbapenem-resistant. Usage positively correlated with resistance for carbapenems in P. aeruginosa, and aminoglycosides and fluoroquinolones in A. baumannii and E coli.  The relative risk (RR) of having a carbapenem-resistant phenotype from a location outside the contiguous U.S. (OCONUS) varied by species, from a low of 0.87 (95% CI 0.74-1.01) for P. aeruginosa to a high of 1.83 (95% CI 1.0-3.03) for Klebsiella pneumoniae. For all taxa combined, over the full observation period, the RR of acquiring a carbapenem-resistant phenotype OCONUS was 1.29 (95% CI 1.18-1.14).

Conclusion: The incidence of carbapenem resistance is roughly 73-fold greater in non-fermenters than in fermenters. Antibiotic usage was correlated with resistance for certain antibiotic classes and species. OCONUS locations are associated with a significantly increased risk of having a resistant organism.

Uzo Chukwuma, MPH1, Michael Sparks, Ph.D.2, Charlotte Neumann, MSc1, Robert Clifford, Ph.D.2, Paige Waterman, M.D.3, Patrick Mc Gann, PhD2, Mary Hinkle, M.D.2 and Emil Lesho, DO, FIDSA2, (1)Navy and Marine Corps Public Health Center, Portsmouth, VA, (2)Walter Reed Army Institute of Research, Silver Spring, MD, (3)GEIS, Armed Forces Health Surveillance Center, Silver Spring, MD


U. Chukwuma, None

M. Sparks, None

C. Neumann, None

R. Clifford, None

P. Waterman, None

P. Mc Gann, None

M. Hinkle, None

E. Lesho, None

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