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.
C. Neumann, None
R. Clifford, None
P. Waterman, None
P. Mc Gann, None
M. Hinkle, None
E. Lesho, None
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