Activity of Omadacycline and Other Tetracyclines Against Contemporary Gram-Negative Pathogens from New York City Hospitals.

Antibiotic-resistant Enterobacteriaceae and are problematic pathogens, with few treatment options for multidrug-resistant (MDR)- and few oral options for extended spectrum β-lactamase (ESBL)-producing and MDR-Enterobacteriaceae. Omadacycline, a newer tetracycline derivative, has activity against some of these pathogens. We tested the activity of omadacycline against a contemporary collection of over 2,600 consecutive unique clinical isolates of Enterobacteriaceae and , a previous collection of carbapenem-resistant and from a surveillance study in 2013-2014, and a group of and isolates with previously defined resistance mechanisms. For the contemporary collection, over 96% of and 70% of isolates were inhibited by omadacycline at ≤4 μg/mL including 95% of and 49% of with presumptive ESBLs. Nearly 90% of were inhibited by omadacycline at ≤4 μg/mL. The omadacycline MIC was 1/4 μg/mL, 4/>8 μg/mL, and 0.5/8 for , , and , respectively. For the carbapenem-resistant collection of isolates, 56% of were inhibited by omadacycline at ≤4 μg/mL, but only 30% of carbapenemase (KPC)-possessing were susceptible. Expression of the efflux gene B appeared to affect the activity of omadacycline against , but could not fully explain resistance to this agent. Omadacycline may prove to be a parenteral or oral option for some infections due to ESBL-producing Enterobacteriaceae and carbapenem-resistant , and clinical studies are warranted.