Tigecycline activity tested against antimicrobial resistant surveillance subsets of clinical bacteria collected worldwide (2011)

Abstract

Tigecycline was approved by the United States Food and Drug Administration in 2005 and has generally retained activity against resistant Gram-positive and Gram-negative organisms. We monitored the in vitro activity of this glycylcycline in 2011 for continued potency worldwide. A total of 22,005 unique clinical isolates were consecutively collected in North America (NA; 9232 isolates), Europe (EU; 6776), Latin America (LA; 2016), and Asia-Pacific region (APAC, 3981) and tested for susceptibility according to the reference broth microdilution method recommendations against tigecycline and numerous comparators. Oxacillin (methicillin) resistance rates in methicillin-resistant Staphylococcus aureus (MRSA) were 49.3%, 30.2%, 42.9%, and 37.8%, and vancomycin resistance rates in enterococci (VRE) were 27.0%, 11.3%, 6.3%, and 4.0% in NA, EU, LA, and APAC, respectively. All MRSA (2839) and >99% of VRE were susceptible to tigecycline. Among Escherichia coli, extended-spectrum β-lactamase (ESBL) rates varied from 12.6% in the NA to 57.4% in APAC, and only one strain was nonsusceptible to tigecycline. Tigecycline was active against ESBL phenotype (96.5-98.4% susceptible) and meropenem-nonsusceptible Klebsiella spp. (94.3-100.0% susceptible). Only 4 of 213 (1.9%) meropenem-nonsusceptible Klebsiella spp. were tigecycline-nonsusceptible, all with tigecycline minimum inhibitory concentration (MIC) of 4 μg/mL (intermediate). Among ceftazidime-nonsusceptible Enterobacter spp., 94.7-98.2% were susceptible to tigecycline. Meropenem-nonsusceptible Acinetobacter spp. varied from 51.2% in NA to 80.9% in APAC; and 83.8% (LA) to 93.9% (APAC) of strains were inhibited at a tigecycline MIC of ≤2 μg/mL. Tigecycline showed potent activity against Stenotrophomonas maltophilia (89.3-98.3% inhibited at ≤2 μg/mL). In summary, tigecycline has sustained potent activity and a broad-spectrum against clinically important bacteria causing infections worldwide, including multidrug-resistant organism subsets.