Background

The Tigecycline Evaluation and Surveillance Trial is an antimicrobial susceptibility surveillance program that collects gram-positive and gram-negative organisms globally.

Objective

This analysis reports on antimicrobial susceptibility among 23,918 gram-negative isolates collected from intensive care units globally between 2004 and 2009.

Methods

MICs and susceptibility were determined according to the guidelines of the Clinical and Laboratory Standards Institute (US Food and Drug Administration breakpoints were applied against tigecycline).

Results

Gram-negative isolates were collected from 6 geographical regions: North America, 8099 isolates; Europe, 9244; Asia-Pacific Rim, 1573; Latin America, 3996; the Middle East, 635; and Africa, 371. North America reported the lowest rates of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae and Escherichia coli both overall (12.8% and 4.7%, respectively) and in each year of collection. High rates of ESBL production were reported among K pneumoniae from Latin America (45.5%) and Africa (54.9%) and for E coli from the Middle East (32.4%). Imipenem and tigecycline maintained >90% susceptibility against K pneumoniae, E coli, Klebsiella oxytoca, Enterobacter cloacae, and Serratia marcescens for all regions. Susceptibility to meropenem was >90% against all K oxytoca and S marcescens. Large regional variations in susceptibility among Acinetobacter baumannii were reported, with the largest variations reported for amikacin (75.2% in North America, 21.8% in the Middle East) and meropenem (60.4% in North America, 15.9% in Africa). MIC(90) values for tigecycline against A baumannii were low (1-2 mg/L) for all regions. Against P aeruginosa, susceptibility to amikacin (97.5% in North America, 67.5% in Latin America) and meropenem (79.1% in North America, 51.4% in Africa) had the largest variations.

Conclusions

Antimicrobial resistance among gram-negative intensive care unit isolates was highly variable between geographic regions. The carbapenems were active in vitro against Enterobacteriaceae, A baumannii and P aeruginosa, and tigecycline continued to be active in vitro against members of the Enterobacteriaceae and A baumannii collected from intensive care units in North America, Europe, the Asia-Pacific Rim, Latin America, the Middle East, and Africa.