Susceptibility rates of clinically important bacteria collected from intensive care units against colistin, carbapenems, and other comparative agents: results from Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART).

OBJECTIVES

This study aimed to determine the in vitro susceptibility of commonly encountered Gram-negative bacilli (GNB) recovered from patients admitted to intensive care units (ICUs) in Taiwan against colistin, carbapenems, and other comparative agents.

METHODS

In total, 758 nonduplicate GNB isolates were obtained from clinical specimens of ICU patients at seven medical centers in 2016. Minimum inhibitory concentrations (MICs) were determined using the Vitek 2 susceptibility system. The reference broth-microdilution method was performed to determine MICs of colistin. Five main carbapenemase genes among carbapenem-non-susceptible GNB and - genes among colistin non-wild-type or -resistant isolates were determined.

RESULTS

After exclusion 38 and 13 spp. among 361 Enterobacteriaceae isolates, 34 (9.4%) isolates were carbapenem-insusceptible, 91.1% (n=31) were colistin wild type, and three and one isolates carried and -like, respectively. Carbapenem-insusceptible isolates were found in 23.4% (30 of 128) and 63.0% (87 of 138) of isolates of the and complex, respectively. was detected in two (1.8%) isolates. Very major errors between two methods of susceptibility to colistin were found in 1.5% of , 27.5% of , 4.7% of , and 10.1% of complex isolates.

CONCLUSION

In this study, 8.7% of Enterobacteriaceae isolates from ICUs were not susceptible to carbapenem, and and -like were found among three and one carbapenem-insusceptible isolates, respectively. Colistin MICs determined by Vitek 2 were not reliable, especially for and complex isolates.