The Role of Uniform Meropenem Usage in Acinetobacter baumannii Clone Replacement

The dominant carbapenem resistant Acinetobacter baumannii harboring bla(OXA-23-like) carbapenemase was replaced by bla(OXA-40-like) carriers in a Hungarian tertiary-care center with high meropenem but relatively low imipenem use. We hypothesized that alterations in antibiotic consumption may have contributed to this switch. Our workgroup previous study examined the relation between resistance spiral and the antibiotic consumption, and the results suggest that the antibiotic usage provoked the increasing resistance in case of A. baumannii. We aimed at measuring the activity of imipenem and meropenem to compare the selection pressure exerted by the different carbapenems in time-kill assays. Strain replacement was confirmed by whole genome sequencing, core-genome multilocus sequence typing (cgMLST), and resistome analysis. Based on results of the time-kill assays, we found a significant difference between two different sequence-types (STs) in case of meropenem, but not in case of imipenem susceptibility. The newly emerged ST636 and ST492 had increased resistance level against meropenem compared to the previously dominant ST2 and ST49. On the other hand, the imipenem and colistin resistance profiles were similar. These results suggest, that the uniform meropenem usage may have contributed to A. baumannii strain replacement in our setting.

Automated summary

The dominant carbapenem resistant Acinetobacter baumannii carrying bla(OXA-23-like) carbapenemase was replaced by strains carrying bla(OXA-40-like) in a Hungarian tertiary-care center with high meropenem but relatively low imipenem usage. Alterations in antibiotic consumption, particularly the uniform usage of meropenem, may have contributed to this strain replacement. Time-kill assays showed significant differences in susceptibility to meropenem between different sequence types, but not in imipenem resistance.