In vitro susceptibility of OXA-48, NDM, VIM and IMP enzyme- producing Klebsiella spp. and Escherichia coli to fosfomycin.

Introduction: Infections caused by Carbapenemase-producing Enterobacterales (CPE) are an important public health issue. Intravenous fosfomycin can be considered as an alternative for the treatment of serious infections caused by CPE. In this study, in vitro activity of fosfomycin was investigated among CPE isolates. Methodology: Overall, 158 clinically relevant isolates obtained from 18 hospitals of 13 cities in Turkey with predetermined carbapenemase types were evaluated in the study, including Escherichia coil (n = 19) and Klebsiella spp. (n = 139). In vitro activity of fosfomycin was determined with agar dilution method. Among Klebsiella spp., 104 harbored bla(OXA-48), 15 isolates carried both bla(OXA-48 )and bla(NDM), three had both bla(OXA-48) and bla(VIM) and nine isolates had bla(NDM) alone. Four isolates carried only bla(VIM) and two isolates harbored bla(IMP) alone. One isolate co-harbored bla(VIM)and bla(NDM). Among E. coil isolates, bla(OXA-48 )is and bla(NDM) were carried by 18 and one isolates, respectively. Results: Resistance to fosfomycin was detected in 43.7% of the isolates. Among Klebsiella spp. and E. coli, these rates were 46.8% and 21.1%, respectively. In Klebsiella spp. resistance to fosfomycin was 49.5% in bla(OXA-48) carricrs; 26.7% in isolates co-harbouring bla(OXA-48 )sand bla(NDM) and 66.7% in bla(NDM) carriers. In E. coli, fosfomycin resistance was detected among 16.7% of the bla(OXA-48) carriers. Conclusions: High level of fosfomycin resistance in these isolates may be attributable to the fact that these isolates are multidrug resistant. The genetic background of resistance should also be investigated in order to understand the co-occurrence and transfer of resistance among the CPE.