Identification of mcr-8 in Clinical Isolates From Qatar and Evaluation of Their Antimicrobial Profiles

This study was performed to investigate the genotypic causes of colistin resistance in 18 colistin-resistant Klebsiella pneumoniae (n = 13), Escherichia coli (n = 3) and Pseudomonas aeruginosa (n = 2) isolates from patients at the Hamad General Hospital, Qatar. MIC testing for colistin was performed using Phoenix (BD Biosciences, Heidelberg, Germany) and then verified with SensiTest Colistin (Liofilchem, Zona Ind. le, Italy). Strains determined to be resistant (MIC > 4-16 μg/mL) were then whole-genome sequenced (MiSeq, Illumina, Inc.). Sequences were processed and analysed using BacPipe v1.2.6, a bacterial whole genome sequencing analysis pipeline. Known chromosomal modifications were determined using CLC Genomics Workbench v.9.5.3 (CLCbio, Denmark). Two K. pneumoniae isolates (KPN-15 and KPN-19) harboured mcr-8.1 on the IncFII(K) plasmids, pqKPN-15 and pqKPN-19, and belonged to ST383 and ST716, respectively. One E. coli isolate harboured mcr-1.1 on the IncI2 plasmid pEC-12. The other 15 isolates harboured known chromosomal mutations linked to colistin resistance in the PhoPQ two-component system. Also, three K. pneumoniae strains (KPN-9, KPN-10 and KPN-15) showed disruptions due to IS elements in mgrB. To our knowledge, this marks the first description of mcr-8.1 in K. pneumoniae of human origin in Qatar. Currently, more research is necessary to trace the source of mcr-8.1 and its variants in humans in this region.