Cooccurrence of NDM-1, ESBL, RmtC, AAC(6')-Ib, and QnrB in Clonally Related Isolates Together with Coexistence of CMY-4 and AAC(6')-Ib in Isolates from Saudi Arabia.

The aim of this study was to investigate the mechanisms responsible for resistance to antimicrobials in a collection of enterobacterial isolates recovered from two hospitals in Saudi Arabia. A total of six strains isolated from different patients showing high resistance to carbapenems was recovered in 2015 from two different hospitals, with four being and two All isolates except one were resistant to tigecycline, but only one was resistant to colistin. All produced a carbapenemase according to the Carba NP test, and all were positive for the EDTA-disk synergy test for detection of MBL. Using PCR followed by sequencing, the four isolates produced the carbapenemase NDM-1, while the two isolates produced the carbapenemase VIM-1. Genotyping analysis by Multilocus Sequence Typing (MLST) showed that three out of the four isolates were clonally related. They had been recovered from the same hospital and belonged to Sequence Type (ST) ST152. In contrast, the fourth isolate belonged to ST572. Noticeably, the NDM-1-producing additionally produced an extended-spectrum ß-lactamase (ESBL) of the CTX-M type, together with OXA-1 and TEM-1. Surprisingly, the three clonally related isolates produced different CTX-M variants, namely, CTX-M-3, CTX-M-57, and CTX-M-82, and coproduced QnrB, which confers quinolone resistance, and the 16S rRNA methylase RmtC, which confers high resistance to all aminoglycosides. The AAC(6')-Ib acetyltransferase was detected in both and . Mating-out assays using as recipient were successful for all isolates. The gene was always identified on a 70-kb plasmid, whereas the gene was located on either a 60-kb or a 150-kb plasmid the two isolates, respectively. To the best of our knowledge, this is the first report of the coexistence of an MBL (NDM-1), an ESBL (CTX-M), a 16S rRNA methylase (RmtC), an acetyltransferase (AAC[6']-Ib), and a quinolone resistance enzyme (QnrB) in isolates recovered from different patients during an outbreak in a Saudi Arabian hospital.