Characterization of cephalosporin-resistant clinical Enterobacteriaceae for CTX-M ESBLs in Bahrain

To detect the presence of specific CTX-M class of extended spectyum β-lactamases (ESBLs) in a collection of cephalosporin-resistant Enterobacteriaceae isolates from Bahrain. A subset of 80 cephalosporin-resistant Enterobacteriaceae collected from Salmaniya Medical Complex, Bahrain, were characterized further for the presence of specific genogroups of CTX-M β-lactamases by multiplex- and monoplex- PCRs. The primers used for the multiplex and monoplex PCRs were of genogroups- 1, 2, 8, 9 and 25. Sequencing of the representative isolates was performed to find the circulating CTX-M-types. A total of 93.8% (75/80) isolates showed the amplicons corresponding to any of the genogroups (1, 2, 8, 9, 25) and the remaining 6.2% isolates turned out negative in multiplex PCR. Some of the isolates demonstrated multiple bands corresponding to the sizes of different genogroups. Further confirmation with respective monoplex PCR on these 75 isolates demonstrated that 93.3% (70/75) harbored CTX-M genogroup-1 and 6.7% (5/75) harbored genogroup-9. We did not find the presence of genogroups 2, 8, and 25 in these isolates by monoplex PCR. Sequencing results of genogroup-1 isolates demonstrated the presence of CTX-M-15-like ESBL, however, discrepant results were noticed in genogroup-9 isolates, sequencing showed them as CTX-M-55-like ESBL. This is the first report from Bahrain characterizing the CTX-M genogroups of ESBLs and reporting the emergence of blaCTX-M-55-like gene in this region.