High prevalence of blaCMYAmpC beta-lactamase in ESBL co-producing Escherichia coliand Klebsiellaspp. clinical isolates in the northeast of Iran

•A total of 55.8% of E. coli and Klebsiellaspp. isolates were identified as putative ESBL-producers.•A total16.7% of ESBL producing E. coliand Klebsiellaspp. were positive for plasmid-borne AmpC genes.•blaCMY-type was the most frequent genotype of pAmpC among ESBL producing E. coliand Klebsiellaspp.