Prevalence of non-extended spectrum β-lactamases SHV-1 and TEM-1 or -2 types in multidrug-resistant Enterobacteriaceae in northern Iran

The present study aimed to evaluate TEM-1 or -2 and SHV-1 β-lactamases frequency in multidrug-resistant (MDR) Enterobacteriaceae isolated from patients’ urine in northern Iran. The resistance pattern to 20 antibiotics and ESBL production in 200 MDR Enterobacteriaceae was detected using the disk diffusion test and double-disk synergy test (DDST), respectively. Multiplex PCR was applied to detect blaTEM-1 or -2 and blaSHV genes in isolates. DDST findings were inconsistent with multiplex PCR results. The distribution of each of blaTEM-1 or -2 and blaSHV genes, either alone or in combination, in the ESBL-producing isolates was higher than the non-ESBL-producing isolates. There was a significant effect of the presence of blaTEM-1 or -2 gene on resistance to cephalotin at the p < 0.01 level and cefepime, tetracycline, and streptomycin at the P < 0.05 level, and the presence of blaSHV-1 gene on resistance to fosfomycin at the P < 0.05 level as well as the presence both blaTEM-1 or -2 and blaSHV-1 genes on resistance to cephalotin and fosfomycin at the P < 0.01 level. In all isolates, ESBL production, except for cephalotin resistance, did not improve resistance to other antibiotics used and even non-ESBL-producing isolates showed higher resistance to antibiotics compared to ESBL-producing isolates. It seems that mechanisms other than production of ESBL to be involved as part of the resistance mechanisms of the studied isolates against the used antibiotics. For epidemiological studies, both phenotypic and molecular tests must be included to identify the blaTEM-1 or -2 and blaSHV-1 genotypes to ensure infection prevention and control.