Distribution of bla(CTX − M), bla(TEM), bla(SHV) and bla(OXA) genes in Extended-spectrum-β-lactamase-producing Clinical isolates: A three-year multi-center study from Lahore, Pakistan

BACKGROUND: Frequency of extended-spectrum-β-lactamase-producing clinical isolates is increasing worldwide. This is a multi-center study which was aimed to check the frequency of third-generation cephalosporin resistance and distribution of the key genetic determinants of Extended-spectrum-β-lactamase-producing Clinical isolates in Pakistan. METHODS: A total of 2372 samples were processed in three tertiary care hospitals and one diagnostic research center of Lahore, Pakistan during Aug-2014 to Sep-2017. Analytical profile index (API 20-E) was used for biochemical characterization of isolates. Antibiotic susceptibility testing (AST) and third generation cephalosporin resistant (3GC-R) isolates were subjected to: double disc synergism test (DDST), combination disc test (CDST) and epsilometric test (E-test) for confirmation of ESBL-production. PCR amplification of isolates with plasmid and genomic DNA was performed. Amplicon sequences were checked for gene-variants and statistical analyses were performed to check the significance of data. RESULTS: A total of 497/995 (50%) isolates including Escherichia coli 65% (n = 321), Klebsiella spp. 25% (n = 124) and Pseudomonas. 5% (n = 24), Enterobacter spp. 4% (n = 20) and Acinetobacter spp. 2% (n = 8) were screened as third generation cephalosporin resistant (3GC-R). Urine 56% (n = 278) followed by pus 20% (n = 99) and wound swab 6% (n = 29) were frequent sources. Incidence of ESBL-producers detected by combination disc test was 79% (n = 392). PCR revealed bla(CTX − M) (76%) gene followed by bla(OXA) (52%), bla(TEM) (28%) and bla(SHV) (21%) were most prevalent among ESBL-producers detected by CDST. bla(CTX − M − 1)(65%), bla(OXA) (78%) and bla(TEM) (57%) genes were carried on plasmids. Amplicon sequencing revealed bla(CTX − M − 15) (75%), bla(OXA − 1) (49%) and bla(TEM − 1B) (34%) and 21 (n = 28) isolates carried three genes in them. CONCLUSION: Prevalence of ESBL-producing isolates has increased 1.13 folds during study years. Isolates had high prevalence of ESBL-encoding bla(CTXM − 15) gene and narrow spectrum bla(OXA − 1) and bla(TEM − 1B) were also prevalent.