Molecular Characterization and Epidemiology of Extended-spectrum-beta-lactamases in Clinical Isolates of Escherichia coli with Special Attention to CTX-M

Extended-spectrum-beta-lactamases (ESBLs) are the most important cause of resistance to beta-lactam antibiotics among members of Enterobacteriaceae family. ESBL-associated infections are on the rise and have become a major public health concern around the world. The goal of this study was to look into the molecular epidemiology of ESBL producing E. coli isolates recovered from various clinical specimens at a tertiary care hospital, as well as to determine the antibiotic sensitivity profile of ESBL positive isolates. Between 2011 and 2014, a total of 300 E. coli isolates were gathered from various clinical samples. Testing for antibiotic susceptibility was conducted. ESBL detection was done using the confirmatory phenotypic CLSI approach. For 100 ESBL isolates, molecular typing of ESBLs was carried out using uniplex PCR. By sequencing PCR product, the genotypes of the bla CTX-M strains were determined. Nucleotide sequences were submitted to Gen Bank and accession numbers were obtained.

Results: 61% isolates were found to be ESBL producers. ESBL and non-ESBL producers compared among in- and out-patients gave statistically significant result (P value=0.002). All isolates (100%) were sensitive to imipenem. Overall 93.9% ESBL producers and 67.5% non- ESBLs were Multi Drug Resistant (Resistance to 3 or more class of antibiotics). The difference was statistically significant (P value=0.001). Majority of the typeable isolates harboured two or more ESBL genes (52%). Sequencing was done for 10 randomly selected blaCTX-M PCR products and majority (90%) were identified as CTXM-15 belonging to CTX-M Cluster-1, while 1 0f 10 (10%) was identified as CTX-M- 27 belonging to CTX-M Cluster-9 on blast analysis.Deduced nucleotide sequences were submitted to Gen Bank. The Gen Bank accession numbers range from KU946005 to KU946009. Our findings show a high prevalence of ESBLs among E.coli isolates, as well as the presence of CTX-M-27 for the first time in North India.