Molecular Detection of blaTEM, blaCTX-M and blaSHV Genes in Extended Spectrum β-Lactamase (ESBL) Escherichia coli from Clinical Samples

Introduction: Extended spectrum β-lactamases are the group of β-lactamase enzymes which confer resistance to the oxyimino-cephalosporins and monobactams.

Study Design: Cross-sectional prospective study.

Place and Duration of Study: This study was conducted over a period of 2 years (September 2018 to April 2020) at microbiology laboratory of Nepal Mediciti Hospital.

Methodology: Clinical samples were processed in microbiology laboratory and culture isolates were characterized by standard microbiological techniques following standard procedures. Antibiotic susceptibility testing was performed by modified Kirby-Bauer disc diffusion method as recommended by Clinical and Laboratory Standard Institute. Extended spectrum βlactamases were phenotypically confirmed by combined disc method. ESBL producing genes i.e. blaTEM, blaCTX-M and blaSHV were confirmed by PCR.

Results: Of the 1449 total Escherichia coli isolates, 323/1449(22.29%) isolates were multidrug resistance. Among total MDR E. coli isolates, 215/323(66.56%) isolates were ESBL producers. The maximum number of ESBL E. coli was isolated from urine 194(90.23%), followed by sputum 12(5.58%), swab 5 (2.32%), pus 2 (0.93%) and blood 2 (0.93%). Antibiotic susceptibility pattern of ESBL E. coli producers showed highest sensitivity towards tigecycline (100%) followed by polymyxin B, colistin and meropenem. Out of 215 phenotypically confirmed ESBL E. coli, only 186(86.51%) isolates were found to positive by PCR. The last 29(13.49%) were negative for any of the resistant genes. Among the ESBL genotypes, most common was blaTEM 118(63.4%) followed by blaCTX-M 68(36.6%).

Conclusion: The emergence of ESBL producing E. coli isolates with high antibiotic resistant rates to commonly used antibiotics and increased predominance of major gene types blaTEM is a serious concern to the clinicians as well as microbiologist. This study forwarded a real massage to all the clinicians for the emergence of XDR and PDR resistant bacteria and preservation of antibiotics for their proper use in near future, if past experience with MDR and ESBLs is any indicator.

Aims: This study was focused to find out the ESBL producing Escherichia coli and detection of TEM, SHV and CTXM genes by Polymerase Chain Reaction (PCR).