Association of Risk Factors, Antimicrobial Resistance Trends and Occurrence of blaTEM, bla SHV and blaCTX M in Escherichia coli Causing Bacteremia

Purpose: Escherichia coli are the most frequent cause of gram negative bloodstream infection. This study was done to evaluate the association of risk factors, antimicrobial susceptibility pattern and detection of TEM, SHV and CTX M genes in the extended spectrum beta lactamase (ESBL) producing E.coli. Materials and Methods: 11,133 blood samples were processed in BacT/Alert bottles. Bacteria grown were identified and antibiotic susceptibility patterns were studied using VITEK2 system. ESBL production was tested using phenotypic method, VITEK system and by PCR. Statistical package SPSS Version 11.5 was used to do the analysis. Results: Blood culture positive isolates were 1530 (13.7%), among which 108 were identified as Escherichia coli. The most common risk factor associated with E.coli bacteremia was diabetes and common source was UTI. E.coli were resistant to Ampicillin (86%), Piperacillin (82.4%), Ceftazidime (80.6%), Ceftriaxone (80.6%), Cefipime (77%), Aztreonam (80.6%) and Fluoroquinolones (80%). Isolates were sensitive to Carbapenems and combination drugs. ESBL was produced by 76%. CTX M bla (betalactamase) gene was common in all the ESBL isolates. Conclusion: ESBL producing E.coli isolates were observed to be multi drug resistant. Owing to the high prevalence of ESBL.Carbapenems are clearly the drug of choice for empirical treatment in these cases.Ertapenem may be used to prevent development of carbepenem resistant pseudomonas or acinetobacter isolates in the hospital settings. To limit the earlier development of resistance to carbepenems, it is better to de-escalate to combination drugs like piperacillin tazobactum with aminoglycosides after the susceptibility report.