10.22376/ijpbs.2019.10.1.p1-12 Volume 5 Issue 1 2014 (January - March) Extended-spectrum β-lactamases producing Enterobacteria represent a rapidly emerging resistance problem in many countries. The present study was undertaken to find out the presence of lessThan i greaterThan blaCTX-M3 lessThan /i greaterThan and lessThan i greaterThan blaSHV lessThan /i greaterThan genes by PCR technique among clinical isolates of lessThan i greaterThan Escherichia coli lessThan /i greaterThan and lessThan i greaterThan Klebsiella pneumoniae. lessThan /i greaterThan A total of 186 faecal specimens were collected in our hospital, were subjected to isolation, identification of lessThan i greaterThan E.coli lessThan /i greaterThan and lessThan i greaterThan K. pneumoniae lessThan /i greaterThan , antimicrobial susceptibility testing was performed by disc diffusion method as per Clinical Laboratory Standard Institute.The PCR detection of lessThan i greaterThan E.coli lessThan /i greaterThan revealed 40/50 (80%) for lessThan i greaterThan CTX-M-3 lessThan /i greaterThan and (24/50) 48% for lessThan i greaterThan blaSHV lessThan /i greaterThan genes were positive. Moreover, antimicrobial resistance for lessThan i greaterThan E. coli lessThan /i greaterThan showed 74% to cefotaxime, 62% to ceftriaxone, lessThan i greaterThan K. pneumoniae lessThan /i greaterThan showed 72% of lessThan i greaterThan CTX-M-3 lessThan /i greaterThan and 80% of lessThan i greaterThan blaSHV lessThan /i greaterThan positive genes and resistance to cefotaxime (84%), ceftriaxone (56%), ceftazidime (66%), cefuraxime (68%), cefoperazone (58%), lessThan i greaterThan blaCTX-M3 lessThan /i greaterThan and lessThan i greaterThan blaSHV lessThan /i greaterThan genes transfers are possible mechanisms for wide prevalence of cephalosporin resistant among lessThan i greaterThan E.coli lessThan /i greaterThan and lessThan i greaterThan K. pneumoniae lessThan /i greaterThan strains. G.MUTHU, G.TAMIL INIYAN, J.SHANMUGAM AND T.MANGAIYARKARASI E.coli, K. pneumoniae, ESBL genes and PCR 689-696