Objective:To delineate the frequency of occurrence of bla_(CTX-M),bla_(TEM),and bla_(SHV) in Enterobacteriaceae from North-Indian tertiary hospital.Methods:A random collection of a subset of 45 Escherichia coli(E.coli) and 28 Klebsiella pneumoniae(K.pneumoniae) that was resistant to a third generation cephalosporin and obtained during 2007-2008 was selected for detailed screening for bla_(CTX-M),bla_(TEM),and bla_(SHV) by monoplex PCRs.The isolates demonstrating the presence of bla_(CTX-M) alleles were characterized for the specific CTX-M-genogroup by using a multiplex PCR.Results:Resistance to cefoperazone,ceftazidime,ceftriaxone,cefotaxime, cefoxitin and piperacillin was 100%each in K.pneumoniae isolates,whereas these resistancerates for E.coli isolates were 93.1%,83.8%,91.9%,93.6%,97.3%and 97.1%,respectively. Concomitant resistance to aminoglycosides,quinolones and aztreonam was also noticed.Presence of any of the bla genes(bla_(CTX-M),bla_(TEM),and bla_(SHV)) was noticed in a total of 28(38.4%) isolates of the 73 isolates studied.Many isolates demonstrated occurrence of these genes in various combinations.bla_(CTX-M),bla_(TEM),and bla_(SHV) were noticed in 28.8%,10.9%and 13.7%isolates, respectively.Multiplex PCR in bla_(CTX-M) harboring isolates demonstrated the presence of CTX-MGenogroup -1 and sequencing for the specific CTX-M-type revealed presence of CTX-M-15 type. RAPD typing showed wide diversity in isolates.Conclusions:This is amongst the premier report describing the simultaneous occurrence of blo_(TEM),bla_(SHV),and bla_(ampC) in Indian Enterobacteriaceae and that wider dissemination of these genes,as demonstrated by diversity of isolates,raises concern and emphasizes a need for extensive search for the presence of these gene pools in Indian subcontinent. Objective: To delineate the frequency of occurrence of bla_ (CTX-M), bla_ (TEM), and bla_ (SHV) in Enterobacteriaceae from North-Indian tertiary hospital. Methods: A random collection of a subset of 45 Escherichia coli coli) and 28 Klebsiella pneumoniae (K. pneumoniae) that was resistant to a third generation cephalosporin and obtained during 2007-2008 was selected for detailed screening for bla_ (CTX-M), bla_ (TEM), and bla_ (SHV) by monoplex PCRs. The isolates demonstrating the presence of bla_ (CTX-M) alleles were characterized for the specific CTX-M-genogroup by using a multiplex PCR. Results: Resistance to cefoperazone, ceftazidime, ceftriaxone, cefotaxime, cefoxitin and piperacillin was 100% each in K. pneumoniae isolates, but these resistance rates for E. coli isolates were 93.1%, 83.8%, 91.9%, 93.6%, 97.3% and 97.1%, respectively. Concomitant resistance to aminoglycosides, quinolones and aztreonam was also not noticed. Presence of any of the bla genes (bla_ (CTX-M), bla_ (TEM), and bla_ (SHV)) was noticed in a total of isolates of the 73 isolates studied. Many isolates were produced among these genes in various combinations. bla_ (CTX-M), bla_ (TEM), and bla_ (SHV) were noticed in 28.8%, 10.9% and 13.7% isolates, respectively. Multiplex PCR in bla_ (CTX-M) harboring isolates demonstrated the presence of CTX-MGenogroup -1 and sequencing for the specific CTX-M-type revealed presence of CTX-M-15 type. RAPD typing showed wide diversity in isolates. Conclusions: This is amongst the premier report describes the simultaneous occurrence of blo TEMs, bla SHV, and bla amps in Indian Enterobacteriaceae and that wider dissemination of these genes, as demonstrated by diversity of isolates, raises concern and emphasizes a need for extensive search for the presence of these gene pools in Indian subcontinent.