The worldwide dissemination of extended-spectrum--lactamase (ESBL)-and carbapenemase-producing Enterobacteriaceae is a major concern in both hospital and community settings. Rapid identification of these resistant pathogens and the genetic determinants they possess is needed to assist in clinical practice and epidemiological studies. A collection of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, and Proteus mirabilis isolates, including phenotypically ESBL-positive (n ؍ 1,093) and ESBL-negative isolates (n ؍ 59), obtained in 2008 -2009 from a longitudinal surveillance study (SMART) was examined using an in vitro nucleic acid-based microarray. This approach was used to detect and identify bla ESBL (bla SHV , bla TEM , and bla CTX-M genes of groups 1, 2, 9, and 8/25) and bla KPC genes and was combined with selective PCR amplification and DNA sequencing for complete characterization of the bla ESBL and bla KPC genes. Of the 1,093 phenotypically ESBL-positive isolates, 1,041 were identified as possessing at least one bla ESBL gene (95.2% concordance), and 59 phenotypically ESBL-negative isolates, used as negative controls, were negative. Several ESBL variants of bla TEM (n ؍ 5), bla SHV (n ؍ 11), bla CTX-M (n ؍ 19), and bla KPC (n ؍ 3) were detected. A new bla SHV variant, bla SHV-129 , and a new bla KPC variant, bla KPC-11 , were also identified. The most common bla genes found in this study were bla CTX-M-15 , bla CTX-M-14 , and bla SHV-12 . Using nucleic acid microarrays, we obtained a "molecular snapshot" of bla ESBL genes in a current global population; we report that CTX-M-15 is still the dominant ESBL and provide the first report of the new -lactamase variants bla SHV-129 and bla KPC-11 .