Association of the Extended-Spectrum -Lactamase Gene blaTLA-1 with a Novel ISCR Element, ISCR20

The blaTLA-1 gene encoding an extended-spectrum -lactamase was identified in 11 enterobacterial isolates from Mexico City, Mexico. This gene was located on different plasmids and plasmid types with different sizes and incompatibility groups. It was associated with a novel insertion sequence, ISCR20, encoding a putative transposase that shared only 20 % amino acid identity with the most closely related transposase of ISCR1. The ISCR20 element provided specific promoter sequences for expression of the blaTLA-1 gene. Although the majority of Ambler class A extended-spectrum -lactamases (ESBLs) identified in the family Enterobacteria-ceae worldwide are mostly of the TEM, SHV, and CTX-M types, some “minor ” ESBLs have been reported, such as VEB-like, GES-like, BES-1, SFO-1, and TLA-1 enzymes (5). The blaTLA-1 gene was first reported in 2000 from an Escherichia coli clinical isolate from Mexico (8). From April 2000 until February 2002, the blaTLA-1 gene was detected from an epi-demic Klebsiella pneumoniae clone in Mexico, and both the blaTLA-1 and blaSHV-5 ESBL genes were located on the sam