Beta-Lactamases produced by amoxicillin-clavulanate-resistant enterobacteria isolated in Buenos Aires: a new blaTEM gene.

DI CONZA JOSÉ; BADARACCO ALEJANDRA; AYALA JUAN; RODRIGUEZ CYNTHIA; FAMIGLIETTI ANGELA; GUTKIND GABRIEL

REVISTA ARGENTINA DE MICROBIOLOGíA

ASOCIACION ARGENTINA MICROBIOLOGIA

Lugar: Buenos Aires; Año: 2014 vol. 46 p. 210 - 217

0325-7541

Resistance to beta-lactam/beta-lactamase inhibitors in enterobacteria is an increasing problem that has not been intensively studied in Argentina. In the present work, 54/843 enterobacteria collected in a teaching hospital of Buenos Aires city were ampicillin-sulbactam-resistant isolates but remained susceptible to second- and third- generation cephalosporins. The enzymatic mechanisms present in the isolates, which were also amoxicillin-clavulanic acid (AMC)- resistant (18/54) were herein analyzed. Sequencing revealed two different variants of blaTEM-1, being blaTEM-1b the most frequently detected (10 E. coli, 3 K. pneumoniae, 2 P. mirabilis and 1 R. terrigena) followed by blaTEM-1a (1 K. pneumoniae). Amoxicillin-clavulanate resistance seems to be mainly associated with TEM-1 overproduction (mostly in E. coli) or co-expressed with OXA-2-like and/or SHV ß-lactamases (K. pneumoniae and P. mirabilis). A new blaTEM variant (TEM-163) was described in an E. coli strain having an AMC MIC value of 16/8 µg/ml. TEM-163 contains Arg275Gln and His289Leu amino acid substitutions. On the basis of the high specific activity and low IC50 for clavulanic acid observed, the resistance pattern seems to be due to overproduction of the new variant of broad spectrum β-lactamase rather than to an IRT-like behaviour.