Abstract

BERTONA, E. et al. Phenotypic and genotypic characterization of resistance to third-generation cephalosporins in Enterobacter spp. Rev. argent. microbiol. [online]. 2005, vol.37, n.4, pp.203-208. ISSN 0325-7541.

Enterobacter spp. are becoming increasingly frequent nosocomial pathogens with multiple resistance mechanism to b-lactam antibiotics. We carried out the phenotypic and genotypic characterization of b-lactamases in 27 Enterobacter spp. (25 Enterobacter cloacae y 2 Enterobacter aerogenes), as well as the ability of different extended spectrum b-lactamase (ESBL) screening methods. Resistance to third generation cephalosporins was observed in 15/27 (63%) isolates. Twelve resistant isolates produced high level chromosomal encoded AmpC b-lactamase; 6 of them were also producers of PER-2. Resistance to third generation cephalosporins in the remaining 3 isolates was due to the presence of ESBLs, PER-2 in 2 cases, and CTX-M-2 in the other. Only CTX-M-2 production was detected with all tested cephalosporins using difusion synergy tests, while cefepime improved ESBLs detection in 7/8 PER-2 producers, 4/8 in the inhibitor aproximation test and 7/8 with double disk test using cefepime containing disk with and without clavulanic acid. Dilution method, including cephalosporins with and without the inhibitor detected 1/9 ESBLs producers.

Keywords : Enterobacter spp.; expanded-spectrum b-lactamases; cefepime.

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