New Chromosomal AmpC β-Lactamase in Enterobacter cloacae
Abstract
New Chromosomal AmpC β-Lactamase in Enterobacter cloacae T. Conceição , N. Faria , M. Pimentel , G. Soveral and A. Duarte * Faculty of Pharmacy University of Lisbon Av. Forças Armadas 1649-019 Lisbon, Portugal L. M. Lito , J. Melo Cristino and M. J. Salgado Faculty of Medicine Hospital de Santa Maria Lisbon, Portugal Several members of the Enterobacteriaceae , including Enterobacter spp., are naturally resistant to amoxicillin and cephalosporins. Enterobacter cloacae produces chromosomally encoded β-lactamases, also called cephalosporinases ( 1 ), and is a serious nosocomial pathogen, the third most prevalent bacterium isolated in intensive care settings ( 5 , 8 ). We report here the study of a new chromosomal AmpC β-lactamase produced by E. cloacae FFUL2En isolated from the blood culture of a patient hospitalized in a medicine ward of Hospital de Santa Maria, Lisbon, Portugal. The antibiogram revealed resistance to aminopenicillins, aztreonam, and broad-spectrum cephalosporins, except imipenem, aminoglycosides, and quinolones. By isoelectrofocusing, the sonicate extracts expressed a pI of 8.68, suggesting the presence of a presumed AmpC enzyme. A total DNA preparation from E. cloacae FFUL2En was used in PCR experiments with two sets of primers, TN5 (5′-CGTTTGTCAGGCACAGTCAAATCCA) and TN4 (5′-TTACTGTAGCGCGTCGAGGATATGG) and the internal