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pubmed:abstractText |
The Enterobacter species E. aerogenes, E. cloacae, and E. hafnia were examined for resistance to penicillin and cephalosporin derivatives. All were resistant to benzyl penicillin, ampicillin, 6 [d(-)alpha-amino-p-hydroxyphenylacetamido] penicillanic acid, cephaloridine, cephalothin, and cephalexin. A significant number were sensitive to carbenicillin and 6 [d(-)alpha-carboxy-3-thienylacetamido] penicillanic acid. No differences among the three species were noted. The beta-lactamase activity was cell-bound, and was not released by osmotic shock, toluene treatment, or diphenylamine treatment. It was rarely released into the growth medium. The beta-lactamase activity was primarily directed against cephalosporin derivatives. Synthesis of beta-lactamase was chromosomally mediated. Resistance to ampicillin seemed to be partly related to entry of the molecule into the bacteria since exposure to ethylenediaminetetraacetate lowered the minimal inhibitory concentration.
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