R Factor-Mediated and Chromosomal Resistance to Ampicillin in Escherichia coli

作者：A. Roupas, J.S. Pitton · 发表于：Antimicrobial Agents and Chemotherapy · 年份：1974 · DOI：10.1128/aac.5.2.186 · 被引用次数：42 · 研究领域：Antibiotic Resistance in Bacteria、Cancer therapeutics and mechanisms、Microbial Natural Products and Biosynthesis

Sixty-four ampicillin-resistant strains of Escherichia coli were studied. Six characters were examined: (i) resistance to ampicillin, cephalothin, and carbenicillin, (ii) synergy between ampicillin and cloxacillin, (iii) level of beta-lactamase activity after osmotic shock, (iv) transferability of ampicillin resistance, (v) immunological characterization of the enzyme, and (vi) determination of substrate profiles. One class of strains was found in which synthesis of beta-lactamase is inferred to be plasmid mediated; these strains are highly resistant to ampicillin and carbenicillin, sensitive to cephalothin, do not show synergism between ampicillin and cloxacillin, and reveal a high enzymatic activity after osmotic shock. A second class is formed by strains for which beta-lactamase synthesis is inferred to be chromosomal; these strains present a low resistance level to ampicillin, are sensitive to carbenicillin and resistant to cephalothin, show a synergism between ampicillin and cloxacillin, and reveal a very low enzymatic activity after osmotic shock. These characters may be used to differentiate periplasmic and cell-bound beta-lactamases.