Activity of clavulanate combinations against TEM-1 beta-lactamase-producing Escherichia coli isolates obtained in 1982 and 1989.
Recent reports of decreased susceptibility to amoxycillin/clavulanate and ticarcillin/clavulanate combinations amongst Escherichia coli isolates have been attributed to an increased frequency of hyperproduction of TEM-1 beta-lactamase. To test this claim we compared the activities of clavulanate combinations against consecutive E. coli isolates producing TEM-1 beta-lactamase that were obtained from clinical material at The London Hospital during 1982 (n = 50) and 1989 (n = 46). Enzyme production was quantified and related to the level of clavulanate required to potentiate amoxycillin and ticarcillin. The levels of TEM-1 enzyme production varied 150-fold amongst the isolates, partly because of variation in the gene copy number. A clear correlation existed between enzyme quantity and levels of resistance to the clavulanate combinations. However, there was no significant difference (P greater than 0.05, Mann-Whitney U test) between the isolates obtained in 1982 and 1989 in terms of the clavulanate concentrations required to potentiate the penicillins, or in the distribution of beta-lactamase activities present.
Department of Medical Microbiology, London Hospital Medical College, UK.
P S
PS
Seetulsingh
L M
LM
Hall
D M
DM
Livermore
D000658:Amoxicillin / Q000494:pharmacology*; D019980:Amoxicillin-Potassium Clavulanate Combination; D002969:Clavulanic Acids / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D004357:Drug Synergism; D004359:Drug Therapy, Combination / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D010957:Plasmids; D013982:Ticarcillin / Q000494:pharmacology*; D013997:Time Factors; D001618:beta-Lactamases / Q000032:analysis / Q000096:biosynthesis*
D002969:Clavulanic Acids; D019980:Amoxicillin-Potassium Clavulanate Combination; D000658:Amoxicillin; C043215:ticarcillin-clavulanic acid; D001618:beta-Lactamases; C034413:beta-lactamase TEM-1; D013982:Ticarcillin