Extended-spectrum beta-lactamases in Escherichia coli and Klebsiella spp. in European septicaemia isolates.

Five per cent of Escherichia coli and klebsiella septicaemia isolates from the European Study Group on Antibiotic Resistance (ESGAR) study in 1987 to 1988 showed reduced susceptibility or resistance to cefotaxime, ceftazidime and/oraztreonam. Six of 15 isolates studied were susceptible to cefoxitin and MICs of cefuroxime, cefotaxime, ceftazidime and aztreonam were reduced by clavulanic acid. The isoelectric points of their beta-lactamases were in the range of 5.3-7.6. DNA hybridization showed that four of these beta-lactamases belonged to the TEM or SHV family. Transfer of cefotaxime resistance by conjugation was seen in two of the strains. Nine strains were resistant to cefoxitin (MIC > 16 mg/L) and MICs of cefuroxime, cefotaxime, ceftazidime and aztreonam were only slightly reduced in the presence of clavulanic acid. All nine strains produced at least one beta-lactamase of chromosomal origin with pI > 8.4, and four of these strains also harboured beta-lactamases with a pI range of 6.6-8.2. Cefoxitin resistance could be transferred by conjugation in one strain. Thus E. coli and Klebsiella spp. from the ESGAR septicaemia isolates were found to produce extended-spectrum beta-lactamases of both chromosomal and plasmid origin.