The beta‐lactamase types present in 75 ampicillin and carbenicillin resistant E. coli were characterized using isoelectric focusing (IEF). The strains were isolated from patients with urinary tract infections from two geographically different areas of Denmark: 38 strains from Copenhagen and 37 strains from North Jutland. For 19 of the strains from Copenhagen and 18 of the strains from North Jutland, their beta‐lactamase activity against nitrocefin and ampicillin, carbenicillin, benzylpenicillin, cloxacillin and cephaloridine was examined by a micro‐iodometric and an UV‐spectrophotometric assay. The strains from Copenhagen showed greater activity (p < 0.001) against nitrocefin than the strains from North Jutland. The rate of hydrolysis of ampicillin was greater for the strains from Copenhagen than for the strains from North Jutland. Ninety‐three per cent of the strains produced plasmid‐mediated beta‐lactamases, of which the most prevalent, TEM‐1, was produced by 97 per cent of these strains, and OXA‐1 by 3 per cent.
The antibacterial activity of cefotetan, 8 other beta‐lactam antibiotics and gentamicin, was tested in vitro on 288 recently isolated bacteria. The activity of cefotetan was generally higher than the 2.generation cephalosporin cefuroxime and lower than the 3.generation cephalosporins tested. In addition, cefotetan was shown to have some antibacterial activity against anaerobic bacteria. Cefotetan is a cephamycin and was found resistant to all 14 plasmid‐mediated and 2 chromosomally‐mediated beta‐lactamases. With its beta‐lactamase resistence and antibacterial activity, cefotetan seems to be a “second‐generation‐like” cephalosporin, almost with 3.generation cephalosporin antibacterial activity against Enterobacteriaceae.
The antibacterial activity of aztreonam, 9 other β-lactam antibiotics and gentamicin was tested in vitro on 383 recently isolated bacteria. The activity of aztreonam against the gram-negative bacteria is similar to the activity of the 3rd generation cephalosporins and gentamicin. With regard to β-lactamase stability only PSE-2 out of 14 plasmid mediated β-lactamases and K-1 out of 2 chromosomally mediated β-lactamases could hydrolyze aztreonam. With its β-lactamase stability, high antibacterial activity and narrow-spectrum aztreonam seems to be a valuable addition to the antibiotic arsenal.
A collection of Enterobacter cloacae strains from Odense University Hospital from 1977 were compared with a collection from 1985 as regards acquired resistance traits. Among the strains with carbenicillin (Ca) resistance, the number of multiresistant strains decreased while the number with sole Ca‐resistance increased. In 1977, a high proportion of the Ca‐resistant (Ca‐r) strains had plasmid‐mediated β‐lactam resistance, but in 1985 the Ca‐r strains were completely dominated by organisms with elevated amounts of chromosomally‐mediated β‐lactamase. The latter, but not the former, strains were resistant to the newer cephalosporins (e.g. cefotaxime (Ctax)). The consumption of Ctax and cefuroxime increased from 0 kg in 1977 to 7.0 kg in 1985. It is therefore probable that this increase was the cause of the change in occurrence of the resistance types. Ninety‐one % of the Ca‐r strains were isolated from urinary samples in 1977. The percentage was only 31 in 1985. This change, concomitant with the increase in Ctax‐r strains, can probably be explained by the better conditions for selection of Ctax‐r mutants, producing greater amounts of chromosomal β‐lactamase, in wounds and respiratory tract than in urine.
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