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Fifty-two strains of Klebsiella pneumoniae producing an AmpC-type plasmid-mediated beta-lactamase were isolated from 13 patients in the same intensive care unit between March 1998 and February 1999. These strains were resistant to ceftazidime, cefotaxime and ceftriaxone, but susceptible to cefoxitin, cefepime and aztreonam. Plasmid content and genomic DNA restriction pattern analysis suggested dissemination of a single clone. Two beta-lactamases were identified, TEM-1 and ACC-1. We used internal bla(ACC-1) primers, to sequence PCR products obtained from two unrelated strains of Hafnia alvei. Our results show that the ACC-1 beta-lactamase was derived from the chromosome-encoded AmpC-type enzyme of H. alvei.

The study was carried out with 50 strains of gonococci. Susceptibility to the antibiotics was determined by standard sensitivity test, by systematic test for beta-lactamase and by measurement of the MICs. The cephalosporins tested were: moxalactam, cefotaxime, ceftriaxone, cefotiam, cefoxitin, cefazolin and cephalothin. Their activities were also compared with other beta-lactams, namely penicillin and ampicillin. The efficacy in vitro of the cephalosporins: in the lead, ceftriaxone, remarkably active, with cefotaxime following very close, and then moxalactam with cefotiam a little behind, and finally all the other beta-lactams tested. The median MICs of the new cephalosporins (moxalactam, cefotaxime, ceftriaxone and cefotiam) were at least 10 times greater than those of the other beta-lactams tested. The MIC values observed with a resistant strain (penicillin, ampicillin; MIC 256 microgram/ml) never exceed the maximum values found with the 50 susceptible strains.