Extended-spectrum beta-lactamase producing strains of Enterobacter cloacaetransferring resistance to cefotaxime and ceftazidime

Transferability of ceftazidime resistance and of extended-spectrum p-lactam ase (ESBL) production was recorded in three strains of Enterobacter cloacae from Frankfurt University Clinics. All three strains were resistant to rif ampicin, carbenicillin, cephaloridine, cefotaxime, ceftazidime, aztreonam, imipenem and meropenem. They transferred directly determinants of resistanc e to carbenicillin and cephaloridine to Escherichia coli K-12 No. 185 nalrecipient strain. All transconjugant colonies also contained determinants o f resistance to cefotaxime, ceftazidime and aztreonam. In the second cycle of transfers, determinants of resistance to carbenicillin, cephaloridine, c efotaxime, ceftazidime and aztreonam were transferred en bloc to the recipi ent Escherichia coil K-12 No. 3110 rif+ indicating that the "transfer facto r" (tra+) mediating the process of conjugational transfer had also been co- transferred. Double-disk diffusion test showed the same pattern of producti on of ESBLs both in original strains and in transconjugants. Transfer of ce fotaxime, ceftazidime and aztreonam was accompanied by the transfer of ESBL production.