Transferable resistance to cefotaxime, cefoxitin, cefamandole and cefuroxime in clinical isolates of Klebsiella pneumoniae and Serratia marcescens.

In conjugational crosses, three Klebsiella pneumoniae strains and one Serratia marcescens strain have been demonstrated to transfer resistance determinants to newer types of cephalosporins. While Klebsiella strains donated cefotaxime, cefamandole and cefuroxime resistance to Escherichia coli K-12 recipients, the genetic analysis of exconjugants after the transfer of plasmids from Serratia strains to Proteus or Salmonella recipients showed that the cefoxitin resistance determinant was also co-transferred. In subsequent transfer cycles of this plasmid, cefotaxime and cefoxitin resistance determinants segregated in contrast to the relative stability of plasmids derived from Klebsiella strains in subsequent transfer cycles. From results obtained in this study, it may be concluded that in some strains of nosocomial Enterobacteriaceae, resistance to newer cephalosporins could be transmissible and thus plasmid-located.