Host range variability in the transfer of antibiotic resistance determinants from Pseudomonas aeruginosa strains

Twelve multiply drug-resistant strains of Pseudomonas aeruginosa, isolated in Frankfurt University Clinics during the year 1998, transferred determina nts of antibiotic resistance with remarkable variability in the host range of transferred plasmids, As a new phenomenon, two of them transferred resis tance genes to both groups of recipients, i.e. to Enterobacteriaceae as wel l as to a strain of P, aeruginosa. Six strains had more restrictive activit y and transferred resistance determinants to Enterobacteriaceae only, while four additional strains demonstrated transferability only to P, aeruginosa . Two isolates transferred imipenem resistance and one cefepime resistance. Differences in selection pressure occurring during therapy of individual p atients seems to be one of the possible factors influencing the spectrum of antibiotic resistance genes present in P, aeruginosa and their transfer to susceptible strains.