Epidemiological and genetical analyses of clinical isolates resistant to newly developed antimicrobials

点击翻译按钮获取中文摘要

We examined 385 clinical isolates of P.aeruginosa and selected 90 strains resistant to at least one of 23 antibacterials tested. Using these strains, we determined their serum type, phage type and plasmid type and analysed their relationship with their drug-resistances. There found greatest differences between drug-resistant and sensitive strains in the case of gentamicin. GM-resistant strains belonged mostly to serum type I or nontypable. All of the GM-resistant isolates from different origin isolated in 1984 expressed the same multiple resistance, were grouped to serum type I and phage nontypable, and possessed nonconjugative miniplasmid encoding the multiple resistance. The same type strains have been isolated sporadically since 1985. Conjugally transmissible GM-resistant isolates showing different multiple resistance were found since 1985 and most of them were serum-nontypable. Thus we suspect the nosocomial infection in our hospital.Developement of drug-resistance owing to the abundant use of antimicrobials was demonstrated in the increase of norfloxacin-resistant P.aeruginosa accompanied with the increased use of new quinolone antimicrobials. The drug-sensitive clinical isolates were able to mutate to higher level of quinolone resistance with or without accompanying the change of sensitivities to other drugs. Mutants expressing the change of sensitivity to 2 or more kind of antimicrobials showed various changes in their outer-membrane proteins, resulting in the change of drug-permeability.