Response of RP1+ and RP1− strains ofEscherichia coli to antibacterial agents and transfer of resistance toPseudomonas aeruginosa

Abstract

The sensitivity of strains ofEscherichia coli, with and without the RP1 R-factor, to antibiotics and other antibacterial agents has been studied. RP1+ strains ofE. coli were resistant to kanamycin, carbenicillin, and tetracycline, resistance to the first two antibiotics being produced by destruction of the drugs. This resistance could be transferred to two strains ofPseudomonas aeruginosa. The parent strain ofE. coli UB 1005, its two mutant strains (DC2 and DC3), and two of the strains with the RP1 R-factor showed a similar order of sensitivity to phenylmercuric nitrate, chlorhexidine, thiomersal, and mercuric chloride.E. coli strains DC2 and DC2 (RP1+) were the most sensitive to benzalkonium chloride and cetrimide. RP1+ strains were more resistant than RP1− strains to lysozyme-ethylenediaminetetraacetic acid, but treatment of the former strains with acriflavine rendered the cells more sensitive to the lytic system. There was no evidence thatP. aeruginosa (RP1+) strains possessed increased resistance to polymyxin or to disinfectants, although they became somewhat less sensitive to lysozyme-ethylenediaminetetraacetic acid.