Phenotypic properties of R factors ofPseudomonas aeruginosa:R factors readily transferable betweenPseudomonasand the Enterobacteriaceae

Abstract

SUMMARY: R factors have been demonstrated in multiply drug resistant strains of enterobacteria andPseudomonas aeruginosain a Birmingham hospital (Lowburyet al.1969; Ingram, Richmond & Sykes, 1973). A comparative genetic analysis of these R factors has been initiated on the basis of a variety of phenotypic characteristics. This paper describes the properties of R factors derived from strains which could transfer multiple drug resistance to the recipient speciesP. aeruginosa, Escherichia coli, Shigella flexneriandSalmonella typhimurium. Two types of R factor could be recognized phenotypically. The single group 1 R factor, R18–1 which is probably the same as RPl-1 (Ingramet al.1972) was different to the group 2 R factors in many respects, including host range, R factor-specific phage plating, cellular location, drug resistance pattern, and stability. The group 2 R factors were found to be very similar to RPl (Grinstedet al.1972) and R1822 (Olsen & Shipley, 1973) with respect to their wide host range, plating of a sex specific phage, extrachromosomal location, and drug resistance pattern. Compatibility was shown between the group 1 R factor and a group 2 R factor, providing additional evidence for significant genetic differences.