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A Transmissible Resistance Element from a Strain of Pseudomonas aeruginosa Containing No Detectable Extrachromosomal DNA
Abstract
SUMMARY
Pseudomonas aeruginosa PS18(RP1) is resistant to carbenicillin, neomycin/kanamycin and tetracycline. This strain gave rise to a derivative: PS18(RP1-1), resistant only to carbenicillin. RP1 was transmissible from PS18(RP1) to other strains of P. aeruginosa, Escherichia coli or Proteus mirabilis while RP1-1 was transmissible to other strains of P. aeruginosa, could not be transferred to Proteus mirabilis and transferred only at a very low frequency to E. coli. DNA hybridization showed that PS18(RP1-1) contained approximately one sixth as much RP1-homologous DNA as PS18(RP1). Although satellite DNA could be detected in strains carrying RP1 by ethidium bromide/CsCl-gradient analysis and by analytical CsCl-gradient centrifuging, no such satellite DNA could be found in strains of P. aeruginosa carrying RP1-1 or E. coli carrying a non-transferable derivative RP1-1*. Drug resistance could be eliminated from RP1-containing strains by treatment with sodium dodecyl sulphate, but the carbenicillin resistance of RP1-1 strains could not be eliminated. The apparent absence of satellite DNA in bacteria carrying RP1-1 or RP1-1*, and the failure to ‘cure’ them of their carbenicillin resistance suggests the possibility that the RP1-1 and RP1-1* genes might be a fragment of RP1 integrated in the chromosome of the strains of P. aeruginosa containing RP1-1 and E. coli containing RP1-1*.
- Accepted:
- Published Online:
© Society for General Microbiology, 1972