The Journal of Medical Microbiology, Vol 33, Issue 4 227-234, Copyright © 1990 by Society for General Microbiology
Excision of a conjugative plasmid from the staphylococcal chromosome
E. E. Udo and W. B. Grubb
School of Medical Technology, Curtin University of Technology, Western Australia.
Staphylococcus aureus isolate WBG1003 resistant to benzyl penicillin,
cadmium, arsenate and streptomycin harbours two plasmids of 38.8 (pWBG621)
and 4.4 (pWBG625) kb. In conjugation experiments two types of
streptomycin-resistant transconjugants were obtained; one carried a 4.4-kb
plasmid and the other, a 34.5-kb and a 4.4-kb plasmid. The 34.5-kb plasmid
(pWBG620) has been found to be conjugative and able to mobilise
non-conjugative plasmids. It has no detectable resistance phenotype and has
not been detected in WBG1003 nor in the recipient used in the conjugation
experiments. Restriction endonuclease analysis and DNA-DNA hybridisation
have revealed that pWBG620 is unrelated to pWBG621 present in strain
WBG1003. The data presented indicate that pWBG620 is in the chromosome of
strain WBG1003 and that it excises during conjugation.
