FEMS Microbiology Letters97 (1992)243-248 © 1992Federationof European Microbiological Societies 0378-1007/92/$05.(X) Publishedby Elsevier 243 FEMSLE 05072 Conjugative trimethoprim resistance in Staphylococcus aureus E.E. Udo, M.-Q. Wei and W.B. Grubb School of Biomedical Sciences, Curtin Unil'ersio"of Technology. Perth. W.A.. Australia Received25 May 1992 Revisionreceived 30 June 1992 Accepted2 July 1992 Key words: Conjugation; Conjugative plasmid; Staphylococcus aureus; Trimethoprim resistance 1. SUMMARY A multiply resistant Staphylococcus aureus iso- late, WBG7410, harbours plasmids of 38, 26, 2.8, 2.4 and 1.9 kb and transfers trimethoprim and kanamycin resistance at high frequencies by con- jugation. The transconjugants contained the 38-kb plasmid, pWBG707, and the 2.8-kb plasmid. Plas- mid pWBG707 was shown to encode trimetho- prim resistance, was conjugative and mobilised at high frequencies the 2.8-kb plasmid which pre- sumably encodes kanamycin resistance. Plasmid pWBG707 was isolated mostly in the open circu- lar form and analysis with EcoRl restriction en- donuclease suggests that pWBG707 is a new con- jugative plasmid distinct from the other conjuga- tive plasmids reported in S. aureus. 2. INTRODUCTION The spread of resistance to antimicrobial agents in Staphylococcus aureus would appear to Correspondence to: W.B. Grubb. School of Bi,'m~edical Sci- ences, Curtin Universityof Technology,GPO Box U 1987. Perth 6001, W.A.,Australia. be largely due to the acquisition of resistance plasmids and/or transposons [1]. Although in the laboratory transfer of resistance between strains can be demonstrated by transformation, trans- duction, phage-mediated conjugation and conju- gation [2] only conjugative transfer appears to be significant in vivo [2,3]. In the staphylococci con- jugative transfer of resistance determinants is usually mediated by conjugative plasmids [4-15] although there is evidence for the conjugative transfer of gentamicin resistance in the absence of a detectable plasmid [16]. Four types of con- jugative plasmids have been reported in S. att- reus. Those that encode resistance to gentamicin, kanamycin and neomycin and sometimes penicil- iinase production and resistance to trimethoprim and ethidium bromide. This type of plasmid is widespread in the USA [4-7], but has also been reported in strains from Japan [8], Europe [9] and Australia [10]. Then there are those that encode the production of diffusible pigment (DIP) and resistance to macrolides, lincosamides, strep- togramin B and spectinomycin and in some cases to aminoglycosides [11,12]. These plasmids have only been reported in isolates from Australia. Another type of conjugative plasmid has no de- tectable resistance phenotyp¢ and these were iso- lated in strains from a Nigerian hospital [13,14]. Downloaded from https://academic.oup.com/femsle/article/97/3/243/563441 by guest on 13 July 2022