Antimicrobial resistance in pathogenic bacteria is an increasing threat to public health. Staphylococcus aureus is an important cause of hospital and community-associated infections and frequently harbours extrachromosomal plasmids encoding multiple antimicrobial-resistance genes and virulence determinants. Horizontal plasmid transfer facilitates evolution of multidrug resistance in a single evolutionary step. CRISPR-Cas is a natural prokaryotic defence mechanism against foreign DNA and can inhibit plasmid transformation/conjugation. CRISPR loci contain arrays of foreign DNA sequences called spacers, which provide memory of past infections and direct Cas nucleases to destroy complementary sequences upon reinfection. The clinical isolate MSHR1132 is one of few S. aureus carrying a complete CRISPR-Cas locus. The MSHR1132 CRISPR array contains a spacer with DNA sequence matching the recently characterised pWBG749-family of conjugative plasmids. pWBG749-family plasmids have been identified carrying vancomycin, aminoglycoside and penicillin-resistance genes and are able to mobilise numerous non-conjugative antimicrobial-resistance plasmids. Few S. aureus have been identified that carry CRISPR-Cas loci, suggesting selective pressure against inhibition of horizontal gene transfer has led to loss of CRISPR-Cas function in this species. Bioinformatic analyses suggest MSHR1132 carries a complete CRISPR-Cas system and may inhibit transfer of pWBG749-family plasmids. Conjugation experiments with donor strains harbouring pWBG749 and plasmids carrying cloned CRISPR-spacer fragments were used to evaluate the functionality of the MSHR1132 CRISPR-Cas system. Conjugative transfer of all plasmids seemed unaffected by the presence of the MSHR1132 CRISPR-Cas when compared to experiments with S. aureus recipients lacking CRISPR-Cas or donors carrying control plasmids. The MSHR1132 CRISPR-Cas system appears to be ineffective in inhibiting the uptake of DNA via conjugation. This suggests it may be non-functional, repressed at a regulatory level, or that the conjugative transfer system of pWBG749 is able to somehow thwart the CRISPR-Cas mechanism. The functionality of the CRISPR-Cas system of MSHR1132 requires further investigation.