Table 2. Presence of antibiotic resistance genes in S. aureus isolated from blood cultures, the resistance mechanisms, and the corresponding antibiotics.

				Numbers of isolates with the indicated gene in each time period
Resistance gene	Protein	Resistance mechanism	Antibiotic	1980-81 n = 100	1990-91 n = 100	2000 n = 100	2010 n = 100
mecA	Alternate penicillin-binding protein 2a (PBP2a)	Change in structure of PBP2a	Methicillin	0	0	0	0
blaZ	Penicillinase (β-lactamase)	Production of β-lactamase enzymes that hydrolyse the β-lactam ring	Penicillin	73	76	78	67
vanA, vanB	Ligase enzyme	Change in structure of cell wall peptidoglycan precursors, resulting in altered binding site for vancomycin	Glycopeptides	0	0	0	0
aacA-aphD	Acetylation and phosphorylation enzyme	Enzyme that catalyse drug modification	Aminoglycosides	1	0	0	0
aphA	Phosphorylation enzyme	Enzyme catalyses drug modification	Aminoglycosides	0	0	0	0
mupR	Mupirocin resistance protein	Target modification	Mupirocin	0	0	0	0
cat	Chloramphenicol acetyltransferase	Acetylation prevent chloramphenicol from binding to the ribosome	Chloramphenicol	1	1	0	0
far1/fusB	FusB-proteins associated with fucidic acid resistance	Binds to and modulate the function of the drug target elongation factor G	Fucidic acid	0	0	0	1
Q6GD50 (fusC)				0	0	0	3
tetK	Tetracycline resistance determinant	Efflux	Glycylcycline	1	2	1	0
tetM	Tetracycline resistance determinant	A protein binds to the ribosome, which interferes with binding of tetracycline	Tetracyclines	1	1	0	0
ermA	Erythromycin ribosomal methylase	Methylation of 23S rRNA, resulting in target modification on ribosome	MLS-antibiotics1	0	2	2	0
ermB				0	0	0	0
ermC				1	1	1	0

¹Macrolides, Lincosamides, Streptogramins