TABLE 1.

Antibiotic resistance in MRSA and derived benzalkonium chloride-resistant mutants

Antibiotic	MIC (μg/ml)a
	MRSAb						MSSAc
	Parent	BZ-R-1	BZ-R-2	BZ-R-3	BZ-R-4	BZ-R-5
Oxacillin	16	512	512	128	64	64	0.3
Cloxacillin	0.5	256	512	128	0.5	8	0.3
Moxalactam	64	256	1024	512	256	256	8
Flomoxef	8	128	128	64	16	16	0.5
Cefmetazole	8	128	64	64	32	32	1
Cefazolin	64	128	128	64	128	128	0.5
Cephalothin	64	128	128	128	128	128	0.5
Ampicillin	16	32	32	16	32	16	0.5
Chloramphenicol	4	4	4	4	4	4	4
Ofloxacin	8	32	32	16	16	16	0.3
Tetracycline	128	128	128	32	128	128	NDd
Kanamycin	256	512	512	512	256	256	ND
Benzalkonium chloride	5	10	10	10	10	10	0.7

^aFull growth of bacteria in LB liquid medium was appropriately diluted, and the bacterial suspension (2 × 10³) was streaked on LB agar plates containing various concentrations of antibiotics, followed by incubation at 37°C for 72 h. 

^bMRSA strains were examined by identifying the mecA gene by PCR (3) in strains of S. aureus isolated in Kyushu Univeristy Hospital. 

^cMSSA, methicillin-susceptible S. aureus. 

^dND, not determined.