Mutations upstream of fabI in triclosan resistant Staphylococcus aureus strains are associated with elevated fabI gene expression

Table 4 fabI / gyrA ratio of laboratory and clinical strains

Strains	Log ₂ *fabI/gyrA* ratio*	t test vs parental strain	t test vs ATCC 6538	t test vs ATCC25923
Laboratory strains
RN4220 (n = 6)	1.69
MO034 (n = 5)	2.49	0.04
MO035 (n = 5)	3.37	0.0002
MO036 (n = 3)	1.41	ns
MU50 (n = 5)	−0.28
ATCC6538 (n = 4)	0.14
MO052 (n = 4)	2.14	0.0002
ATCC25923 (n = 4)	−0.51
Clinical strains
QBR-102278-1052 (n = 4)	4.22		<0.0001	<0.0001
QBR-102278-1889 (n = 4)	1.25		0.0026	0.0137
QBR-102278-1969 (n = 4)	1.56		0.0002	0.0059
QBR-102278-2363 (n = 4)	1.16		0.004	0.016
QBR-102278-1016 (n = 3)	0.23		ns	ns
QBR-102278-1027 (n = 4)	0.13		ns	ns
QBR-102278-2628 (n = 5)	0.03		ns	ns

*Log₂ ratio was independently determined for each chip using the data before stage-wise quantile normalization, by subtracting the Log₂ mean gyrA values obtained from the eight probes for gyrA printed on the chip from the Log₂ mean fabI values from the two probes. Ratio was then further averaged for the number of chips used by strains (n). Student’s unpaired t-test was performed by comparing the mutants to their parental strains in the case of laboratory strains, or to two reference strains in the case of clinical isolates. ns = not significant.

ISSN: 1471-2164