TABLE 3.

Possible mechanisms of resistance and phenotype alterations to biocides

Species and biocide phenotypea	Colony morphology	Fitness cost (%)	FabI mutation	Differential gene expression	Mutant designationb
E. coli
TRIr	Changed	75	NDc	acrF (1.99 ± 0.81)	Ec_CIP/CIP
				marA (4.31 ± 0.71)
	Not changed	26	1 nt, Gly93→Val	Not changed	Ec_TRI/TRI2
	Not changed	6	ND	acrB (0.26 ± 0.17)	Ec_BKC/BKC2
				acrF (0.18 ± 0.15)
				marA (0.32 ± 0.18)
				soxS (0.21 ± 0.18)
TRIr CHXhs	Not changed	1	1 nt, Leu94→Phe (E. coli K-12 F)d	Not changed	Ec_NE/TRI1
K. pneumoniae
TRIr	Changed	11	0	ND	Kpn_AMP/TRI2
	Not changed	9	ND	ND	Kpn_NE/CIP
	Changed	8	0	ND	Kpn_TRI/CIP
	Not changed	ND	0	ND	Kpn_CHX/CIP
	Not changed	ND	ND	ND	Kpn_BKC/CIP
	Not changed	15	ND	acrF (357.44 ± 246.36)	Kpn_SHC/CIP
	Not changed	ND	ND	ND	Kpn_NE/TRI1
	Not changed	4	0	acrB (62.62 ± 40.01)	Kpn_TRI/TRI2
				acrF (2,923.37 ± 1,101.81)
				marA (1.64 ± 0.26)
	Not changed	ND	ND	ND	Kpn_BKC/TRI2
	Not changed	ND	ND	ND	Kpn_CHX/TRI2
	Not changed	ND	ND	ND	Kpn_SHC/TRI2
	Not changed	ND	ND	ND	Kpn_CIP/TRI2
	Not changed	ND	ND	ND	Kpn_TRI/BKC1
	Not changed	ND	ND	ND	Kpn_BKC/BKC1
	Changed	66	0	ramA (45.01 ± 40.81)	Kpn_CIP/BKC2
	Not changed	ND	ND	ND	Kpn_AMP/CIP
	Not changed	9	ND	ND	Kpn_NE/CIP
TRIhs	Not changed	NCe	0	acrB (0.29 ± 0.11)	Kpn_NE/CHX2
				acrF (0.01 ± 0.00)
				marA (2.21 ± 0.18)
	Not changed	NC	ND	acrB (35.50 ± 13.52)	Kpn_CIP/CHX2
				acrD (3.02 ± 0.83)
				marA (0.28 ± 0.13)

^aTRI, triclosan; CHX, chlorhexidine.

^bCIP, ciprofloxacin; BKC, benzalkonium chloride; NE, no exposure; AMP, ampicillin; SHC, sodium hypochlorite.

^cND, not determined.

^dThis amino acid change was identified here for the first time.

^eNC, no cost.