TABLE 3

Possible mechanisms of resistance and phenotype alterations to biocides

Species and biocide phenotypeaColony morphologyFitness cost (%)FabI mutationDifferential gene expressionMutant designationb
E. coli
    TRIrChanged75NDcacrF (1.99 ± 0.81)Ec_CIP/CIP
marA (4.31 ± 0.71)
Not changed261 nt, Gly93→ValNot changedEc_TRI/TRI2
Not changed6NDacrB (0.26 ± 0.17)Ec_BKC/BKC2
acrF (0.18 ± 0.15)
marA (0.32 ± 0.18)
soxS (0.21 ± 0.18)
    TRIr CHXhsNot changed11 nt, Leu94→Phe (E. coli K-12 F)dNot changedEc_NE/TRI1
K. pneumoniae
    TRIrChanged110NDKpn_AMP/TRI2
Not changed9NDNDKpn_NE/CIP
Changed80NDKpn_TRI/CIP
Not changedND0NDKpn_CHX/CIP
Not changedNDNDNDKpn_BKC/CIP
Not changed15NDacrF (357.44 ± 246.36)Kpn_SHC/CIP
Not changedNDNDNDKpn_NE/TRI1
Not changed40acrB (62.62 ± 40.01)Kpn_TRI/TRI2
acrF (2,923.37 ± 1,101.81)
marA (1.64 ± 0.26)
Not changedNDNDNDKpn_BKC/TRI2
Not changedNDNDNDKpn_CHX/TRI2
Not changedNDNDNDKpn_SHC/TRI2
Not changedNDNDNDKpn_CIP/TRI2
Not changedNDNDNDKpn_TRI/BKC1
Not changedNDNDNDKpn_BKC/BKC1
Changed660ramA (45.01 ± 40.81)Kpn_CIP/BKC2
Not changedNDNDNDKpn_AMP/CIP
Not changed9NDNDKpn_NE/CIP
    TRIhsNot changedNCe0acrB (0.29 ± 0.11)Kpn_NE/CHX2
acrF (0.01 ± 0.00)
marA (2.21 ± 0.18)
Not changedNCNDacrB (35.50 ± 13.52)Kpn_CIP/CHX2
acrD (3.02 ± 0.83)
marA (0.28 ± 0.13)
  • a TRI, triclosan; CHX, chlorhexidine.

  • b CIP, ciprofloxacin; BKC, benzalkonium chloride; NE, no exposure; AMP, ampicillin; SHC, sodium hypochlorite.

  • c ND, not determined.

  • d This amino acid change was identified here for the first time.

  • e NC, no cost.