TABLE 1

MIC values of various antibiotics and disinfectants for chlorhexidine-adapted strains

StrainMIC (mg/liter)a
CHDCHD + CCCPBClOctHDPCMEtOH (%)CSTCST + CCCPAZMFEPTEC
M109 WT80.5–11644–83.125228–160.06–0.125>64
M109 CA32–64b0.5–18–162–44–86.252–40.5–18–160.06–0.125>64
NCTC 13439 WT8–162–4162–4166.254232>64>64
NCTC 13439 CA256b1–2162–48–166.25>64b132>64>64
M3 WT8–161–28–162–486.252–4216–32>64>64
M3 CA32–64b0.5–28–162–48–163.125>64b1–28–16>64>64
NCTC 13443 WT8–161–28–1648–163.1252264>64>64
NCTC 13443 CA256–512b1–28–1628–163.125>64b216–32>64>64
NCTC 13368 WT322–4324–832–646.252–42–46464>64
NCTC 13368 CA256b1–2164–8166.25>64b2–46464>64
MGH 78578 WT8–161–28–1648–166.252–42–432>64>64
MGH 78578 CA256–512b0.5–28–16483.125>64b1–232–640.5b>64
  • a The disinfectants used were chlorhexidine digluconate (CHD), benzalkonium chloride (BCl), octenidine dihydrochloride (Oct), hexadecylpyridinium chloride monohydrate (HDPCM), and ethanol (EtOH). The antibiotics used were CST, AZM, FEP, and TEC. All the MICs are shown as ranges of the results of at least three independent experiments. “+ CCCP” indicates the addition of the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone. Additional antibiotics are shown in Table S2 in the supplemental material.

  • b There was a ≥4-fold increase or decrease in the MIC for chlorhexidine-adapted strains (CA) relative to nonadapted strains (WT).