High-level tolerance to triclosan may play a role in Pseudomonas aeruginosa antibiotic resistance in immunocompromised hosts: evidence from outbreak investigation

Table 1 Antibiotic susceptibility in unadapted and triclosan-adapted P.aeruginosa

P. aeruginosa L2	Antibiotic MIC (mg/L) ^b
	TET	CIP	AMK	LVX	CAR	CHL
Unadapted	32	16	4	8	128	128
Unadapted plus PAβN (50 μM)	16	4	2	2	64	64
Unadapted plus CCCP (100 μM)	16	8	2	4	64	64
Adapted ^a to 3,400 mg/L triclosan	64	32	8	16	256	256
Adapted ^a to 3,400 mg/L triclosan plus PAβN (50 μM)	32	8	4	4	64	64
Adapted ^a to 3,400 mg/L triclosan plus CCCP (100 μM)	32	16	4	8	64	64

^aAdaptation was achieved by serial subculturing in stepwise increasing triclosan concentrations up to 3,400 mg/L triclosan (see Methods). The experimental data were confirmed by three independent replicates
^bBreakpoint criteria were as follows. TET: susceptible, ≤ 4 mg/L; intermediate, 8 mg/L; resistant, ≥ 16 mg/L; CIP: susceptible, ≤ 1 mg/L; intermediate, 2 mg/L; resistant, ≥ 4 mg/L; AMK: susceptible, ≤ 16 mg/L; resistant, ≥ 32 mg/L; LVX: susceptible, ≤ 2 mg/L; intermediate, 4 mg/L; resistant, ≥ 8 mg/L; CAR: susceptible, ≤ 128 mg/L; intermediate, 256 mg/L; resistant, ≥ 512 mg/L; CHL: susceptible, ≤ 8 mg/L; intermediate, 16 mg/L; resistant, ≥ 32 mg/L [12]
MIC minimal inhibitory concentration; PAβN RND pump inhibitor phenyl-arginine-β-naphthylamide; CCCP protonophore carbonyl cyanide m-chlorophenylhydrazone; TET tetracycline; CIP ciprofloxacin; AMK amikacin; LVX levofloxacin; CAR carbenicillin; CHL chloramphenicol

ISSN: 1756-0500