Effects of chronic triclosan exposure upon the antimicrobial susceptibility of 40 ex-situ environmental and human isolates
Article first published online: 8 MAR 2006
Journal of Applied Microbiology
Volume 100, Issue 5, pages 1132–1140, May 2006
How to Cite
Ledder, R.G., Gilbert, P., Willis, C. and McBain, A.J. (2006), Effects of chronic triclosan exposure upon the antimicrobial susceptibility of 40 ex-situ environmental and human isolates. Journal of Applied Microbiology, 100: 1132–1140. doi: 10.1111/j.1365-2672.2006.02811.x
- Issue published online: 16 MAR 2006
- Article first published online: 8 MAR 2006
- 2005/0354: received 5 April 2005, revised 5 September 2005 and accepted 6 October 2005
- low passage isolates;
Background: Triclosan (TCS) exposure of Escherichia coli selects for tolerant clones, mutated in their enoyl–acyl carrier protein reductase (FabI). It has been inferred that this phenomenon is widespread amongst bacterial genera and might be associated with resistance to third party agents.
Methods: Ex-situ, low passage isolates of enteric, human axilla, human oral origin and bacteria isolated from a domestic drain, together with selected type cultures were exposed to escalating concentrations of TCS over 10 passages using a gradient plate technique. One fresh faecal isolate of E. coli was included as a positive control. TCS susceptibility was determined for all strains before and after exposure, whilst enteric isolates were additionally assessed for susceptibility towards chlorhexidine, tetracycline, chloramphenicol, nalidixic acid and ciprofloxacin, and the oral isolates towards chlorhexidine, tetracycline and metronidazole.
Results: Triclosan exposure of E. coli markedly decreased TCS susceptibility. TCS susceptibility also decreased for Klebsiella oxytoca, Aranicola proteolyticus and Stenotrophomonas maltophilia. Susceptibility of the remaining 35 strains to TCS and the other test agents remained unchanged.
Conclusions: These data suggest that selection for high level resistance by TCS exposure is not widespread and appears to be confined to certain enteric bacteria, especially E. coli. Change in TCS susceptibility did not affect susceptibility towards chemically unrelated antimicrobials.
Significance and impact: Acquired high-level TCS resistance is not a widespread phenomenon.