Triclosan-tolerant bacteria: changes in susceptibility to antibiotics
ABSTRACT There is no clear consensus regarding the effect of biocide tolerance on antibiotic susceptibility. In this work, triclosan-tolerant strains of Escherichia coli, Staphylococcus aureus and Acinetobacter johnsonii were compared with sensitive strains in order to ascertain their susceptibility to a range of antibiotics. The minimum inhibitory concentrations of triclosan were measured using broth- and agar-dilution techniques. Antibiotic susceptibilities were determined using the British Society for Antimicrobial Chemotherapy guidelines. No triclosan-tolerant strains were resistant to antibiotics, and there was no overall tendency for triclosan-tolerant strains to have significantly smaller zones of inhibition compared with counterpart strains. Triclosan-tolerant strains of E. coli were significantly more susceptible to aminoglycoside antibiotics. The mechanism by which E. coli develops tolerance to triclosan appears to be linked to aminoglycoside susceptibility. It is proposed that changes in outer membrane, or the loss of plasmids, may be responsible for this relationship.
Full-textDOI: · Available from: Jean-Yves Maillard, Jan 08, 2014
Click to see the full-text of:
Article: Triclosan-tolerant bacteria: changes in susceptibility to antibiotics
- SourceAvailable from: Henrik Westh
[Show abstract] [Hide abstract]
- "Here, no alterations were observed for (gentamicin (0.5 μg/ml for non-adapted and adapted S. aureus 8325–3 and 1 μg/ml for non-adapted and adapted S. aureus USA300 strains) and the glycopeptide antibiotic vancomycin (2 μg/ml for S. aureus 8325–4 and S. aureus USA300 with no differences between non-adapted and adapted)). These findings agree with an earlier study where a triclosan tolerant S. aureus was examined for its susceptibility to a number of antibiotics belonging to different classes but with no changes compared to the triclosan sensitive strain . "
ABSTRACT: The ability of pathogens to adapt to the widely used biocide, triclosan, varies substantially. The purpose of the study was to examine bacterial adaptation over an extended period of time to low increments of triclosan concentrations. Focus was two human pathogens, S. aureus and L. monocytogenes that previously have displayed inherent high and low adaptability, respectively. Three strains of L. monocytogenes and two strains of S. aureus including the community-acquired USA300 were exposed to increasing, sub-lethal concentrations of triclosan in triclosan-containing agar gradients. Following 25 days of exposure on agar plates to sub-lethal concentrations of triclosan with a twofold concentration increase every second day, minimum inhibitory concentration (MIC) for S. aureus increased from 0.125 (8325--4) and 0.0625 (USA 300) mg/L to 4 mg/L. The MIC of all three L. monocytogenes strains was initially 4 mg/L and remained unaltered by the exposure. The adapted S. aureus isolates retained normal colony size but displayed increased expression of fabI encoding an essential enzyme in bacterial fatty acid synthesis. Also, they displayed decreased or no expression of the virulence associated agrC of the agr quorum sensing system. While most adapted strains of USA300 carried mutations in fabI , none of the adapted strains of 8325--4 did. Adaptability to triclosan varies substantially between Gram positive human pathogens. S. aureus displayed an intrinsically lower MIC for triclosan compared to L. monocytogenes but was easily adapted leading to the same MIC as L. monocytogenes. Even though all adapted S. aureus strains over-expressed fabI and eliminated expression of the agr quorum sensing system, adaptation in USA300 involved fabI mutations whereas this was not the case for 8325--4. Thus, adaptation to triclosan by S. aureus appears to involve multiple genetic pathways.BMC Microbiology 07/2013; 13(1):177. DOI:10.1186/1471-2180-13-177 · 2.73 Impact Factor
[Show abstract] [Hide abstract]
- "Differences in MIC values did not affect classifications of all strains, which were all susceptible to antimicrobial agents according to EUCAST breakpoint guidelines. Similar findings were reported by Jurgens et al. , Birošová and Mikulášová , and Cottell et al. . However, our result was not in agreement with those obtained by Karatzas et al.  or Randall et al. . "
ABSTRACT: Sensitivity to commercial teat dips (nonoxinol-9 iodine complex and chlorhexidine digluconate) of 56 Staphylococcus (S.) aureus strains isolated from quarter milk samples of various German dairy herds treated with different teat dipping schemes was investigated in this study. The minimum inhibitory concentration was determined using a broth macrodilution method according to the German Veterinary Association guidelines. The main objective of the current study was to induce in vitro resistance induction of S. aureus to chemical disinfectants. Ten different strains were repeatedly passed ten times in growth media with sub-lethal concentrations of disinfectants. Nine strains showed a significant reduction in susceptibility to the nonoxinol-9 iodine complex but only one strain developed resistance to chlorhexidine digluconate. Stability of the acquired resistance was observed in all S. aureus strains adapted to the nonoxinol-9 iodine complex and chlorhexidine digluconate. In contrast, simultaneous resistance to different antibiotics was not observed in any of the ten investigated S. aureus strains. However, the isolates exhibited a high degree of resistance to penicillin G. Based on these results, resistance of S. aureus to chemical disinfectants may be more likely to develop if the chemicals are used at concentrations lower than that required for an optimal biocidal effect.Journal of veterinary science (Suwŏn-si, Korea) 06/2012; 13(2):153-61. DOI:10.4142/jvs.2012.13.2.153 · 1.16 Impact Factor
[Show abstract] [Hide abstract]
- "Furthermore, for some antiseptics and antibiotics, increased resistance against antiseptics was correlated with increased antibiotic resistance , ; however, increased antibiotic resistance has not been associated with antiseptic resistance so far. Russel et al.  could demonstrate in an in-vitro study that after Pseudomonas stutzeri was exposed to increasing concentrations of chlorhexidine after multiple passages, a stable chlorhexidine resistance was achieved. "
ABSTRACT: Background: An in-vitro study was conducted investigating the antimicrobial efficacy of polihexanide and triclosan against clinical isolates and reference laboratory strains of Staphylococcus aureus and Escherichia coli. Methods: The minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC) were determined following DIN 58940-81 using a micro-dilution assay and a quantitative suspension test following EN 1040. Polihexanide was tested in polyethylene glycol 4000, triclosan in aqueous solutions. Results: Against all tested strains the MIC of polihexanide ranged between 1–2 µg/mL. For triclosan the MICs varied depending on strains ranging between 0.5 µg/mL for the reference strains and 64 µg/mL for two clinical isolates. A logRF >5 without and logRF >3 with 0.2% albumin burden was achieved at 0.6 µg/mL triclosan. One exception was S. aureus strain H-5-24, where a triclosan concentration of 0.6 µg/mL required 1 minute without and 10 minutes with albumin burden to achieve the same logRFs. Polihexanide achieved a logRF >5 without and logRF >3 with albumin burden at a concentration of 0.6 µg/mL within 30 sec. The exception was the North-German epidemic MRSA strain, were an application time of 5 minutes was required. Conclusion: The clinical isolates of E. coli generally showed higher MICs against triclosan, both in the micro-dilution assay as well in the quantitative suspension test than comparable reference laboratory strains. For polihexanide and triclosan strain dependant susceptibility was shown. However, both antimicrobial compounds are effective when used in concentrations common in practice.12/2011; 6(1):Doc06. DOI:10.3205/dgkh000163