Effect of triclosan on Salmonella typhimurium at different growth stages and in biofilms (original) (raw)
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E¡ect of triclosan on Salmonella typhimurium at di¡erent growth stages and in bio¢lms
Triclosan is a potent biocide that is included in a diverse range of products. This research was aimed to investigate the susceptibility of planktonic and biofilm- associated Salmonella enterica serovar Typhimurium to triclosan, and to identify potential mechanisms of adaptation. The effect of triclosan was studied on planktonic Salmonella (log and stationary phases), on biofilm-associated cells, on bacteria derived from disrupted biofilms and on a biofilm-deficient mutant. An eight-log reduction of exponentially growing cells was observed with 1000mgmL1 triclosan within 10min, a 3.6-log reduction in stationary cells and a 6.3-log reduction in stationary cells of a biofilm-deficient mutant (Po0.05). Biofilm- associated cells were tolerant (1-log reduction). However, biofilm-derived cells showed sensitivity to triclosan similar to stationary-phase cells. Triclosan induced the transcription of fabI and micF. Within biofilms, triclosan also up-regulated the transcription of acrAB, enco...
Impairment of the Bacterial Biofilm Stability by Triclosan
The accumulation of the widely-used antibacterial and antifungal compound triclosan (TCS) in freshwaters raises concerns about the impact of this harmful chemical on the biofilms that are the dominant life style of microorganisms in aquatic systems. However, investigations to-date rarely go beyond effects at the cellular, physiological or morphological level. The present paper focuses on bacterial biofilms addressing the possible chemical impairment of their functionality, while also examining their substratum stabilization potential as one example of an important ecosystem service. The development of a bacterial assemblage of natural composition – isolated from sediments of the Eden Estuary (Scotland, UK) – on non-cohesive glass beads (,63 mm) and exposed to a range of triclosan concentrations (control, 2 – 100 mg L 21) was monitored over time by Magnetic Particle Induction (MagPI). In parallel, bacterial cell numbers, division rate, community composition (DGGE) and EPS (extracellular polymeric substances: carbohydrates and proteins) secretion were determined. While the triclosan exposure did not prevent bacterial settlement, biofilm development was increasingly inhibited by increasing TCS levels. The surface binding capacity (MagPI) of the assemblages was positively correlated to the microbial secreted EPS matrix. The EPS concentrations and composition (quantity and quality) were closely linked to bacterial growth, which was affected by enhanced TCS exposure. Furthermore, TCS induced significant changes in bacterial community composition as well as a significant decrease in bacterial diversity. The impairment of the stabilization potential of bacterial biofilm under even low, environmentally relevant TCS levels is of concern since the resistance of sediments to erosive forces has large implications for the dynamics of sediments and associated pollutant dispersal. In addition, the surface adhesive capacity of the biofilm acts as a sensitive measure of ecosystem effects.
Triclosan resistance in Salmonella enterica serovar Typhimurium
Journal of Antimicrobial Chemotherapy, 2008
The aim of this study was to characterize the mechanisms of resistance to triclosan in Salmonella enterica serovar Typhimurium. Methods: Mutants resistant to triclosan were selected from nine S. enterica serovar Typhimurium strains. Mutants were characterized by genotyping, mutagenesis and complementation of fabI and analysis of efflux activity. Fitness of triclosan-resistant mutants was determined in vitro and in vivo. Results: Three distinct resistance phenotypes were observed: low-(LoT), medium-(MeT) and highlevel (HiT) with MICs of 4-8, 16-32 and >32 mg/L of triclosan, respectively, for inhibition. The genotype of fabI did not correlate with triclosan MIC. Artificial overexpression and mutagenesis of fabI in SL1344 each resulted in low-level triclosan resistance, indicating that FabI alone does not mediate high-level triclosan resistance in Salmonella Typhimurium. Active efflux of triclosan via AcrAB-TolC confers intrinsic resistance to triclosan as inactivation of acrB and tolC in wild-type strains and the triclosan-resistant mutants led to large decreases in triclosan resistance, which were reversed by complementation. Exemplars of each phenotype were evaluated for fitness in vivo; no fitness cost was seen and mutants colonized and persisted in chickens throughout a 28 day competitive index experiment. Conclusions: These data show that triclosan resistance can occur via distinct pathways in salmonella and that mutants selected after single exposure to triclosan are fit enough to compete with wild-type strains.
Triclosan and Antimicrobial Resistance in Bacteria: An Overview
Microbial Drug Resistance, 2006
Triclosan is a widely used biocide that is considered as an effective antimicrobial agent against different microorganisms. It is included in many contemporary consumer and personal health-care products, like oral and dermal products, but also in household items, including plastics and textiles. At bactericidal concentrations, triclosan appears to act upon multiple nonspecific targets, causing disruption of bacterial cell wall functions, while at sublethal concentrations, triclosan affects specific targets. During the 1990s, bacterial isolates with reduced susceptibility to triclosan were produced in laboratory experiments by repeated exposure to sublethal concentrations of the agent. Since 2000, a number of studies have verified the occurrence of triclosan resistance amongst dermal, intestinal, and environmental microorganisms, including some of clinical relevance. Of major concern is the possibility that triclosan resistance may contribute to reduced susceptibility to clinically important antimicrobials, due to either cross-resistance or co-resistance mechanisms. Although the number of studies elucidating the association between triclosan resistance and resistance to other antimicrobials in clinical isolates has been limited, recent laboratory studies have confirmed the potential for such a link in Escherichia coli and Salmonella enterica. Thus, widespread use of triclosan may represent a potential public health risk in regard to development of concomitant resistance to clinically important antimicrobials.
Resistance and recovery of river biofilms receiving short pulses of Triclosan and Diuron
Science of The Total Environment, 2011
The effects of the herbicide Diuron (DIU) and the bactericide Triclosan (TCS) were assessed on laboratorygrown stream biofilms. Four week-old biofilms were exposed in mesocosms to 48-hours of short pulses of either DIU or TCS. The direct and indirect effects of each toxicant on the biofilms, and the subsequent recovery of the biofilms, were evaluated according to structural and functional biomarkers. These parameters were analyzed immediately before exposure, immediately after exposure, and 9 and 16 days post-exposure. DIU caused an increase in diatom mortality (+ 79%), which persisted until the end of the experiment. TCS also affected diatom mortality (+ 41%), although the effect did not appear until 1 week post-exposure. TCS caused an increase in bacterial mortality (+45%); however, this parameter returned to normal values 1 week postexposure. TCS compromised the cellular integrity of the green alga Spirogyra sp., whereas DIU did not. TCS also strongly inhibited phosphate uptake (− 71%), which did not return to normal values until 2 weeks postexposure. DIU directly affected algae, but barely affected the heterotrophs, whereas TCS seriously impaired bacteria (direct effect) as well as autotrophs (indirect effect). However, the biofilms recovered their normal structure and function within only a few days to a few weeks. These findings demonstrate the capacity of biofilms to cope with periodic inputs of toxicants, but also the risks associated to repeated exposure or multicontamination in aquatic ecosystems.
Proteomic analysis of triclosan resistance in Salmonella enterica serovar Typhimurium
Journal of Antimicrobial Chemotherapy, 2008
The aim of this study was to determine and compare the proteomes of three triclosanresistant mutants of Salmonella enterica serovar Typhimurium in order to identify proteins involved in triclosan resistance. Methods: The proteomes of three distinct but isogenic triclosan-resistant mutants were determined using two-dimensional liquid chromatography mass separation. Bioinformatics was then used to identify and quantify tryptic peptides in order to determine protein expression. Results: Proteomic analysis of the triclosan-resistant mutants identified a common set of proteins involved in production of pyruvate or fatty acid with differential expression in all mutants, but also demonstrated specific patterns of expression associated with each phenotype. Conclusions: These data show that triclosan resistance can occur via distinct pathways in Salmonella, and demonstrate a novel triclosan resistance network that is likely to have relevance to other pathogenic bacteria subject to triclosan exposure and may provide new targets for development of antimicrobial agents.
Triclosan is a commonly used bactericide that survives several degradation steps in WWTP (wastew-ater treatment plants) and potentially reaches fluvial ecosystems. In Mediterranean areas, where water scarcity results in low dilution capacity, the potential environmental risk of triclosan is high. A set of experimental channels was used to examine the short-term effects of triclosan (from 0.05 to 500 g L −1) on biofilm algae and bacteria. Environmentally relevant concentrations of triclosan caused an increase of bacterial mortality with a no effect concentration (NEC) of 0.21 g L −1. Dead bacteria accounted for up to 85% of the total bacterial population at the highest concentration tested. The toxicity of triclosan was higher for bacteria than algae. Photosynthetic efficiency was inhibited with increasing triclosan concentrations (NEC = 0.42 g L −1), and non-photochemical quenching mechanisms decreased. Diatom cell viability was also affected with increasing concentrations of triclosan. Algal toxicity may be a result of indirect effects on the biofilm toxicity, but the clear and progressive reduction observed in all the algal-related endpoints suggest the existence of direct effects of the bac-tericide. The toxicity detected on the co-occurring non-target components of the biofilm community, the capacity of triclosan to survive through WWTP processes and the low dilution capacity that characterizes Mediterranean systems extend the relevance of triclosan toxicity beyond bacteria in aquatic habitats.