Iron sequestration on skin: a new route to improved deodorancy.

Axillary malodour is caused by the biotransformation of non-odorous precursors present in apocrine sweat and sebum by the axillary microflora. To counter this, underarm products typically contain high levels of bactericides. However, after an initial decrease in bacterial numbers, the surviving cells grow, producing a concomitant rise in axillary odour. A sustained deodorant effect might be achieved without recourse to bactericidal action if this bacterial growth could be inhibited for extended periods. The current study attempted to inhibit axillary bacterial growth by nutrient deprivation, primarily that of iron (Fe(III)). In vitro analyses identified iron (Fe(III)) as the trace metal whose deprivation had the most profound effect on bacterial growth. Further in vitro investigations with Fe-chelating agents demonstrated that a number of compounds with high binding constants for Fe(III) showed optimal activity. One candidate molecule, diethylenetriaminepentaacetic acid (DTPA), was capable of effectively inhibiting bacterial growth in vitro and on the skin of the lower back. Some bacterial species could additionally utilize iron bound to the iron carrier protein transferrin present in eccrine sweat. This was minimized by the use of an agent, butylated hydroxytoluene (BHT), capable of liberating iron from transferrin via reduction of transferrin-bound ferric ions, allowing subsequent sequestration of Fe(II). Deodorant efficacy evaluation of the combination of DTPA and BHT showed deodorancy benefits over and above that afforded by DTPA alone. This mixture of DTPA and BHT supplemented to a standard ethanolic deodorant, used on 50 people for 2 weeks, was highly effective in limiting bacterial growth in the axilla. Total aerobic bacteria in the axillae were reduced from a mean of log 5.75 (+/-0.73) to log 4.50 (+/-0.90) colony-forming units (cfu) cm(-2) (n = 27, P < 0.01) compared with a non-fortified standard ethanolic deodorant. This was reflected in significant decreases in axillary malodour production, as determined by malodour assessments (P < 0.01). The profile of the axillary microflora was maintained, and all populations were rapidly returned to preuse levels after cessation of product use. This new deodorant technology was benchmarked against leading antimicrobial-based deodorant systems. In three separate deodorant efficacy evaluations, the combination of DTPA and BHT was tested against Triethyl citrate, Triclosan and Farnesol in standard unfragranced ethanolic formulations. The combination of DTPA and BHT showed highly significant deodorancy benefits over and above all these antimicrobial-based deodorant technologies. The combination of an efficient iron chelator with an agent capable of liberating iron from transferrin offers significant benefits in terms of bacterial growth inhibition on the skin and provides a new route to axillary deodorancy.

Recalcitrance of Streptococcus mutans biofilms towards detergent-stimulated detachment.

The biofilm mode of growth protects the plaque microorganisms against environmental attacks, such as from antimicrobials or detergents. Detergents have a demonstrated ability to detach initially adhering bacteria from enamel surfaces, but the ability of detergent components to detach plaque bacteria is not always obvious from in vivo experiments and reports on their clinical efficacy are inconsistent. It is likely that antimicrobials or detergents are unable to penetrate the plaque and reach the bacteria that actually link the plaque mass to the substratum surface. Attenuated total reflectance/Fourier transform infrared spectroscopy was used to measure the transport of sodium lauryl sulphate (SLS) through Streptococcus mutans HG 985 biofilms. The transport of SLS to the base of the S. mutans biofilms was not hindered, while moreover an accumulation of SLS near the base of the biofilms was found, suggesting that SLS was adsorbed to biofilm components. X-ray photoelectron spectroscopy confirmed the ability of S. mutans, grown on sucrose supplemented medium, to adsorb SLS, and simultaneously indicated that exposure of cells to SLS might lead to a loss of surface proteins. Furthermore, experiments in a parallel-plate flow chamber demonstrated that initially adhering S. mutans HG 985 could be stimulated to detach by SLS, but that, depending on the growth stage of the biofilm, only maximally 27% of biofilm bacteria could be stimulated to detach by a 4% (w/v) SLS solution.

Efficacy of ophthalmic solutions to detach adhering Pseudomonas aeruginosa from contact lenses.

PURPOSE: To compare the efficacies of two all-in-one contact lens (CL) cleaning solutions and a detergent mixture on the detachment of a pathogenic bacterium adhering to two types of contact lenses in the absence and presence of a tear film. METHODS: Bacterial-detachment studies were carried out in a parallel-plate flow chamber. Rigid gas permeable (RGP) CLs with and without a tear film were fixed on the bottom plate of the flow chamber. After adhesion of Pseudomonas aeruginosa no. 3, bacterial detachment was stimulated by perfusing the system either with an all-in-one CL-cleaning solution, for soft contact lenses (SCL solution) and for rigid lenses (RCL solution), or with a detergent mixture of 0.25% (wt/vol) sodium lauryl sulfate (SLS) and 0.2% sodium methyl cocoyl taurate (Tauranol). In addition, the all-in-one RCL-cleaning solution supplemented with 0.025% (wt/vol) SLS and 0.02% (wt/vol) Tauranol was evaluated. A surface physical-chemical analysis of the lenses before and after application of the solutions was done to determine whether remnants of the ophthalmic solutions or detergents could be found adsorbed to the CL surfaces. RESULTS: Both all-in-one CL-cleaning solutions stimulated minor bacterial detachment from CL surfaces with or without a tear film. The SLS/Tauranol detergent mixture, however, removed < or = 95% of the adhering P. aeruginosa cells, whereas the RCL-cleaning solution supplemented with detergents also stimulated significant detachment. Surface physical-chemical analysis clearly demonstrated the presence of a tear film on the CL surfaces, but remnants neither of the ophthalmic solutions nor of the detergents could be found. CONCLUSION: Ophthalmic solutions are not effective in stimulating detachment of adhering bacteria from CL surfaces. Supplementing of an all-in-one CL-cleaning solution with only small amounts of detergents yielded a solution much more effective in stimulating bacterial detachment while leaving no detectable remnants of the ophthalmic solution or of the detergents on the CL surfaces.

Detachment of linking film bacteria from enamel surfaces by oral rinses and penetration of sodium lauryl sulphate through an artificial oral biofilm.

The biofilm mode of growth protects plaque micro-organisms against environmental attacks, such as from antimicrobials or detergents. Dental plaque is linked to enamel through the adhesion of initial colonizers. Once this link is disrupted, the entire plaque mass adhering to it detaches. Experiments in a parallel-plate flow chamber demonstrated that bacteria adhering to saliva-coated enamel could not be stimulated to detach by perfusion of the flow chamber with two traditional mouthrinses (Corsodyl and Scope), whereas perfusion with a prebrushing rinse (Plax) or its detergent components stimulated detachment from saliva-coated enamel of a wide variety of bacterial strains. Following perfusion of the flow chamber with the mouthrinses, little additional detachment of adhering bacteria by the passage of a liquid-air interface occurred. After perfusion with the prebrushing rinse, however, significant numbers of still-adhering bacteria could be stimulated to detach by passage of a liquid-air interface, indicating that Plax had weakened their adhesive bond. The ability of Plax or its detergent components to detach plaque bacteria is not always obvious from in vivo experiments, and reports on its clinical efficacy are inconsistent. Likely, antimicrobials or detergents are unable to penetrate the plaque and reach the linking film bacteria, as demonstrated here by Fourier transform infrared spectroscopy.

Cometabolic degradation of trichloroethylene by Pseudomonas cepacia G4 in a chemostat with toluene as the primary substrate.

Pseudomonas cepacia G4 is capable of cometabolic degradation of trichloroethylene (TCE) if the organism is grown on certain aromatic compounds. To obtain more insight into the kinetics of TCE degradation and the effect of TCE transformation products, we have investigated the simultaneous conversion of toluene and TCE in steady-state continuous culture. The organism was grown in a chemostat with toluene as the carbon and energy source at a range of volumetric TCE loading rates, up to 330 mumol/liter/h. The specific TCE degradation activity of the cells and the volumetric activity increased, but the efficiency of TCE conversion dropped when the TCE loading was elevated from 7 to 330 mumol/liter/h. At TCE loading rates of up to 145 mumol/liter/h, the specific toluene conversion rate and the molar growth yield of the cells were not affected by the presence of TCE. The response of the system to varying TCE loading rates was accurately described by a mathematical model based on Michaelis-Menten kinetics and competitive inhibition. A high load of 3,400 mumol of TCE per liter per h for 12 h caused inhibition of toluene and TCE conversion, but reduction of the TCE load to the original nontoxic level resulted in complete recovery of the system within 2 days. These results show that P. cepacia can stably and continuously degrade toluene and TCE simultaneously in a single-reactor system without biomass retention and that the organism is more resistant to high concentrations and shock loadings of TCE than Methylosinus trichosporium OB3b.

Identification of chloroacetaldehyde dehydrogenase involved in 1,2-dichloroethane degradation.

The degradation of 1,2-dichloroethane and 2-chloroethanol by Xanthobacter autotrophicus GJ10 proceeds via chloroacetaldehyde, a reactive and potentially toxic intermediate. The organism produced at least three different aldehyde dehydrogenases, of which one is plasmid encoded. Two mutants of strain GJ10, designated GJ10M30 and GJ10M41, could no longer grow on 2-chloroethanol and were found to lack the NAD-dependent aldehyde dehydrogenase that is the predominant protein in wild-type cells growing on 2-chloroethanol. Mutant GJ10M30, selected on the basis of its resistance to 1,2-dibromoethane, also had lost haloalkane dehalogenase activity and Hg resistance, indicating plasmid loss. From a gene bank of strain GJ10, different clones that complemented one of these mutants were isolated. In both transconjugants, the aldehyde dehydrogenase that was absent in the mutants was overexpressed. The enzyme was purified and was a tetrameric protein of 55-kDa subunits. The substrate range was rather broad, with the highest activity measured for acetaldehyde. The K(m) value for chloroacetaldehyde was 160 muM, higher than those for other aldehydes tested. It is concluded that the ability of GJ10 to grow with 2-chloroethanol is due to the high expression level of an aldehyde dehydrogenase with a rather low activity for chloroacetaldehyde.