Antimicrobial efficacy of the silver wound dressing Biatain Ag in a disc carrier test simulating wound secretion.

AIM: The efficacy of antimicrobial compounds included in wound dressings has been determined using the quantitative suspension test according to EN 13727 before. However, as suspension tests are not an accurate reflection of the conditions under which wound antiseptics are used, it was investigated if a disc carrier test would yield results simulating practical conditions on wound surfaces. A silver-leaching foam wound dressing was used for evaluation of the disc carrier test method. METHOD: The disc carriers consisted of circular stainless-steel discs measuring 2 cm in diameter and 1.5 mm in thickness, complying with the requirements of EN 10088-2. Carriers were contaminated with Staphylococcus aureus, methicillin-resistant S. aureus or Pseudomonas aeruginosa, respectively, together with an artificial wound secretion and left to dry at room temperature for 30 min. The wound dressings being tested were placed on the discs for the length of the exposure time, and after neutralization by thioglycolate in phosphate-buffered saline the number of surviving test organisms was then counted. The logarithmic reduction factor was calculated from the difference between the initial inoculum and the number of recovered test organisms. RESULTS: The disc carrier test allowed determination of an antimicrobial efficacy in a realistic setting. It also imposed more stringent requirements on efficacy over time than the quantitative suspension test. The silver foam wound dressing showed a time-dependent antimicrobial efficacy. After 24-hour application time, the reduction factors against S. aureus, P. aeruginosa and the methicillin-resistant S. aureus were 1.9 ± 0.15, 2.1 ± 0.14 and 3.1 ± 0.18, respectively. CONCLUSION: The disc carrier test was a useful method for testing the antimicrobial efficacy of a foam silver dressing. The antimicrobial dressing exhibited an antimicrobial effect after 3 h and achieved a reduction >2 log against the tested bacterial strains in the presence of a simulated wound secretion after 24 h.

Determination of antiseptic efficacy of rubs on the forearm and consequences for surgical hand disinfection.

While hands are acknowledged to be the most important source of pathogens from the skin of the surgical team, the transmission of pathogens from the forearms may also be relevant. Preoperative hand disinfection is recommended, but evidence-based standards for the forearms are lacking. As neither the European standard EN 12791 nor the American guidelines ASTM 1115 are applicable to the forearms, a new test method based on the European standard EN 12791 and the German Society for Hygiene and Microbiology (DGHM) method for testing for the efficacy of skin antiseptics was developed to address the forearms. The antiseptic efficacy of a commercially available alcohol-based hand rub [76.7% (w/w) ethanol] was assessed on the upper arm after 15s, 2.5 min, and 30 min, and on the lower arm after 2.5 min, 30 min, and 3 h. On the upper arm, application of the product followed the DGHM standard procedure. On the forearm, the product was applied by the participants themselves with the right hand over the left forearm and vice versa as performed during preoperative hand disinfection. Sampling and culture were performed according to the DGHM method for skin antisepsis on the upper arm. Twenty-two volunteers were investigated. The efficacy of the antiseptic treatment on the forearm was not significantly lower than on the upper arm for any of the areas tested (P > 0.05). Reduction factors for all tested areas and times were quite similar, with confidence intervals ranging between 1.43 and 2.31 log10. We suggest that an application time of 10s may be sufficient for the treatment of the forearm as part of preoperative hand disinfection, provided that an appropriate product is used.

Standardized comparison of antiseptic efficacy of triclosan, PVP-iodine, octenidine dihydrochloride, polyhexanide and chlorhexidine digluconate.

BACKGROUND: This study presents a comparative investigation of the antimicrobial efficacy of the antiseptics PVP-iodine, triclosan, chlorhexidine, octenidine and polyhexanide used for pre-surgical antisepsis and antiseptic treatment of skin, wounds and mucous membranes based on internationally accepted standards. METHODS: MICs and MBCs were determined in accordance with DIN 58940-7 and 58940-8 using Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus), Enterococcus faecalis (including vancomycin-resistant Enterococcus), Streptococcus pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Clostridium perfringens, Haemophilus influenzae and Candida albicans. The microbicidal efficacy was determined in accordance with DIN EN 1040 and 1275 using S. aureus, P. aeruginosa and C. albicans. RESULTS: For chlorhexidine, octenidine and polyhexanide, MIC(48) and MBC(24) ranged from 16 to 32 mg/L. Maximum values for triclosan ranged from 256 to 512 mg/L, with an efficacy gap against P. aeruginosa, while the maximum values of PVP-iodine were 1024 mg/L, with a gap against S. pneumoniae. Comparing the minimal effective concentrations, octenidine was most effective. After 1 min, only octenidine and PVP-iodine fulfil the requirements for antiseptics. CONCLUSIONS: Tests under standardized and harmonized conditions help to choose the most efficacious agent. When a prolonged contact time is feasible, ranking of agents would be polyhexanide = octenidine > chlorhexidine > triclosan > PVP-iodine. This is consistent with the recommendations for antisepsis of acute wounds. Polyhexanide seems to be preferable for chronic wounds due to its higher tolerability. If an immediate effect is required, ranking would be octenidine = PVP-iodine>> polyhexanide > chlorhexidine > triclosan.

Impact of the amount of hand rub applied in hygienic hand disinfection on the reduction of microbial counts on hands.

Two different hand rubs were tested in order to investigate the minimum volume required for microbicidal efficacy according to the European Norm EN 1500; we also sought to determine whether there is a correlation with hand size. Eight male volunteers with big hands (mean 184 cm(2)) and eight female volunteers with significantly smaller hands (mean 148 cm(2); P<0.001) participated in our study. Application of 2 mL of both products (P) provided mean log(10) reductions significantly smaller than those of the reference disinfectant (R) (product A: P=3.34, R=4.00, P=0.001; product B: P=3.37, R=3.75, P=0.022). Higher volumes (product A: 3 and 4 mL; product B: 2.5, 3 and 4 mL) ensured that the pass criteria of the European Norm (EN) 1500 were fulfilled. For both products log(10) reductions increased with increasing product volume until a plateau was reached. For the smaller female hands, this plateau level was reached after applying 3 mL of product A and 2.5 mL of product B. The plateau level on male hands was observed after treating the hands with > or =4 mL of product A and 3 mL of product B. The increase in product volume also correlated with the decrease in the number of volunteers considering the product volume applied as insufficient. In conclusion, the applied volume for hygienic hand rub should not fall below 3 mL in order to achieve maximum benefit.

Identification of sigma(B)-dependent genes in Bacillus subtilis using a promoter consensus-directed search and oligonucleotide hybridization.

A consensus-directed search for sigma(B) promoters was used to locate potential candidates for new sigma(B)-dependent genes in Bacillus subtilis. Screening of those candidates by oligonucleotide hybridizations with total RNA from exponentially growing or ethanol-stressed cells of the wild type as well as a sigB mutant revealed 22 genes that required sigma(B) for induction by ethanol. Although almost 50% of the proteins encoded by the newly discovered sigma(B)-dependent stress genes seem to be membrane localized, biochemical functions have so far not been defined for any of the gene products. Allocation of the genes to the sigma(B)-dependent stress regulon may indicate a potential function in the establishment of a multiple stress resistance. AldY and YhdF show similarities to NAD(P)-dependent dehydrogenases and YdbP to thioredoxins, supporting our suggestion that sigma(B)-dependent proteins may be involved in the maintenance of the intracellular redox balance after stress.