Inhibitory effect of biocides on the viable masses and matrices of **Staphylococcus aureus** and **Pseudomonas aeruginosa** biofilms
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences. Pharmacy
Applied and environmental microbiology. - Baltimore, Md
, p. 3135-3142
University of Antwerp
Bacteria and matrix are essential for the development of biofilms and assays should therefore target both components. The current European guidelines for biocidal efficacy testing are not adequate for sessile growing microorganisms; hence alternative discriminatory test protocols should be used. The activity of a broad range of biocides was evaluated on Staphylococcus aureus and Pseudomonas aeruginosa biofilms using such in vitro assays. Nearly all selected biocides showed a significant decrease in S. aureus biofilm viability, with sodium hypochlorite and peracetic acid as the most active biocides. When focusing on the matrix, only hydrogen peroxide and sodium hypochlorite showed some inhibitory effect. Treatment of P. aeruginosa biofilms was roughly comparable to S. aureus. Peracetic acid was the most active on viable mass within 1 min of contact. Isopropanol ensured a greater than 99.999 % reduction of P. aeruginosa viability after a least 30 min of contact. Comparable to S. aureus, sodium hypochlorite and hydrogen peroxide markedly reduced P. aeruginosa matrix. This study clearly demonstrated that despite their aspecific mechanisms of action, most biocides were only active against biofilm bacteria, leaving the matrix undisturbed. Only hydrogen peroxide and sodium hypochlorite were active on both biofilm matrix and viable mass, making them the better anti-biofilm agents. In addition, this study also emphasises the need for updated and standardized guidelines for biofilm susceptibility testing of biocides.