MONITORING THE GROWTH OF BACTERIAL BIOFILMS IN THE PRESENCE OF ANTIMICROBIAL AGENTS

摘要

The prevention of industrial and medical microbiological problems like corrosion, biofouling and infections is better than cure. Toxic chemicals aimed at destroying or inhibiting the growth of microorganisms are commonly used to avoid biofilm growth inconveniences. The effect of antimicrobial agents (AA) against planktonic cells is frequently known but it is not often related with the results obtained from the sessile counterpart. The aim of this work is to monitor the growth of Streptococci and Pseudomonas fluorescens (P. fluorescens) biofilms on stainless steel sheets (SS) in the presence and in the absence of AA. The efficacies of glutaraldehyde and two mixtures of AA (NaF (F) + xylitol (X), and chlorhexidine (C) + X) on biofilms were evaluated. Thin SS sheets were immersed in the medium inoculated with the Streptococci consortium or P. fluorescens. The growth of the biofilm was monitored at real time through optical microscopy made in situ using an assemblage specially designed. Irregular colonies of different shapes and density could be distinguished. The sessile bacteria attached on the SS were also observed using epifluorescence microscopy. It could be concluded that the antimicrobial agents assayed were able to diffuse into the biofilm, modify the morphology of bacterial colonies and inhibit the growth of the sessile bacteria favouring the detachment of biofilm patches. However, re-growth of microorganisms can eventually occur after biocidal treatment.