Antimicrobial substances and effects on sessile bacteria

Biofilms occur in natural aquatic ecosystems and on surfaces of biomaterial s. They are generally associated with clinical infections predominantly of prothetic hip joints, heart valves and catheters. Sessile microorganisms may be intimately associated with each other and to solid substratum through binding to and inclusion into exopolymer matrices an biofilms. The establishment of functional colonies within the exopolymer ic matrices generate physico-chemical gradients within biofilms, that modif y the metabolism and cell-wall properties of the microorganism. A consequen ce of biofilm growth is enhanced microbial resistance to chemical antimicro bial agents and antibiotics. Investigations on the antimicrobial efficacy o f antibiotics, antiseptics and antimicrobial heavy ions, however, gave cont roversial results. No single antimicrobial substance has been developed for the efficient eradication of adherent bacteria. This review elucidates the mechanisms of microbial resistance in biofilms a nd strategies for the prevention of biofilm development. Pharmacokinetical and pharmacodynamical issues for the screening of biofilm-active drugs are presented. Combinations of antistaphylococcal antibiotics with rifampin may be advantageous for preventing and curing biomaterial infections.