Antimicrobial strategies effective against infectious bacterial biofilms

Bacteria are able to adapt to undesirable changes in nutrient availability, environmental conditions and presence of antimicrobial products, as well as to immunological defenses. One particularly important example of bacterial adaptation is the ability to grow as part of a sessile community, commonly referred to as biofilm. It is a natural tendency of microorganisms to attach to biotic or abiotic surfaces, to multiply and to embed themselves in a slimy matrix, resulting in biofilms. Biofilms are the leading example of physiological adaptation and are one of the most important sources of bacterial resistance to antimicrobials. It is now recognized that most bacterial-associated infections, including endocarditis, dental caries, middle ear infections, osteomyelitis, medical device-related infections and chronic lung infections in cystic fibrosis patients are problematic because of biofilms. Bacteria in biofilms demonstrate intrinsic resistance to antimicrobial stress more effectively than the planktonic counterparts. Antimicrobial concentrations necessary to inhibit bacterial biofilms can be up to 10-1000 times higher than those needed to inhibit the same bacteria grown planktonically. Thus, in the presence of therapeutically available antibiotic concentrations biofilms remain viable after treatment. Therefore, the identification of new antimicrobials that inhibit or destroy biofilms is needed. The aim of this review is to cover the recent advances on the studies of antimicrobial strategies effective against infectious bacterial biofilms, including the current developments in the structure-activity relationship of those effective antimicrobials.