Abstract
Biofilms are assemblages of microorganisms attached to each other, or to a surface, and encased in a protective, self-produced matrix. Such associations are now recognized as the predominant microbial growth mode. The physiology of cells in biofilms differs from that of the planktonic cells on which most research has been conducted. Consequently, there are significant gaps in our knowledge of the biofilm lifestyle. Filling this gap is particularly important, given that biofilm cells may respond differently to antibiotics than do planktonic cells of the same species. Understanding the effects of antibiotics on biofilms is of paramount importance for clinical practice due to the increased levels of antibiotic resistance and resistance dissemination in biofilms. From a wider environmental perspective antibiotic exposure can alter the ecology of biofilms in nature, and hence disrupt ecosystems. Biofilm cells display increased resilience toward antibiotics. This resilience is often explained by mechanisms and traits such as decreased antibiotic penetration, metabolically inactive persister cells, and intrinsic resistance by members of the biofilm community. Together, these factors suggest that cells in biofilms are often exposed to subinhibitory concentrations of antimicrobial agents. Here we discuss how cells in biofilms are affected by the presence of antibiotics at subinhibitory concentrations, and the possible ramifications of such secondary effects for healthcare and the environment.
Highlights
Biofilms are usually defined as microbial assemblages that can be either surface-associated, or present as an unattached but aggregated cell biomass
In this review we focus on rarely considered but important effects that antimicrobials have on biofilm cells at subinhibitory concentrations
The macrolide antibiotic azithromycin is reported to interfere with quorum-sensingdependent virulence factor production, biofilm formation, and oxidative stress resistance in P. aeruginosa. This organism is a major bacterial pathogen associated with cystic fibrosis chronic infections, and azithromycin treatment led to improved patient outcomes (Equi et al, 2002; Saiman et al, 2003; Nalca et al, 2006)
Summary
Biofilms are assemblages of microorganisms attached to each other, or to a surface, and encased in a protective, self-produced matrix. There are significant gaps in our knowledge of the biofilm lifestyle Filling this gap is important, given that biofilm cells may respond differently to antibiotics than do planktonic cells of the same species. Biofilm cells display increased resilience toward antibiotics This resilience is often explained by mechanisms and traits such as decreased antibiotic penetration, metabolically inactive persister cells, and intrinsic resistance by members of the biofilm community. Together, these factors suggest that cells in biofilms are often exposed to subinhibitory concentrations of antimicrobial agents.
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