Effect of antibacterials on biofilms.

Indwelling catheters are the most common cause of health care-associated bloodstream infections (BSIs). BSIs arise from a bacterial biofilm that consists of bacteria embedded within an extracellular polysaccharide matrix on the catheter surface. The initial step in biofilm formation is adherence of planktonic organisms to the catheter surface. Attached organisms divide to form microcolonies and secrete an extracellular polysaccharide matrix. Under stress conditions, these organisms can detach and become planktonic, resulting in bacteremia that can allow the bacteria to colonize a new site. Systemic antibiotics are able to eliminate planktonic organisms released from the biofilm but are often ineffective in treating infections resulting from biofilm-embedded organisms. Biofilm resistance is usually multifactorial, which makes biofilm eradication difficult, and, thus, most biofilm-related infections require prompt removal of the device. Intervention strategies for biofilm-associated infections include (1) prevention of initial device contamination, (2) minimization of initial microbial cell attachment, (3) use of agents such as high-dose antibiotics or antibiofilm agent in a catheter lock solution to penetrate the biofilm matrix and kill the embedded organisms, and (4) removal of the infected device. Some antibacterials are better than others in treating biofilm-associated bacteria, such as rifampin (in combination with other antibiotics), tigecycline, daptomycin, N-acetylysteine (in combination with tigecycline), and ethanol.