Outcome of antimicrobial therapy in documented biofilm-associated infections: a review of the available clinical evidence.

Numerous laboratory findings indicate that microbial biofilms may be encountered in several types of human infections, affecting the activity of antimicrobial agents. We evaluated the clinical evidence regarding the effectiveness of antimicrobial therapy for infections documented to be biofilm-associated, by performing a review of 15 relevant studies, excluding dental and eye infections. In a clinical trial, a significant difference was noted in the effectiveness of antibacterial agents used for catheter-related urinary tract infections in which substantial bacterial adherence on uroepithelial cells was observed. In case series and case reports, 28 patients with biofilm-associated infections documented by electron microscopy scanning were identified. Infection sites included ear, urinary tract, CNS, bloodstream and foreign body implantation site. Pseudomonas and Staphylococcus spp. were the predominant microorganisms among the bacterial or fungal causative pathogens. In 24 cases, infections related to the presence of foreign bodies. Treatment failure or recurrence was noted in all eight patients in whom targeted antimicrobial therapy was instituted before foreign body removal. Foreign body removal coupled with antimicrobial therapy was effective in all ten relevant cases. In four cases of native tissue urinary tract infections, the outcome of the initial antimicrobial therapy was poor. The limited available relevant clinical evidence indicates that conventional antimicrobial therapy alone is not adequately effective against documented biofilm-associated infections. Although some regimens might be more appropriate in this setting, further research on novel therapeutic strategies is needed to improve the outcome of patients with biofilm-associated infections.