Benzalkonium Chloride

Abstract

Benzalkonium chloride (BAC) is mostly bactericidal at 1% and yeasticidal at 0.2% (5 min). A mycobactericidal activity cannot be expected. Epidemiological cut-off values to determine acquired resistance have been proposed for Salmonella spp. (128 mg/l), E. coli (64 mg/l), K. pneumoniae and Enterobacter spp. (32 mg/l), S. aureus and C. albicans (16 mg/l), and E. faecalis and E. faecium (8 mg/l). Elevated MIC values suggestive of BAC resistance have been reported among numerous species including A. hydrophila (≤31,300 mg/l), B. cereus and E. meningoseptica (≤7,800 mg/l), P. aeruginosa (≤5,000 mg/l) and L. monocytogenes (≤625 mg/l). Specific resistance mechanisms are often known, e.g. resistance genes, efflux pumps, membrane changes or plasmids. Cross-tolerance to chlorhexidine, triclosan, hexachlorophene and selected antibiotics can occur in numerous species. Low-level exposure leads to no MIC change in 19 species, a weak MIC change in 25 species and a strong MIC change in 31 species (14 of them being stable) resulting in MIC values as high as 3,000 mg/l (S. Typhimurium) or 2,500 mg/l (P. aeruginosa). Bacterial biofilm formation is rather inhibited than enhanced by BAC. Biofilm removal by BAC is poor.