Octenidine Dihydrochloride

Octenidine dihydrochloride (OCT), usually in combination with 2% phenoxyethanol, is bactericidal (1 min) and yeasticidal (30 s–2 min) at 0.1%. Its mycobactericidal activity is unknown. Its antimicrobial activity is explained by membrane disruption and alteration of cellular structural integrity. Cellular defence mechanisms include efflux pumps in A. baumannii and P. aeruginosa. OCT reduces biofilm mass in developing and existing biofilms in several species. The effect of OCT on biofilm fixation is unknown. High MIC values indicating tolerance to OCT have been reported for isolates of S. salivarius (800 mg/l) and S. mutans (120 mg/l). Low-level exposure results in no MIC change in three species, a weak MIC change in six species and a strong and stable MIC change in P. aeruginosa, resulting in an MIC value as high as 128 mg/l. Cross-tolerance to chlorhexidine may occur in P. aeruginosa. Cross-resistance to selected antibiotics may also occur. OCT-resistant isolates have been described in an outbreak of B. cepacia complex infections or colonisations in intensive care patients caused by a contaminated commercial mouthwash (0.1% OCT). A recall of a commercial mouthwash contaminated with B. cepacia complex has also been reported. The overall probability of resistance to OCT of practical relevance is low in the absence of biofilm.