Biocide susceptibility in bifidobacteria of human origin

Disinfectants have been used in a variety of environmental applications, in products for personal care and in the food industry. The food industry has increased the use of biocides and chemical-based disinfectants to control microbial ecology at production sites in an effort to improve hygiene measures and food safety. However, the susceptibility profile of micro-organisms to disinfectants has been largely neglected. This study therefore aimed to provide this type of information by focusing on the four most commonly used biocides in the food industry, determining their minimum inhibitory concentrations (MICs) and analysing the distribution of MICs across a variety of micro-organisms. In total, 99 different strains of Bifidobacterium spp. were studied. Results showed a unimodal distribution of MICs for chlorhexidine, triclosan (Irgasan) and sodium hypochlorite with no apparent species-specific correlation. Conversely, part of the tested bifidobacteria population (20%) showed reduced susceptibility to benzalkonium chloride compared with the susceptibility exhibited by the majority of the tested bacterial community. The highest MICs were distributed among almost all of the considered Bifidobacterium spp. In generally, the sensitivity of the studied strains to the four tested biocides appeared to be a genus-related trait.