Prolongation of Bacillus firmus survival on human skin by a spore inoculum.

A case report is presented of an individual who carried vegetative cells of Baccillus firmus on multiple sites of his body for over a year. With the aim of investigating the survival mechanisms of Bacillus species on human skin, vegetative cells or spores of this microorganism were applied to the forearms of volunteers. Whereas vegetative cells were rapidly eliminated, the bacillus was recovered up to 2 weeks following an inoculum of spores. Persistence was not passive since germination, growth, and possible sporulation were demonstrated. We observed strong individual differences in the carriage of bacilli.