Emergence and development of resistance to antimicrobial chemicals and heat in spores of Bacillus subtilis

Abstract

The emergence and development of chemical and thermal resistance in spores of B. subtilis was examined. The chemicals studied were of the disinfectant type: glutaraldehyde, hypochlorite, hypochlorite-methanol and povidone-iodine. Growth and sporulation were followed by EM and resistance assigned to specific stages in reltion to 45Ca and dipimelic acid accumulation. A sequential development of resistance was observed with thermal resistance appearing first at early Stage V corresponding to maturation of cortex and deposition of rudimentary spore coat material. Chemical resistance coincided with middle to late Stage V dependent on the chemical concerned. A progressive development of resistance was observed on prolonged incubation in sporulation medium and was affected by inclusion of lysozyme in the spore washing sequence.