Hypochlorite injury of Clostridium botulinum spores alters germination responses

Abstract

C. botulinum spores were sublethally damaged by exposure to 12 or 28 μg of available chlorine per ml for 2 min at 25°C and pH 7.0. The damaging dose was 2.7 x 10-6 to 3.1 x 10-6 μg of available chlorine per spore. Damage was manifested by a consistent 1.6 to 2.4 log difference between the most probable number enumeration of spores (modified peptone colloid medium) and the colony count (modified peptone yeast extract glucose agar); this did not occur with control spores. Damaged spores could be enumerated by the colony count procedure. Germination responses were measured in several defined and nondefined media. Hypochlorite treatment altered the rate and extent of germination in some of the media. Calcium lactate (9 mM) permitted L-alanine (4.5 mM) germination of hypochlorite-treated spores in a medium containing 12 or 55 mM sodium bicarbonate, 0.8 mM sodium thiosulfate, and 100 mM Tris-hydrochloride (pH 7.0) buffer. Tryptose inhibited L-alanine germination of the spores. Treatments with hypochlorite and with hydrogen peroxide (7%, 25°C, 2 min) caused similar enumeration and germination responses, indicating that the effect was due to a general oxidation phenomenon.