Sporulation and viability of B. anthracis in relation to environmental temperature and humidity

Effects of Experimental Exclusion of Scavengers from Carcasses of Anthrax-Infected Herbivores on Bacillus anthracis Sporulation, Survival, and Distribution

“…As a further speculation, we note that while it has previously been noted that B. anthracis sporulation occurs within the first 72 h after host death (16,19,20), we noted a relatively consistent trend of spore density increasing between samples taken from blood-stained soil 4 and 8 days after host death. While redistribution of spores between sampling occasions and sampling error could explain these patterns, we note that the soil spore density in several samples increased by tens of times between the 4-and 8-day sampling occasions.…”

“…Temperature affects both vegetative cell survival and sporulation efficiency (16). The ambient temperature during the first 8 days after host death was in the range allowing sporulation (15 to 38°C) but varied more with the time of day than between carcasses, and thus we were unable to include this in our analysis.…”

“…These bacteria may inhibit sporulation by antagonizing vegetative B. anthracis cells. Support for this comes from early experimental work indicating that vegetative reproduction occurred in a variety of media as long as they were sterilized (7,15), that sporulation in blood taken from experimentally infected anthrax carcasses was greatly reduced when exposed to contaminated air (16), and that the B. anthracis vegetative cell population diminished at the onset of putrefaction (17,18). Processes that release B. anthracis-laden blood into the aerobic environment, such as terminal hemorrhaging and scavenging, provide an escape from microbial competition with anaerobes.…”

“…Given the above body of evidence, it is commonly held that "if the carcass is not opened the anaerobic decomposition and acidification will kill the contained vegetative cells within 4 days resulting in minimal environmental contamination" (5), with this time window extrapolated from experiments suggesting that B. anthracis vegetative cells sporulate or die within 72 h of host death (16,19,20). To our knowledge, however, only anecdotal evidence exists supporting the inability of vegetative cells to survive or sporulate in unopened carcasses (1,2,5,(21)(22)(23)(24)(25)(26).…”

The ecology of Bacillus anthracis

“…It would appear that the vegetative cells were less subject to drying at the lower temperature. Minett (1950) noted that sporulation in an opened carcass was largely dependent on the ambient temperature. At 32.2°C spores formed in the blood exuding from severed neck vessels (goats and guinea pigs) within 17-24 h, whereas at 15.6 and 21.1°C the bacilli gradually disintegrated with the growth of contaminants; in blood removed from the cooler carcasses and protected from gross contamination spores were present by 44 h but in small numbers.…”