The Bacillus cereus Group comprises organisms that are widely distributed in the environment and are of health and economic interest. We demonstrate an 'ecotypic' structure of populations in the B. cereus Group using (i) molecular data from Fluorescent Amplified Fragment Length Polymorphism patterns, ribosomal gene sequences, partial panC gene sequences, 'psychrotolerant' DNA sequence signatures and (ii) phenotypic and descriptive data from range of growth temperature, psychrotolerance and thermal niches. Seven major phylogenetic groups (I to VII) were thus identified, with ecological differences that provide evidence for a multiemergence of psychrotolerance in the B. cereus Group. A moderate thermotolerant group (VII) was basal to the mesophilic group I, from which in turn distinct thermal lineages have emerged, comprising two mesophilic groups (III, IV), an intermediate group (V) and two psychrotolerant groups (VI, II). This stepwise evolutionary transition toward psychrotolerance was particularly well illustrated by the relative abundance of the 'psychrotolerant' rrs signature (as defined by Pruss et al.) copies accumulated in strains that varied according to the phylogenetic group. The 'psychrotolerant' cspA signature (as defined by Francis et al.) was specific to group VI and provided a useful way to differentiate it from the psychrotolerant group II. This study illustrates how adaptation to novel environments by the modification of temperature tolerance limits has shaped historical patterns of global ecological diversification in the B. cereus Group. The implications for the taxonomy of this Group and for the human health risk are discussed.

Minimal standards for describing new taxa within the aerobic endospore-forming bacteria are proposed, following Recommendation 30b of the Bacteriological Code (1990 Revision). These minimal standards are recommended as guidelines to assist authors in the preparation of descriptions for novel taxa. They encourage broad polyphasic characterization and the construction of descriptions that are practically useful in routine diagnostic laboratories. The proposals have been endorsed by the Subcommittee on the Taxonomy of the Genus Bacillus and Related Organisms of the International Committee on Systematics of Prokaryotes

Bacillus cereus is a well-known cause of food-borne illness, but infection with this organism is not commonly reported because of its usually mild symptoms. A fatal case due to liver failure after the consumption of pasta salad is described and demonstrates the possible severity of the emetic syndrome.

In many parts of the world, coagulase-negative staphylococci (CNS) are the predominant pathogens causing intramammary infections (IMI) in dairy cows. The cows' environment is thought to be a possible source for CNS mastitis and this was investigated in the present paper. A longitudinal field study was carried out in 6 well-managed dairy herds to determine the distribution and epidemiology of various CNS species isolated from milk, causing IMI and living freely in the cows' environment, respectively. In each herd, quarter milk samples from a cohort of 10 lactating cows and environmental samples from stall air, slatted floor, sawdust from cubicles, and sawdust stock were collected monthly (n=13). Isolates from quarter milk samples (n=134) and the environment (n=637) were identified to species level using amplified fragment length polymorphism (AFLP) genotyping. Staphylococcus chromogenes, S. haemolyticus, S. epidermidis, and S. simulans accounted for 81.3% of all CNS milk isolates. Quarters were considered infected with CNS (positive IMI status) only when 2 out of 3 consecutive milk samples yielded the same CNS AFLP type. The species causing IMI were S. chromogenes (n=35 samples with positive IMI status), S. haemolyticus (n=29), S. simulans (n=14), and S. epidermidis (n=6). The observed persistent IMI cases (n=17) had a mean duration of 149.4 d (range 63.0 to 329.8 d). The CNS species predominating in the environment were S. equorum, S. sciuri, S. haemolyticus, and S. fleurettii. Herd-to-herd differences in distribution of CNS species were observed in both milk and the environment, suggesting that herd-level factors are involved in the establishment of particular species in a dairy herd. Primary reservoirs of the species causing IMI varied. Staphylococcus chromogenes and S. epidermidis were rarely found in the environment, indicating that other reservoirs were more important in their epidemiology. For S. haemolyticus and S. simulans, the environment was found as a reservoir, suggesting that IMI with these species were possibly environmental in origin.

No abstract