Development of a novel selective agar for the isolation and detection of Bacillus anthracis.

AIMS: The aim of this study was to develop a novel selective agar for the specific isolation and detection of Bacillus anthracis. METHODS AND RESULTS: Based on published data on antibiotic resistance and susceptibility of B. anthracis and other closely related species of the Bacillus cereus sensu lato group, a new selective agar formulation termed CEFOMA (Bacillus CEreus sensu lato group-specific antibiotics, FOsfomycin, MAcrolides) was developed and evaluated. All tested strains of B. anthracis were able to grow on CEFOMA with the same colony number as on non-selective media, whereas CEFOMA inhibited the growth of the other species within the B. cereus sensu lato group. In comparison to other selective agars, CEFOMA had a superior performance and considerably reduced the total amount of accompanying flora in soil. Furthermore, B. anthracis was successfully isolated from deliberately spiked soil samples. CONCLUSIONS: CEFOMA is a highly promising selective agar for the efficient isolation of B. anthracis from environmental samples with a large bacterial background flora. SIGNIFICANCE AND IMPACT OF THE STUDY: The isolation of B. anthracis from environmental samples is severely impaired by the lack of adequate selective agars which suppress the growth of other bacteria. CEFOMA agar represents an important improvement and suitable alternative to currently used selective agars.

Decontamination of a BSL3 laboratory by hydrogen peroxide fumigation using three different surrogates for Bacillus anthracis spores.

AIMS: Two independent trials investigated the decontamination of a BSL3 laboratory using vaporous hydrogen peroxide and compared the effect on spores of Bacillus cereus, Bacillus subtilis and Bacillus thuringiensis as surrogates for Bacillus anthracis spores, while spores of Geobacillus stearothermophilus served as control. METHODS AND RESULTS: Carriers containing 1·0 × 10(6) spores were placed at various locations within the laboratory before fumigation with hydrogen peroxide following a previously validated protocol. Afterwards, carriers were monitored by plating out samples on agar and observing enrichment in nutrient medium for up to 14 days. Three months later, the experiment was repeated and results were compared. On 98 of 102 carriers, no viable spores could be detected after decontamination, while the remaining four carriers exhibited growth of CFU only after enrichment for several days. Reduction factors between 4·0 and 6·0 log levels could be reached. CONCLUSIONS: A validated decontamination of a laboratory with hydrogen peroxide represents an effective alternative to fumigation with formaldehyde. Spores of B. cereus seem to be more resistant than those of G. stearothermophilus. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provide important results in the field of hydrogen peroxide decontamination when analysing the effect on spores other than those of G. stearothermophilus.