ABSTRACT
ABSTRACT In this study, B. cereus was detected in dialysis fluids within international parameters (ultrapure - maximum limit of 0.1 CFU/mL for heterotrophic bacteria count) by analyzing the pellet obtained through the centrifugation method. We also investigated the ability of the B. cereus isolate to form a biofilm at different temperatures, the production of virulence factors, and the susceptibility to commercial antimicrobial agents. This study demonstrated a high ability of B. cereus to persist in the hemodialysis system, which can be explained by its broad ability to produce a biofilm at 25 °C, its relevant production of virulence factors, such as β-hemolysin, lecithinase and cereulide, and its important resistance pattern to antimicrobial drugs. In conclusion, these new findings expand the understanding that this microorganism should not be neglected and new methods for tracking it should be considered.
ABSTRACT
Bacillus megaterium strains are commonly used in microbial fertilizer(MF) . MF products are often contaminated by other B. cereus group members,which have similar phenotype such as Bacillus cereus,B. thuringiensis,B. mycoide. For quality control and safety of MF,a rapid and accurate method is needed to distinguish the strains of Bacillus megaterium from B. cereus group. Based on specific nucleotide sequences of the spoOA genes,2 pairs of species-specific primers were designed and a multiplex-PCR(mPCR) was developed for this purpose. When the optimized mPCR was used to detect the DNAs of 24 reference strains from three genera of Bacillus,Paenibacillus,and Brevibacillus,all B. megaterium strains showed singlefragment of 443 bp and Bacillus cereus group showed a fragment of 411 bp. However,no any amplified product was from the other bacteria. The sensitivity of mPCR was 105 CFU/mL. The mPCR results of 10 isolates of B. megaterium/B. cereus group and 8 products of MF coincided with the biochemical assay. Taken together,our newly developed mPCR assay was species-specific and effective in application. It can be used to detect and identify the strains of B. megaterium and B. cereus group from microbial fertilizer products.
ABSTRACT
The Bacillus cereus group includes B. anthracis, B. cereus, B. thuringiensis, B. mycoides, B. weihenstephanensis, B. pseudomycoides. The members of B. cereus group shares strong degree of DNA sequence similarity. Even though the biochemical test and bacteriological test have been used to identify the B. cereus group, an accurate identification system of the B. cereus group is required. We have developed a highly specific PCR-based assay for the B. cereus group chromosome using a sequence motif found within a spore structural gene (sspE). Using the assay, we were able to discriminate B. anthracis from the other members of B. cereus group. We also tried to find a new system for the B. cereus group identification. Five bacteriological tests (hemolysis, motility, penicillin susceptibility, rhizoid growth, toxic crystal formation), API system (API 50CHB & API 20E), MLST and sspE PCR were performed on 28 strains of the B. cereus group. The dendrogram generated from API system and bacteriological tests revealed that B. cereus and B. thuringiensis are grouped into the same cluster. In combination of sspE PCR and bacteriological tests, the dendrogram showed that 4 strains of B. cereus clustered within the same group. B. thuringiensis formed the subgroup in the same cluster. All strains of B. mycoides were encompassed together. Another cluster only included B. anthracis. The best system was determined to be sspE PCR and bacteriological tests. It is concluded that sspE PCR and bacteriological tests could be used for rapid discrimination and identification of B. anthracis and provided an effective means of differentiation between the B. cereus group.