Whole-genome sequence-based comparison and profiling of virulence-associated genes of Bacillus cereus group isolates from diverse sources in Japan

Screening and characterization of PHA producing bacteria from sewage water identifying Bacillus paranthracis RSKS-3 for bioplastic production

Polyhydroxyalkanoate (PHA) as bioplastic is considered a replacement for conventional plastic due to its more beneficial properties. The ability of PHA to biodegrade in a shorter period is a major advantage. Different sewage water samples were collected from the Budha Nala near the Maheru regions of Punjab. PHA-producing bacteria were isolated using minimal salt media supplemented with Nile blue. Further screening was carried out using Sudan Black B stain and Nile red stain. The positive isolates were characterized for gram reaction, motility, and biochemical tests. The individual isolates were later screened for maximum PHA accumulation using minimal salt supplemented with glucose. The extracted PHA was characterized using FTIR, XRD, SEM, UV spectroscopy, NMR, and TGA. Twenty-six different PHA-producing bacteria were isolated on minimal salt media supplemented with Nile blue. Upon Sudan Black B stain and Nile red stain, nineteen isolates showed black granules and orange fluorescence bodies under 100X magnification that confirmed polyhydroxyalkanoates. The biochemical tests partially characterized isolates belonging to the Bacillus genus. All the isolates produced PHA in granular form, however, isolate P-3 showed maximum production of 0.068 g/L. The extracted PHA was characterized using FTIR and XRD for its chemical and crystallinity studies and the UV spectroscopy confirmed the extracted PHA by analyzing absorption spectra at 235 nm of standard crotonic acid and sulfuric acid conversion of PHA to crotonic acid. The isolated P-3, Bacillus paranthracis RSKS-3 is the first reported bacterium to produce polyhydroxyalkanoates. Further studies is necessary to optimize the production efficiency of the bacterium for maximum PHA yield.

Genetic diversity and virulence of Bacillus cereus group isolates from bloodstream infections

Bacillus cereus catheter-related bloodstream infections (CRBSIs) are an increasing concern in Japanese hospitals. Although their clinical characteristics have been explored, the genetic relationships and virulence profiles of B. cereus isolates from CRBSIs remain understudied. Here, using advanced genomic techniques, we investigated the genetic diversity, phylogenetic relationships, and virulence profiles of B. cereus isolates from patients with bloodstream infections. We analyzed 28 B. cereus group strains isolated from blood samples at the University of Tokyo Hospital between 2005 and 2017 using whole-genome sequencing, core-genome single-nucleotide polymorphism (SNP) typing, and virulence gene profiling. Core-genome SNP analysis revealed significant genetic diversity among the isolates, suggesting multiple independent sources of infection. The isolates predominantly belonged to panC clades III and IV, with distinct virulence gene profiles. All panC clade III isolates contained hbl operon genes, whereas four isolates from clade IV harbored cereulide synthetase genes (cesABCD). One isolate possessed a capsule gene operon (capBCADE), a rare finding among clinical B. cereus strains. Biofilm formation ability was observed in 50% of catheter-related isolates, although this ability was not significantly different from that of the noncatheter-related isolates.IMPORTANCEThis study provides novel insights into the genetic diversity and virulence potential of B. cereus strains causing bloodstream infections in a Japanese hospital setting. These findings suggest diverse infection pathways and highlight the importance of continuous molecular epidemiological surveillance for effective infection control.

Draft genome sequence including the capsule operon of a Bacillus cereus strain isolated from a patient with bacteremia in Japan

Bacillus cereus, which causes opportunistic infections in hospitals as well as food poisoning, is genetically similar to Bacillus anthracis. We herein report the draft genome including the capsule operon of B. cereus BCER1 isolated from the blood of a hospital patient in Japan.

Contamination of Plant Foods with Bacillus cereus in a Province and Analysis of Its Traceability

Bacillus cereus is an important zoonotic foodborne conditional pathogen. It is found in vegetables, dairy products, rice, and other foods, thereby greatly endangering human health. Investigations on B. cereus contamination in China primarily focus on raw milk, dairy products, meat, and others, and limited research has been conducted on plant-based foodstuffs. The rapid development of sequencing technology and the application of bioinformatics-related techniques means that analysis based on whole-genome sequencing has become an important tool for the molecular-epidemiology investigation of B. cereus. In this study, we investigated the contamination of B. cereus in six types of commercially available plant foods from eight regions of a province. The molecular epidemiology of the isolated B. cereus was analyzed by whole-genome sequencing. We aimed to provide fundamental data for the surveillance and epidemiology analysis of B. cereus in food products in China. The rapid traceability system of B. cereus established in this study can provide a basis for rapid molecular epidemiology analysis of B. cereus, as well as for the prevention and surveillance of B. cereus. Moreover, it can also be expanded to monitoring and rapid tracing of more foodborne pathogens.

Characterization and spoilage potential of Bacillus cereus isolated from farm environment and raw milk

Bacillus cereus sensu lato (B. cereus sl) is important spoilage bacteria causing milk structure and flavor changes and is ubiquitous in the environment. This study addresses the biodiversity, toxicity, and proteolytic activity of B. cereus sl from 82 environmental samples and 18 raw bovine milk samples from a dairy farm in the region of Tianjin. In sum, 47 B. cereus sl isolates were characterized through biochemical tests, 16S rRNA gene sequencing, and panC gene analysis. Fourteen sequence types (STs) of B. cereus sl were found in raw bovine milk samples, and five new STs (ST2749, ST2750, ST2751, ST2752, and ST2753) were identified in this study. ST1150 was the dominant ST, associated with fecal, air, drinking water, teat skin, teat cup, and teat dip cup. The results of toxin gene analyses showed that 12.77% and 8.51% of isolates carried hblACD and nheABC operons, respectively. In addition, the detection rate of emetic cesB gene was 21.28%. B. cereus sl demonstrated high spoilage potentials even at 7°C, which has the proteolytic activity of 14.32 ± 1.96 μmol of glycine equivalents per ml. Proteolytic activities were significantly (p < 0.05) decreased after the heat treatment. The residual activity of protease produced at 7°C was significantly higher than that produced at 25°C and 37°C after treatment at 121°C for 10 s and 135°C for 5 s (p < 0.01). Together, the results provide insights into the characteristics of B. cereus sl from farm environment and raw bovine milk and revealed that B. cereus sl contamination should also be monitored in raw milk for ultra-high temperature (UHT) products. This knowledge illustrates that strict cleaning management should be implemented to control B. cereus sl and assure high-quality milk products.

Rapidly fatal infection with Bacillus cereus/thuringiensis: genome assembly of the responsible pathogen and consideration of possibly contributing toxins

Bloodstream infection with Bacillus cereus/thuringiensis can be life threatening, particularly in patients who are severely immunocompromised. In this report we describe a case that progressed from asymptomatic to fatal over approximately 5 hours despite extensive resuscitation efforts. We identify the pathogen and assemble its genome, in which we find genes for toxins that may have contributed to the precipitous demise. In the context of this and other cases we discuss the possible indication for rapid appropriate antibiotic administration and potentially antitoxin treatment or toxin removal in fulminant illness in immunocompromised patients.

Bacillus cereus in Packaging Material: Molecular and Phenotypical Diversity Revealed

The Bacillus cereus group has been isolated from soils, water, plants and numerous food products. These species can produce a variety of toxins including several enterotoxins [non-hemolytic enterotoxin (Nhe), hemolysin BL (Hbl), cytotoxin K, and enterotoxin FM], the emetic toxin cereulide and insecticidal Bt toxins. This is the first study evaluating the presence of B. cereus in packaging material. Among 75 different isolates, four phylogenetic groups were detected (II, III, IV, and VI), of which the groups III and IV were the most abundant with 46.7 and 41.3%, respectively. One isolate was affiliated to psychrotolerant group VI. Growth experiments showed a mesophilic predominance. Based on PCR analysis, nhe genes were detectable in 100% of the isolates, while hbl genes were only found in 50.7%. The cereulide encoding gene was found in four out of 75 isolates, no isolate carried a crystal toxin gene. In total, thirteen different toxin gene profiles were identified. We showed that a variety of B. cereus group strains can be found in packaging material. Here, this variety lies in the presence of four phylogenetic groups, thirteen toxin gene profiles, and different growth temperatures. The results suggest that packaging material does not contain significant amounts of highly virulent strains, and the low number of cereulide producing strains is in accordance with other results.

The Food Poisoning Toxins of Bacillus cereus

Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.