Nosocomial bacteremia caused by biofilm-forming Bacillus cereus and Bacillus thuringiensis

Exploring biodegradative efficiency: a systematic review on the main microplastic-degrading bacteria

Introduction

Microplastics (MPs) are widely distributed in the environment, causing damage to biota and human health. Due to their physicochemical characteristics, they become resistant particles to environmental degradation, leading to their accumulation in large quantities in the terrestrial ecosystem. Thus, there is an urgent need for measures to mitigate such pollution, with biological degradation being a viable alternative, where bacteria play a crucial role, demonstrating high efficiency in degrading various types of MPs. Therefore, the study aimed to identify bacteria with the potential for MP biodegradation and the enzymes produced during the process.

Methods

The methodology used followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol.

Results and Discussion

The research yielded 68 eligible studies, highlighting bacteria from the genera Bacillus, Pseudomonas, Stenotrophomonas, and Rhodococcus as the main organisms involved in MP biodegradation. Additionally, enzymes such as hydrolases and alkane hydroxylases were emphasized for their involvement in this process. Thus, the potential of bacterial biodegradation is emphasized as a promising pathway to mitigate the environmental impact of MPs, highlighting the relevance of identifying bacteria with biotechnological potential for large-scale applications in reducing MP pollution.

Recombinant mannan-binding lectin magnetic beads increase pathogen detection in immunocompromised patients

The microbiological diagnosis of infection for hematological malignancy patients receiving chemotherapy or allogeneic hematopoietic stem cell transplantation (allo-HSCT) patients relies primarily on standard microbial culture, especially blood culture, which has many shortcomings, such as having low positive rates, being time-consuming and having a limited pathogenic spectrum. In this prospective observational self-controlled test accuracy study, blood, cerebrospinal fluid (CSF), and bronchoalveolar lavage fluid (BALF) samples were collected from chemotherapy or allo-HSCT patients with clinical symptoms of infections who were hospitalized at Peking University First Hospital. Possible pathogens were detected by the method based on recombinant mannan-binding lectin (MBL) magnetic bead enrichment (M1 method) and simultaneously by a standard method. The analytical sensitivity of M1 method was close to that of standard culture method. Besides, the turn-around time of M1-method was significantly shorter than that of standard culture method. Moreover, the M1 method also added diagnostic value through the detection of some clinically relevant microbes missed by the standard method. M1 method could significantly increase the detection efficiency of pathogens (including bacteria and fungi) in immunocompromised patients. KEY POINTS: • The detection results of M1-method had a high coincidence rate with that of standard method • M1 method detected many pathogens which had not been found by standard clinic method.

Risk factors associated with infection-related mortality of Bacillus cereus bacteremia in hematologic disorders

The mortality risk factors in B. cereus bacteremia in hematologic disorders are still unknown. In this study, patients with B. cereus bacteremia in hematologic disorders were selected in St. lukes international hospital and from electronic databases. A total of 176 patients [median age, 41 years (3-88 years); 99 (56%) males] were included. Of these patients, 141 (80%) had acute leukemia, and 93 (53%) died. Univariate analysis showed that neutropenia, CNS, gastrointestinal, and respiratory infections/symptoms were significantly associated with infection-related death. Meanwhile, glycopeptide use and management with source control were protective factors. Multivariate logistic regression analysis showed that infection-related death was significantly associated with CNS [odds ratio (OR): 3.49, 95% confidence interval (CI) 1.25-9.80], gastrointestinal (OR: 5.22, 95% CI 1.82-8.99), and respiratory infections/symptoms (OR: 8.98, 95% CI 1.62-49.9), as well as glycopeptide use (OR: 0.10, 95% CI 0.03-0.31) and source control (OR: 0.11, 95% CI 0.03-0.37). In conclusion, early glycopeptide administration and source control should be performed upon detection of infections suspicious for B. cereus.

Advancing understanding of microbial biofilms through machine learning-powered studies

Microbial biofilms are prevalent in various environments and pose significant challenges to food safety and public health. The biofilms formed by pathogens can cause food spoilage, foodborne illness, and infectious diseases, which are difficult to treat due to their enhanced antimicrobial resistance. While the composition and development of biofilms have been widely studied, their profound impact on food, the food industry, and public health has not been sufficiently recapitulated. This review aims to provide a comprehensive overview of microbial biofilms in the food industry and their implication on public health. It highlights the existence of biofilms along the food-producing chains and the underlying mechanisms of biofilm-associated diseases. Furthermore, this review thoroughly summarizes the enhanced understanding of microbial biofilms achieved through machine learning approaches in biofilm research. By consolidating existing knowledge, this review intends to facilitate developing effective strategies to combat biofilm-associated infections in both the food industry and public health.

Resistance determinants of emerging pathogens isolated from an intensive care unit as a parameter of population health conditions of the Legal Amazon microregion

Abstract Bacteria responsible for causing infections are common in hospital environments, water, soil, and food products. The infection risk is intensified by the absence of public sanitation, poor quality of life, and food scarcity. These external factors promote the dissemination of pathogens by direct contamination or biofilm formation. In this work, we identified bacterial isolates obtained from intensive care units in the southern region of Tocantins, Brazil. We compared matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) techniques and 16S ribosomal ribonucleic acid (rRNA) molecular analysis; we also performed phenotypic characterization. Fifty-six isolates characterized using morphotinctorial tests were classified as gram-positive (80.4%; n = 45) and gram-negative (19.6%; n = 11) and were resistant to several antibiotic classes; notably, we identified the blaOXA-23 resistance gene in the ILH10 isolate. Microbial identification using MALDI-TOF MS resulted in the identification of Sphingomonas paucimobilis and Bacillus circulans. 16S rRNA sequencing revealed four isolates belonging to the genera Bacillus and Acinetobacter. The similarity was superior to 99% for Acinetobacter schindleri in the Basic Local Alignment Search Tool (BLAST), grouped in the clade superior to 90%. Several strains isolated from intensive care units (ICU) were resistant to various antibiotic classes. These techniques allowed for the identification of several microorganisms of importance in public health, enabling improvements in human infection control and proving the quality of inputs, food, and water.

Prevalence and characterization of toxigenic Bacillus cereus group isolated from low-moisture food products

The present study was conducted to determine the occurrence of B. cereus group members in low-moisture food products by phenotypic and genetic assessment and to evaluate the toxigenic potential of B. cereus group isolates. According to the results of their morphological shape, growth temperature range, strain-specific gene distribution, 79.5% and 20.5% among 112 isolates were identified as B. cereus sensu stricto (s.s.) and B. thuringiensis, respectively and other toxigenic B. cereus group members was not found. All B. cereus group isolates possessed nheABC, hblACD, cytK, entFM genes, and the most frequent gene was nheA. Only three B. cereus s. s. isolates exhibited as emetic toxin gene-harboring B. cereus group. Several B. cereus s.s. and B. thuringiensis isolates from a low-moisture food products were moderate biofilm formers and showed resistance to rifampicin, tetracycline, or clindamycin. The existence of B. cereus s.s. and B. thuringiensis in low-moisture food products indicates the possible risk of foodborne infections due to their virulence potential.

A Flagella Hook Coding Gene flgE Positively Affects Biofilm Formation and Cereulide Production in Emetic Bacillus cereus

Bacillus cereus, an important foodborne pathogen, poses a risk to food safety and quality. Robust biofilm formation ability is one of the key properties that is responsible for the food contamination and food poisoning caused by B. cereus, especially the emetic strains. To investigate the mechanism of biofilm formation in emetic B. cereus strains, we screened for the mutants that fail to form biofilms by using random mutagenesis toward B. cereus 892-1, an emetic strain with strong biofilm formation ability. When knocking out flgE, a flagellar hook encoding gene, the mutant showed disappearance of flagellar structure and swimming ability. Further analysis revealed that both pellicle and ring presented defects in the null mutant compared with the wild-type and complementary strains. Compared with the flagellar paralytic strains ΔmotA and ΔmotB, the inhibition of biofilm formation by ΔflgE is not only caused by the inhibition of motility. Interestingly, ΔflgE also decreased the synthesis of cereulide. To our knowledge, this is the first report showing that a flagellar component can both affect the biofilm formation and cereulide production in emetic B. cereus, which can be used as the target to control the biohazard of emetic B. cereus.

Characterization of Bacillus cereus Group Isolates From Human Bacteremia by Whole-Genome Sequencing

Members of the Bacillus cereus group are spore-forming organisms commonly associated with food poisoning and intestinal infections. Moreover, some strains of the group (i.e., B. cereus sensu stricto and Bacillus thuringiensis) can cause bacteremia in humans, mainly in immunocompromised individuals. Here we performed the genetic characterization of 17 human clinical strains belonging to B. cereus group isolated from blood culture. The whole-genome sequencing (WGS) revealed that the isolates were closely related to B. cereus sensu stricto and B. thuringiensis-type strain. Multilocus sequence typing analysis performed on the draft genome revealed the genetic diversity of our isolates, which were assigned to different sequence types. Based on panC nucleotide sequence, the isolates were grouped in the phylogenetic groups III and IV. The NHE, cer, and inhA gene cluster, entA, entFM, plcA, and plcB, were the most commonly detected virulence genes. Although we did not assess the ability to generate biofilm by phenotypic tests, we verified the prevalence of biofilm associated genes using an in silico approach. A high prevalence of pur gene cluster, xerC, clpY, codY, tasA, sipW, sinI, and sigB genes, was found. Genes related to the resistance to penicillin, trimethoprim, and ceftriaxone were identified in most of the isolates. Intriguingly, the majority of these virulence and AMR genes appeared to be evenly distributed among B. cereus s.s. isolates, as well as closely related to B. thuringiensis isolates. We showed the WGS represents a good approach to rapidly characterize B. cereus group strains, being able to give useful information about genetic epidemiology, the presence of virulence and antimicrobial genes, and finally about the potential hazard related to this underestimated risk.

The fliK Gene Is Required for the Resistance of Bacillus thuringiensis to Antimicrobial Peptides and Virulence in Drosophila melanogaster

Antimicrobial peptides (AMPs) are essential effectors of the host innate immune system and they represent promising molecules for the treatment of multidrug resistant microbes. A better understanding of microbial resistance to these defense peptides is thus prerequisite for the control of infectious diseases. Here, using a random mutagenesis approach, we identify the fliK gene, encoding an internal molecular ruler that controls flagella hook length, as an essential element for Bacillus thuringiensis resistance to AMPs in Drosophila. Unlike its parental strain, that is highly virulent to both wild-type and AMPs deficient mutant flies, the fliK deletion mutant is only lethal to the latter's. In agreement with its conserved function, the fliK mutant is non-flagellated and exhibits highly compromised motility. However, comparative analysis of the fliK mutant phenotype to that of a fla mutant, in which the genes encoding flagella proteins are interrupted, indicate that B. thuringiensis FliK-dependent resistance to AMPs is independent of flagella assembly. As a whole, our results identify FliK as an essential determinant for B. thuringiensis virulence in Drosophila and provide new insights on the mechanisms underlying bacteria resistance to AMPs.

Bacillus cereus: Epidemiology, Virulence Factors, and Host-Pathogen Interactions

The toxin-producing bacterium Bacillus cereus is an important and neglected human pathogen and a common cause of food poisoning. Several toxins have been implicated in disease, including the pore-forming toxins hemolysin BL (HBL) and nonhemolytic enterotoxin (NHE). Recent work revealed that HBL binds to the mammalian surface receptors LITAF and CDIP1 and that both HBL and NHE induce potassium efflux and activate the NLRP3 inflammasome, leading to pyroptosis. These mammalian receptors, in part, contribute to inflammation and pathology. Other putative virulence factors of B. cereus include cytotoxin K, cereulide, metalloproteases, sphingomyelinase, and phospholipases. In this review, we highlight the latest progress in our understanding of B. cereus biology, epidemiology, and pathogenesis, and discuss potential new directions for research in this field.

Characterization of Ba813 harbouring Bacillus cereus in patients with haematological malignancy and hospital environments at a medical centre in Japan

Introduction. Bacillus cereus harbouring Ba813, a specific chromosomal marker of Bacillus anthtacis, is found in patients with severe manifestations and causes nosocomial outbreaks.Aim. We assessed the genetic characteristics and virulence of Ba813(+) B. cereus in a hospital setting.Methodology. Three neutropenic patients with haematological malignancy developed B. cereus bacteraemia within a short period. Fifteen B. cereus were isolated from different sites in a haematology ward. A total of 18 isolates were evaluated for Ba813- and B. anthracis-related virulence, food poisoning-related virulence, genetic diversity, bacteria motility and biofilm formation.Results. Ba813(+) B. cereus was detected in 33 % (1/3) of patients and 66 % (9/15) of the hospital environment. The 18 strains were divided into 2 major clusters (clade 1 and clade 2), and 14 strains were classified into clade 1. All Ba813(+) strains, including four sequence types, were classified into clade 1/the cereus III lineage, which is most closely related to the anthracis lineage. Two strains belonging to clade 1/non-cereus III carried the B. anthracis-associated cap gene, but not Ba813. B. cereus, including Ba813(+) strains, had significantly lower prevalence of enterotoxin genes than clade 2 strains. In clade 1, B. cereus, Ba813(+) strains showed significantly higher swimming motility and biofilm formation ability than Ba813(-) strains.Conclusion. Ba813(+) B. cereus, which are genetically closely related to B. anthracis, were abundant in a haematological ward. Ba813(+) B. cereus with high motility and biofilm formation abilities may spread easily in hospital environments, and could become a hospital-acquired infection.

Ba813 harboring Bacillus cereus, genetically closely related to Bacillus anthracis, causing nosocomial bloodstream infection: Bacterial virulence factors and clinical outcome

Bacillus cereus commonly causes catheter-related bloodstream infections (BSIs) in hospital settings, and occasionally occurs fatal central nervous system (CNS) complications. B. cereus harboring Ba813, a specific chromosomal marker of Bacillus anthracis, has been found in patients with severe infection and nosocomial BSI. However, the bacteriological profile and clinical feature of Ba813 (+) B. cereus are unclear. Fifty-three patients with B. cereus BSI were examined. Isolates were evaluated for Ba813, B. anthracis-related and food poisoning-related virulence, multilocus sequencing typing, and biofilm formation. Patients’ clinical records were reviewed retrospectively. The 53 isolates were comprised of 29 different sequence types in two distinct clades. Seventeen of the 53 (32%) B. cereus isolates including five sequence types possessed Ba813 and were classified into Clade-1/Cereus-III lineage which is most closely related to Anthracis lineage. No B. cereus possessed B. anthracis-related virulence genes. Ba813 (+) strains showed a lower prevalence of enterotoxin genes than Clade-2 strains (n = 4), but no difference from Clade-1. Ba813 (+) strains showed significantly lower biofilm formation than Clade-1/non-Cereus-III (n = 22) and Clade-2 strains, respectively. Compared to Clade-1/non-Cereus-III and Clade-2 B. cereus, Ba813 (+) strains were isolated more frequently from elderly patients, patients with indwelling central venous catheter rather than peripheral venous catheter, and patients who remained in the hospital for longer before BSI onset. No significant differences in disease severity or mortality were observed. Though two of the ten Ba813 (-) strains in Clade-1/Cereus III were isolated from the patients with CNS complication, no significant difference was observed in the bacterial profile and clinical characteristics among Clade-1/Cereus III strains. In conclusion, our report suggested that Ba813-harboring B. cereus strains, genetically closely related to B. anthracis, were abundant among B. cereus strains in the hospital setting, and might cause catheter-related nosocomial BSI. However, it did not affect the clinical outcomes.

Potential synergistic antimicrobial efficiency of binary combinations of essential oils against Bacillus cereus and Paenibacillus amylolyticus-Part A

The checkerboard method was used to study the potential interactions between eight essential oils (Basil, Cinnamon, Eucalyptus, Mandarin, Oregano, Peppermint, Tea tree, and Thyme) when used as antibacterial agents against Bacillus cereus LSPQ 2872 and Paenibacillus amylolyticus ATCC 9995. The minimum inhibitory concentration (MIC) of each essential oil (EO) and the fractional inhibitory concentration (FIC) index for the binary combinations of essential oils (EOs) were determined. According to FIC index values, some of the compound binary combinations showed an additive effect; however, Thyme/Tea tree and Cinnamon/Thyme EOs exhibited a synergistic effect against P. amylolyticus and B. cereus, respectively. Cinnamon/Thyme EOs mixture exhibited no interactive effect against P. amylolyticus, but a synergistic effect against B. cereus. The combination of Oregano/Thyme EOs displayed the best antibacterial activity and showed a synergistic effect against B. cereus and P. amylolyticus bacteria. The Oregano/Thyme EOs mixture has potential application in food preservation to reduce the contamination of B. cereus and P. amylolyticus.

Infected aneurysm of the thoracic aorta probably caused by Bacillus cereus: a case report

BACKGROUND

An infected aneurysm of the thoracic aorta is a rare clinical condition with significant morbidity and mortality. Patients with fast-growing aortic aneurysms show a high incidence of rupture. Gram-positive organisms, such as the Staphylococcus and Enterococcus species, are the most common cause of infection.

CASE PRESENTATION

A 91-year-old man presented at our facility with high grade fever and tachypnea, which he had experienced for the previous two days. He had a history of end-stage renal disease and had been undergoing regular chest computed tomography (CT) follow-up for a left lower lung nodule. CT imaging with intravenous contrast media showed a thoracic aortic aneurysm with hemothorax. Rupture of the aneurysm was suspected. CT imaging performed a year ago showed a normal aorta. Blood samples showed a Bacillus cereus infection. The patient was successfully treated for a mycotic aortic aneurysm secondary to Bacillus cereus bacteremia.

CONCLUSIONS

Here, we report a rare of an infected aneurysm of the thoracic aorta probably caused by Bacillus cereus. Although infected aneurysms have been described well before, an aneurysm infected with Bacillus cereus is rare. Bacillus cereus, a gram-positive spore-building bacterium, can produce biofilms, which attach to catheters. It has recently emerged as a new organism that can cause serious infection.

Bacillus cereus biofilm formation on central venous catheters of hospitalised cardiac patients

Formation of bacterial biofilms is a risk with many in situ medical devices. Biofilm-forming Bacillus species are associated with potentially life-threatening catheter-related blood stream infections in immunocompromised patients. Here, bacteria were isolated from biofilm-like structures within the lumen of central venous catheters (CVCs) from two patients admitted to cardiac hospital wards. Isolates belonged to the Bacillus cereus group, exhibited strong biofilm formation propensity, and mapped phylogenetically close to the B. cereus emetic cluster. Together, whole genome sequencing and quantitative PCR confirmed that the isolates constituted the same strain and possessed a range of genes important for and up-regulated during biofilm formation. Antimicrobial susceptibility testing demonstrated resistance to trimethoprim-sulphamethoxazole, clindamycin, penicillin and ampicillin. Inspection of the genome revealed several chromosomal β-lactamase genes and a sulphonamide resistant variant of folP. This study clearly shows that B. cereus persisting in hospital ward environments may constitute a risk factor from repeated contamination of CVCs.

Poultry and beef meat as potential seedbeds for antimicrobial resistant enterotoxigenic Bacillus species: a materializing epidemiological and potential severe health hazard

Although Bacillus cereus is of particular concern in food safety and public health, the role of other Bacillus species was overlooked. Therefore, we investigated the presence of eight enterotoxigenic genes, a hemolytic gene and phenotypic antibiotic resistance profiles of Bacillus species in retail meat samples. From 255 samples, 124 Bacillus isolates were recovered, 27 belonged to B. cereus and 97 were non-B. cereus species. Interestingly, the non-B. cereus isolates carried the virulence genes and exhibited phenotypic virulence characteristics as the B. cereus. However, correlation matrix analysis revealed the B. cereus group positively correlates with the presence of the genes hblA, hblC, and plc, and the detection of hemolysis (p < 0.05), while the other Bacillus sp. groups are negatively correlated. Tests for antimicrobial resistance against ten antibiotics revealed extensive drug and multi-drug resistant isolates. Statistical analyses didn't support a correlation of antibiotic resistance to tested virulence factors suggesting independence of these phenotypic markers and virulence genes. Of special interest was the isolation of Paenibacillus alvei and Geobacillus stearothermophilus from the imported meat samples being the first recorded. The isolation of non-B. cereus species carrying enterotoxigenic genes in meat within Egypt, suggests their impact on food safety and public health and should therefore not be minimised, posing an area that requires further research.

In defense of Bacillus thuringiensis, the safest and most successful microbial insecticide available to humanity - a response to EFSA

The Bacillus cereus group contains vertebrate pathogens such as B. anthracis and B. cereus and the invertebrate pathogen B. thuringiensis (Bt). Microbial biopesticides based on Bt are widely recognised as being among the safest and least environmentally damaging insecticidal products available. Nevertheless, a recent food-poisoning incident prompted a European Food Safety Authority review which argued that Bt poses a health risk equivalent to B. cereus, a causative agent of diarrhoea. However, a critical examination of available data, and this latest incident, provides no solid evidence that Bt causes diarrhoea. Although relatively high levels of B. cereus-like spores can occur in foods, genotyping demonstrates that these are predominantly naturally occurring strains rather than biopesticides. Moreover, MLST genotyping of >2000 isolates show that biopesticide genotypes have never been isolated from any clinical infection. MLST data demonstrate that B. cereus group is heterogeneous and formed of distinct clades with substantial differences in biology, ecology and host association. The group posing the greatest risk (the anthracis clade) is distantly related to the clade containing all biopesticides. These recent data support the long-held view that Bt and especially the strains used in Bt biopesticides are very safe for humans.

Comparative efficacies of daptomycin, vancomycin, and linezolid in experimental enterococcal peritonitis

Enterococci have become increasingly important pathogens for nosocomial infection (e.g. bacteremia, intra-abdominal infection, endocarditis, etc.), related to their intrinsic resistance to many antibiotics. Although the in vitro susceptibility of daptomycin (DAP) against Enterococci is well established, the Food and Drug Administration has only approved its use for complicated skin and skin structure infections induced by Enterococcus faecalis. In this study we evaluated the potential therapeutic application of DAP in a murine model of enterococcal experimental peritonitis. Mice were injected intraperitoneally with 4 × 10¹⁰ colony-forming units of Enterococcus faecium. DAP alone, DAP combined with ampicillin, vancomycin, or linezolid were administered 2 h after enterococcal inoculation and examined the survival, viable bacteria counts, the level of KC/CXCL1 in the peritoneal fluid. The viable bacteria counts in the peritoneal fluid of the DAP- or DAP plus ampicillin-treated groups were decreased significantly compared to those of the vancomycin- and linezolid-treated groups (P < 0.05) at 6 and 12 h after the inoculation of Enterococcus. The level of neutrophil chemoattractants KC in the peritoneal fluid at 12 h after enterococcal inoculation was significantly decreased in the DAP plus ampicillin-treated group (P < 0.05). In addition DAP showed the inhibitory effect of enterococcal biofilm formation dose-dependently by a microtiter biofilm assay. These results indicate that DAP, particularly with β-lactams, is a possible alternative agent to treat severe enterococcal infection such as peritonitis.

Transferrin Impacts Bacillus thuringiensis Biofilm Levels

The present study examined the impact of transferrin on Bacillus thuringiensis biofilms. Three commercial strains, an environmental strain (33679), the type strain (10792), and an isolate from a diseased insect (700872), were cultured in iron restricted minimal medium. All strains produced biofilm when grown in vinyl plates at 30°C. B. thuringiensis 33679 had a biofilm biomass more than twice the concentration exhibited by the other strains. The addition of transferrin resulted in slightly increased growth yields for 2 of the 3 strains tested, including 33679. In contrast, the addition of 50 μg/mL of transferrin resulted in an 80% decrease in biofilm levels for strain 33679. When the growth temperature was increased to 37°C, the addition of 50 μg/mL of transferrin increased culture turbidity for only strain 33679. Biofilm levels were again decreased in strain 33679 at 37°C. Growth of B. thuringiensis cultures in polystyrene resulted in a decrease in overall growth yields at 30°C, with biofilm levels significantly decreased for 33679 in the presence of transferrin. These findings demonstrate that transferrin impacts biofilm formation in select strains of B. thuringiensis. Identification of these differences in biofilm regulation may be beneficial in elucidating potential virulence mechanisms among the differing strains.

Genotypic heterogeneity of emetic toxin producing Bacillus cereus isolates from China

Emetic toxin-producing Bacillus cereus (emetic B. cereus) is the third member of B. cereus group whose toxins are encoded by megaplasmids, beside anthrax and insecticidal toxins of B. anthracis and B. thuringiensis, respectively. A total of 18 emetic isolates collected from food poisoning events, clinical and non-random food samples in Zhejiang province of China, were analyzed by plasmid screening, pulse field gel electrophoresis, multilocus sequence typing, and toxic gene identification to investigate their genotypic diversity. In this study, 13 plasmid profile types, 14 pulse types and 6 different STs from emetic isolates were detected, in which ST 1035,1038,1053,1054 and 1065 were first assigned and reported. The toxic gene ces existed on its own, or coexisted with other toxic genes bceT, cytk, entFM and nhe, but never with hbl in emetic isolates. The results demonstrated that the emetic B. cereus strains from China were heterologous at genotypic level.

Bacillus cereus Biofilms-Same, Only Different

Bacillus cereus displays a high diversity of lifestyles and ecological niches and include beneficial as well as pathogenic strains. These strains are widespread in the environment, are found on inert as well as on living surfaces and contaminate persistently the production lines of the food industry. Biofilms are suspected to play a key role in this ubiquitous distribution and in this persistency. Indeed, B. cereus produces a variety of biofilms which differ in their architecture and mechanism of formation, possibly reflecting an adaptation to various environments. Depending on the strain, B. cereus has the ability to grow as immersed or floating biofilms, and to secrete within the biofilm a vast array of metabolites, surfactants, bacteriocins, enzymes, and toxins, all compounds susceptible to act on the biofilm itself and/or on its environment. Within the biofilm, B. cereus exists in different physiological states and is able to generate highly resistant and adhesive spores, which themselves will increase the resistance of the bacterium to antimicrobials or to cleaning procedures. Current researches show that, despite similarities with the regulation processes and effector molecules involved in the initiation and maturation of the extensively studied Bacillus subtilis biofilm, important differences exists between the two species. The present review summarizes the up to date knowledge on biofilms produced by B. cereus and by two closely related pathogens, Bacillus thuringiensis and Bacillus anthracis. Economic issues caused by B. cereus biofilms and management strategies implemented to control these biofilms are included in this review, which also discuss the ecological and functional roles of biofilms in the lifecycle of these bacterial species and explore future developments in this important research area.

Comparative Bioinformatics and Experimental Analysis of the Intergenic Regulatory Regions of Bacillus cereus hbl and nhe Enterotoxin Operons and the Impact of CodY on Virulence Heterogeneity

Bacillus cereus is a food contaminant with greatly varying enteropathogenic potential. Almost all known strains harbor the genes for at least one of the three enterotoxins Nhe, Hbl, and CytK. While some strains show no cytotoxicity, others have caused outbreaks, in rare cases even with lethal outcome. The reason for these differences in cytotoxicity is unknown. To gain insight into the origin of enterotoxin expression heterogeneity in different strains, the architecture and role of 5′ intergenic regions (5′ IGRs) upstream of the nhe and hbl operons was investigated. In silico comparison of 142 strains of all seven phylogenetic groups of B. cereus sensu lato proved the presence of long 5′ IGRs upstream of the nheABC and hblCDAB operons, which harbor recognition sites for several transcriptional regulators, including the virulence regulator PlcR, redox regulators ResD and Fnr, the nutrient-sensitive regulator CodY as well as the master regulator for biofilm formation SinR. By determining transcription start sites, unusually long 5′ untranslated regions (5′ UTRs) upstream of the nhe and hbl start codons were identified, which are not present upstream of cytK-1 and cytK-2. Promoter fusions lacking various parts of the nhe and hbl 5′ UTR in B. cereus INRA C3 showed that the entire 331 bp 5′ UTR of nhe is necessary for full promoter activity, while the presence of the complete 606 bp hbl 5′ UTR lowers promoter activity. Repression was caused by a 268 bp sequence directly upstream of the hbl transcription start. Luciferase activity of reporter strains containing nhe and hbl 5′ IGR lux fusions provided evidence that toxin gene transcription is upregulated by the depletion of free amino acids. Electrophoretic mobility shift assays showed that the branched-chain amino acid sensing regulator CodY binds to both nhe and hbl 5′ UTR downstream of the promoter, potentially acting as a nutrient-responsive roadblock repressor of toxin gene transcription. PlcR binding sites are highly conserved among all B. cereus sensu lato strains, indicating that this regulator does not significantly contribute to the heterogeneity in virulence potentials. The CodY recognition sites are far less conserved, perhaps conferring varying strengths of CodY binding, which might modulate toxin synthesis in a strain-specific manner.

Identification and Pathogenic Potential of Clinical Bacillus and Paenibacillus Isolates

The soil-related Bacillus and Paenibacillus species have increasingly been implicated in various human diseases. Nevertheless, their identification still poses problems in the clinical microbiology laboratory and, with the exception of Bacillus anthracis and Bacillus cereus, little is known on their pathogenicity for humans. In this study, we evaluated the use of matrix-assisted laser desorption—ionization time of flight mass spectrometry (MALDI-TOF MS) in the identification of clinical isolates of these genera and conducted genotypic and phenotypic analyses to highlight specific virulence properties. Seventy-five clinical isolates were subjected to biochemical and MALDI-TOF MS identification. 16S rDNA sequencing and supplemental tests were used to solve any discrepancies or failures in the identification results. MALDI-TOF MS significantly outperformed classical biochemical testing for correct species identification and no misidentification was obtained. One third of the collected strains belonged to the B. cereus species, but also Bacillus pumilus and Bacillus subtilis were isolated at high rate. Antimicrobial susceptibility testing showed that all the B. cereus, B. licheniformis, B. simplex, B. mycoides, Paenibacillus glucanolyticus and Paenibacillus lautus isolates are resistant to penicillin. The evaluation of toxin/enzyme secretion, toxin-encoding genes, motility, and biofilm formation revealed that B. cereus displays the highest virulence potential. However, although generally considered nonpathogenic, most of the other species were shown to swim, swarm, produce biofilms, and secrete proteases that can have a role in bacterial virulence. In conclusion, MALDI-TOF MS appears useful for fast and accurate identification of Bacillus and Paenibacillus strains whose virulence properties make them of increasing clinical relevance.

Use of Peripheral Parenteral Nutrition Solutions as a Risk Factor for Bacillus cereus Peripheral Venous Catheter-Associated Bloodstream Infection at a Japanese Tertiary Care Hospital: a Case-Control Study

The risk factors are unclear for peripheral venous catheter-associated bloodstream infections (PVCBSIs) caused by Bacillus cereus. We aimed to examine for these risk factors in patients with B. cereus PVCBSI by conducting a 2-year case-control study in a large teaching hospital. We analyzed all adult cases of B. cereus PVCBSI (37 patients) and 180 controls who were randomly selected from among patients who had a PVC in place for at least 2 days. Multivariate analysis using a conditional logistic regression model indicated that independent risk factors were use of a peripheral parenteral nutrition (PPN) solution with an adjusted odds ratio (OR) of 88.7 (95% confidence interval [CI], 17.4-451.9), and steroid therapy (adjusted OR, 5.7 [95% CI, 1.3-24.4]). In conclusion, use of PPN solutions or steroids was an independent risk factor for B. cereus PVCBSI. Appropriate use of PPN solutions may help prevent B. cereus PVCBSI. Prospective studies are needed to confirm these results.

Massive horizontal gene transfer, strictly vertical inheritance and ancient duplications differentially shape the evolution of Bacillus cereus enterotoxin operons hbl, cytK and nhe

Background

Bacillus cereus sensu lato comprises eight closely related species including the human pathogens Bacillus anthracis and Bacillus cereus. Within B. cereus sensu lato, chromosomally and plasmid-encoded toxins exist. While plasmid-mediated horizontal gene transfer of the emetic toxin, anthrax and insecticidal toxins is known, evolution of enterotoxin genes within the group has not been studied.

Results

We report draft genome assemblies of 25 strains, a phylogenetic network of 142 strains based on ANI derived from genome sequences and a phylogeny based on whole-genome SNP analysis. The data clearly support subdivision of B. cereus sensu lato into seven phylogenetic groups. While group I, V and VII represent B. pseudomycoides, B. toyonensis and B. cytotoxicus, which are distinguishable at species level (ANI border ≥ 96 %), strains ascribed to the other five species do not match phylogenic groups. The chromosomal enterotoxin operons nheABC and hblCDAB are abundant within B. cereus both isolated from infections and from the environment. While the duplicated hbl variant hbl_a is present in 22 % of all strains investigated, duplication of nheABC is extremely rare (0.02 %) and appears to be phylogenetically unstable. Distribution of toxin genes was matched to a master tree based on seven concatenated housekeeping genes, which depicts species relationships in B. cereus sensu lato as accurately as whole-genome comparisons. Comparison to the phylogeny of enterotoxin genes uncovered ample evidence for horizontal transfer of hbl, cytK and plcR, as well as frequent deletion of both toxins and duplication of hbl. No evidence for nhe deletion was found and stable horizontal transfer of nhe is rare. Therefore, evolution of B. cereus enterotoxin operons is shaped unexpectedly different for yet unknown reasons.

Conclusions

Frequent exchange of the pathogenicity factors hbl, cytK and plcR in B. cereus sensu lato appears to be an important mechanism of B. cereus virulence evolution, including so-called probiotic or non-pathogenic species, which might have consequences for risk assessment procedures. In contrast, exclusively vertical inheritance of nhe was observed, and since nhe-negative strains appear to be extremely rare, we suggest that fitness loss may be associated with deletion or horizontal transfer of the nhe operon.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-015-0529-4) contains supplementary material, which is available to authorized users.

Bacillus cereus infection: 57 case patients and a literature review

OBJECTIVES

We aimed to study the characteristics of patients presenting with a Bacillus cereus infection in a university hospital.

METHODS

We performed a retrospective analysis of the clinical, biological, and treatment-related data of patients hospitalized in our university hospital between January 1st, 2008 and December 31st, 2012 and diagnosed with a B. cereus infection. We identified a subgroup of patients presenting with bacteremia and looked for risk factors for death within that group of patients.

RESULTS

We included 57 patients in our study; 31 (54.4%) were hospitalized in a medical ward. We identified 24 bacteremia case patients, including 17 patients presenting with bacteremia alone (29.8%). Other frequently observed infection sites were skin infections (16; 28.1%) and bone and joint infections (10; 17.5%). We recorded 9 deaths (11.8%); 2 patients, despite being on an appropriate antibiotic therapy, died from a medical device-related infection that had not been removed. The empirical administration of a beta-lactam antibiotic was significantly associated with death (P=0.022). Three patients presenting with recurrent bacteremia were identified. The patients only recovered once the infected device had been removed.

CONCLUSION

B. cereus infections may have various clinical presentations. Prospective data is needed to put forward a consensual treatment approach and guide physicians in choosing the appropriate antibiotic therapy and in removing the infected device.

Bacteria that Travel: The Quality of Aircraft Water

The travelling population is increasing globally year on year. International tourist arrival figures reached 1087 million in 2013 and 1133 million in 2014; of which 53% and 54% respectively accounted for air transport. The water on board aircraft is sourced from surface or ground water; piped to a central filling point and distributed to each aircraft by water service vehicles at the home base or at the destination airport. The purpose of this study was to ascertain the microbial, chemical (pH; Total and Free chlorine) and physical (temperature) quality of water from two aircraft, long- and short-haul, as well as from the original water source and the water service vehicle. A total of 154 water samples were collected and analysed. Long-haul flights were found to be significantly poorer in terms of microbial quality than short haul flights (p = 0.015). Furthermore, correlation and regression analysis showed that the water service vehicle was a significant source of increased microbial load in aircraft. Microbial diversity was also demonstrated, with 37 bacterial species identified belonging to eight classes: γ-Proteobacteria; β-Proteobacteria; α-Proteobacteria; Bacilli; Actinobacteria; Flavobacteria; Sphingobacteria and Cytophaga; using phenotypic and 16S rDNA sequence-based analysis. We present a novel quantified study of aircraft-related potable water supplies.

Bacillus thuringiensis membrane-damaging toxins acting on mammalian cells

Bacillus thuringiensis is widely used as a biopesticide in forestry and agriculture, being able to produce potent species-specific insecticidal toxins and considered nonpathogenic to other animals. More recently, however, repeated observations are documenting the association of this microorganism with various infectious diseases in humans, such as food-poisoning-associated diarrheas, periodontitis, bacteremia, as well as ocular, burn, and wound infections. Similar to B. cereus, B. thuringiensis produces an array of virulence factors acting against mammalian cells, such as phosphatidylcholine- and phosphatidylinositol-specific phospholipase C (PC-PLC and PI-PLC), hemolysins, in particular hemolysin BL (HBL), and various enterotoxins. The contribution of some of these toxins to B. thuringiensis pathogenicity has been studied in animal models of infection, following intravitreous, intranasal, or intratracheal inoculation. These studies lead to the speculation that the activities of PC-PLC, PI-PLC, and HBL are responsible for most of the pathogenic properties of B. thuringiensis in nongastrointestinal infections in mammals. This review summarizes data regarding the biological activity, the genetic basis, and the structural features of these membrane-damaging toxins.

Variability of Bacillus thuringiensis strains by ERIC-PCR and biofilm formation

Bacillus thuringiensis (Bt) is a soil-dwelling bacterium of great interest for agronomical research because of its use as biological pesticide. There are some limitations regarding the subspecies classification. Phenotyping and genotyping studies are important to ascertain its variability. The diversity of 40 environmental strains, isolated from different regions in Mexico, was analyzed by ERIC-PCR and the ability of biofilm formation. Thirty-nine different fingerprinting patterns revealed enough data to discriminate among the 40 strains. A total of 24 polymorphic fragments with sizes between 139 and 1,468 bp were amplified. Almost all (95 %) strains showed biofilm formation after 96 h of incubation. At 96 h of incubation the biofilm-forming strains from the CINVESTAV collection showed a more heterogeneous ability as biofilms producers. Results showed a large intra-species genomic variability in Bt. However, some strains could be correlated as they were found within clusters depending on the location of isolation.

Comparison study of single and concurrent administrations of carbapenem, new quinolone, and macrolide against in vitro nontypeable Haemophilus influenzae mature biofilms

Nontypeable Haemophilus influenzae (NTHi) is an opportunistic pathogen and a common cause of otitis media in children, chronic bronchitis, and pneumonia in patients with chronic obstructive pulmonary disease. Many studies have reported that NTHi is capable of producing biofilms, which may be one of the important factors involved in chronic diseases and accelerating antimicrobial resistance. Unfortunately, there is still no consensus about the elimination of biofilms. In this study, concurrent administrations of levofloxacin (LVFX)-imipenem (IPM) and clarithromycin (CAM)-IPM, as well as the single administration of IPM, LVFX, and CAM, were performed to treat the mature biofilms produced by NTHi, respectively. Biofilm inhibition was quantified using microtiter biofilm assay (MBA), and relative biomass was calculated as the ratio compared to that of untreated control biofilms. The relative biomasses of biofilms treated with IPM, LVFX-IPM, and CAM-IPM against a β-lactamase-negative ampicillin-resistant strain was 1.10, 0.08, and 0.13 at 1× minimum inhibitory concentration (MIC), 0.90, 0.05, and 0.07 at 10× MIC, and 0.80, 0.06, and 0.07 at 100× MIC, respectively. Biofilms were also visually observed by scanning electron microscopy, and a focused ion-beam system showed that high concentrations of combined administration strongly inhibited the biofilms, which was consistent with the results of MBA. Our data demonstrated the antibiofilm effect of concurrent administration against mature NTHi biofilms, which indicated a rationale for the potential use of concurrent administrations in diseases involving chronic NTHi biofilms.

Host cell cytotoxicity and cytoskeleton disruption by CerADPr, an ADP-ribosyltransferase of Bacillus cereus G9241

Bacillus cereus G9241 was isolated from a welder suffering from an anthrax-like inhalation illness. B. cereus G9241 encodes two megaplasmids, pBCXO1 and pBC210, which are analogous to the toxin- and capsule-encoding virulence plasmids of Bacillus anthracis. Protein modeling predicted that the pBC210 LF homologue contained an ADP-ribosyltransferase (ADPr) domain. This putative bacterial ADP-ribosyltransferase domain was denoted CerADPr. Iterative modeling showed that CerADPr possessed several conserved ADP-ribosyltransferase features, including an α-3 helix, an ADP-ribosyltransferase turn-turn loop, and a "Gln-XXX-Glu" motif. CerADPr ADP-ribosylated an ~120 kDa protein in HeLa cell lysates and intact cells. EGFP-CerADPr rounded HeLa cells, elicited cytoskeletal changes, and yielded a cytotoxic phenotype, indicating that CerADPr disrupts cytoskeletal signaling. CerADPr(E431D) did not possess ADP-ribosyltransferase or NAD glycohydrolase activities and did not elicit a phenotype in HeLa cells, implicating Glu431 as a catalytic residue. These experiments identify CerADPr as a cytotoxic ADP-ribosyltransferase that disrupts the host cytoskeleton.

Bacillus cereus G9241 makes anthrax toxin and capsule like highly virulent B. anthracis Ames but behaves like attenuated toxigenic nonencapsulated B. anthracis Sterne in rabbits and mice

Bacillus cereus G9241 was isolated from a welder with a pulmonary anthrax-like illness. The organism contains two megaplasmids, pBCXO1 and pBC218. These plasmids are analogous to the Bacillus anthracis Ames plasmids pXO1 and pXO2 that encode anthrax toxins and capsule, respectively. Here we evaluated the virulence of B. cereus G9241 as well as the contributions of pBCXO1 and pBC218 to virulence. B. cereus G9241 was avirulent in New Zealand rabbits after subcutaneous inoculation and attenuated 100-fold compared to the published 50% lethal dose (LD(50)) values for B. anthracis Ames after aerosol inoculation. A/J and C57BL/6J mice were comparably susceptible to B. cereus G9241 by both subcutaneous and intranasal routes of infection. However, the LD(50)s for B. cereus G9241 in both mouse strains were markedly higher than those reported for B. anthracis Ames and more like those of the toxigenic but nonencapsulated B. anthracis Sterne. Furthermore, B. cereus G9241 spores could germinate and disseminate after intranasal inoculation into A/J mice, as indicated by the presence of vegetative cells in the spleen and blood of animals 48 h after infection. Lastly, B. cereus G9241 derivatives cured of one or both megaplasmids were highly attenuated in A/J mice. We conclude that the presence of the toxin- and capsule-encoding plasmids pBCXO1 and pBC218 in B. cereus G9241 alone is insufficient to render the strain as virulent as B. anthracis Ames. However, like B. anthracis, full virulence of B. cereus G9241 for mice requires the presence of both plasmids.

Bacillus species infective arthritis after knee arthroscopy

BACKGROUND

Bacillus species infection of the joints is a very rare occurrence, with sporadic reports in the medical literature.

CASE REPORT

A 67-year-old woman with osteoarthritis developed infection in the knee joint after arthroscopy. Percutaneous needle aspiration of articular fluid performed post-operatively showed a positive culture for Bacillus species. The diagnosis of septic arthritis was, however, not confirmed as the results were considered contamination. Failure of treatment with beta-lactam antibiotics on two occasions and successful cure of infective arthritis by long-term administration of a fluoroquinolone confirmed iatrogenic clinical joint infection with Bacillus species.

CONCLUSION

Any clinically suspected joint infection must be treated as septic arthritis until proved otherwise.

Spore-forming Bacilli and Clostridia in human disease

Many Gram-positive spore-forming bacteria in the Firmicute phylum are important members of the human commensal microbiota, which, in rare cases, cause opportunistic infections. Other spore-formers, however, have evolved to become dedicated pathogens that can cause a striking variety of diseases. Despite variations in disease presentation, the etiologic agent is often the spore, with bacterially produced toxins playing a central role in the pathophysiology of infection. This review will focus on the specific diseases caused by spores of the Clostridia and Bacilli.

Bacillus cereus, a volatile human pathogen

Bacillus cereus is a Gram-positive aerobic or facultatively anaerobic, motile, spore-forming, rod-shaped bacterium that is widely distributed environmentally. While B. cereus is associated mainly with food poisoning, it is being increasingly reported to be a cause of serious and potentially fatal non-gastrointestinal-tract infections. The pathogenicity of B. cereus, whether intestinal or nonintestinal, is intimately associated with the production of tissue-destructive exoenzymes. Among these secreted toxins are four hemolysins, three distinct phospholipases, an emesis-inducing toxin, and proteases. The major hurdle in evaluating B. cereus when isolated from a clinical specimen is overcoming its stigma as an insignificant contaminant. Outside its notoriety in association with food poisoning and severe eye infections, this bacterium has been incriminated in a multitude of other clinical conditions such as anthrax-like progressive pneumonia, fulminant sepsis, and devastating central nervous system infections, particularly in immunosuppressed individuals, intravenous drug abusers, and neonates. Its role in nosocomial acquired bacteremia and wound infections in postsurgical patients has also been well defined, especially when intravascular devices such as catheters are inserted. Primary cutaneous infections mimicking clostridial gas gangrene induced subsequent to trauma have also been well documented. B. cereus produces a potent beta-lactamase conferring marked resistance to beta-lactam antibiotics. Antimicrobials noted to be effective in the empirical management of a B. cereus infection while awaiting antimicrobial susceptibility results for the isolate include ciprofloxacin and vancomycin.