Comparative analysis of quantitative reverse transcription real-time PCR and commercial enzyme imunoassays for detection of enterotoxigenic Bacillus thuringiensis isolates

Biosurfactant and biopolymer producing microorganisms from West Kazakhstan oilfield

Microbiological enhanced oil recovery (MEOR) uses indigenous or exogenous microorganisms and nutrients to enhance oil production through synthesis of metabolites reducing oil viscosity and surface tension. In order to find bacteria suitable for MEOR, we studied 26 isolates from wells in the Akingen oilfield in West Kazakhstan. Six of them were selected for further analysis based on their ability to reduce surface tension to less than 40 mN/m, with the A9 isolate exhibiting tension reduction values of 32.76 ± 0.3 mN/m. Based on the morphological features, biochemical activities, and the 16S rRNA gene, the isolates were classified to the Bacillus subtilis group. In the phylogenetic analysis the isolates grouped into two main clusters. Genes encoding the surfactin synthetase subunits were found in A2, A8, A9, A12, PW2, only the PW2 strain had lchAA encoding lichenysin, while sacB encoding levan was noted in A2, A8, A9, and A12. The expression of srfAB, srfAC, and sacB tested with qPCR varied among strains. Nevertheless, whereas temperature moderately affects the expression level, with the highest level recorded at 40 °C, salinity significantly impacts the expression of the genes encoding biosurfactants. B. subtilis strains isolated in the study, especially A9, are promising for microbial-enhanced oil recovery.

Synergistic Antibacterial Potential of 6-Pentyl-α-pyrone Lactone and Zinc Oxide Nanoparticles against Multidrug-Resistant Enterobacterales Isolated from Urinary Tract Infections in Humans

Urinary tract infection (UTI) is one of the most common bacterial infections in the world, which is associated with high morbidity and mortality rates. Enterobacterales species are considered the most causative agent for UTI, especially uropathogenic Escherichia coli (UPEC). Here, we investigated the antibacterial activity of the green fungal metabolite, 6-pentyl α pyrone lactone, alone or in combination with zinc oxide nanoparticles (ZnONPs) against multidrug-resistant Enterobacterales recovered from UTI. The results revealed that 57.27% of human urine samples were positive for Enterobacterales, where E. coli was the most prevalent bacterial pathogen (66.67%). Of note, 98.41% of Enterobacterales isolates were multidrug-resistant (MDR) with multiple antimicrobial resistance (MAR) indices ranged from 0.437 to 1. Fifty percent of the examined isolates were positive for the integrase gene; 60% out of them harbored class 2 integron, whereas the other 40% carried class 1 integrons. The broth microdilution assay ensured that the 6-pentyl-α-pyrone lactone had a reasonable antimicrobial effect against the examined isolates (Minimum inhibitory concentration (MIC) values of 16–32 μg/mL). However, ZnONPs showed a strong antimicrobial effect against the investigated isolates with MIC values ranging from 0.015 to 32 μg/mL. Interestingly, the MICs decreased 5–12 fold and 3–11 fold for 6-pentyl-α-pyrone lactone and ZnONPs, respectively, against examined isolates after their combination. This is the first report suggesting the use of 6-pentyl α pyrone lactone and ZnONPs combination as a promising candidate against MDR Enterobacterales recovered from UTI.

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.

Potential Enterotoxicity of Phylogenetically Diverse Bacillus cereus Sensu Lato Soil Isolates from Different Geographical Locations

Bacillus cereus sensu lato comprises Gram-positive spore-forming bacteria producing toxins associated with foodborne diseases. Three pore-forming enterotoxins, nonhemolytic enterotoxin (Nhe), hemolysin BL (Hbl), and cytotoxin K (CytK), are considered the primary factors in B. cereus sensu lato diarrhea. The aim of this study was to determine the potential risk of enterotoxicity among soil B. cereus sensu lato isolates representing diverse phylogroups and originated from different geographic locations with various climates (Burkina Faso, Kenya, Argentina, Kazakhstan, and Poland). While nheA- and hblA-positive isolates were present among all B. cereus sensu lato populations and distributed across all phylogenetic groups, cytK-2-positive strains predominated in geographic regions with an arid hot climate (Africa) and clustered together on a phylogenetic tree mainly within mesophilic groups III and IV. The highest in vitro cytotoxicity to Caco-2 and HeLa cells was demonstrated by the strains clustered within phylogroups II and IV. Overall, our results suggest that B. cereus sensu lato pathogenicity is a comprehensive process conditioned by many intracellular factors and diverse environmental conditions.IMPORTANCE This research offers a new route for a wider understanding of the dependency between pathogenicity and phylogeny of a natural bacterial population, specifically within Bacillus cereus sensu lato, that is widely distributed around the world and easily transferred into food products. Our study indicates differences in the phylogenetic and geographical distributions of potential enterotoxigenic B. cereus sensu lato strains. Hence, these bacilli possess a risk for human health, and rapid testing methods for their identification are greatly needed. In particular, the detection of the CytK enterotoxin should be a supporting strategy for the identification of pathogenic B. cereus sensu lato.

Use of ceragenins as a potential treatment for urinary tract infections

BACKGROUND

Urinary tract infections (UTIs) are one of the most common bacterial infections. High recurrence rates and the increasing antibiotic resistance among uropathogens constitute a large social and economic problem in current public health. We assumed that combination of treatment that includes the administration ceragenins (CSAs), will reinforce the effect of antimicrobial LL-37 peptide continuously produced by urinary tract epithelial cells. Such treatment might be an innovative approach to enhance innate antibacterial activity against multidrug-resistant E. coli.

METHODS

Antibacterial activity measured using killing assays. Biofilm formation was assessed using crystal violet staining. Viability of bacteria and bladder epithelial cells subjected to incubation with tested agents was determined using MTT assays. We investigated the effects of chosen molecules, both alone and in combinations against four clinical strains of E. coli, obtained from patients diagnosed with recurrent UTI.

RESULTS

We observed that the LL-37 peptide, whose concentration increases at sites of urinary infection, exerts increased bactericidal effect against E. coli when combined with ceragenins CSA-13 and CSA-131.

CONCLUSION

We suggest that the employment of combination of natural peptide LL-37 with synthetic analogs might be a potential solution to treat urinary tract infections caused by drug-resistant bacteria.

Inhibition of inflammatory response in human keratinocytes by magnetic nanoparticles functionalized with PBP10 peptide derived from the PIP2-binding site of human plasma gelsolin

Background

Human plasma gelsolin (pGSN) is a multifunctional actin-binding protein involved in a variety of biological processes, including neutralization of pro-inflammatory molecules such as lipopolysaccharide (LPS) and lipoteichoic acid (LTA) and modulation of host inflammatory response. It was found that PBP10, a synthetic rhodamine B-conjugated peptide, based on the phosphoinositide-binding site of pGSN, exerts bactericidal activity against Gram-positive and Gram-negative bacteria, interacts specifically with LPS and LTA, and limits microbial-induced inflammatory effects. The therapeutic efficiency of PBP10 when immobilized on the surface of iron oxide-based magnetic nanoparticles was not evaluated, to date.

Results

Using the human keratinocyte cell line HaCaT stimulated by bacterially-derived LPS and LTA as an in vitro model of bacterial infection, we examined the anti-inflammatory effects of nanosystems consisting of iron oxide-based magnetic nanoparticles with aminosilane (MNP@NH₂) or gold shells (MNP@Au) functionalized by a set of peptides, derived from the phosphatidylinositol 4,5-bisphosphate (PIP2)-binding site of the human plasma protein gelsolin, which also binds LPS and LTA. Our results indicate that these nanosystems can kill both Gram-positive and Gram-negative bacteria and limit the production of inflammatory mediators, including nitric oxide (NO), reactive oxygen species (ROS), and interleukin-8 (IL-8) in the response to heat-killed microbes or extracted bacterial cell wall components. The nanoparticles possess the potential to improve therapeutic efficacy and are characterized by lower toxicity and improved hemocompatibility when compared to free peptides. Atomic force microscopy (AFM) showed that these PBP10-based nanosystems prevented changes in nanomechanical properties of cells that were otherwise stimulated by LPS.

Conclusions

Neutralization of endotoxemia-mediated cellular effects by gelsolin-derived peptides and PBP10-containing nanosystems might be considered as potent therapeutic agents in the improved therapy of bacterial infections and microbial-induced inflammation.

Comparison of four commercial DNA extraction kits for the recovery of Bacillus spp. spore DNA from spiked powder samples

Bacillus spp. include human pathogens such as Bacillus anthracis, the causative agent of anthrax and a biothreat agent. Bacillus spp. form spores that are physically highly resistant and may remain active over sample handling. We tested four commercial DNA extraction kits (QIAamp DNA Mini Kit, RTP Pathogen Kit, ZR Fungal/Bacterial DNA MiniPrep, and genesig Easy DNA/RNA Extraction kit) for sample inactivation and DNA recovery from two powders (icing sugar and potato flour) spiked with Bacillus thuringiensis spores. The DNA was analysed using a B. thuringiensis-specific real-time PCR assay. The detection limit was 3×10(1)CFU of spiked B. thuringiensis spores with the QIAamp DNA Mini, RTP Pathogen, and genesig Easy DNA/RNA Extraction kits, and 3×10(3)CFU with the ZR Fungal/Bacterial DNA MiniPrep kit. The results showed that manual extraction kits are effective and safe for fast and easy DNA extraction from powder samples even in field conditions. Adding a DNA filtration step to the extraction protocol ensures the removal of Bacillus spp. spores from DNA samples without affecting sensitivity.

MALDI-TOF MS portrait of emetic and non-emetic Bacillus cereus group members

The number of foodborne intoxications caused by emetic Bacillus cereus isolates has increased significantly. As such, rapid and reliable methods to identify emetic strains appear to be clinically relevant. In this study, intact cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to differentiate emetic and non-emetic bacilli. The phyloproteomic clustering of 34 B. cereus emetic and 88 non-emetic isolates classified as B. cereus, Bacillus thuringiensis, Bacillus weihenstephanensis, and Bacillus mycoides, showed (i) a clear separation of both groups at a similarity level of 43%, and (ii) a high relatedness among the emetic isolates (similarity of 78%). Specifically, 83 mass peak classes were recognized in the spectral window range between m/z 4000 and 12 000 that were tentatively assigned to 41 protein variants based on a bioinformatic approach. Mass variation between the emetic and the non-emetic subsets was recorded for 27 of them, including ten ribosomal subunit proteins, for which inter-strain polymorphism was confirmed by gene sequencing. Additional peaks were assigned to other proteins such as small acid soluble proteins, cold shock proteins and hypothetical proteins, e.g., carbohydrate kinase. Moreover, the results were supported by in silico analysis of the biomarkers in 259 members of B. cereus group, including Bacillus anthracis, based on their whole-genome sequences. In conclusion, the proteomic profiling by MALDI-TOF MS is a promising and rapid method for pre-screening B. cereus to identify medically relevant isolates and for epidemiologic purposes.

The worldwide distribution of genetically and phylogenetically diverse Bacillus cereus isolates harbouring Bacillus anthracis-like plasmids

Bacillus cereus is a close relative of B. anthracis, the causative agent of anthrax whose pathogenic determinants are located on pXO1 and pXO2 plasmids. Bacillus anthracis-like plasmids have been also noted among B. cereus, however, genetic features of B. cereus harbouring these elements remain largely undescribed, especially from the global perspective. Herein, we present the genetic polymorphism, population structure and phylogeny of B. cereus with pXO1-/pXO2-like plasmids originating from Argentina, Kazakhstan, Kenya and Poland. The plasmids were found in about 17% of the isolates, but their frequencies and expression of replicons differed within and between populations. In the multi-locus sequence typing, the bacteria exhibited high genetic polymorphism reflected by 116 sequencing types, including 84 singletons and 10 clonal complexes, which mainly consisted of isolates of the same origin. The phylogenetic analysis of pXO1-/pXO2-like positive B. cereus isolates revealed six independent clades; in certain clades individual populations predominated. Generally, B. cereus with pXO1-/pXO2-like plasmids did not indicate the genetic relationship with B. anthracis, and cannot be classified into an evolutionary independent anthrax line within the B. cereus group. Our report is of a crucial importance for discovering the genetic specificity and evolution of B. cereus bacilli.