Exposure to polystyrene nanoparticles leads to changes in the zeta potential of bacterial cells.

Polymer molecules, the main components of plastics, are an emerging pollutants in various environmental compartments (water, air, soil) that may induce several ecotoxicological effects on live organisms. Therefore, understanding how plastic particles interact with bacterial cell membranes is crucial in analysing their associated risks in ecosystems and human microbiota. However, relatively little is known about the interaction between nanoplastics and bacteria. The present work focuses on Staphylococcus aureus and Klebsiella pneumoniae, representing the Gram-positive and Gram-negative bacteria respectively, exposed to 100 nm diameter polystyrene nanoparticles (PS NPs). The nanoparticles attach to the cells' membranes of both bacteria, changing their electrical charge, but without the effect of killing the cells. PS NPs caused a change in zeta potential values (both species of bacterial strains), dependent on particle concentration, pH, as well as on exposure time of bacteria to them. Through the application of AFM and FTIR techniques, the presence of PS NPs on bacterial surfaces was detected, suggesting the affinity of the particles to bacterial components, but without any changes in the morphology of the tested bacteria. The zeta potential can be more widely used in the study of interactions between nanostructures and cells.

Chemical Composition and Antimicrobial Properties of Honey Bee Venom.

Due to its great medical and pharmaceutical importance, honey bee venom is considered to be well characterized both chemically and in terms of biomedical activity. However, this study shows that our knowledge of the composition and antimicrobial properties of Apis mellifera venom is incomplete. In this work, the composition of volatile and extractive components of dry and fresh bee venom (BV) was determined by GC-MS, as well as antimicrobial activity against seven types of pathogenic microorganisms. One-hundred and forty-nine organic C1-C19 compounds of different classes were found in the volatile secretions of the studied BV samples. One-hundred and fifty-two organic C2-C36 compounds were registered in ether extracts, and 201 compounds were identified in methanol extracts. More than half of these compounds are new to BV. In microbiological tests involving four species of pathogenic Gram-positive and two species of Gram-negative bacteria, as well as one species of pathogenic fungi, the values of the minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC) were determined for samples of dry BV, as well as ether and methanol extracts from it. Gram-positive bacteria show the greatest sensitivity to the action of all tested drugs. The minimum MIC values for Gram-positive bacteria in the range of 0.12-7.63 ng mL-1 were recorded for whole BV, while for the methanol extract they were 0.49-125 ng mL-1. The ether extracts had a weaker effect on the tested bacteria (MIC values 31.25-500 ng mL-1). Interestingly, Escherichia coli was more sensitive (MIC 7.63-500 ng mL-1) to the action of bee venom compared to Pseudomonas aeruginosa (MIC ≥ 500 ng mL-1). The results of the tests carried out indicate that the antimicrobial effect of BV is associated with the presence of not only peptides, such as melittin, but also low molecular weight metabolites.

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.

Tick-borne infections and co-infections in patients with non-specific symptoms in Poland.

AIM: The aim of the study was the evaluation of the frequency of infections and co-infections among patients hospitalized because of non-specific symptoms after a tick bite. MATERIALS AND METHODS: Whole blood, serum and cerebrospinal fluid samples from 118 patients hospitalised for non-specific symptoms up to 8 weeks after tick bite from 2010 to 2013 were examined for tick-borne infections. ELISA, Western blot and/or molecular biology (PCR; fla gene; 16S rRNA; sequencing) and thin blood smears (MDD) were used. Control group included 50 healthy blood donors. All controls were tested with PCR and serology according to the same procedure as in patients. RESULTS: Out of 118 patients 85 (72%) experienced headaches, 15 (13%) vertigo, 32 (27%) nausea, 17 (14%) vomiting, 37 (31%) muscle pain, 73 (62%) fever and 26 (22%) meningeal signs. 47.5% were infected with at least one tick-borne pathogen. Borrelia burgdorferi sensu lato infection was confirmed with ELISA, Western blot in serum and/or (PCR (fla gene) in whole blood in 29.7% cases. In blood of 11.9% patients Anaplasma phagocytophilum DNA (16S rRNA gene) was detected; in 0.9% patients 1/118 Babesia spp. DNA (18S rRNA gene) was also detected. Co-infections were observed in 5.1% of patients with non-specific symptoms. B. burgdorferi s.l. - A. phagocytophilum co-infection (5/118; 4.2%) was most common. In 1/118 (0.8%) A. phagocytophilum - Babesia spp. co-infection was detected. All controls were negative for examined pathogens. CONCLUSIONS: Non-specific symptoms after tick bite may be caused by uncommon pathogens or co-infection, therefore it should be considered in differential diagnosis after tick bite.

Infection with Babesia microti in humans with non-specific symptoms in North East Poland.

AIM: The aim of the study was to evaluate the clinical course and effectiveness of diagnostics tools for Babesia spp. infection in patients bitten by ticks. MATERIALS AND METHODS: Five hundred and forty-eight patients hospitalised or seen in outpatients department because of various symptoms after a tick bite were included in the study. PCR, nucleotide sequencing of Babesia 18S rRNA gene fragment, blood smears and serological tests for Babesia spp., TBEV, A. phagocytophilum and B. burgdorferi were performed in all patients. Six patients infected with Babesia were included in the final analysis. They had PCR, Babesia 18S rRNA gene fragment nucleotide sequencing, blood smears and serological tests for Babesia spp., TBEV, A. phagocytophilum and B. burgdorferi performed twice. RESULTS: Tick-borne infection with Babesia microti in six immunocompetent patients with non-specific symptoms was confirmed for the first time in Poland. No severe course of the disease was seen. No piroplasm forms were noticed within erythrocytes on blood smear. Three patients developed a serological response. CONCLUSIONS: Immunocompetent patients may be unaware of infection with Babesia microti after a tick bite. It must be included in the differential diagnosis after the tick bite. In patients with low parasitaemia PCR and serology seem useful when blood smear is negative. Self-elimination of Babesia spp. is possible, especially in cases with low parasitaemia.

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.