Mechanistic research:Selenium regulates virulence factors,reducing adhesion ability and inflammatory damage of Helicobacter pylori

BACKGROUND The pathogenicity of Helicobacter pylori is dependent on factors including the environment and the host.Although selenium is closely related to pathogenicity as an environmental factor,the specific correlation between them remains unclear.AIM To investigate how selenium acts on virulence factors and reduces their toxicity.METHODS H.pylori strains were induced by sodium selenite.The expression of cytotoxin-associated protein A(CagA)and vacuolating cytotoxin gene A(VacA)was determined by quantitative PCR and Western blotting.Transcriptomics was used to analyze CagA,CagM,CagE,Cag1,Cag3,and CagT.C57BL/6A mice were infected with the attenuated strains subjected to sodium selenite induction,and H.pylori colonization,inflammatory reactions,and the cell adhesion ability of H.pylori were assessed.RESULTS CagA and VacA expression was upregulated at first and then downregulated in the H.pylori strains after sodium selenite treatment.Their expression was significantly and steadily downregulated after the 5th cycle(10 d).Transcriptome analysis revealed that sodium selenite altered the levels affect H.pylori virulence factors such as CagA,CagM,CagE,Cag1,Cag3,and CagT.Of these factors,CagM and CagE expression was continuously downregulated and further downregulated after 2 h of induction with sodium selenite.Moreover,CagT expression was upregulated before the 3rd cycle(6 d)and significantly downregulated after the 5th cycle.Cag1 and Cag3 expression was upregulated and downregulated,respectively,but no significant change was observed by the 5th cycle.C57BL/6A mice were infected with the attenuated strains subjected to sodium selenite induction.The extent of H.pylori colonization in the stomach increased;however,sodium selenite also induced a mild inflammatory reaction in the gastric mucosa of H.pylori-infected mice,and the cell adhesion ability of H.pylori was significantly weakened.CONCLUSION These results demonstrate that H.pylori displayed virulence attenuation after the 10th d of sodium selenite treatment.Sodium selenite is a low toxicity compound with strong stability that can reduce the cell adhesion ability of H.pylori,thus mitigating the inflammatory damage to the gastric mucosa.

Role of nickel-regulated small RNA in modulation of Helicobacter pylori virulence factors

Helicobacter pylori(H.pylori)is a Gram-negative bacterium that infects about half of the world's population.H.pylori infection prevails by several mechanisms of adaptation of the bacteria and by its virulence factors including the cytotoxin associated antigen A(CagA).CagA is an oncoprotein that is the protagonist of gastric carcinogenesis associated with prolonged H.pylori infection.In this sense,small regulatory RNAs(sRNAs)are important macromolecules capable of inhibiting and activating gene expression.This function allows sRNAs to act in adjusting to unstable environmental conditions and in responding to cellular stresses in bacterial infections.Recent discoveries have shown that nickelregulated small RNA(NikS)is a post-transcriptional regulator of virulence properties of H.pylori,including the oncoprotein CagA.Notably,high concentrations of nickel cause the reduction of NikS expression and consequently this increases the levels of CagA.In addition,NikS expression appears to be lower in clinical isolates from patients with gastric cancer when compared to patients without.With that in mind,this minireview approaches,in an accessible way,the most important and current aspects about the role of NikS in the control of virulence factors of H.pylori and the potential clinical repercussions of this modulation.

Structural Changes of Lignified Tissues from Sugarcane Leaves Induced by Smut （Sporisorium scitamineum） Virulence Factors

Sugarcane leaf shows the classical arrangement of cells, which defines a C4 species. Vascular bundles consist of xylem, phloem and fibres, surrounded by an outer layer ofsclereids and an inner ring of stone cells associated with the phloem. Some sclereids located below and above the vascular bundles act as docking cells and connect the vascular bundle to the internal surfaces of upper and lower layers of the epidermis. A compact mass ofsclereids occupies the total internal volume of the leaf edge. Neither docking cells nor the internal mass of sclereids in the edge were markedly coloured by phloroglucinol, indicating the absence of lignin in their cell walls. However, such staining indicated that fibres of the vascular bundle and the external layer of sclereids were strongly lignified. Incubation of leaf discs with an virulence factors produced by the pathogen Sporisorium scitamineum increased the thickness of the lignified cell walls of sclereids as well as the mid and small xylem vessels, as a possible mechanical defence response to the potential entry of the pathogen. This mechanism was mainly revealed for the resistant cv. Mayari 55-14, whereas lignification decreased for the susceptible cv. B 42231.

Characterization of Virulence Factors in Enteroaggregative and Atypical Enteropathogenic Escherichia coli Strains Isolated from Children with Diarrhea

Enteroaggregative (EAEC) and atypical enteropathogenic (EPEC) Escherichia coli are important bacterial etiologic agents causing diarrhea among children. The aim of the present study was to examine the impact of virulence factors predisposes to diarrhea. In this study some virulence properties were examined on 11 EAEC and 8 EPEC strains identified by Polymerase Chain Reaction (PCR), isolated from stool samples of children were analyzed genotypically and phenoltypically for the prevalence of virulence factors. The most frequently detected factor was resistance to serum (94%), followed by curli fimbriae (78%), biofilm production (73%), and gene coding for Extended-Spectrum Beta-Lactamase (ESBL) (68%). EPEC isolates showed at least three of the evaluated properties, while EAEC isolates showed at least two. The prevalence of these virulence factors between the two strains showed no statistical difference. This study showed the heterogeneity of the virulence profile of the isolates of EAEC and atypical EPEC strains and suggests that this diversity may influence in the disease severity.

New insights of Helicobacter pylori host-pathogen interactions: The triangle of virulence factors, epigenetic modifications and non-coding RNAs

Helicobacter pylori(H. pylori) is a model organism for understanding host-pathogen interactions and infection-mediated carcinogenesis. Gastric cancer and H. pylori colonization indicates the strong correlation. The progression and exacerbation of H. pylori infection are influenced by some factors of pathogen and host. Several virulence factors involved in the proper adherence and attenuation of immune defense to contribute the risk of emerging gastric cancer, therefore analysis of them is very important. H. pylori also modulates inflammatory and autophagy process to intensify its pathogenicity. From the host regard, different genetic factors particularly affect the development of gastric cancer. Indeed, epigenetic modifications, Micro RNA and long non-coding RNA received more attention. Generally, various factors related to pathogen and host that modulate gastric cancer development in response to H. pylori need more attention due to develop an efficacious therapeutic intervention. Therefore, this paper will present a brief overview of host-pathogen interaction especially emphases on bacterial virulence factors, interruption of host cellular signaling, the role of epigenetic modifications and non-coding RNAs.

Virulence factors of Enterococcus strains isolated from patients with inflammatory bowel disease

AIM: To determine the features of Enterococcus that contribute to the development and maintenance of the inflammatory process in patients with inflammatory bowel disease (IBD). METHODS: Multiplex polymerase chain reaction (PCR) was applied to assess the presence of genes that encode virulence factors [surface aggregating protein (asa1), gelatinase (gelE), cytolysin (cylA), extracellular surface protein (esp) and hyaluronidase (hyl)] in the genomic DNA of 28 strains of Enterococcus isolated from the intestinal tissues of children with IBD (n =16) and of children without IBD (controls; n = 12). Additionally, strains with confirmed presence of the gelE gene were tested by PCR for the presence of quorum sensing genes (fsrA, fsrB, fsrC) that control the gelatinase production. Gelatinase activity was tested on agar plates containing 1.6% gelatin. We also analysed the ability of Enterococcus strains to release and decompose hydrogen peroxide (using Analytical Merckoquant peroxide test strips) and tested their ability to adhere to Caco-2 human gut epithelium cells and form biofilms in vitro. RESULTS: A comparison of the genomes of Enterococcus strains isolated from the inflamed mucosa of patients with IBD with those of the control group showed statistically significant differences in the frequency of theasa1 gene and thegelE gene. Furthermore, the cumulative occurrence of different virulence genes in the genome of a single strain ofEnterococcus isolated from the IBD patient group is greater than in a strain from the control group, although no significant difference was found. Statistically significant differences in the decomposition of hydrogen peroxide and adherence to the Caco-2 epithelial cell line between the strains from the patient group and control group were demonstrated. The results also showed that profuse biofilm production was more frequent amongEnterococcus strains isolated from children with IBD than in control strains. CONCLUSION: Enterococcus strains that adhere strongly to the intestinal epithelium, form biofilms and possess antioxidant defence mechanisms seem to have the greatest influence on the inflammatory process.

Role of polymorphisms in genes that encode cytokines and Helicobacter pylori virulence factors in gastric carcinogenesis

The Helicobacter pylori(H. pylori) infection is a determinant factor in gastric cancer(GC) development. However, the infection outcomes are variable and depend on both host and bacterial characteristics. Some host cytokines such as interleukin(IL)-1β, IL-1 Ra, IL-8, IL-10 and tumor necrosis factor-α play important roles in the host immune system response to the pathogen, in the development of gastric mucosal lesions and in cell malignant transformation. Therefore, these host factors are crucial in neoplastic processes. Certain polymorphisms in genes that encode these cytokines have been associated with an increased risk of GC. On the other hand, various virulence factors found in distinct H. pylori bacterial strains, including cytotoxinassociated antigen A, vacuolating cytotoxin, duodenal ulcer promoting gene A protein, outer inflammatory protein and blood group antigen binding adhesin, have been associated with the pathogenesis of different gastric diseases. The virulent factors mentioned above allow the successful infection by the bacterium and play crucial roles in gastric mucosa lesions, including malignant transformation. Moreover, the role of host polymorphisms and bacterial virulence factors in gastric carcinogenesis seems to vary among different countries and populations. The identification of host and bacterium factors that are associated with an increased risk of GC development may be useful in determining the prognosis of infection in patients, what could help in clinical decision-making and in providing of an optimized clinical approach.

Can bacterial virulence factors predict antibiotic resistant Helicobacter pylori infection?

AIM To evaluate the association between virulence factor status and antibiotic resistance in Helicobacter pylori(H. pylori)-infected patients in Ireland. METHODS DNA was extracted from antral and corpus biopsies obtained from 165 H. pylori-infected patients. Genotyping for clarithromycin and fluoroquinolone-mediating mutations was performed using the Genotype Helico DR assay. cag A and vac A genotypes were investigated using PCR. RESULTS Primary, secondary and overall resistance rates for clarithromycin were 50.5%(n = 53/105), 78.3%(n = 47/60) and 60.6%(n = 100/165), respectively. Primary, secondary and overall resistance rates for fluoroquinolones were 15.2%(n = 16/105) and 28.3%(n = 17/60) and 20%(n = 33/165), respectively. Resistance to both antibiotics was 12.4%(n = 13/105) in treatment-na?ve patients, 25%(n = 15/60) in those previously treated and 17%(n = 28/165) overall. A cag A-positive genotype was detected in 22.4%(n = 37/165) of patient samples. The dominant vac A genotype was S1/M2 at 44.8%(n = 74/165), followed by S2/M2 at 26.7%(n = 44/165), S1/M1 at 23.6%(n = 39/165) and S2/M1 at 4.8%(n = 8/165). Primary clarithromycin resistance was significantly lower in cag A-positive strains than in cag A-negative strains [32%(n = 8/25) vs 56.3%(n = 45/80); P = 0.03]. Similarly, in patients infected with more virulent H. pylori strains bearing the vac A s1 genotype, primary clarithromycin resistance was significantly lower than in those infected with less virulent strains bearing the vac A s2 genotype, [41%(n = 32/78) vs 77.8%(n = 21/27); P = 0.0001]. No statistically significant association was found between primary fluoroquinolone resistance and virulence factor status.CONCLUSION Genotypic H. pylori clarithromycin resistance is high and cag A-negative strains are dominant in our population. Less virulent(cag A-negative and vac A S2-containing) strains of H. pylori are associated with primary clarithromycin resistance.

<i>In Vitro</i>Mitigation of Pathogenic Bacteria and Virulence Factors Using a Hydroconductive Dressing

Wound infections can have devastating effects on healing as well as the health of the patient. Complications increase when the pathogens are capable of producing virulence factors and/or are drug resistant. Novel methods are needed to take on the challenges of treating such wounds. Drawtex&reg;?dressing is purported to have hydroconductive properties that allow it to draw away debris and exudate from the wound into the dressing. The goal of this work is to better define these interactions of this experimental dressing with bacteria and virulence factors. Two series of in vitro experiments were performed. First, pieces of experimental dressing were submerged in a series of cultures in flasks and samples of the dressing and cultures were taken over 90 minutes and assayed for bacteria and virulence factor levels. Second, experimental or standard care (control) dressings were placed on selective agar plated with pathogens of interest. Dressings and the agar covered by them were used to quantify bacteria and virulence factors over time. The experimental dressing took up both bacteria and virulence factors to a larger extent than the control dressing. Experimental dressing significantly reduced the load of bacteria and virulence factors in cultures compared to control culture without dressing. Based on the ability of the dressing to take up bacteria and virulence factors in this study, the data point to the potential for this dressing to be similarly effective in reducing or eliminating pathogen from wounds, potentially increasing the chances of successful wound healing.

N-Acylhomoserine Lactones (AHLs), QseB/C Gene Detection, Virulence Factors and Antibiotics Resistance of <i>Aeromonas hydrophila</i>

The aim of this research was to detect the N-acyl homoserine lactones (AHLs) production and QseB/C gene of Aeromonas hydrophila. We analyzed the potentials of these isolates of Aeromonas hydrophila in causing biofilm formation, hemolysis, protease, and lipase. The antibiotic susceptibility of the 15 Aeromonas hydrophila isolates was also investigated. The detection of AHLs was carried out using the Chromobacterium violaceum strain CV026 as biosensors. The isolated strains were tested for the reaction of C. violaceum CV026 by cross-streaking on an agar plate. Production of AHLs was determined by the diffusing via the agar plates and the tinge of the biosensor strains. All isolated strains produced AHLs. A polymerase chain reaction (PCR) showed the isolated strains had qseB and qseC genes. Susceptibility tests of A. hydrophila isolates were administered against 25 different antibiotic disks representing 12 classes of antibiotics. The strains were highly resistant to β-Lactam with 96.7% showing resistibility, whereas 97.7% susceptibility was found towards Aminoglycoside class of the antibiotic used. 60% showed intermediate resistant to Polypeptide. 100% of the strains showed no resistant to Aminoglycoside, Polypeptide, Monobactam, and Carbapenems class of antibiotics. Each of the isolates was found to be associated with at least one virulent factor. Our results clearly demonstrated that there is a presence of QseB/C genes in A. hydrophila and also produces AHLs molecule and virulence factors. The investigated isolates showed the pathogenic potential of Aeromonas hydrophila which makes it a serious threat to public health.

A Survey of <i>Escherichia coli</i>O157:H7 Virulence Factors: The First 25 Years and 13 Genomes

Escherichia coli O157:H7 is a human pathogen that was first identified from a foodborne outbreak in 1982, and in the 25 years that followed, many new strains were identified and emerged in numerous outbreaks of human disease. Extensive research has been conducted to identify virulence factor genes involved in the pathogenesis of E. coli O157:H7 and many genome sequences of E. coli O157:H7 strains have become available to the scientific community. Here, we provide a comprehensive overview of the research that has been conducted over the first 25 years to identify 394 known or putative virulence factor genes present in the genomes of E. coli O157:H7 strains. Finally, an examination of the conservation of these 394 virulence factor genes across additional genomes of E. coli O157:H7 is provided which summarizes the first 25 years and 13 genomes of this human pathogen.

Virulence Factors in Methicillin-Resistant Staphylococcus aureus Isolated from ICU Units in Brazil

Species of Staphylococcus are common in hospital infection (HI). Methicillin resistant S. aureus (MRSA) has also become a serious problem in Brazilian HI. The aim of this study was to characterize the pathogenicity of methicillin-resistant S. aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) isolated in public hospitals. The clinical isolates were obtained from intensive care unit. The MRSA and MSSA strains were genotyped by PCR for detection genes related to virulence factors. Moreover, the strains were tested for biofilm formation and cytokine induction in macrophages. Three strains of MRSA (9.68%) expressed the Sea gene, one (3.23%) Seb, 17 (54.84%) Spa and seven (22.58%) had PVL. Two MSSA strains (2.98%) expressed the Sea gene, three (4.48%) Seb, 18 (26.87%) Spa and 11 (16.42%) showed positive results for the PVL gene. There was no expression of Sec and CflA between MRSA and MSSA strains. Among MRSA and MSSA isolates, none statistical differences were observed in biofilm production. The analysis of cytokine induction in the inflammatory response of J774 macrophages by MRSA and MSSA isolates did not show statistical difference. Understanding the mechanisms of pathogenesis of S. aureus could provide important clues for both preventing and treating infection caused by these organisms.

Understanding carbapenem-resistant hypervirulent Klebsiella pneumoniae:Key virulence factors and evolutionary convergence

The emergence of hypervirulence(hv)and carbapenem resistance(CR)as distinct evolutionary directions for Klebsiella pneumoniae presents a significant threat in clinical settings.However,in recent years,there has been a growing identification of K.pneumoniae strains that integrate both phenotypes,resulting in severe clinical outcomes.Carbapenemresistant hypervirulent K.pneumoniae(CRhvKP)typically emerges through the acquisition of plasmids carrying either virulence or CR-encoded genes by carbapenem-resistant K.pneumoniae or hypervirulent K.pneumoniae.Furthermore,the acquisition of a hybrid plasmid can confer a combination of CR and hv.CRhvKP can cause a variety of infections,including pneumonia,urinary tract infections,bloodstream infections,liver abscesses,and other related conditions.While the sequence type 11(ST11)dominates the majority of CRhvKP strains in China,the molecular factors responsible for the success of ST11 CRhvKP largely remain unknown.Here,we provide an overview of the current understanding of the variation and distribution of crucial virulence determinants,the mechanisms driving the merging of hv and CR,and the potential molecular factors influencing the epidemiological success of ST11 CRhvKP.This research aims to contribute to a comprehensive understanding of the complexities surrounding CRhvKP.It is imperative to underscore the development of combination therapies,precision medicine,and vaccine strategies as pivotal approaches in effectively combating CRhvKP.Considering the widespread prevalence of CRhvKP,a prioritized,multifaceted approach encompassing infection control,active surveillance,and the development of innovative therapeutics is essential.

Epilithic biofilm as a reservoir for functional virulence factors in wastewater-dominant rivers after WWTP upgrade

Virulence factors(VFs)confer upon pathogens the ability to cause various types of damage or diseases.Wastewater treatment plants(WWTPs)are important point sources for the emission of pathogens and VFs into receiving rivers.Conventional WWTP upgrades are often implemented to improve the water quality of receiving ecosystems.However,knowledge on the pathogens,VFs,and health risks to receiving aquatic ecosystems after upgrade remains limited.In this study,we investigated detailed pathogenic information,including taxa,pathogenicity,and health risk,in two wastewater-dominant rivers after WWTP upgrade.Using 16S rRNA gene sequencing,we screened 14 potential pathogens in water and epilithic biofilm samples,though they were significantly more enriched in the biofilms.Combining 16S rRNA and metagenomic sequencing data,we identified Pseudomonas and Aeromonas as the dominant pathogenic taxa carrying functional VFs(e.g.,mobility and offensive)in the epilithic biofilm.Moreover,strong pathogen-specific VF-host co-occurrence events were observed in the epilithic biofilm samples,indicating the importance of biofilms as reservoirs and vehicles for VFs.Further,we demonstrated that mobility VF is crucial for biofilm formation and pathogens in biofilm carrying offensive VF may be highly invasive.Quantification and health risk assessment suggested that the skin contact risk of P.aeruginosa carrying VFs was higher than the acceptable probability of 10^(-4)in both water and epilithic biofilm samples,which may threaten ecological and human health.

Two-component signal transduction systems and regulation of virulence factors in Xanthomonas: a perspective

Two-component signal transduction systems(TCSTSs),consisting of a histidine kinase and a response regulator,play a critical role in regulating virulence gene expression in Gram-negative phytopathogenic bacteria Xanthomonas spp..To date,12 TCSTS genes have been identified,accounting for approximately 10%of the TCSTS genes in each genome that have been experimen-tally identified to be related to pathogenesis.These TCSTSs modulate the expression of a number of virulence factors through diverse molecular mechanisms such as interacting with DNA,protein-binding and involvement in second messenger metabolism,which generates a high level of regulatory versatility.Here we summarize the current knowledge in thisfield and discuss the emerging themes and remaining questions that are important in deciphering the signaling network of TCSTSs in Xantho-monas.

Helicobacter pylori's virulence and infection persistence define pre-eclampsia complicated by fetal growth retardation

AIM: To better understand the pathogenic role of Helicobacter pylori (H. pylori) in pre-eclampsia (PE), and whether it is associated or not with fetal growth retardation (FGR). METHODS: Maternal blood samples were collected from 62 consecutive pregnant women with a diagnosis of PE and/or FGR, and from 49 women with uneventful pregnancies (controls). Serum samples were evaluated by immunoblot assay for presence of specific antibodies against H. pylori antigens [virulence: cytotoxin-associated antigen A (CagA); ureases; heat shock protein B; flagellin A; persistence: vacuolating cytotoxin A (VacA)]. Maternal complete blood count and liver enzymes levels were assessed at delivery by an automated analyzer. RESULTS: A significantly higher percentage of H. pyloriseropositive women were found among PE cases (85.7%) compared to controls (42.9%, P < 0.001). There were no differences between pregnancies complicated by FGR without maternal hypertension (46.2%) and controls. Importantly, persistent and virulent infections (VacA/ CagA seropositive patients, intermediate leukocyte blood count and aspartate aminotransferase levels) were exclusively associated with pre-eclampsia complicated by FGR, while virulent but acute infections (CagA positive/ VacA negative patients, highest leukocyte blood count and aspartate aminotransferase levels) specifically correlated with PE without FGR. CONCLUSION: Our data strongly indicate that persistent and virulent H. pylori infections cause or contribute to PE complicated by FGR, but not to PE without feto-placental compromise.

鼠伤寒沙门氏菌群体感应干扰策略研究进展

鼠伤寒沙门氏菌(Salmonella enterica serovar Typhimurium)作为常见的食源性致病菌,由于其耐药性问题而严重危害公共健康。研究表明干扰致病菌的群体感应(quorum sensing,QS)系统是解决其耐药性问题的有效方案之一。QS是细胞间的一种通讯机制,涉及多种代谢活动,例如生物被膜形成、运动性、毒力因子、黏附和侵袭等过程。为了系统地总结鼠伤寒沙门氏菌的群体感应及其相应的干扰策略,该文首先介绍了S.Typhimurium包含的N-高丝氨酸内酯类、2型自诱导分子、3型自诱导分子、吲哚和扩散信号分子等介导的5种QS系统。然后从信号分子合成、胞外运输及反应、与受体蛋白相互作用3方面总结了对不同QS系统的抑制和促进策略。指出了未来QS干扰策略的开发应更多立足于多靶点和多层次的系统网络,以期为解决沙门氏菌耐药性开辟新的思路。

Food Safety Risks and Contributing Factors of Cronobacter spp.

Cronobacter species are a group of Gram-negative opportunistic pathogens,which cause meningitis,sep-ticemia,and necrotizing enterocolitis in neonates and infants,with neurological sequelae in severe cases.Interest in Cronobacter has increased significantly in recent years due to its high virulence in children.In this review,we summarize the current understanding of the prevalence of Cronobacter species in several important food types.We discuss the response mechanisms enabling persistence in adverse growth con-ditions,as well as its pathogenicity.We emphasize the food safety concerns caused by Cronobacter and subsequent control methods and clinical treatments.

环境中抗生素抗性基因的健康风险分级

细菌耐药性的快速传播和蔓延是全球公共健康领域的重大挑战。除了医疗和动物养殖业外,抗生素抗性基因可在多种环境介质中传播扩散进而转移到人类病原菌中,影响人类健康。甄别环境中高风险抗性基因是实现抗性基因有效环境监测和风险评估的基础。对环境中抗性基因的研究现状进行了总结,聚焦质粒携带的抗性基因,提出了环境中抗性基因风险分级框架,进而对制药厂和养殖厂场地环境样品进行了质粒组分析,形成了风险分级清单。结果表明,按抗性基因的移动性(与可移动遗传元件共存)、质粒类型、在人类病原菌中的流行度、致病潜力(与毒力因子共存)等4个标准,从制药厂和养殖厂场地环境样品中共检测到425个质粒携带的抗性基因,其中最高风险Ⅰ级抗性基因0种,Ⅱ级2种,Ⅲ级33种,Ⅳ级89种,最低风险Ⅴ级301种,形成了制药厂和养殖厂场地环境抗性基因风险分级清单。所检测到的高风险抗性基因,为环境抗性基因污染监测及人群暴露健康风险评估提供了理论和数据支撑。