Pathogenicity Island Genes Research Articles

Roles of the components of the cag-pathogenicity island encoded type IV secretion system in Helicobacter pylori.

The Helicobacter pylori (H. pylori) cytotoxin-associated gene pathogenicity island (cagPAI) encodes 31 genes that assemble the cag type IV secretion system (T4SS) apparatus, which includes structures such as the outer membrane core complex, periplasmic ring, inner membrane complex and bacterial hairs. These proteins interact with each other to inject CagA into the host gastric epithelium. There are also individual unique functions that help H. pylori interfere with host cellular pathways, modulate the immune response and colonize the host for a long time. However, the functions of some of the proteins remain unclear. This review summarizes what is known about the structure and function of these auxiliary components and discusses their role in H. pylori pathogenesis.

Detection of Salmonella Pathogenicity Islands and Antimicrobial-Resistant Genes in Salmonella enterica Serovars Enteritidis and Typhimurium Isolated from Broiler Chickens.

Rapid growth in commercial poultry production is one of the major sources of Salmonella infections that leads to human salmonellosis. The two main Salmonella enterica serovars associated with human salmonellosis are enteritidis and typhimurium. The aim of this study was to determine the prevalence of S. enterica serovars Enteritidis and S. Typhimurium as well as their Salmonella pathogenicity islands (SPI) and antibiotic resistance profiles in broiler chicken feces from slaughterhouses. A total of 480 fecal samples from broiler chickens that were grouped into 96 pooled samples were identified to have Salmonella spp. using the invA gene, whilst the Spy and sdfI genes were used to screen for the presence of S. Enteritidis and S. Typhimurium serovars, respectively, by polymerase chain reaction (PCR) assays. The isolates were also screened for the presence of Salmonella pathogenicity islands (SPIs) using PCR. The disc diffusion assay was performed to determine the antibiotic resistance profiles of the isolates. A total of 36 isolates were confirmed as Salmonella spp. through amplification of the invA gene. Out of 36 confirmed Salmonella spp. a total of 22 isolates were classified as S. Enteritidis (n = 8) and were S. Typhimurium (n = 14) serovars. All (n = 22) S. Enteritidis and S. Typhimurium isolates possessed the hilA (SPI-1), ssrB (SPI-2) and pagC (SPI-11) pathogenicity islands genes. Amongst these serovars, 50% of the isolates (n = 11/22) were resistant to tetracycline and nalidixic acid. Only 22% of the isolates, S. Typhimurium (13.6%) and S. Enteritidis (9.1%) demonstrated resistance against three or more antibiotic classes. The most detected antibiotic resistance genes were tet(K), mcr-1, sulI and strA with 13 (59.1%), 9 (40.9%), 9 (40.9%) and 7 (31.8%), respectively. The findings of this study revealed that S. Typhimurium is the most prevalent serotype detected in chicken feces. To reduce the risk to human health posed by salmonellosis, a stringent public health and food safety policy is required.

Isolation and characterization of novel Staphylococcus aureus bacteriophage Hesat from dairy origin.

A novel temperate phage, named Hesat, was isolated by the incubation of a dairy strain of Staphylococcus aureus belonging to spa-type t127 with either bovine or ovine milk. Hesat represents a new species of temperate phage within the Phietavirus genus of the Azeredovirinae subfamily. Its genome has a length of 43,129 bp and a GC content of 35.11% and contains 75 predicted ORFs, some of which linked to virulence. This includes (i) a pathogenicity island (SaPln2), homologous to the type II toxin-antitoxin system PemK/MazF family toxin; (ii) a DUF3113 protein (gp30) that is putatively involved in the derepression of the global repressor Stl; and (iii) a cluster coding for a PVL. Genomic analysis of the host strain indicates Hesat is a resident prophage. Interestingly, its induction was obtained by exposing the bacterium to milk, while the conventional mitomycin C-based approach failed. The host range of phage Hesat appears to be broad, as it was able to lyse 24 out of 30 tested S. aureus isolates. Furthermore, when tested at high titer (108 PFU/ml), Hesat phage was also able to lyse a Staphylococcus muscae isolate, a coagulase-negative staphylococcal strain. KEY POINTS: • A new phage species was isolated from a Staphylococcus aureus bovine strain. • Pathogenicity island and PVL genes are encoded within phage genome. • The phage is active against most of S. aureus strains from both animal and human origins.

Transcriptional analysis of Helicobacter pylori cytotoxic-associated gene-pathogenicity islandin response to different pH levels and proton pump inhibitor exposure.

Long-term use of proton pump inhibitors (PPIs) can increase therisk of gastric cancer in Helicobacter pylori-infected patients; nevertheless, there is no data about their impact on the pathogenicity of H. pylori. This study aimed at investigating thetranscriptional alteration of key gene mediators of cytotoxin-associated gene-pathogenicity island (cag-PAI) among clinical H. pylori isolates in response to omeprazole at different pH levels. Accordingly, H. pylori isolates with the same virulence genotypes selected from the gastric biopsies of patients and transcriptional alteration in the cag-PAI genes studied in the presence or absence of omeprazole (2mg/mL) at pH 2.0, 4.0 and 7.0 after 30 and 90minutes of the treatment. Relative changes in the transcriptional levels were recorded in each assay, separately. Of 18 H. pylori isolates, the cag-PAI empty site was detected in four strains, while the presence of cagA, cagL and cagY was characterized in 77.7%, 83.3% and 83.3% of the cag-PAI-positive strains, respectively. Transcriptional analysis of the selected strains showed up-regulation of cagA and cagL, mainly at pH 2.0 and 4.0 after 30 and 90-minute exposure. A diversity in the expression levels of cag-PAI genes was seen among the strains at the extent and time of induction. Our results showed that omeprazole could increase the expression of H. pylori cagA and cagL at acidic pH. Heterogeneity among the strains probably has an impact on the extent of their interplay with PPIs. Further studies are needed to establish this correlation.

Examining the effect of Helicobacter pylori cagPAI variety on gene expression pattern related to gastric cancer.

We aimed to determine possible association between heterogeneity of Helicobacter pylori cytotoxin-associated gene pathogenicity island and gene expression profiles in patients with distinct histopathological changes. Gastric biopsies were obtained from seventy five patients. Microbiological and pathological examinations were done and intactness of Helicobacter pylori cagPAI was determined by PCR using 11 pairs of primers flanking cagζ-cagA regions and cagPAI empty site. Alterations at mRNA levels of eight genes were investigated by real-time PCR and their association with cagPAI intactness and histopathological changes examined statistically. A larger proportion of cagPAI positive strains colonized patients with SAG (52.4%), followed by CG (33.3%), and IM (14.3%). Intact cagPAI was found in 87.5% of the strains obtained from patients with SAG, while significantly lower frequency was detected among those with CG (12.5%) and IM (0%). No significant difference was found among thestudied histological groups and fold changes in gene expression of gastric biopsies of Helicobacter pylori infected patients with distinct cagPAI status. However, in each histological group, the strains with more complete gene cluster induced (ErbB2, CCNE1, CTNNB1, and MMP7 in SAG and IM groups) or reduced (TP53, in CG group) expression of the GC associated genes in relatively higher levels. APC, TP53 and E-cadherin were down-regulated in patients with SAG and IM compared with CG patients, irrespective to the status of cagPAI integrity. Helicobacter pylori strains that carry more complete cagPAI segment could induce remarkably higher levels of mRNA changes of GC associated genes in all histopathological groups.

Clinical Pathogenesis, Molecular Mechanisms of Gastric Cancer Development.

The human pathogen Helicobacter pylori is the strongest known risk factor for gastric disease and cancer, and gastric cancer remains a leading cause of cancer-related death across the globe. Carcinogenic mechanisms associated with H. pylori are multifactorial and are driven by bacterial virulence constituents, host immune responses, environmental factors such as iron and salt, and the microbiota. Infection with strains that harbor the cytotoxin-associated genes (cag) pathogenicity island, which encodes a type IV secretion system (T4SS) confer increased risk for developing more severe gastric diseases. Other important H. pylori virulence factors that augment disease progression include vacuolating cytotoxin A (VacA), specifically type s1m1 vacA alleles, serine protease HtrA, and the outer-membrane adhesins HopQ, BabA, SabA and OipA. Additional risk factors for gastric cancer include dietary factors such as diets that are high in salt or low in iron, H. pylori-induced perturbations of the gastric microbiome, host genetic polymorphisms, and infection with Epstein-Barr virus. This chapter discusses in detail host factors and how H. pylori virulence factors augment the risk of developing gastric cancer in human patients as well as how the Mongolian gerbil model has been used to define mechanisms of H. pylori-induced inflammation and cancer.

Serotypes, Antibiotic Resistance Genes, and Salmonella Pathogenicity Island Genes of Salmonella from Patients in a Hospital in Weifang, China

Background: Salmonella is an important foodborne pathogen that causes diarrhea in humans worldwide. Objectives: This study aimed to determine the serotype distribution, antibiotic-resistant genes, and Salmonella pathogenicity island (SPI) genes of clinical isolates of Salmonella in Weifang. Methods: A total of 111 Salmonella strains were collected from Weifang People’s Hospital between 2018 and 2020 and subjected to serotyping using the Kauffmann-White antigen table. Meanwhile, the polymerase chain reaction detected eleven SPI1-6 genes and six antibiotic resistance genes. Results: Among the 111 Salmonella strains, 17 serotypes were identified, with S. Typhimurium, S. Typhi, and S. Enteritidis being the most prevalent. The hilA, ssaB, sseC, marT, siiE, pipB, sopB, and pagN SPI1-6 genes were all found during analysis. The InvA, misL, and siiD genes were detected at 98.2, 97.30, and 97.30% rates, respectively. Also, sul2 and blaTEM were the most prevalent antibiotic resistance genes in this investigation, accounting for 68.47 and 21.62% of the total, respectively. Conclusions: Salmonella isolated from the clinical samples was found to have a diversity of serotypes and possessed various SPI and antibiotic resistance genes.

DNMT1 Gene Expression in Patients with Helicobacter pylori Infection.

DNMT1, as a critical enzyme affecting epigenetics through methylation of DNA cytosine-rich sequences, regulates gene expression. Exterior factors including long-term infections, in this study Helicobacter pylori infection, could change host cells' epigenetics by affecting DNMT1 gene expression. This study investigated the statistical correlation between H. pylori virulence genes and DNMT1 gene expression in gastric antral epithelial cells of gastric adenocarcinoma and gastritis patients. In a case-control study, 50 and 53 gastritis and gastric adenocarcinoma antral biopsies, including 23 and 21 patients with H. pylori infection, respectively, were collected from hospitals in the west of Iran. Having extracted total RNA from gastric biopsy samples, cDNA was synthesized and virulence genes of H. pylori were detected by using the PCR method. Relative real-time RT PCR was used to detect ΔΔCt fold changes of the DNMT1 gene expression in divided groups of patients based on H. pylori infection and clinical manifestations. The results showed that along with increasing patients' age, the DNMT1 gene expression will increase in gastric antral epithelial cells of gastric cancer patients (P ≤ 0.05). On the other hand, the biopsy samples with infection of H. pylori cagA, cagY, and cagE genotypes revealed a direct correlation along with increased DNMT1 gene expression. This study revealed the correlations of H. pylori cag pathogenicity island genes with increased DNMT1 gene expression.

Genotyping Helicobacter pylori and fgf7 gene expression in gastric cancer.

Helicobacter pylori as the causative agent of the most common chronic bacterial infectious disease in human still involves a range of clinical challenging complications. In this meantime, the survey of the interaction between H. pylori virulence genes expression and its consequences on gastric antral epithelial cells is Controversial. This study surveyed the correlations between H. pylori cag Pathogenicity Island and virulence factors genes with Fgf7 gene expression as an angiogenic factor in developing gastric cancer in gastric antral epithelial cells of patients with H. pylori infection. Gastric antral biopsy samples collected from patients out of exclusion criteria, including consumption of tobacco, alchohol and anti-H. pylori drugs, were categorized into gastric cancer (case group n:53) and gastritis (control group n:50) with and without H. pylori infection to detect changes in cDNA of fgf7 in gastric antral epithelial cells by using Real Time RT PCR. Extracted total RNA from gastric antral biopsy samples was used to synthesize cDNA for real time PCR. Furthermore, the cDNA of H. pylori cag Pathogenicity Island and other virulence factors genes were detected by using specific designed primers and simple PCR. Fgf7 gene expression revealed a significantly increase in gastric antral epithelial cells of gastric cancer and H. pylori-positive patients in contrast with gastritis and H. pylori-negative patients (p < 0.05). In the meanwhile, cag Pathogenicity Island and hopQ genotypes showed a positive correlation with Fgf7 gene expression (fold changes of cDNA) in gastric antral epithelial cells (p < 0.05). This study revealed an obvious correlation between Fgf7 gene expression in gastric antral epithelial cells of patients with H. pylori carcinogenic genotypes infection and some host factors including age.

Tannic Acid Inhibits Salmonella enterica Serovar Typhimurium Infection by Targeting the Type III Secretion System.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a zoonotic pathogen that can cause food poisoning and diarrhea in both humans and animals worldwide. The Salmonella pathogenicity island (SPI) genes encoded type III secretion system (T3SS) is important for S. Typhimurium invasion and replication in host cells. Due to the increasing problem of antibiotic resistance, antibiotic treatment for clinical Salmonella infection has gradually been limited. Anti-virulence inhibitors are a promising alternative to antibiotics because they do not easily induce bacterial antibiotic resistance. Here, we systematically evaluated the therapeutic effect of tannic acid (TA) on Salmonella-infected mice and elucidated its anti-infection mechanism. TA treatment improved the survival rate of S. Typhimurium-infected mice and alleviated cecum pathological lesions. In addition, TA inhibited S. Typhimurium invasion to HeLa cells without affecting their growth. Further studies showed that TA could inhibit the expression of sipA and sipB. This inhibition may be implemented by inhibiting the transcription of key regulatory and structural genes of the T3SS. This study provides an alternative anti-virulence strategy for Salmonella infection treatment.

Streptomyces rhizophilus Causes Potato Common Scab Disease.

Common scab (CS) caused by Streptomyces spp. is a significant soilborne potato disease that results in tremendous economic losses globally. Identification of CS-associated species of the genus Streptomyces can enhance understanding of the genetic variation of these bacterial species and is necessary for the control of this epidemic disease. The present study isolated Streptomyces strain 6-2-1(1) from scabby potatoes in Keshan County, Heilongjiang Province, China. PCR analysis confirmed that the strain harbored the characteristic Streptomyces pathogenicity island (PAI) genes (txtA, txtAB, nec1, and tomA). Pathogenicity assays proved that the strain caused typical scab lesions on potato tuber surfaces and necrosis on radish seedlings and potato slices. Subsequently, the strain was systemically characterized at morphological, physiological, biochemical, and phylogenetic levels. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 6-2-1(1) shared 99.86% sequence similarity with Streptomyces rhizophilus JR-41T, isolated initially from bamboo in rhizospheric soil in Korea. PCR amplification followed by Sanger sequencing of the 16S rRNA gene of 164 scabby potato samples collected in Heilongjiang Province from 2019 to 2020 demonstrated that approximately 2% of the tested samples were infected with S. rhizophilus. Taken together, these results demonstrate that S. rhizophilus is capable of causing potato CS disease and may pose a potential challenge to potato production in Heilongjiang Province of China.

In silico analysis of pathogenicity island and resistance genes carried by different Salmonella Typhimurium strains

Salmonella Typhimurium, dünyada en sık izole edilen Salmonella serotiplerinden birisidir. Tüm genom analizi gibi yeni moleküler yöntemlerin gelişmesi ile, antibiyotik direnci ve farklı genlerin karşılaştırmalı analizleri daha kolay yapılabilmektedir. Çalışmamızda farklı S. Typhimurium kökenlerine ait genomik verilerin, taşıdıkları patojenite adaları, MLST, seqserotipleri ve direnç genleri açısından karşılaştırmalı in silico analizini gerçekleştirmeyi amaçladık. Çalışmamıza genomik verileri NCBI’da yer alan 15 farklı S. Typhimurium kökenini dahil edildi. Kökenlerin birbirleri ile evrimsel olarak yakınlıkları CSI filogeni ile antimikrobiyal direnç belirteçlerinin varlığı ise ResFinder yazılımı ile gerçekleştirildi. Salmonella kökenlerine ait patojenite adaları, MLST ve serotip tespiti için sırasıyla SPIFinder, MLST ve SeqSero yazılımları kullanıldı. Çalışmamıza dahil edilen 15 S. Typhimurium kökeninin birbirlerine %97 ve üstünde genomik benzerlik gösterdikleri tespit edildi. MLST analizlerine göre 9 köken (%60) ST19 olarak bulundu. Tüm kökenlerin SPI-1, SPI-2, SPI-3, SPI-4, SPI-5, SPI-9, SPI-12, SPI-13, SPI-14 patojenite adalarını taşıdıkları gözlenirken, SGI1 patojenite adası sadece 3 kökende tespit edildi. Aminoglikozid direnci ile ilişkili aac(6')-Iaa geni tüm kökenlerde saptandı. Yeni nesil dizileme tekniklerinin gelişimi, S. Typhimurium gibi önemli enfeksiyon etkenlerine ait yeni moleküler epidemiyolojik veriler elde edilmesini sağlamaktadır. Bu verilerin karşılaştırmalı in silico analizleri ile enfeksiyonlarda kullandıkları virülans genlerinin analizleri ve moleküler patogenez mekanizmalarının aydınlatılması sağlanabilecektir.

Genotyping of Helicobacter pylori Virulence Genes cagA and vacA: Regional and National Study.

Helicobacter pylori (H. pylori) plays a crucial role in the pathogenesis of gastritis, peptic ulcer, and gastric cancer. The presence of pathogenicity islands (PAI) genes contributes to the pathogenesis of many gastrointestinal disorders. Cytotoxin-associated gene A (cagA) and vacuolating cytotoxin gene (vacA) are the most known virulence genes in H. pylori. So, our aim was to study H. pylori virulence genes' role in gastric disorders pathogenesis. Our study included 150 adult patients who suffered dyspeptic symptoms and were referred to the GIT endoscopy unit. Gastric biopsies were attained for rapid urease test (RUT) and histopathological examination, and multiplex PCR technique for detection of virulence genes was performed. It was found that 100 specimens were (RUT) positive, of which sixty samples (60%) were PCR positive for H. pylori ureC gene. The vacA and cagA genes were identified in 61.6% and 53% of H. pylori strains, respectively. Only 5 cases were vacA-positive and cagA-negative. The most virulent vacA s1 allele existed in 56.6% of cases. Out of the 60 H. pylori strains, 66% had at least one virulence gene and 34% did not show any virulence gene. H. pylori infection showed significant increase with age. H. pylori are prevalent amid dyspeptic patients in our region. The main genotype combinations were vacA+/cagA+ of s1m1 genotype and they were frequently associated with peptic ulcer diseases, gastritis, and gastroesophageal reflux disease.

Influence of genetic characteristics of Helicobacter pylori on pathomorphology of gastric mucosa in young persons with chronic gastritis

Objective. To evaluate the effect of the genetic characteristics of Helicobacter pylori on the nature of pathomorphological disorders in the gastric mucosa in chronic Hp-associated gastritis in young people.&#x0D; Material and methods. Forty-two adults (25 men and 17 women) aged 19 to 40 years with Hp-associated chronic gastritis were examined. The severity and activity of inflammation, as well as the presence of atrophy and intestinal metaplasia were determined in gastrobioptates. Genetic typing of Hp was performed for 16 pathogenicity factors of infect: CagA, CagM, CagT, CagH, CagC, CagF, CagE, VacAs1 and As2, IceA, Baba; HpaA; OipA, AlpB; UreB and UreI using polymerase chain reaction.&#x0D; Results. Pathogenic Hp strains were detected in 59.5 % of patients. Factors of adhesion HpaA (83.3 %), OipA (81 %), and AlpB (83.3 %) were identified with the highest frequency. In 57.1 % of cases, cytotoxin of the Cag group was detected, and 54.8 % of patients had a positive CagA-status. The VacA S1 allele was registered in 73.8 %, VacA S2 in 4.8 %, IceA in 38.1 %, and BabA in 45.2 % of cases. The presence of Hp strains in the gastric mucosa, which have three or more pathogenicity island genes, significantly increases the severity and activity of the inflammatory process, revealing signs of moderate atrophy of the digestive tract and intestinal metaplasia.&#x0D; Conclusions. Colonization of the gastric mucosa in young patients with Hp-associated chronic gastritis by highly pathogenic Hp strains leads to severe violations of its morphology.

BlastFrost: fast querying of 100,000s of bacterial genomes in Bifrost graphs

BlastFrost is a highly efficient method for querying 100,000s of genome assemblies, building on Bifrost, a dynamic data structure for compacted and colored de Bruijn graphs. BlastFrost queries a Bifrost data structure for sequences of interest and extracts local subgraphs, enabling the identification of the presence or absence of individual genes or single nucleotide sequence variants. We show two examples using Salmonella genomes: finding within minutes the presence of genes in the SPI-2 pathogenicity island in a collection of 926 genomes and identifying single nucleotide polymorphisms associated with fluoroquinolone resistance in three genes among 190,209 genomes. BlastFrost is available at https://github.com/nluhmann/BlastFrost/tree/master/data.

Anti-Listeria monocytogenes biofilm mechanism of cold nitrogen plasma

In this study, the anti-L monocytogenes biofilm mechanism of cold nitrogen plasma (CNP) treatment by the generation of reactive oxygen species (ROS) and the changes of gene expression were explored. The treatment of L. monocytogenes (EDG-e, cultured in peptone yeast glucose) biofilm by CNP (600 W, for 220 s, at a gas flow rate of 100 SCCM) led to intracellular oxidative stress where ROS contents increased to 15.38% and the CNP-generated hydroxyl free radicals increased. It also indicated that CNP could activate the environmental response factor (σB) and the expression of sigB was increased by 3.43 times. Real-time PCR revealed that CNP treatment could inhibit the transcription levels of quorum sensing-related genes (agrA, agrB, agrC, agrD, pfs and luxS) and the two pathogenicity island genes (prfA, plcA, hly, actA, plcB, inlA and inlB) in L. monocytogenes. Finally, the application of CNP on cantaloupe preservation indicated that CNP can eliminate the biofilm of L. monocytogenes (approximately 108 CFU/cm2) on cantaloupe by 2–3 log CFU/cm2, thus CNP was proved as a feasible technology to reduce the risk of L. monocytogenes contamination on cantaloupe without affecting the peel color.

Structural Basis for Virulence Activation of Francisella tularensis

The bacterium Francisella tularensis (Ft) is one of the most infectious agents known. Ft virulence is controlled by a unique combination of transcription regulators: the MglA-SspA heterodimer, PigR, and the stress signal, ppGpp. MglA-SspA assembles with the σ70-associated RNAP holoenzyme (RNAPσ70), forming a virulence-specialized polymerase. These factors activate Francisella pathogenicity island (FPI) gene expression, which is required for virulence, but the mechanism is unknown. Here we report FtRNAPσ70-promoter-DNA, FtRNAPσ70-(MglA-SspA)-promoter DNA, and FtRNAPσ70-(MglA-SspA)-ppGpp-PigR-promoter DNA cryo-EM structures. Structural and genetic analyses show MglA-SspA facilitates σ70 binding to DNA to regulate virulence and virulence-enhancing genes. Our Escherichia coli RNAPσ70-homodimeric EcSspA structure suggests this is a general SspA-transcription regulation mechanism. Strikingly, our FtRNAPσ70-(MglA-SspA)-ppGpp-PigR-DNA structure reveals ppGpp binding to MglA-SspA tethers PigR to promoters. PigR in turn recruits FtRNAP αCTDs to DNA UP elements. Thus, these studies unveil a unique mechanism for Ft pathogenesis involving a virulence-specialized RNAP that employs two (MglA-SspA)-based strategies to activate virulence genes.

Integrative and Conjugative Elements of Helicobacter pylori Are Hypothetical Virulence Factors Associated With Gastric Cancer.

Helicobacter pylori is a bacteria with high genome plasticity that has been associated with diverse gastric pathologies. The genetic diversity of this bacteria has limited the characterization of virulence factors associated with gastric cancer (GC). To identify potentially helpful disease biomarkers, we compared 38 complete genomes and 108 draft genomes of H. pylori isolated worldwide from patients with diverse gastric pathologies and 53 draft genomes of H. pylori isolated from Mexican patients with GC, intestinal metaplasia, gastritis, peptic ulcer, and dyspepsia. H. pylori strains isolated from GC were 3–11 times more likely to harbor any of seven genes encoded within an integrative and conjugative element (ICE) than H. pylori isolated from subjects with other gastric pathologies. We tested the cytopathic effects on AGS cells of selected H. pylori strains with known cytotoxin-associated gene pathogenicity island (cag-PAI) and ICE status (H. pylori strains 29CaP, 29CaCe, 62A9, 7C, 8822, and 26695) and the histopathological damage of H. pylori 29CaP and 62A9 in a mouse model. H. pylori 29CaP, which harbors a complete ICEHptfs3 but lacks cag-PAI, elicited distinctive morphology changes and higher histopathological scores compared with other H. pylori strains carrying cag-PAI and hybrid ICE with incomplete TFSS. The presence of intact segments of ICE regions might be a risk factor to develop GC that needs to be addressed in future studies.

Some aspects of development of typhoid fever and persistent brucellosis infection

Bacterial vacuolated intracellular parasites, such as Salmonella spp. and Brucella spp., possess the ability to cause persistent, long-life chronic infection during which the microbe continues to replicate inside the host organism in spite of the development of an immune response. Such bacteria develop a strategy to evade the immune response, which plays a key role in the development of chronic infection. The implementation of this strategy is aimed at inhibiting the action of factors of innate immunity. In brucella, this process is mediated by the noncanonical structure of lipopolysaccharide (LPS), as a result of which the pathogen is not recognized by the cells of innate immunity, as well as by the functioning of T4CC, the effector proteins of which block the development of the inflammatory response. The strategy of S. Typhi is realized via the expression of genes of pathogenicity island 7 encoding Vi-antigen and genotoxin. Vi-antigen inhibits recognition of the microbe by cells of the innate immune system. Typhoid genotoxin causes the death of immune cells. Brucella realizes this strategy via the noncanonical structure of LPS and T4SS, effector proteins of which block the development of inflammation. Alternative activated macrophages appear during chronic infection caused by both pathogens. These microbes are able to regulate the metabolism of macrophages according to their needs while persisting in them. A review of the sources of information on this problem allows us to conclude that both the causative agent of typhoid fever S. Typhi and the causative agents of brucellosis use the same strategies for the development of a chronic infectious process, but the implementation of these strategies is carried out specifically.

Identification of Pathogenicity Island Genes Associated with Loss of Type IV Secretion Function during Murine Infection with Helicobacter pylori.

Chronic Helicobacter pylori colonization in animal models often leads to downregulation of the type IV secretion system (T4SS), typically by recombination in cagY, which is an essential T4SS gene. However, 17 other cag pathogenicity island (cagPAI) genes, as well as some non-cagPAI genes, are also essential for T4SS function. To get a more complete picture of how H. pylori regulates the T4SS during animal colonization, we examined cagY in 534 mouse-passaged isolates that lost T4SS function, defined as a normalized interleukin-8 (IL-8) value of <0.3 relative to the input H. pylori strain PMSS1. In order to analyze the genetic changes in the strains with unchanged cagY, we sequenced the entire pathogenicity island of 60 such isolates using single-molecule, real-time (SMRT) sequencing technology (PacBio, Menlo Park, CA), and we compared the results to the PMSS1 wild type (WT). Of the 534 strains, 271 (51%) showed evidence of recombination in cagY, but we also found indels or nonsynonymous changes in 13 other essential cagPAI genes implicated in H. pylori T4SS function, most commonly cag5, cag10, and cagA While cagY recombination is the most common mechanism by which H. pylori downregulates T4SS function during murine infection, loss of function is also associated with changes in other essential cagPAI genes.