In Silico Signature Prediction Modeling in Cytolethal Distending Toxin-Producing Escherichia coli Strains

In this study, cytolethal distending toxin (CDT) producer isolates genome were compared with genome of pathogenic and commensal Escherichia coli strains. Conserved genomic signatures among different types of CDT producer E. coli strains were assessed. It was shown that they could be used as biomarkers for research purposes and clinical diagnosis by polymerase chain reaction, or in vaccine development. cdt genes and several other genetic biomarkers were identified as signature sequences in CDT producer strains. The identified signatures include several individual phage proteins (holins, nucleases, and terminases, and transferases) and multiple members of different protein families (the lambda family, phage-integrase family, phage-tail tape protein family, putative membrane proteins, regulatory proteins, restriction-modification system proteins, tail fiber-assembly proteins, base plate-assembly proteins, and other prophage tail-related proteins). In this study, a sporadic phylogenic pattern was demonstrated in the CDT-producing strains. In conclusion, conserved signature proteins in a wide range of pathogenic bacterial strains can potentially be used in modern vaccine-design strategies.

Antibiotic susceptibilities and virulence genes of clinically isolated Salmonella enterica serovars ;Schwarzengrund strains / 中华微生物学和免疫学杂志

Objective To investigate the antibiotic susceptibilities and the profiles of virulence genes of clinically isolated Salmonella enterica serovars Schwarzengrund ( S. Schwarzengrund) strains for bet-ter understanding the epidemiological trend of this type of non-typhoidal Salomonella and to provide guide-lines for the prevention and treatment of S. Schwarzengrund infection. Methods Stool samples and clinical data of patients with acute diarrhea who received treatment in the Second Hospital of Tianjin Medical Univer-sity during May, 2014 to October, 2014 were collected for this study. Enrichment culture and biochemical identification were used to isolate and identify the S. Schwarzengrund strains. The isolated strains were fur-ther analyzed with serotyping analysis, drug susceptibility test, pulsed field gel electrophoresis ( PFGE) and multiple locus sequence typing ( MLST ) . The representative genes carried by Salmonella pathogenicity islands (SPI) 1-5, SPI regulators and virulence plasmids were amplified by PCR. The coding genes of CdtB-islet, which were cdtB, pltA and pltB were amplified and sequenced. Results In total, 16 (14. 8%) out of 108 non-typhoidal Salmonella strains were identified as S. Schwarzengrund strains and all of them were sus-ceptible to 11 kinds of antibiotics such as fluoroquinolone, ampicillin, ceftriaxone and trimethoprim-sulfame-thoxazole. PFGE categorized the 16 S. Schwarzengrund strains into 3 clusters including A clone ( 14 strains), B clone (1 strain) and C clone (1 strain). The strains that isolated from 8 patients who ate the same food belonged to one cluster ( A clone ) , suggesting that it was an outbreak of infection. The 16 S. Schwarzengrund strains showed identical MLST type, which was ST241. The representative genes carried by SPI1-5 ( invA, sitC, hilA, sseL, sifA, mgtC, siiE and sopB) , the regulatory gene ( phoP) and the cytole-thal distending toxin islet (CdtB-islet) coding genes (cdtB, pltA and pltB) were positive, while the genes carried by virulence plasmids (pefA, prot6E and spvB) were negative. The similarities in CdtB-islet coding genes and amino acids sequences between Salmonella typhi and S. Schwarzengrund strains in this study were more than 97% and 98%, respectively. Conclusion In this study, polyclonal S. Schwarzengrund strains of ST241 type were isolated from the patients. They were susceptible to common antibiotics, but carried the virulence genes contained in SPI1-5 and CdtB-islet coding genes and might cause an outbreak of infection. Attention should be paid to the tendency and threat of clinical S. Schwarzengrund infection and continuous surveillance and investigation should be performed.

Detection of CDT toxin genes in Campylobacter spp. strains isolated from broiler carcasses and vegetables in São Paulo, Brazil

Campylobacteriosis is a worldwide distributed zoonosis. One of the main virulence factors related to Campylobacter spp. in animals and humans is the cytolethal distending toxin (CDT), encoded by three adjacent genes (cdtA, cdtB, cdtC). The occurrence of Campylobacter spp. in samples of vegetables has not been reported in Brazil yet, and has seldom been described in the international literature. The detection of CDT in these strains has not been reported, either. The objectives of the present study were to determine the occurrence of Campylobacter spp. strains carrying virulence factors in samples of poultry and vegetables (lettuce and spinach) from different points of sale, thus verifying if vegetables are as an important vehicle for potentially virulent Campylobacter spp. strains as poultry. Twenty four strains were identified as Campylobacter jejuni by phenotypic and genotypic methods: 22 from broiler carcasses and two from lettuce samples. Three strains were identified as Campylobacter coli: two from broiler carcasses and one from lettuce. The presence of the cdt genes were detected in 20/24 (83.3%) C. jejuni strains, and 3/3 (100%) C. coli strains. The isolation of Campylobacter spp. strains with the cdt gene cluster in lettuce samples points to a new possible source of contamination, which could have an impact in the vegetable production chain and risk to public health. Results show that potentially virulent C. jejuni and C. coli strains remain viable in samples of broiler carcasses and vegetables at the points of sale.

Role of Cytolethal Distending Toxin in Altered Stool Form and Bowel Phenotypes in a Rat Model of Post-infectious Irritable Bowel Syndrome

BACKGROUND/AIMS: Campylobacter jejuni infection is a leading cause of acute gastroenteritis, which is a trigger for post-infectious irritable bowel syndrome (PI-IBS). Cytolethal distending toxin (CDT) is expressed by enteric pathogens that cause PI-IBS. We used a rat model of PI-IBS to investigate the role of CDT in long-term altered stool form and bowel phenotypes. METHODS: Adult Sprague-Dawley rats were gavaged with wildtype C. jejuni (C+), a C. jejuni cdtB knockout (CDT-) or saline vehicle (controls). Four months after gavage, stool from 3 consecutive days was assessed for stool form and percent wet weight. Rectal tissue was analyzed for intraepithelial lymphocytes, and small intestinal tissue was stained with anti-c-kit for deep muscular plexus interstitial cells of Cajal (DMP-ICC). RESULTS: All 3 groups showed similar colonization and clearance parameters. Average 3-day stool dry weights were similar in all 3 groups, but day-to-day variability in stool form and stool dry weight were significantly different in the C+ group vs both controls (P < 0.01) and the CDT- roup (P < 0.01), but were not different in the CDT- vs controls. Similarly, rectal lymphocytes were significantly higher after C. jejuni (C+) infection vs both controls (P < 0.01) and CDT-exposed rats (P < 0.05). The counts in the latter 2 groups were not significantly different. Finally, c-kit staining revealed that DMP-ICC were reduced only in rats exposed to wildtype C. jejuni. CONCLUSIONS: In this rat model of PI-IBS, CDT appears to play a role in the development of chronic altered bowel patterns, mild chronic rectal inflammation and reduction in DMP-ICC.

Detecção dos genes da toxina citoletal distensiva em estirpes de Campylobacter jejuni isoladas de carcaças de frangos / Detection of cytolethal distending toxin genes in strains of Campylobacter jejuni isolated from broiler carcasses

Foram analisadas 80 amostras de sobrecoxas de frangos de corte resfriados provenientes de feiras livres e hipermercados do município de São Paulo, SP. Treze estirpes de Campylobacter spp. foram isoladas em 10 (12,5 por cento) sobrecoxas, sendo cinco amostras originárias de feiras livres e cinco de hipermercados. Onze estirpes foram identificadas como Campylobacter jejuni e duas como Campylobacter coli. As 11 estirpes foram confirmadas como C. jejuni pela PCR do gene da hipuricase (hip), e destas, quatro (36,4 por cento) apresentaram os três genes (cdtA, cdtB e cdtC) codificantes da toxina citoletal distensiva pela multiplex-PCR, sendo três estirpes provenientes de hipermercados e uma de feira livre. Observou-se a presença de estirpes virulentas de C. jejuni, portadoras do complexo de genes cdt, nas amostras de frango resfriado, não só na linha de abate, mas até o ponto final da cadeia de distribuição, nos dois principais centros de venda a varejo.

Eighty samples of refrigerated broiler thighs purchased in street markets and supermarkets in the city of São Paulo, SP, were analyzed. Thirteen Campylobacter spp. strains were isolated in 10 (12.5 percent) thighs, five of them from street market samples and other five from supermarkets. Eleven strains were identified as Campylobacter jejuni and two of them as Campylobacter coli. The 11 strains were confirmed to be C. jejuni using PCR for hippuricase (hip) gene. From these, multiplex-PCR showed that four (36.4 percent) strains presented the three genes (cdtA, cdtB, and cdtC) encoding cytolethal distending toxin: three strains from supermarket and one from street market samples. These results are important, because they demonstrate the presence of virulent C. jejuni strains in refrigerated broiler thigh samples, not only in the slaughterhouse but in the final point of the distribution chain, at the two most important food retail commercer.

Cell cycle arrest & apoptosis of epithelial cell line by cytolethal distending toxin positive Campylobacter jejuni.

Background & objectives: Campylobacter jejuni is the leading cause of gastroenteritis worldwide; cytolethal distending toxin (CDT) being an important virulence determinant. As its role in pathogenesis remains unclear, this study aims to investigate cell cycle arrest and apoptosis by CDT (+ve) and CDT (-ve) C. jejuni isolates on HeLa cells. Methods: Culture supernatants and lysates from 10 C. jejuni isolates [CDT (+ve) and CDT (-ve), five each] were incubated with HeLa cells. CDT activity on HeLa cells was confirmed by cell distension, cell cycle arrest by flowcytometry, and apoptosis by DNA fragmentation and flowcytometry. Results: Culture supernatant and lysate of only CDT (+ve) C. jejuni isolates produced cell distension. For CDT (+ve) and CDT (-ve) isolates, the cells at G2/M phase after 24, 48 and 72 h were 25.8 ± 3.79 per cent and 11.2 ± 0.58 per cent, 72.9 ± 2.44 and 14.3 ± 1.88 per cent, 93.5 ± 0.54 per cnet and 18.0 ± 1.80 per cent respectively (P<0.001). All CDT (+ve) isolates induced DNA fragmentation. Apoptosis induced by CDT (+ve) C. jejuni was significantly greater than CDT (-ve) (26.3 ± 3.49 % vs. 10.4 ± 1.01% at 24 h, 43.9 ± 2.40% vs. 17.6 ± 0.88% at 48 h, 68.4 ± 1.61% vs. 28.4 ± 1.62% at 72 h); (P<0.001). Interpretation & conclusion: The present study shows that CDT (+ve) C. jejuni contributes to the pathogenesis through epithelial cell G2/M phase arrest and apoptosis.

Cloning and protein expression of Aggregatibacter actinomycetemcomitans cytolethal distending toxin C / 대한치주과학회지

PURPOSE: Aggregatibacter actinomycetemcomitans was associated with localized aggressive periodontitis, endocarditis, meningitis, and osteomyelitis. The cytolethal distending toxin (CDT) of A. actinomycetemcomitans was considered as a key factor of these diseases is composed of five open reading frames (ORFs). Among of them, An enzymatic subunit of the CDT, CdtB has been known to be internalized into the host cell in order to induce its genotoxic effect. However, CdtB can not be localized in host cytoplasm without the help of a heterodimeric complex consisting of CdtA and CdtC. So, some studies suggested that CdtC functions as a ligand to interact with GM3 ganglioside of host cell surface. The precise role of the CdtC protein in the mechanism of action of the holotoxin is unknown at the present time. The aim of this study was to generate recombinant CdtC proteins expression from A. actinomycetemcomitans, through gene cloning and protein used to investigate the function of Cdt C protein in the bacterial pathogenesis MATERIALS AND METHODS: The genomic DNA of A. actinomycetemcomitans Y4 (ATCC29522) was isolated using the genomic DNA extraction kit and used as template to yield cdtC genes by PCR. The amplifed cdtC genes were cloned into T-vector and cloned cdt C gene was then subcloned to pET28a expression vector. The pET28a-cdtC plasmid expressed in BL21 (DE3) Escherichia coli system. Diverse conditons were tested to opitimize the expression and purification of functional CdtC protein in E. coli. RESULTS: In this study we reconstructed CdtC subunit of A. actinomycetemcomitans Y4 and comfirmed the recombinant CdtC expression by SDS-PAGE and Western Blotting. The expression level of the recombinant CdtC was about 2% of total bacterial proteins. CONCLUSION: The lab condition of procedure for the purification of functionally active recombinant CdtC protein is established. The active recombinant CdtC protein will serve to examine the role of CdtC proteins in the host recognition and enzyme activity of CDT and investigate the pathological process of A. actinomycetemcomitans in periodontal disease.

Production of the polyclonal subunit C protein antibody against Aggregatibacter actinomycetemcomitans cytolethal distending toxin / 대한치주과학회지

PURPOSE: Cytolethal distending toxin (CDT) considered as a key factor of localized aggressive periodontitis, endocarditis, meningitis, and osteomyelitis is composed of five open reading frames (ORFs). Among of them, the individual role of CdtA and CdtC is not clear; several reports presents that CDT is an AB2 toxin and they enters the host cell via clathrin-coated pits or through the interaction with GM3 ganglioside. So, CdtA, CdtC, or both seem to be required for the delivery of the CdtB protein into the host cell. Moreover, recombinant CDT was suggested as good vaccine material and antibody against CDT can be used for neutralization or for a detection kit. MATERIALS AND METHODS: We constructed the pET28a-cdtC plasmid from Aggregatibacter actinomycetemcomitans Y4 by genomic DNA PCR and expressed in BL21 (DE3) Escherichia coli system. We obtained the antibody against the recombinant CdtC in mice system. Using the anti-CdtC antibody, we test the native CdtC detection by ELISA and Western Blotting and confirm the expression time of native CdtC protein during the growth phase of A. actinomycetemcomitans. RESULTS: In this study we reconstructed CdtC subunit of A. actinomycetemcomitans Y4 and generated the anti CdtC antibody against recombinant CdtC subunit expressed in E. coli system. Our anti CdtC antibody can be interacting with recombinant CdtC and native CDT in ELISA and Western system. Also, CDT holotoxin existed at 24h but not at 48h meaning that CDT holotoxin was assembled at specific time during the bacterial growth. CONCLUSION: In conclusion, we thought that our anti CdtC antibody could be used mucosal adjuvant or detection kit development, because it could interact with native CDT holotoxin.

Purification and refolding of the recombinant subunit B protein of the Aggregatibacter actinomycetemcomitans cytolethal distending toxin / 대한치주과학회지

PURPOSE: Aggregatibacter actinomycetemcomitans is associated with localized aggressive periodontitis. It produces cytolethal distending toxin (CDT), which induces cell cycle arrest in the G2/M phase. The CDT holotoxin is composed of CdtA, CdtB, and CdtC. CdtB has structural homology to human DNase I and is an active component of the CDT complex acting as a DNase. In particular, the pattern homology seen in the CdtB subunit has been associated with specific DNase I residues involved in enzyme catalysis, DNA binding, and metal ion binding. So, to study the functions and regulation of recombinant CdtB, we made up a quantity of functional recombinant CdtB and tested it in relation to the metal ion effect. MATERIALS AND METHODS: We constructed the pET28a-cdtB plasmid from A. actinomycetemcomitans Y4 by genomic DNA PCR and expressed it in the BL21 (DE3) Escherichia coli system. We obtained the functional recombinant CdtB by the refolding system using the dialysis method and then analyzed the DNase activity and investigated the metal ion effect from plasmid digestion. RESULTS: The recombinant CdtB subunit was expressed as the inclusion bodies. We were able to obtain functional recombinant CdtB subunit using refolding system. We confirmed that our refolded recombinant CdtB had DNase activity and was influenced by the metal ions Mg2+ and Ca2+. CONCLUSION: We suggest that the factors influencing recombinant CdtB may contribute to CDT associated diseases, such as periodontitis, endocarditic, meningitis, and osteomyelitis.

Cloning and protein expression of Actinobacillus actinomycetemcomitans cytolethal distending toxin subunit CdtA / 대한치주과학회지

No abstract available.