Cdt Genes Research Articles

A plasmid-mediated type III secretion system associated with invasiveness and diarrheagenicity of Providencia rustigianii.

We have recently described a clinical isolate of Providencia rustigianii strain JH-1 carrying the genes for cytolethal distending toxin (CDT) in a conjugative plasmid. A cdtB mutant of strain JH-1, which lost CDT activity, was still found to retain invasiveness and diarrheagenicity. The strain was subjected to phenotypic and genetic analyses including whole genome sequencing (WGS) to explore the genetic determinants of the observed invasiveness and diarrheagenic properties. Analysis and annotation of WGS data revealed the presence of two distinct type III secretion systems (T3SS) in strain JH-1, one of which was located on the chromosome designated as cT3SS (3,992,833 bp) and the other on a mega-plasmid designated as pT3SS (168,819 bp). Comparative genomic analysis revealed that cT3SS is generally conserved in Providencia spp. but pT3SS was limited to a subset of Providencia spp., carrying cdt genes. Strain JH-1 was found to invade HeLa cells and induce fluid accumulation with characteristic pathological lesions in rabbit ileal loops. Remarkably, these phenomena were associated with the pT3SS but not cT3SS. The plasmid could be transferred by conjugation from strain JH-1 to other strains of P. rustigianii, Providencia rettgeri, and Escherichia coli with concomitant transfer of these virulence properties. This is the first report of a functional and mobile T3SS in P. rustigianii and its association with invasiveness and diarrheagenicity of this bacterium. These data suggest that P. rustigianii and other CDT-producing Providencia strains might carry T3SS and exert their diarrheagenic effect by exploiting the T3SS nano-machinery.IMPORTANCEThe precise mechanism of virulence of Providencia rustigianii is unclear, although some strains produce cytolethal distending toxin as a putative virulence factor. We have detected the presence of a type III secretion system (T3SS) for the first time on a plasmid in a P. rustigianii strain. Plasmid-mediated T3SS seems to be directly involved in virulence of P. rustigianii and may serve as a means of horizontal transfer of T3SS genes. Our results may have implication in understanding the mechanism of emergence of new pathogenic strains of P. rustigianii.

Misregulation of bromotyrosine compromises fertility in male Drosophila

Biological regulation often depends on reversible reactions such as phosphorylation, acylation, methylation, and glycosylation, but rarely halogenation. A notable exception is the iodination and deiodination of thyroid hormones. Here, we report detection of bromotyrosine and its subsequent debromination during Drosophila spermatogenesis. Bromotyrosine is not evident when Drosophila express a native flavin-dependent dehalogenase that is homologous to the enzyme responsible for iodide salvage from iodotyrosine in mammals. Deletion or suppression of the dehalogenase-encoding condet (cdt) gene in Drosophila allows bromotyrosine to accumulate with no detectable chloro- or iodotyrosine. The presence of bromotyrosine in the cdt mutant males disrupts sperm individualization and results in decreased fertility. Transgenic expression of the cdt gene in late-staged germ cells rescues this defect and enhances tolerance of male flies to bromotyrosine. These results are consistent with reversible halogenation affecting Drosophila spermatogenesis in a process that had previously eluded metabolomic, proteomic, and genomic analyses.

Campylobacter fetus isolates from both human patients and healthy cattle carry three distinct cytolethal distending toxin (cdt) gene clusters.

Campylobacter fetus is a zoonotic pathogen. Although the precise virulence mechanisms have not yet been fully elucidated, cytolethal distending toxin (CDT) is considered as one of the well-characterized virulence factors in Campylobacter. In silico analysis of the genome of C. fetus type strain of ATCC27374T indicates that there are three cdt gene clusters, Cfcdt-I, Cfcdt-II and Cfcdt-III. However, it is not clear whether these clusters are ubiquitously present in C. fetus and their association with diseases in humans and animals. In this study, we have analyzed the distribution and nucleotide sequences of these cdt gene clusters in 137 C. fetus strains isolated from human patients and healthy cattle. MLST and PFGE were also applied to determine clonal relationship between C. fetus strains isolated from patients and cattle. We found all C. fetus strains carry three Cfcdt gene clusters by colony hybridization assay and the strains belonged to 38 different pulsotypes. Whole genome sequencing of 38 C. fetus strains was carried out to determine the entire cdt gene cluster sequences and their sequence type (ST). Among 38 strains, six STs were identified, and each cdt gene cluster showed high similarity (>99%). Interestingly, some of these Cfcdt genes are more similar to the cdt genes of other Campylobacter species than other Cfcdt gene types. Altogether, the results suggest that three Cfcdt gene clusters are highly conserved in C. fetus and the strains belonging to ST-6 may be more pathogenic to human.

Presence of Functionally Active Cytolethal Distending Toxin Genes on a Conjugative Plasmid in a Clinical Isolate of Providencia rustigianii.

Providencia rustigianii is potentially enteropathogenic in humans. Recently, we identified a P. rustigianii strain carrying a part of the cdtB gene homologous to that of Providencia alcalifacines that produces an exotoxin called cytolethal distending toxin (CDT), encoded by three subunit genes (cdtA, cdtB, and cdtC). In this study, we analyzed the P. rustigianii strain for possible presence of the entire cdt gene cluster and its organization, location, and mobility, as well as expression of the toxin as a putative virulence factor of P. rustigianii. Nucleotide sequence analysis revealed the presence of the three cdt subunit genes in tandem, and over 94% homology to the corresponding genes carried by P. alcalifaciens both at nucleotide and amino acid sequence levels. The P. rustigianii strain produced biologically active CDT, which caused distension of eukaryotic cell lines with characteristic tropism of CHO and Caco-2 cells but not of Vero cells. S1-nuclease digested pulsed-field gel electrophoresis followed by Southern hybridization analysis demonstrated that the cdt genes in both P. rustigianii and P. alcalifaciens strains are located on large plasmids (140 to 170 kb). Subsequently, conjugation assays using a genetically marked derivative of the P. rustigianii strain showed that the plasmid carrying cdt genes in the P. rustigianii was transferable to cdt gene-negative recipient strains of P. rustigianii, Providencia rettgeri, and Escherichia coli. Our results demonstrated the presence of cdt genes in P. rustigianii for the first time, and further showed that the genes are located on a transferable plasmid, which can potentially spread to other bacterial species.

Extended-Spectrum β-Lactamase-Producing Escherichia coli and Virulence Genes in Pediatric Patients with Health-Care Urinary Tract Infections.

Healthcare-associated urinary tract infection (UTI) represents a significant health problem, especially in infants and young children. The most common pathogen associated with this infection is Escherichia coli (E. coli). The present study aimed to detect the frequency of virulence genes among clinical isolates of E. coli isolated from healthcare-associated urinary tract infections in children and the correlation between these virulence genes and the presence of the blaCTX gene. The study included one hundred clinical isolates of E. coli isolated from healthcareassociated urinary tract infections in children in intensive care units. The isolates were subjected to antibiotics sensitivity by disc diffusion method and detection of extended-spectrum beta-lactamase by double disc diffusion method. In addition, multiplex polymerase chain reaction (PCR) was used to detect some virulence genes, and PCR was used to detect the blaCTX-M gene. E. coli producing ESBL by double discs method was identified in 74 isolates. blaCTX-M gene detection by PCR was identified among 38 isolates representing 51.4% of ESBL-producing E. coli. There was a significant association between ESBL and blaCTX-M Gene, P = 0.0001. The frequency of the studied virulence genes by multiplex PCR in the isolated E. coli was 66% for the Fim gene, 75% for the Aer gene, 68% for the FliC gene, 53% for each of IucD gene and Usp gene, 40% for pap gene, 35% for each of AFA and ironN genes and 17% for sfa gene. None of the isolated E. coli had the Cdt gene. There was a significant association between the presence of the FimH gene (P = 0.0001), Pap gene (P = 0.05), sfa (P = 0.026), Afa gene (P = 0.018), and aer gene (P = 0.035) and the presence of the blaCTX-M gene in the isolated E. coli. The present study highlights the presence of virulence genes and blaCTX-M gene in uropathogenic E. coli isolated from pediatric patients with healthcare-associated urinary tract infections. There was an association between the blaCTX-M gene and virulence genes FimH, pap, sfa, Afa, and aer. Various distributions of the studied genes with a high frequency of fimbria are flic genes. Moreover, the ESBL had high frequency in E. coli with the presence of blaCTX-M in about one-third of the isolates.

Frequency of Cytolethal Distending Toxin (CDT) Genes in Escherichia coli Isolates from Bovine Mastitis in Tabriz City in 2020

Background: Cytolethal distending toxin (CDT) gene is one of the important virulence factors in Escherichia coli isolated from different human and animal sources strains. Objectives: The aim of this study was to investigate the frequency of cytolethal distending toxin (CDT) genes in E. coli isolates from bovine mastitis in Tabriz City (East Azarbaijan province) in 2020. Methods: In this cross-sectional descriptive study, after isolation and biochemical and molecular identification of 100 E. coli from bovine mastitis, the frequency of cdt-I, cdt-III, and cdt-IV genes was assessed by PCR method. Results: Of a total of 100 tested E. coli samples, 94 isolates were confirmed as E. coli by PCR test. Of the 96 E. coli isolates, none had the cdt-I, cdt-III, and cdt-IV genes. Conclusions: The results of this study showed that the frequency of the cdt gene in E. coli isolates from cow mastitis is very low, like the other animal sources in past studies.

Comparison of clinical severity, genotype and toxin gene expression of binary toxin-producing Clostridioides difficile clinical isolates in Japan.

The emerging Clostridioides difficile strain BI/NAP1/027 has been reported to be associated with more severe clinical symptoms and higher mortality rates, thought in part due to production of a novel binary toxin alongside conventional A and B toxins. However, recent studies suggest that this may not always be the case. Therefore, the purpose of this report was to investigate the correlation between clinical severity and microbiological characteristics of CDT-producing C. difficile isolates in Japan. Eight Japanese isolates of CDT producing C. difficile were investigated using genotyping, cytotoxic activity assays and toxin gene expression. Correlation with clinical severity was performed retrospectively using the patient record. Three of eight patients were assessed as having severe C. difficile infection (CDI). PCR ribotyping resolved six ribotypes including ribotype 027. No specific genes were identified determining severe compared with non-severe cases. Positive correlation of expression levels of tcdA, tcdB and cdtB were observed although these expression levels were not correlated with cytotoxicity. CDI severity index neither correlated with toxin gene expression level nor cytotoxicity. These data indicate that the possession of the CDT gene and toxin gene expression levels may not relate to C. difficile cytotoxicity or clinical severity.

Host-associated variability of the cdtABC operon, coding for the cytolethal distending toxin, in Campylobacter jejuni.

Campylobacter, a major cause of food-borne gastroenteritis worldwide, colonize the gastrointestinal tract of a wide range of animals, being birds the main reservoir. The mechanisms involved in the interaction of Campylobacter with the different hosts are poorly understood. The cytolethal distending toxin, encoded in the cdtABC operon, is considered a pivotal virulence factor during human infection. Differences in the prevalence of cdtABC genes in Campylobacter isolates from three distinct origins (wild birds, broiler chickens and humans) prompted us to further characterize their allelic variability. The sequence of cdtABC is highly conserved among broiler and human isolates. A high diversity of cdtABC alleles was found among wild bird isolates, including several alleles that do not produce any functional CDT. These results suggest that specific variants of the cdtABC operon might define the host range of specific Campylobacter jejuni isolates. Moreover, our data indicate that PCR methodology is inaccurate to characterize the prevalence of the cdt genes, since negative PCR detection can be the result of divergences in the sequence used for primer design rather than indicating the absence of a specific gene.

Prevalence, Abundance, and Virulence of Adherent-Invasive Escherichia coli in Ulcerative Colitis, Colorectal Cancer, and Coeliac Disease

Background & AimsAdherent-invasive E. coli (AIEC) has largely been implicated in the pathogenesis of Crohn’s disease (CD). E. coli strains with similar genetic backgrounds and virulence genes profiles have been associated with other intestinal disorders, such as ulcerative colitis (UC), colorectal cancer (CRC), and coeliac disease (CeD), but the role of AIEC in these diseases remains unexplored. We aimed to assess the distribution, abundance, and pathogenic features of AIEC in UC, CRC, and CeD.MethodsThe AIEC phenotype was investigated in 4,233 E. coli isolated from the ileum and colon of 14 UC and 15 CRC patients and in 38 fecal E. coli strains obtained from 17 CeD and 10 healthy (H) children. AIEC prevalence and abundance were compared with previous data from CD patients and H controls. Clonality, virulence gene carriage, and phylogenetic origin were determined for the AIEC identified.ResultsIn UC, AIEC prevalence was intermediate between CD and H subjects (UC: 35.7%, CD: 55.0%, H: 21.4%), and similar to CD patients with colonic disease (C-CD: 40.0%). In CRC, the prevalence was lower (6.7%) than these groups. In patients with AIEC, the estimated abundance was similar across all intestinal conditions. All AIEC strains isolated from UC and CRC belonged to the B1 phylogroup, except for a strain of the A phylogroup, and the majority (75% of clonally distinct AIEC) harbored the Afa/Dr operon and the cdt gene. None of the E. coli isolated from the CeD cohort were AIEC. Nonetheless, E. coli strains isolated from active CeD patients showed higher invasion indices than those isolated from H and inactive CeD pediatric patients.ConclusionWe support the hypothesis that AIEC-like strains can be involved not only in CD but also in UC. Further works are needed to study the virulence particularities of these groups of strains and to determine if there is a causative link between AIEC and UC. In contrast, we rule out the possible association of AIEC with CRC. In addition, to further study the E. coli strains in CeD for their possible pathogenic role would be of interest.

Clostridioides difficile from Brazilian hospitals: characterization of virulence genes by whole genome sequencing

Clostridioides difficile (CD) is the most frequent cause of healthcare related diarrhea and its severity has increased in the last decade by the spread of hypervirulent strains. Most important CD virulence factor is toxin production; however, not only toxins are responsible for Clostridioides virulence. We sequenced 38 strains and analyzed the presence and integrity of 24 virulence (including toxin) genes. We identified 28 toxigenic strains, six also presented the cdt genes. Only six strains didn't present all others genes searched. All absent genes were adhesion related. Understand others CD virulence factors can lead to a best understanding on this matter.

Isolation Rate of Campylobacter Spp. and Detection of Virulence Genes of Campylobacter jejuni Across the Broiler Chain

Abstract The aim of the study was to identify the isolation rate of thermotolerant campylobacters in a small-scale broiler-meat production farm over a one-year period. The second deliverable of the study was to determine the potential virulence markers. The laboratory investigation was performed on 283 samples (cloacal swabs, caeca, carcass swabs) collected on three sampling points (farm, slaughter line, and cold storage). The isolates obtained with the conventional microbiological method were confirmed with multiplex PCR for identification of campylobacters. The presence of 10 virulence genes was analyzed in the C. jejuni isolates (flaA, racR, virB11, dnaJ, wlaN, cadF, ciaB, cdtA, cdtB, cdtC). Out of 283 samples, 169 (59.7%) were confirmed as Campylobacter spp., 111 (39.2%) C. jejuni, and 43 (15.2%) C. coli. C. jejuni was the most prevalent in all sampling points. Campylobacter spp. showed a characteristically seasonal prevalence with the highest isolation rate during the warmer period of the year. We detected the cadF and ciaB genes in all C. jejuni isolates. The flaA gene was present in 50% of the examined strains. The cdt genes (cdtA, cdtB, and cdtC) were confirmed in 52.8%, 52.8%, and 47.2% of the C. jejuni strains, respectively. C. jejuni showed 15 profiles of virulence patterns with four predominant profiles.

Virulence determinants and antimicrobial resistance of E. coli isolated from bovine clinical mastitis in some selected dairy farms of Bangladesh.

E. coli is one of the major significant pathogens causing mastitis, the most complex and costly diseases in the dairy industry worldwide. Present study was undertaken to isolate, detect the virulence factors, phylogroup, antimicrobial susceptibility and antimicrobial resistance genes in E. coli from cows with clinical mastitis. A total of 68 milk samples comprising 53 from clinical mastitis and 15 from apparently healthy cattle were collected from four different established dairy farms in Bangladesh. E. coli was isolated from the milk samples and identified by PCR targeting malB gene and sequencing of 16S rRNA gene. E. coli isolates were screened by PCR for the detection of major virulence genes (stx, eae and cdt) of diarrheagenic E. coli followed by phylogenetic grouping. Antimicrobial susceptibility of the E. coli isolates was determined by disk diffusion test and E. coli showing resistance was further screened for the presence of antimicrobial resistance genes. E. coli was isolated from 35.8% of the mastitis milk samples but none from the apparently healthy cattle milk. All the E. coli isolates were negative for stx, eae and cdt genes and belonged to the phylogenetic groups A and B1 which comprising of commensal E. coli. Antibiotic sensitivity testing revealed 84.2% (16/19) of the isolates as multidrug resistant. Highest resistance was observed against amoxicillin (94.5%) followed by ampicillin (89.5%) and tetracycline (89.5%). E. coli were found resistant against all the classes of antimicrobials used at the farm level. Tetracycline resistance gene (tetA) was detected in 100% of the tetracycline resistant E. coli and blaTEM-1 was present in 38.9% of the E. coli isolates. Findings of this study indicate a potential threat of developing antimicrobial resistance in commensal E. coli and their association with clinical mastitis. Occurrence of multidrug resistant E. coli might be responsible for the failure of antibiotic therapies in clinical mastitis as well as pose potential threat of transmitting and development of antibiotic resistance in human.

Antimicrobial Resistance and Virulence Factors of Campylobacter coli Isolated from Chicken in Côte d’Ivoire

Aims: Campylobacters species are major causes of gastroenteritis in human. The main risk factor of infection is consumption of contaminated or by cross-contaminated poultry meat. The aims of this study were to analyze antimicrobial profile and virulence factors associated to Campylobacter coli isolated from chicken’s ceaca in commercial slaughter in Abidjan.
 Methodology: A total of 336 chicken ceaca samples were collected from market of two municipality of Abidjan and were examined by conventional microbiological methods and molecular test using PCR. The antibiotic susceptibility tests of the isolates were determined by disk diffusion method the presence of virulence genes was examined using simple PCR method.
 Results: From these samples, 210/336 (62.50%) were positives for Campylobacter. Among the isolates, 53 strains confirmed as C. coli by using PCR detection were used for phenotypic and genotypic analysis. Of these strains, 51/53 were positive for one or more antibiotics molecules tested. The highest rate of antimicrobial resistance was found for nalidixic acid 51/53 (96.22%), tetracyclin 49/53 (92.45%) and ciprofloxacin 38/53 (71.69%). Moreover, MDR including 3, 4, 5 and 6 antibiotics families was detected in 11/53 (20.75%) of isolates. On the other hand, detection of virulence gene shows presence of cadF gene in 86.01% of isolates while 82.21% were positive for the three cdt (A, B and C) genes.
 Conclusion: We reported in this study the presence of high pathogenic Campylobacter coli contamination of the studied chickens. Molecular identification of the bacteria was performed and determination of high resistance to antimicrobials of the fluoroquinolone family was revealed.

Molecular detection of Campylobacter species and Cytolethal distending toxin isolated from chicken livers in Tabriz

Introduction and purpose: Campylobacter jejuni and coli are zoonotic bacteria commonly associated With human diarrhea and usually transmit through consumption of meat and poultry contaminated products such as heart and liver. Cytolethal distending toxin (cdt) in Campylobacter spp. is among the significant virulence factors of these bacteria in the intestine. The purpose of this study was to determine the prevalence of Campylobacter spp. and presence of cdt genes among isolated bacteria. Materials and methods: In this cross sectional study, 100 chicken livers were examined. Detection, bacterial enumeration and isolation of Campylobacter spp. was done using Campylobacter selective agar media containing Campylobacter growth supplement, gram staining, catalase and oxidase production, hippurate hydrolysis and PCR molecular technique. Also the presence of cdt genes were detected using PCR assay. Results: From 100 studied liver samples, 43 were contaminated with Campylobacter spp. Among them 31(72 %) samples had Campylobacter jejuni and 12 (28 %) had Campylobacter coli. All Campylobacter jejuni isolates contained cdtA ،cdtB and cdtC genes. However, all of these genes detected in 9 (75 %) of isolated coli. Conclusion: The results of this study showed that great percentages of chicken livers in Tabriz were contaminated with Campylobacter.

Emergence of Genetic Diversity and Multi-Drug Resistant Campylobacter jejuni From Wild Birds in Beijing, China.

Campylobacter jejuni (C. jejuni) is considered as an opportunistic zoonotic pathogen that may cause gastroenteritis in humans and other animals. Wild birds may be as potential vectors of C. jejuni around urban and suburban areas. Here, 520 samples were collected from 33 wild bird species in urban and suburban areas, Beijing. In total 57 C. jejuni were isolated from seven species. It was found that Nineteen (33.33%, 19/57) isolates were resistant to at least one of 11 antibiotics, especially streptomycin (36.84%) and four isolates resistant to all. Nineteen (33.33%, 19/57) isolates were multi-drug resistance. Multilocus sequence typing (MLST) analysis of the isolates showed that 36 different sequence types (STs) belonged to four Clonal complexes and unassigned. Twenty STs (55.56%) and six alleles among them were first detected. Virulence genes including flaA, cadF, and the cytolethal distending toxin (CDT) gene cluster, were detected in all isolates, but truncated cdt gene clusters only detected in the isolates from the crow, daurian jackdaw and silver pheasant. In conclusion, it was the first detection of C. jejuni involved truncated cdt gene clusters from the silver pheasant. These wild birds around urban and suburban areas may pose potential public health problems as reservoir vectors of C. jejuni.

Detection of virulent thermophilic Campylobacter species in communal chickens

Campylobacter is a foodborne pathogen found in the gut of poultry and other animals, which thereby act as reservoirs for human infection. Campylobacter produces various virulence factors which contribute to the establishment of disease. The aim of this study was to detect virulence genes in Campylobacter isolated from chicken faeces. A total of 408 poultry cloacal samples were analysed through culture, PCR and DNA sequencing. Campylobacter were detected in 24 (5.9 %) of the samples, of which 21 were C. jejuni while 3 were C. coli. The cdtB gene was detected in all Campylobacter isolates while cdtA and cdtC genes were detected in 20 (83.3%) and 18 (75.0%) of the isolates, respectively. The cadF gene was detected in 18 (85.7%) C. jejuni but not in C. coli. Eight genotypes designated G1 to G8 were detected among the isolates. Genotypes G1 and G7 possessed all three cdt genes, a potential for producing functionally active toxins. A large proportion (70.8%) of the isolates possessed both genes for toxin production and adhesion. The high prevalence of cdt and cadF genes in Campylobacter species in this study indicates the pathogenic potential of the isolates. There is a need to implement control measures to curb the spread of these virulent strains.
 Significance:
 
 Virulent thermophilic campylobacters cause severe health complications in humans.
 Although chicken meat is the main source of human infections, there is limited data on the occurrence of Campylobacter in chicken faeces in southern Africa.
 This study adds to literature on the occurrence of virulent strains of Campylobacter species, notably through the deposition of the DNA sequences of our local strains into GenBank®.
 Communal chickens may serve as a source of virulent thermophilic campylobacters to humans, resulting in serious public health implications.
 
 Open data sets: 
 MF872608 - https://www.ncbi.nlm.nih.gov/nuccore/MF872608.1 MF872609 - https://www.ncbi.nlm.nih.gov/nuccore/MF872609.1MF872610 - https://www.ncbi.nlm.nih.gov/nuccore/MF872610.1MF872611 - https://www.ncbi.nlm.nih.gov/nuccore/MF872611.1MF872612 - https://www.ncbi.nlm.nih.gov/nuccore/MF872612.1

Differences in virulence gene expression between human blood and stool Campylobacter coli clade 1 ST828CC isolates

BackgroundCampylobacter colonise the gastrointestinal tract of warm-blooded animals and are major enteropathogens in humans. C. coli is less common than C. jejuni and accounts for about 10% of the total number of Campylobacter infections although the two species seem to share many virulence determinants. Campylobacter bacteraemia is rare, estimated to occur in less than 1% of the infections, and the exact mechanisms regulating the progression of the infection from the gastrointestinal tract to the blood stream are unclear. Here, we looked at the contribution of C. coli to Campylobacter infections and further compared various virulence traits in C. coli clade 1 blood and stool isolates.ResultsWe assessed the numbers of C. jejuni and C. coli among typed isolates in the PubMLST database and found that C. coli accounted for 25.9% of blood isolates, but only 8.9% of the stool isolates. Phylogenetic analysis of 128 C. coli clade 1 whole genome sequences deposited to NCBI revealed no specific clustering of the human blood, stool or animal isolates. Of the six C. coli isolates chosen for phenotypic analyses, stool isolates adhered significantly better to human HT-29 colon cancer cells than the blood isolates, while there was no difference in induced IL-8 levels between the isolates. Furthermore, the stool isolates had two- to fourfold higher RNA expression levels of the flpA, ciaB, iamA and cdt virulence genes than the blood isolates. Finally, we looked at the gene structure of the cdtA, B and C toxin genes and found numerous nucleotide additions and deletions disrupting the open reading frames. In contrast to 58% isolates of animal origin, only 38% and 32% of human blood and stool isolates, respectively, had all three cdt genes intact, a prerequisite to produce functional toxins.ConclusionsThis study reveals interesting differences between C. coli clade 1 isolates of human and animal origin on one hand, and also between human blood and stool isolates, on the other. The results suggest that C. coli might downregulate and/or inactivate various virulence determinants as the isolates pass from the animal host to the human gastrointestinal tract and enter the human blood stream.

Expression of virulence and antimicrobial resistance genes among Escherichia coli clinical isolates from blood and stool samples

Objective: As major nosocomial pathogens, Escherichia coli isolates exhibit antibiotic resistance and also express adhesive structures and antibiotic resistance genes. The objective of this study was the comparison of virulence gene expression of extended-spectrum beta-lactamase (ESBL)-producing E. coli between blood and stool samples. Methods: In this study, 20 E. coli clinical isolates (10 ESBL-producers including 5 from blood, 5 from stool samples and 10 non-ESBL-producer strains) were included. The existence of fimA, kpsMII and cdt (adhesives and toxin), acr-ab (efflux-encoding) and bla(CTX-M1) genes were confirmed by PCR. The quantitative real-time PCR was performed for evaluation of gene expression. Results: ESBL-producing E. coli isolates from stool samples could express fimA, kpsMII and cdt genes significantly higher than blood samples, whereas those isolates from blood samples significantly expressed the acr-ab (efflux-encoding) genes. In addition, the bla(CTXM1) gene was expressed among isolates from stool samples significantly higher (P = 0.022) than those from blood samples according to the analysis of variance (ANOVA) test. In addition, among non-ESBL-producers, the expression of fimA, kpsMII and cdt genes was significantly lower than ESBL-producing isolates from blood samples, but not significantly different than those from stool samples. Moreover, the expression of acr-ab genes was significantly lower than those from stool samples. Conclusion: The results exhibited that the expression of virulence genes among clinical isolates of E. coli is not the same or similar in various conditions or from various clinical origins. Thus determining the profile of gene expression in each of clinical situations can be helpful in tracking the infectious pathogens. ESBL-producing strains possibly have regulatory factors for inducing higher virulence gene expression. Copyright (C) 2019 Wolters Kluwer Health, Inc. All rights reserved.

Serogroup distribution, diversity of exotoxin gene profiles, and phylogenetic grouping of CTX-M-1- producing uropathogenic Escherichia coli

The emergence of CTX-M-1 producing Uropathogenic Escherichia coli (UPEC) has become a serious challenge. In addition to antimicrobial resistance, a number of virulence factors have been shown. Therefore, this study was designed to determine the prevalence of O- serogroups, phylogenetic groups, exotoxin genes, and antimicrobial resistance properties of CTX-M-1- producing UPEC. A total of 248 UPEC isolates were collected. The antibiotic resistance was performed, and PCR was used to detect the blaCTX-M1, exotoxins, serogroups and phylogroups of UPEC. Of 248 isolates, 95 (38.3%) harbored blaCTX-M-1. Of them, serogroups O1 and O25 were predominant, accounting for 20% and 13.7%, respectively. The hlyA was the dominant exotoxin gene (32.6%), followed by sat (28.4%), vat (22.1%), cnf (13.7%), picU (8.4%), and cdt (2.1%). The hlyA gene was significantly associated with pyelonephritis (P = 0.003). Moreover, almost half of the isolates (45.4%) belonged to phylogenetic group B2. Most of exotoxin genes were present in significantly higher proportions in group B2 isolates except cdt gene (P < 0.05). All of the isolates were susceptible to imipenem, nitrofurantoin, and fosfomycin. The CTX-M-1-producing UPEC strains causing nosocomial infections are more likely to harbor certain exotoxin genes, raising the possibility that this increase in virulence genes may result in an increased risk of complicated UTI.

Development of a specific cytolethal distending toxin (cdt) gene (Eacdt)–based PCR assay for the detection of Escherichia albertii

Many Escherichia albertii isolates, an emerging pathogen of human and birds, might have been misidentified due to the difficulty of differentiating this bacterium from Escherichia coli and Shigella spp. by routine biochemical tests, resulting in underestimation of E. albertii infections. We have developed a polymerase chain reaction (PCR) assay that targets E. albertii cytolethal distending toxin (Eacdt) genes, which include the genes previously identified as Escherichia coli cdt-II. This assay could generate a single 449-bp PCR product in each of 67 confirmed E. albertii strains but failed to produce PCR product from any of the tested non–E. albertii enteric strains belonging to 37 different species, indicating 100% sensitivity and specificity of the PCR assay. The detection limit was 10 CFU per PCR tube and could detect 105 CFU E. albertii per gram of spiked healthy human stool. The Eacdt gene-based PCR could be useful for simple, rapid, and accurate detection and identification of E. albertii.