Group B2 Strains Research Articles

The distinct transcriptome of virulence-associated phylogenetic group B2 Escherichia coli.

Escherichia coli strains of phylogenetic group B2 are often associated with urinary tract infections (UTIs) and several other diseases. Recent genomic and transcriptomic analyses have not suggested or identified specific genes required for virulence, but have instead suggested multiple virulence strategies and complex host-pathogen interactions. Previous analyses have not compared core gene expression between phylogenetic groups or between pathogens and nonpathogens within phylogenetic groups. We compared the core gene expression of 35 strains from three phylogenetic groups that included both pathogens and nonpathogens after growth in a medium that allowed comparable growth of both types of strains. K-means clustering suggested a B2 cluster with 17 group B2 strains and two group A strains; an AD cluster with six group A strains, five group D strains and one B2 strain; and four outliers which included the highly studied model uropathogenic E. coli strains UTI89 and CFT073. Half of the core genes were differentially expressed between B2 and AD cluster strains, including transcripts of genes for all aspects of macromolecular synthesis-replication, transcription, translation, and peptidoglycan synthesis-energy metabolism, and environmental-sensing transcriptional regulators. Notably, core gene expression between nonpathogenic and uropathogenic transcriptomes within phylogenetic groups did not differ. If differences between pathogens and nonpathogens exist, then the differences do not require transcriptional reprogramming. In summary, B2 cluster strains have a distinct transcription pattern that involves hundreds of genes. We propose that this transcription pattern is one factor that contributes to virulence. IMPORTANCE Escherichia coli is a diverse species and an opportunistic pathogen that is associated with various diseases, such as urinary tract infections. When examined, phylogenetic group B2 strains are more often associated with these diseases, but the specific properties that contribute to their virulence are not known. From a comparative transcriptomic analysis, we found that group B2 strains grown in a nutrient-rich medium had a distinct transcription pattern, which is the first evidence that core gene expression differs between phylogenetic groups. Understanding the consequences of group B2 transcription pattern will provide important information on basic E. coli biology, the basis for E. coli virulence, and possibly for developing therapies for a majority of urinary tract infections and other group B2-associated diseases.

Geographic distribution of the major clone of extended-spectrum beta-lactamase-producing Escherichia coli infection in a pediatric community in southern Taiwan

BackgroundThe geographic distribution of the major clone of sequence type 131 (ST131) in extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) infections is not known. We analyzed the clinical features, resistance mechanisms, and geographic distribution of ESBL-producing E. coli clones in 120 children. MethodsWe studied the 120 ESBL-producing E. coli strains from children younger than 18 years. A VITEK 2 automated system was used to determine bacterial identification and ESBL production. Sequence type was determined by multi-locus sequence typing (MLST). The genetic relationship of the ESBL-producing strains was studied using pulsed-field gel electrophoresis (PFGE). Phylogenetic group and blaCTX-M group was performed using polymerase chain reaction (PCR). Multiplex PCR for detecting the common group 9 variant, CTX-M-14, and group 1 variant, CTX-M-15, was also performed. The addresses of the 120 children were collected, and plotted on the Taiwan map. ResultsThe groups in the center of Kaohsiung City lived mainly in urban areas with a population density of over 10,000 people per square kilometer, and the majority of the Kaohsiung groups on the outskirts of the city center lived in suburban areas with a population density of under 6000 people per square kilometer. There was no statistically significant difference between the city center and outskirt groups in terms of clinical presentation, laboratory, and imaging data. However, more ST131 clones, major pulsotype groups, and phylogenetic group B2 strains were found in the center of Kaohsiung than on the outskirts. ConclusionESBL-producing E. coli clones may be more challenging to treat clinically. Most infections were community-acquired, and there appeared to be major pulsotype clones, mainly in urban areas. This reinforces the necessity of environmental surveillance and sanitary procedures for ESBL-producing E. coli.

Comparative Biotypic and Phylogenetic Profiles of Escherichia coli Isolated from Resident Stool and Lagoon in Fresco (Côte d'Ivoire).

Anthropogenic activities could expose Fresco lagoon to microbial pollution. The objective of this study was to determine the level of pollution in Fresco lagoon related to fecal contaminations. Two hundred and seventy (270) samples including 216 water and 54 human stools samples from local residents were collected. Escherichia coli was isolated and identified according to classical bacteriology procedure. Strains were characterized by biotyping on API 20E gallery and phylogenetic typing by PCR triplex of Clermont. A set of 392 strains of E. coli was distributed into 18 biotypic profiles. Five biotypes were common to water and human. Classification of all biotypes revealed close relationship between water and human strains because of their repartition in the same groups. Phylogenetic groups A, B1, B2, and D were identified in all strains. Strains belonging to phylogenetic group A were most frequent in water (69.82%) and human stool (44.44%) followed by group B1 in water (24%) and human stool (40.7%). Strains of group B2 were scarce in water (4.4%) and humans (7.41%). The diversity of E. coli biotypes observed in this study revealed animal and human origins of contaminations. A close relationship was found between water and human strains, and the presence of commensal and extraintestinal pathogenic E. coli in all samples could represent a potential reservoir of extraintestinal infections for resident populations.

Correlation of Escherichia coli Strains Isolated from Wild Bird Feces and Human Urinary Tract Infections from Phylogenetic Point of View

Background: Escherichia coliis a typical occupant of the enteric system of vertebrates. Some E. coli strains are related to urinary tract infections (UTIs) in human. E. coli strains are divided namely to the four phylogenetic groups, A, B1, B2, and D. Some investigations have indicated the relationship between phylogenetic characteristics and pathogenicity of E. coli. Thus, determining the phylogeny of unknown E. coli strains may be useful in predicting the pathogenesis. Objectives: In the present study, we aimed to compare the distribution of E. coli phylogroups in human UTIs and wild bird feces as a possible source of infection for human in a cross-sectional survey. Methods: A total of 264 E. coli isolates were obtained from human UTIs and feces of wild birds around and phylogenetic determination was carried out using the Clermont Triplex-PCR technique. Results: Our results showed that phylogenetic group B2 strains were the most prevalent in UTI cases (47.2%) followed by group D (30.2%). Group B1 contained 32.5% of the isolates in feces of wild birds, followed by group A (27.5%). There was a significant difference in E. coli phylogeny between hosts so that groups B2 and D were more prevalent in human UTIs and groups B1 and A in wild birds. Also, when comparing the phylogroups within a host, group B1 showed a higher rate in wild birds than in human UTIs. Conclusions: Although the majority of isolates from wild birds belonged to nonpathogenic phylogenetic groups B1 and A, further research seems to necessary to assess the exact relation of wild birds as pathogen sources for human by genotyping E. coli strains via high throughput genotyping assays.

Characterization and virulence clustering analysis of extraintestinal pathogenic Escherichia coli isolated from swine in China

BackgroundSwine extraintestinal pathogenic Escherichia coli (ExPEC) is an important pathogen that leads to economic and welfare costs in the swine industry worldwide, and is occurring with increasing frequency in China. By far, various virulence factors have been recognized in ExPEC. Here, we investigated the virulence genotypes and clonal structure of collected strains to improve the knowledge of phylogenetic traits of porcine ExPECs in China.ResultsWe isolated 64 Chinese porcine ExPEC strains from 2013 to 14 in China. By multiplex PCR, the distribution of isolates belonging to phylogenetic groups B1, B2, A and D was 9.4%, 10.9%, 57.8% and 21.9%, respectively. Nineteen virulence-related genes were detected by PCR assay; ompA, fimH, vat, traT and iutA were highly prevalent. Virulence-related genes were remarkably more prevalent in group B2 than in groups A, B1 and D; notably, usp, cnf1, hlyD, papA and ibeA were only found in group B2 strains. Genotyping analysis was performed and four clusters of strains (named I to IV) were identified. Cluster IV contained all isolates from group B2 and Cluster IV isolates had the strongest pathogenicity in a mouse infection model. As phylogenetic group B2 and D ExPEC isolates are generally considered virulent, multilocus sequence typing (MLST) analysis was performed for these isolates to further investigate genetic relationships. Two novel sequence types, ST5170 and ST5171, were discovered. Among the nine clonal complexes identified among our group B2 and D isolates, CC12 and CC95 have been indicated to have high zoonotic pathogenicity. The distinction between group B2 and non-B2 isolates in virulence and genotype accorded with MLST analysis.ConclusionThis study reveals significant genetic diversity among ExPEC isolates and helps us to better understand their pathogenesis. Importantly, our data suggest group B2 (Cluster IV) strains have the highest risk of causing animal disease and illustrate the correlation between genotype and virulence.

Escherichia coli strains of phylogenetic group B2 and D and bacteriocin production are associated with advanced colorectal neoplasia.

BackgroundColorectal cancer (CRC) is the 3rd most common cancer worldwide and the Czech Republic has the 6th highest incidence of CRC worldwide. Large intestinal microbiota play in its etiopathogenesis important role. Bacteriocins are proteins, produced by bacteria from the Enterobacteriaceae family. The aim of our prospective study was to assess the colonization of large intestinal mucosa by Escherichia coli strains and to investigate their bacteriocin production.MethodsA total of 30 consecutive patients with colorectal adenoma, CRA (17 men, 13 women, aged 39–79, mean age 63 ± 9), 30 patients with CRC (23 men, 7 women, aged 38–86, mean age 67 ± 11) and 20 healthy controls (9 men, 11 women, age 23–84, mean age 55 ± 15) were enrolled into prospective study. Mucosal biopsies were taken in the caecum, transverse colon and rectum during pancolonoscopy. Microbiological culture, isolation and identification of bacteria followed. Bacteriocin production was assessed by growth inhibition of indicator strains E. coli K12-Row, E. coli C6 (phi), and Shigella sonnei 17. Identification of bacteriocin-encoding determinants and E. coli phylogroups was performed using PCR methods.ResultsA total of 622 strains were isolated and further investigated. A significantly higher frequency of simultaneous production of colicins and microcins was revealed in the group of patients with CRC, when compared to patients with CRA, p = 0.031. A significantly higher frequency of E. coli phylogroup D was found in patients with CRC, when compared to controls, p = 0.044. A significantly higher prevalence of bacteriocinogeny was confirmed in patients with advanced adenoma when compared to patients with non-advanced adenoma, p = 0.010. Increasing bacteriocinogeny was associated with an increasing stage of CRC (assessed according to TNM classification). Either E. coli phylogroup B2 or E. coli phylogroup D were isolated in biopsies of patients with right-sided CRC. A statistically higher incidence of E. coli phylogroup B2 was found in patients with right-sided CRC when compared to patients with left-sided CRC, p = 0.028.ConclusionsLarge intestinal mucosa of patients with more advanced colorectal neoplasia is colonized with more virulent strains of E. coli and higher production of bacteriocins is observed in these patients when compared to those with less advanced colorectal neoplasia.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-014-0733-7) contains supplementary material, which is available to authorized users.

Elevated recombinant clyA gene expression in the uropathogenic Escherichia coli strain 536, a clue to explain pathoadaptive mutations in a subset of extraintestinal E. coli strains.

BackgroundAnalysis of the Escherichia coli collection of reference strains (ECOR) for the presence of the gene locus clyA, which encodes the pore-forming protein ClyA (cytolysin A), revealed that a non-functional clyA locus is common among certain extraintestinal pathogenic E. coli (ExPEC). In fact, all 15 ECOR group B2 strains and several additionally examined extraintestinal pathogenic (uropathogenic (UPEC) and neonatal meningitis (NBM)) E. coli strains contained various ΔclyA alleles.ResultsThere are at least four different variants of ΔclyA, suggesting that such deletions in clyA have arisen at more than one occasion. On the basis of this occurrence of the truncated clyA genes, we considered that there may be a patho-adaptive selection for deletions in clyA in extraintestinal pathogenic E. coli. In E. coli K-12 the clyA gene has been viewed as “cryptic” since it is tightly silenced by the nucleoid structuring protein H-NS. We constructed a restored clyA+ locus in derivatives of the UPEC strain 536 for further investigation of this hypothesis and, in particular, how the gene would be expressed. Our results show that the level of clyA+ expression is highly increased in the UPEC derivatives in comparison with the non-pathogenic E. coli K-12. Transcription of the clyA+ gene was induced to even higher levels when the SfaX regulatory protein was overproduced. The derivative with a restored clyA+ locus displayed a somewhat slower growth than the parental UPEC strain 536 when a sub-inhibitory concentration of the antimicrobial peptide Polymyxin B was added to the growth medium.ConclusionsTaken together, our findings show that the clyA+ locus is expressed at an elevated level in the UPEC strain and we conclude that this is at least in part due to the effect of the SfaX/PapX transcriptional regulators.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0216-4) contains supplementary material, which is available to authorized users.

Correlation between the genomic o454-nlpD region polymorphisms, virulence gene equipment and phylogenetic group of extraintestinal Escherichia coli (ExPEC) enables pathotyping irrespective of host, disease and source of isolation.

BackgroundThe mutS-rpoS intergenic region in E. coli displays a mosaic structure which revealed pathotype specific patterns. To assess the importance of this region as a surrogate marker for the identification of highly virulent extraintestinal pathogenic E. coli (ExPEC) strains we aimed to: (i) characterize the genetic diversity of the mutS gene and the o454-nlpD genomic region among 510 E. coli strains from animals and humans; (ii) delineate associations between the polymorphism of this region and features such as phylogenetic background of E. coli, pathotype, host species, clinical condition, serogroup and virulence associated genes (VAG)s; and (iii) identify the most important VAGs for classification of the o454-nlpD region.MethodsSize variation in the o454-nlpD region was investigated by PCR amplification and sequencing. Phylogenetic relationships were assessed by Ecor- and Multilocus sequence- typing (MLST), and a comparative analysis between mutS gene phylogenetic tree obtained with RAxML and the MLST grouping method was performed. Correlation between o454-nlpD patterns and the features described above were analysed. In addition, the importance of 47 PCR-amplified ExPEC-related VAGs for classification of o454-nlpD patterns was investigated by means of Random Forest algorithm.ResultsFour main structures (patterns I-IV) of the o454-nlpD region among ExPEC and commensal E. coli strains were identified. Statistical analysis showed a positive and exclusive association between pattern III and the ExPEC strains. A strong association between pattern III and either the Ecor group B2 or the sequence type complexes known to represent the phylogenetic background of highly virulent ExPEC strains (such as STC95, STC73 and STC131) was found as well. RF analyses determined five genes (csgA, malX, chuA, sit, and vat) to be suitable to predict pattern III strains.ConclusionThe significant association between pattern III and group B2 strains suggested the o454-nlpD region to be of great value in identifying highly virulent strains among the mixed population of E. coli promising to be the basis of a future typing tool for ExPEC and their gut reservoir. Furthermore, top-ranked VAGs for classification and prediction of pattern III were identified. These data are most valuable for defining ExPEC pathotype in future in vivo assays.

Distribución de grupos filogenéticos y factores de virulencia en cepas de Escherichia coli uropatógena productora de β-lactamasa CTX-M-15 aisladas de pacientes de la comunidad en Mérida, Venezuela

In this study, the distribution of phylogenetic groups and the genetic detection of virulence factors in CTX-M-15 β-lactamase-producing uropathogenic Escherichia coli (UPEC) strains were analyzed. Twenty eight strains were isolated between January 2009 and July 2011 from patients with urinary tract infection (UTI) who attended the Public Health Laboratory at Mérida, Venezuela. Determination of phylogenetic groups and detection of six virulence genes, fimH, fyuA, kpsMTII, usp, PAI and papAH, were performed by PCR amplification. Fifteen of the 28 isolates were mainly located in the phylogenetic group A, followed by B2 (12/28) and D (1/28). No direct relationship between the severity or recurrence of UTI and the distribution of phylogroups was observed. All studied virulence factors were found in group B2 strains with the highest frequency. The prevalent virulence profile included the combination of three main genes: fimH, kpsMTII and fyuA and, to a lesser extent, the presence of other determinants such as usp, PAI and/or papAH. These results indicate that virulent UPEC incorporated three important properties: adhesion, iron uptake and evasion of phagocytosis, which favored the production of recurrent UTI. This is the first report describing the association of phylogenetic groups with the potential virulence of CTX-M-15 β-lactamase producing UPEC strains in Venezuela.

Mo1141 Association of Right-Sided Colorectal Cancer and Ulcerative Colitis With Escherichia coli Strains of Phylogenetic Group B2, Which Harbour Genotoxic “PKS” Island

Mo1141 Association of Right-Sided Colorectal Cancer and Ulcerative Colitis With Escherichia coli Strains of Phylogenetic Group B2, Which Harbour Genotoxic “PKS” Island

Phylogenetic association of fluoroquinolone and cephalosporin resistance of D-O1-ST648 Escherichia coli carrying bla CMY-2 from faecal samples of dogs in Japan

This study aimed to investigate the genetic association between fluoroquinolone (FQ) and/or cephalosporin (CEP) resistance in Escherichia coli isolates from dogs, and the risk to human health. We characterized E. coli clinical isolates, derived from faecal samples of dogs attending veterinary hospitals, using phylogenetic grouping, determination of virulence factor (VF) prevalence, multilocus sequence typing (MLST) and O serotyping. The D group was the dominant phylogenetic group among strains resistant to FQ and/or CEP. In contrast, the dominant group among susceptible strains was group B2. Group D strains showed a significantly higher prevalence of VFs than strains belonging to groups A and B1, and were resistant to significantly more antimicrobials than group B2 strains. The phylogenetic distribution of FQ-CEP-resistant E. coli groups (FQ-CEPRECs) and FQ-resistant groups was significantly correlated (r = 0.98), but FQ-CEPRECs and CEP-resistant E. coli groups were not correlated (r = 0.58). Data from PFGE, O serotype and MLST analyses indicated that the majority of FQ-resistant strains derived from a particular lineage of phylogenetic group D: serotype O1 and sequence type (ST) 648. Some D-O1-ST648 strains carried blaCMY-2, showed multidrug resistance and possessed a higher prevalence of the VFs kspMT, ompT and PAI compared with other group D strains. Our data indicate that the emergence of FQ-CEP-resistant E. coli is based primarily on FQ-resistant E. coli. Moreover, as strains of the D-O1-ST648 lineage have been found in clinical isolates derived from humans at a relatively high frequency, our findings indicate that the spreading of D-O1-ST648 strains may cause serious difficulties in both veterinary and human clinical fields in the future.

Escherichia coli strains with the capacity for long-term persistence in the bowel microbiota carry the potentially genotoxic pks island

The pks genomic island found in Escherichia coli strains of phylogenetic group B2 encodes colibactin, a polyketide-peptide genotoxin that causes DNA double-strand breaks. We investigated the relationship between carriage of the pks island and the capacity of E. coli strains to persist in the gut microbiota of 130 Swedish infants, who were followed from birth to 18 months of age. Long-term colonizers were significantly more likely to have the pks island than either intermediate-term colonizers or transient strains, which suggests that the pks island contributes to the pronounced gut-colonizing capacity of group B2 strains. Long-term persistence in the colon of pks island-containing E. coli strains may be associated with the induction of genomic mutations in the host intestine.

Virulence Potential and Genomic Mapping of the Worldwide Clone Escherichia coli ST131

Recently, the worldwide propagation of clonal CTX-M-15-producing Escherichia coli isolates, namely ST131 and O25b:H4, has been reported. Like the majority of extra-intestinal pathogenic E. coli isolates, the pandemic clone ST131 belongs to phylogenetic group B2, and has recently been shown to be highly virulent in a mouse model, even though it lacks several genes encoding key virulence factors (Pap, Cnf1 and HlyA). Using two animal models, Caenorhabditis elegans and zebrafish embryos, we assessed the virulence of three E. coli ST131 strains (2 CTX-M-15- producing urine and 1 non-ESBL-producing faecal isolate), comparing them with five non-ST131 B2 and a group A uropathogenic E. coli (UPEC). In C. elegans, the three ST131 strains showed intermediate virulence between the non virulent group A isolate and the virulent non-ST131 B2 strains. In zebrafish, the CTX-M-15-producing ST131 UPEC isolates were also less virulent than the non-ST131 B2 strains, suggesting that the production of CTX-M-15 is not correlated with enhanced virulence. Amongst the non-ST131 B2 group isolates, variation in pathogenic potential in zebrafish embryos was observed ranging from intermediate to highly virulent. Interestingly, the ST131 strains were equally persistent in surviving embryos as the non-ST131-group B2 strains, suggesting similar mechanisms may account for development of persistent infection. Optical maps of the genome of the ST131 strains were compared with those of 24 reference E. coli strains. Although small differences were seen within the ST131 strains, the tree built on the optical maps showed that these strains belonged to a specific cluster (86% similarity) with only 45% similarity with the other group B2 strains and 25% with strains of group A and D. Thus, the ST131 clone has a genetic composition that differs from other group B2 strains, and appears to be less virulent than previously suspected.

Acute Escherichia coli Prostatitis in Previously Health Young Men: Bacterial Virulence Factors, Antimicrobial Resistance, and Clinical Outcomes

To investigate clinical outcomes, bacterial virulence factors, and antimicrobial resistance in E. coli from young men presenting with acute bacterial prostatitis. Initial E. coli isolates from previously healthy young men with no factors compromising urinary tract anatomy or function were tested for virulence-associated genes by polymerase chain reaction (PCR) assays, phylogenetic grouping by triplex polymerase PCR, and antibiotic resistance. All 18 patients responded to treatment, including 2 who required long-term therapy. E. coli were allocated to phylogenetic groups B2 (13 strains) and D (5 strains). Prostatitis isolates belonged to clones mainly represented by extraintestinal pathogenic E. coli (ExPEC) and preferentially uropathogenic E. coli and displayed marked accumulation of virulence genes (hly, cdt1, clb, pap, sfa/foc, fyuA, iroN, kpsMT(II), and traT) characteristic of highly virulent ExPEC. All phylogenetic group B2 strains coded for at least 1 toxin with carcinogenic potential (Colibactin, cytolethal distending toxins, or cytotoxic necrotizing factor). In contrast to their accumulation of virulence-associated traits, prostatitis strains were sensitive to standard antibiotics. The phylogenetic background and accumulation of an exceptional repertoire of extraintestinal pathogenic virulence-associated genes indicate that these E. coli strains belong to a highly virulent subset of uropathogenic variants. In contrast, antibiotic resistance was minimal in these E. coli strains from previously healthy, young outpatients.

Animal and human pathogenic Escherichia coli strains share common genetic backgrounds

Escherichia coli is a versatile species encompassing both commensals of the digestive tracts of many vertebrates, including humans, and pathogenic strains causing various intra- and extraintestinal infections. Despite extensive gene flow between strains, the E. coli species has a globally clonal population structure, consisting of distinct phylogenetic groups. Little is known about the relationships between phylogenetic groups and host specificity. We therefore used multilocus sequence typing (MLST) to investigate phylogenetic relationships and evaluated the virulence gene content of 35 E. coli strains representative of the diverse diseases encountered in domestic animals. We compared these strains with a panel of 101 human pathogenic and 98 non-human and human commensal strains representative of the phylogenetic and pathovar diversity of this species. A global factorial analysis of correspondence indicated that extraintestinal infections were caused mostly by phylogenetic group B2 strains, whereas intraintestinal infections were caused mostly by phylogenetic group A/B1/E strains, with strains responsible from extraintestinal or intraintestinal infections having specific virulence factors. It was not possible to distinguish between strains of human and animal origin. A detailed phylogenetic analysis of the MLST data showed that numerous pathogenic animal and human strains are very closely related, and had a number of virulence genes in common. However, a set of specific adhesins was identified in animal non-B2 group strains of all pathotypes. In conclusion, human and animal pathogenic strains share common genetic backgrounds, but non-B2 strains of different origins seem to have different sets of adhesins that could be involved in host specificity.

Prevalence and phylogenetic history of the TcpC virulence determinant in Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPECs) possess an armament of virulence factors to colonize and infect the host, such as adhesins, toxins, capsules and iron-uptake systems. Recently, we could identify a novel virulence factor of ExPECs that interferes with the innate immune response of the host by interrupting the NF-κB signaling pathway. This protein named TcpC shows considerable homology to motifs of the Tir domain of Toll-like receptors. Here we demonstrate that the tcpC gene is widely distributed among clinical ExPEC isolates with almost half of the E. coli strains from patients suffering pyelonephritis shown to be tcpC positive as compared to only 8% in commensal isolates. However, this gene is only present in phylogenetic group B2 strains. Interestingly, the tcpC gene is strongly associated with presence of the high-pathogenicity island (HPI). The phylogenetic history of the tcpC gene, in the E. coli reference collection (ECOR) and other well-defined E. coli strains, compared to the phylogenetic histories of the HPI and the strains, showed that the tcpC gene (i) is scattered among various B2 subgroups with specific O-types, (ii) has a phylogeny incongruent with the strain phylogeny, but (iii) congruent with the HPI phylogenetic history. This, together with the strong conservation of the tcpC gene, indicates a very recent introduction of this virulence factor into E. coli by horizontal gene transfer which occurred “en bloc” with the HPI at one major hot spot of recombination in the E. coli genome. The present data provide evidence for a strong impact of homologous recombination events in the spread of the TcpC virulence trait among E. coli.

Clinical and Phylogenetic Characteristics of Escherichia coli Urinary Tract Infections

Purpose : We aimed to investigate the clinical and phylogenetic characteristics of Escherichia coli Urinary Tract Infections (E. coli UTI). Methods : We enrolled patients with culture-proven E. coli UTI, who were admitted at the study hospital from September 2008 to August 2009. We investigated clinical data of patients with E. coli UTI and characteristics of isolated E. coli strains. The phylogenetic groups were classified using triplex polymerase chain reaction (PCR), and the distribution of nine virulent genes was determined by multiplex PCR. Results : A total of 47 patients have participated in this study. Thirty (63.8%) were under 6 months; eight (17.0%) were between 6-12 months; and nine (19.1%) were over 12 months. We compared two age groups between under 6-month and over 6-month. In the age group under 6-month, higher proportion of male (P =0.002) and group B2 strains (P =0.020) were observed. In contrast, higher proportion of female and group non-B2 strains were observed in age group over 6-month. Frequencies of papC, papGII, papGIII, sfa/foc, hlyC, cnf1, fyuA, iroN and iucC were estimated as 68.1%, 57.4%, 42.6%, 46.8%, 46.8%, 31.9%, 87.2%, 48.9% and 63.8%, respectively. In the comparison of phylogenetic groups, group B2 showed higher distribution of virulent genes, while group D included more strains resistant to trimethoprim/sulfamethoxazole (TMP/SMZ) than other groups. Conclusion : We showed the age group-specific difference in the distribution of sex ratios and phylogenetic groups; more male and group B2 strains in age group under 6-month, while more female and group non-B2 in age group over 6-month. However, further evaluation including larger number of patients will be necessary to confirm above thesis in future molecular epidemiological studies.

Absence of Escherichia coli Phylogenetic Group B2 Strains in Humans and Domesticated Animals from Jeonnam Province, Republic of Korea

Multiplex PCR analyses of DNAs from genotypically unique Escherichia coli strains isolated from the feces of 138 humans and 376 domesticated animals from Jeonnam Province, South Korea, performed using primers specific for the chuA and yjaA genes and an unknown DNA fragment, TSPE4.C2, indicated that none of the strains belonged to E. coli phylogenetic group B2. In contrast, phylogenetic group B2 strains were detected in about 17% (8 of 48) of isolates from feces of 24 wild geese and in 3% (3 of 96) of isolates obtained from the Yeongsan River in Jeonnam Province, South Korea. The distribution of E. coli strains in phylogenetic groups A, B1, and D varied depending on the host examined, and there was no apparent seasonal variation in the distribution of strains in phylogenetic groups among the Yeongsan River isolates. The distribution of four virulence genes (eaeA, hlyA, stx(1), and stx(2)) in isolates was also examined by using multiplex PCR. Virulence genes were detected in about 5% (38 of 707) of the total group of unique strains examined, with 24, 13, 13, and 9 strains containing hlyA, eaeA, stx(2), and stx(1), respectively. The virulence genes were most frequently present in phylogenetic group B1 strains isolated from beef cattle. Taken together, results of these studies indicate that E. coli strains in phylogenetic group B2 were rarely found in humans and domesticated animals in Jeonnam Province, South Korea, and that the majority of strains containing virulence genes belonged to phylogenetic group B1 and were isolated from beef cattle. Results of this study also suggest that the relationship between the presence and types of virulence genes and phylogenetic groupings may differ among geographically distinct E. coli populations.

Phylogenetic group B2 Escherichia coli strains from the bowel microbiota of Pakistani infants carry few virulence genes and lack the capacity for long-term persistence

Escherichia coli strains of phylogenetic group B2 obtained from Western human hosts are enriched in virulence-associated genes and have a superior capacity to persist in the colonic microbiota. Here, E. coli strains from 22 infants born in Pakistan whose rectal flora was sampled regularly over the first 6 months of life were examined. B2 strains did not carry the virulence-associated genes sfaD/E, papC, neuB or hlyA more often than strains of other phylogenetic groups. B2 origin was not associated with persistence in the bowel microbiota. As compared with B2 strains from Swedish infants, Pakistani B2 strains carried significantly less often the virulence genes fimH (p 0.04), papC (p 0.02), papG class III (p 0.01), sfaD/E (p ≤0.0001), neuB (p ≤0.0001), and hlyA (p 0.005), and also the high-pathogenicity island (p ≤0.0001). A minority of Pakistani B2 strains belonged to recognized uropathogenic O-groups, which are common among ‘Western’ B2 strains. Thus, extra-intestinal pathogenicity may be the foremost characteristic of B2 strains colonizing Western populations.

Characterization of a β-Glucoside Operon (bgc) Prevalent in Septicemic and UropathogenicEscherichia coliStrains

Escherichia coli strains, in general, do not ferment cellobiose and aryl-beta-D-glucosidic sugars, although "cryptic" beta-d-glucoside systems have been characterized. Here we describe an additional cryptic operon (bgc) for the utilization of cellobiose and the aryl-beta-d-glucosides arbutin and salicin at low temperature. The bgc operon was identified by the characterization of beta-glucoside-positive mutants of an E. coli septicemia strain (i484) in which the well-studied bgl (aryl-beta-d-glucoside) operon was deleted. These bgc* mutants appeared after 5 days of incubation on salicin indicator plates at 28 degrees C. The bgc operon codes for proteins homologous to beta-glucoside/cellobiose-specific phosphoenolpyruvate-dependent phosphotransfer system permease subunits IIB (BgcE), IIC (BgcF), and IIA (BgcI); a porin (BgcH); and a phospho-beta-D-glucosidase (BgcA). Next to the bgc operon maps the divergent bgcR gene, which encodes a GntR-type transcriptional regulator. Expression of the bgc operon is dependent on the cyclic-AMP-dependent regulator protein CRP and positively controlled by BgcR. In the bgc* mutants, a single nucleotide exchange enhances the activity of the bgc promoter, rendering it BgcR independent. Typing of a representative collection of E. coli demonstrated the prevalence of bgc in strains of phylogenetic group B2, representing mainly extraintestinal pathogens, while it is rare among commensal E. coli strains. The bgc locus is also present in the closely related species Escherichia albertii. Further, bioinformatic analyses demonstrated that homologs of the bgc genes exist in the enterobacterial Klebsiella, Enterobacter, and Citrobacter spp. and also in gram-positive bacteria, indicative of horizontal gene transfer events.