Characterization of AfaE adhesins produced by extraintestinal and intestinal human Escherichia coli isolates: PCR assays for detection of Afa adhesins that do or do not recognize Dr blood group antigens

Investigation of the biofilm formation in extra-intestinal pathogenic Escherichia coli ST131 strains and its correlation with the presence of fimH, afa, and kpsMSTII genes

Escherichia coli sequence type 131 (ST131) is a multidrug-resistant strain with the global dissemination. Biofilm formation-related factors include the most important virulence factors in extra-intestinal pathogenic E. coli (ExPEC) ST131 strains causing infections with treatment-limited subjects. This study aims to investigate the biofilm formation ability and its correlation with the presence of fimH, afa, and kpsMSTII genes in clinical isolates of ExPEC ST131. In this regard, the prevalence and characteristics of these strains collected and evaluated. The results revealed strong, moderate, and weak attachment abilities related to biofilm formation attributes in 45%, 20%, and 35% of strains, respectively. In the meantime, the frequency of the fimH, afa, and kpsMSTII genes among the isolates was observed as follows: fimH positive: 65%; afa positive: 55%; and kpsMSTII positive: 85%. The results convey a significant different of biofilm formation ability between clinical E. coli ST131 and non-ST131 isolates. Furthermore, while 45% of ST131 isolates produced strong biofilms, only 2% of non-ST131 isolates showed the ability to form strong biofilms. The attending of fimH, afa, and kpsMSTII genes in the majority of ST131 strains demonstrated a key role leading to biofilm formation. These findings suggested the application of fimH, afa, and kpsMSTII gene suppressors for treating biofilm infections caused by drug-resistant ST131 strains.

Molecular characterization of Dr/Afa genes prevalent among multi drug resistant Escherichia coli isolated from urinary tract infections

Introduction and Aim: Escherichia coli strains are derived from several phylogenetic groups and have an array of virulence factors such as fimbrial adhesins, which are expressed by the Dr/Afa gene clusters and contribute to overcoming diverse defense mechanisms, resist drugs, and causing disease. The study sought to ascertain the prevalence of the Dr/Afa genes and resistance patterns among E. coli isolated from patients suffering from recurrent urinary tract infections.  Materials and Methods: In this prospective cross-sectional study, a maximum of 500 mid-stream urine samples were collected from UTI patients identified at medical centers in Baghdad, Iraq. Antimicrobial susceptibility tests and polymerase chain reaction were used to determine the resistance pattern and gene distribution among isolates, respectively, as well as biochemical tests to diagnose isolates.   Results: Research data revealed that recurrent urinary tract infections were associated with the pathogen E. coli (43.88%), followed by Klebsiella pneumoniae (12.82%). The results demonstrated significant antibiotic resistance patterns among isolates associated with recurrent UTIs and the most common antibiotic resistance was observed with penicillin (81.4%), followed by 81 (68.6%) sulfonamides and 63 (53.4%) fluoroquinolones. Molecular studies of the Dr/Afa operon using polymerase chain reaction, revealed several genotypes for genes within the operon. Among isolates studied the prevalence of the gene draA gene was 62 (52.5%), draB 41 (34.7%), draC 66 (55.9%), draD 65 (55.1%), draE 64 (54.2%), and draP 95 (80.5%). Furthermore, XDR and MDR-resistant phenotypes were significantly prevalent in isolates harboring hetero Dr/Afa fimbriae. Conclusion: The results of this study indicate an inverse correlation between the presence of antibiotic resistance patterns and the prevalence of Dr/Afa genes wherein, the isolates with fewer fimbrial adhesion genes were found to be highly resistant. This study implies the Dr/Afa genes involvement in developing UTIs, suggesting that they might be associated with antibiotic resistance and  recurrent UTIs.

Comparative Pathogenomics of Escherichia coli: Polyvalent Vaccine Target Identification through Virulome Analysis

Comparative genomics of bacterial pathogens has been useful for revealing potential virulence factors. Escherichia coli is a significant cause of human morbidity and mortality worldwide but can also exist as a commensal in the human gastrointestinal tract. With many sequenced genomes, it has served as a model organism for comparative genomic studies to understand the link between genetic content and potential for virulence. To date, however, no comprehensive analysis of its complete “virulome” has been performed for the purpose of identifying universal or pathotype-specific targets for vaccine development. Here, we describe the construction of a pathotype database of 107 well-characterized completely sequenced pathogenic and nonpathogenic E. coli strains, which we annotated for major virulence factors (VFs). The data are cross referenced for patterns against pathotype, phylogroup, and sequence type, and the results were verified against all 1,348 complete E. coli chromosomes in the NCBI RefSeq database. Our results demonstrate that phylogroup drives many of the “pathotype-associated” VFs, and ExPEC-associated VFs are found predominantly within the B2/D/F/G phylogenetic clade, suggesting that these phylogroups are better adapted to infect human hosts. Finally, we used this information to propose polyvalent vaccine targets with specificity toward extraintestinal strains, targeting key invasive strategies, including immune evasion (group 2 capsule), iron acquisition (FyuA, IutA, and Sit), adherence (SinH, Afa, Pap, Sfa, and Iha), and toxins (Usp, Sat, Vat, Cdt, Cnf1, and HlyA). While many of these targets have been proposed before, this work is the first to examine their pathotype and phylogroup distribution and how they may be targeted together to prevent disease.

A One Health Perspective for Defining and Deciphering Escherichia coli Pathogenic Potential in Multiple Hosts

E. coli is one of the most common species of bacteria colonizing humans and animals. The singularity of E. coli 's genus and species underestimates its multifaceted nature, which is represented by different strains, each with different combinations of distinct virulence factors. In fact, several E. coli pathotypes, or hybrid strains, may be associated with both subclinical infection and a range of clinical conditions, including enteric, urinary, and systemic infections. E. coli may also express DNA-damaging toxins that could impact cancer development. This review summarizes the different E. coli pathotypes in the context of their history, hosts, clinical signs, epidemiology, and control. The pathotypic characterization of E. coli in the context of disease in different animals, including humans, provides comparative and One Health perspectives that will guide future clinical and research investigations of E. coli infections.

Horizontally acquired papGII-containing pathogenicity islands underlie the emergence of invasive uropathogenic Escherichia coli lineages

Escherichia coli is the leading cause of urinary tract infection, one of the most common bacterial infections in humans. Despite this, a genomic perspective is lacking regarding the phylogenetic distribution of isolates associated with different clinical syndromes. Here, we present a large-scale phylogenomic analysis of a spatiotemporally and clinically diverse set of 907 E. coli isolates, including 722 uropathogenic E. coli (UPEC) isolates. A genome-wide association approach identifies the (P-fimbriae-encoding) papGII locus as the key feature distinguishing invasive UPEC, defined as isolates associated with severe UTI, i.e., kidney infection (pyelonephritis) or urinary-source bacteremia, from non-invasive UPEC, defined as isolates associated with asymptomatic bacteriuria or bladder infection (cystitis). Within the E. coli population, distinct invasive UPEC lineages emerged through repeated horizontal acquisition of diverse papGII-containing pathogenicity islands. Our findings elucidate the molecular determinants of severe UTI and have implications for the early detection of this pathogen.

Characterization and antibiotic resistance pattern of diffusely adherent Escherichia coli (DAEC), isolated from paediatric diarrhoea in Shiraz, southern Iran

Diarrhoea is a major health concern, especially in developing countries. Research has implicated diffusely adherent Escherichia coli (DAEC) strains as a cause of diarrhoea. In this study, we investigated the prevalence, adherence assay, virulence gene profiles and antimicrobial resistance of DAEC at a hospital in southern Iran. In this cross-sectional study, 309 infants and children under the age of 13 years with diarrhoea who had been referred to Shahid Dastgheib Hospital, Shiraz between October 2018 and May 2019 were recruited. Microbiological methods, PCR, HEp-2 adherence assay and antimicrobial susceptibility test were used. Of the 309 stool samples, 207 (66.9%) were found to contain E. coli by biochemical tests and culture. Molecular analysis of Afa/Dr and AIDA-I adhesin-encoding genes showed that 14 (6.7%) out of 207 E. coli isolates were DAEC. All DAEC isolates in HEp-2 cells showed a diffusely adherent pattern. The virulence genes sat, pet, sigA, pic, astA and fimH were found in 50%, 0%, 14.2%, 14.2%, 21.4% and 100% of DAEC isolates, respectively. The most effective antibiotic against the DAEC isolates was imipenem (92.8%) and the least effective was ampicillin (0%). Our findings expand the knowledge on DAEC prevalence and its characteristics in Iran. It also explains the role of virulence genes in DAEC pathogenesis. The results showed that although the prevalence of DAEC is low, these strains exhibit a high rate of antimicrobial resistance as well as high frequency for carrying virulence genes.

Pathogenicity Factors of Genomic Islands in Intestinal and Extraintestinal Escherichia coli

Escherichia coli is a versatile bacterial species that includes both harmless commensal strains and pathogenic strains found in the gastrointestinal tract in humans and warm-blooded animals. The growing amount of DNA sequence information generated in the era of "genomics" has helped to increase our understanding of the factors and mechanisms involved in the diversification of this bacterial species. The pathogenic side of E. coli that is afforded through horizontal transfers of genes encoding virulence factors enables this bacterium to become a highly diverse and adapted pathogen that is responsible for intestinal or extraintestinal diseases in humans and animals. Many of the accessory genes acquired by horizontal transfers form syntenic blocks and are recognized as genomic islands (GIs). These genomic regions contribute to the rapid evolution, diversification and adaptation of E. coli variants because they are frequently subject to rearrangements, excision and transfer, as well as to further acquisition of additional DNA. Here, we review a subgroup of GIs from E. coli termed pathogenicity islands (PAIs), a concept defined in the late 1980s by Jörg Hacker and colleagues in Werner Goebel's group at the University of Würzburg, Würzburg, Germany. As with other GIs, the PAIs comprise large genomic regions that differ from the rest of the genome by their G + C content, by their typical insertion within transfer RNA genes, and by their harboring of direct repeats (at their ends), integrase determinants, or other mobility loci. The hallmark of PAIs is their contribution to the emergence of virulent bacteria and to the development of intestinal and extraintestinal diseases. This review summarizes the current knowledge on the structure and functional features of PAIs, on PAI-encoded E. coli pathogenicity factors and on the role of PAIs in host-pathogen interactions.

Distribution of virulence genes and phylogenetics of uropathogenic Escherichia coli among urinary tract infection patients in Addis Ababa, Ethiopia

Background

Urinary tract infection (UTI) is a common cause of morbidity worldwide. Uropathogenic Escherichia coli (UPEC) bacteria are the major cause of urinary tract infections. UPEC strains derive from different phylogenetic groups and possess an arsenal of virulence factors that contribute to their ability to overcome different defense mechanisms and cause disease. The objective of this study was to identify phylogroup and virulence genes of UPEC among urinary tract infection patients.

Methods

A cross sectional study was conducted from January 1, 2017 to October 9, 2017. E. coli bacteria were isolated from UTI patients using culture and conventional biochemical tests. Identification of phylogroup and genes that encodes for virulence factors was done using multiplex polymerase chain reaction (PCR). Data was processed and analyzed with SPSS version16.0 and Epi-info version 3.4.1 software.

Results

The most common urologic clinical manifestation combinations in this study were dysuria, urine urgency and urgency incontinence. The frequent UPEC virulence gene identified was fimH 164 (82%), followed by aer 109 (54.5%), hly 103 (51.5%), pap 59 (29.5%), cnf 58 (29%), sfa 50 (25%) and afa 24 (12%).There was significant association between pap gene and urine urgency (p-0.016); sfa and dysuria and urine urgency (p-0.019 and p-0.043 respectively); hly and suprapubic pain (p-0.002); aer and suprapubic pain, flank pain and fever (p-0.017, p-0.040, p-0.029 respectively). Majority of E. coli isolates were phylogroup B2 60(30%) followed by D 55(27.5%), B1 48(24%) and A 37(18.5%). There was significant association between E. coli phylogroup B2 and three virulence genes namely afa, pap, and sfa (p-0.014, p-0.002, p-0.004 respectively).

Conclusion

In this study the most frequent E. coli virulence gene was fimH, followed by aer, hly, pap, cnf, sfa and afa respectively. There was significant association between E. coli virulence genes and clinical symptoms of UTI. The phylogenetic analysis indicates majority of uropathogenic E. coli isolates were phylogroup B2 followed by phylogroup D. Phylogroup B2 carries more virulence genes. Hence, targeting major UPEC phylogroup and virulence genes for potential vaccine candidates is essential for better management of UTI and further research has to be conducted in this area.

Typical and Atypical Enteroaggregative Escherichia coli Are Both Virulent in the Galleria mellonella Model

Enteroaggregative Escherichia coli (EAEC) is an emerging pathotype responsible for acute and persistent diarrhea. It can be classified as typical and atypical strains, respectively, based on the presence or absence of the AggR regulon, suggesting a higher virulence for typical EAEC. This study aims to evaluate in the Galleria mellonella model if there are differences in the virulence profiles among clinical strains of typical and atypical EAEC, prototype strains EAEC C1096, 042 and its aggR mutant. The clinical EAEC strains (n = 20) were analyzed for the presence of 22 putative virulence factors of EAEC or extraintestinal E. coli by PCR, as well as phenotypic characteristics of virulence (enzymes, siderophore, and biofilm). The survival of the larvae was analyzed after inoculation of 10⁴-10⁷ CFU/larva; the monitoring of bacterial growth in vivo and hemocyte quantification was determined after inoculation of the prototype strains (10⁵ CFU/larva) at different periods after infection. The strains of typical and atypical EAEC presented the same virulence profile for the larva, regardless of the amount or type of genes and phenotypic aspects of virulence analyzed. In addition, the EAEC 042 aggR mutant strain showed a significant reduction in the mortality of the inoculated larvae compared to the wild-type strain. In conclusion, the results obtained herein demonstrate that the virulence of EAEC seems to be related to the AggR regulon, but not exclusively, and atypical EAEC strains may be as virulent as typical ones in vivo in the G. mellonella model.

Phenotypic and genotypic characterization of enterotoxigenic Escherichia coli isolated from diarrheic calves in Argentina

Enterotoxigenic Escherichia coli (ETEC) is the most common and global cause of neonatal calf diarrhea, but there is a little information regarding calf ETEC strains in Argentina. In this study, five ETEC isolates from diarrheic dairy calves (2–10 d old) from Buenos Aires and Cordoba, Argentina were characterized on the basis of virulence gene (VG) pattern, O:H serotyping, hemolytic phenotype, phylogenetic group affiliation, antimicrobial (AM) resistance profile, and presence of integron class 1 and 2. The five isolates were examined by polymerase chain reaction (PCR) for the presence of 18 bovine VGs and showed the following genotypes: F5⁺/F41⁺/sta⁺ (D242), F5⁺/sta⁺ (D158), F5⁺/sta⁺ (D157), F5⁺ (D151-9), and F5⁺/iucD⁺ (D151-5). These VGs confer pathogenic potential and most of them are associated with the ETEC pathotype. The five isolates showed a non-hemolytic phenotype, belonged to five different serotypes: O101:H⁻, O141:H⁻, O60:H⁻, ONT:H10, and ONT:H⁻, and were assigned to the phylogenetic group A by the quadruplex Clermont PCR method. The AM resistance of the three isolates D242, D157, and D151-5 was determined by agar disk diffusion method for 24 AMs and they exhibited a multi-resistance phenotype (resistance to four different AM classes: Cephalosporins, Penicillins, Macrolides, and Ansamycins). In addition, class 1 integrons were found in the isolate D151-5 containing the dfrA17-aadA5 gene cassette and in the bovine ETEC reference strain FV10191 containing the dfrA1-aadA1 gene cassette. The present study revealed for the first time the occurrence of multi-resistant ETEC associated with neonatal diarrhea in dairy calves in Argentina. This finding may be used for diagnostic and therapeutic purposes.

PacBio Genome Sequences of Escherichia coli Serotype O157:H7, Diffusely Adherent E. coli, and Salmonella enterica Strains, All Carrying Plasmids with an mcr-1 Resistance Gene

We report here Illumina-corrected PacBio whole-genome sequences of an Escherichia coli serotype O157:H7 strain (2017C-4109), an E. coli serotype O[undetermined]:H2 strain (2017C-4173W12), and a Salmonella enterica subsp. enterica serovar Enteritidis strain (2017K-0021), all of which carried the mcr-1 resistance gene on an IncI2 or IncX4 plasmid.

We report here Illumina-corrected PacBio whole-genome sequences of an Escherichia coli serotype O157:H7 strain (2017C-4109), an E. coli serotype O[undetermined]:H2 strain (2017C-4173W12), and a Salmonella enterica subsp. enterica serovar Enteritidis strain (2017K-0021), all of which carried the mcr-1 resistance gene on an IncI2 or IncX4 plasmid. We also determined that pMCR-1-CTSe is identical to a previously published plasmid, pMCR-1-CT.

Molecular Epidemiology of Extraintestinal Pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC) are important pathogens in humans and certain animals. Molecular epidemiological analyses of ExPEC are based on structured observations of E. coli strains as they occur in the wild. By assessing real-world phenomena as they occur in authentic contexts and hosts, they provide an important complement to experimental assessment. Fundamental to the success of molecular epidemiological studies are the careful selection of subjects and the use of appropriate typing methods and statistical analysis. To date, molecular epidemiological studies have yielded numerous important insights into putative virulence factors, host-pathogen relationships, phylogenetic background, reservoirs, antimicrobial-resistant strains, clinical diagnostics, and transmission pathways of ExPEC, and have delineated areas in which further study is needed. The rapid pace of discovery of new putative virulence factors and the increasing awareness of the importance of virulence factor regulation, expression, and molecular variation should stimulate many future molecular epidemiological investigations. The growing sophistication and availability of molecular typing methodologies, and of the new computational and statistical approaches that are being developed to address the huge amounts of data that whole genome sequencing generates, provide improved tools for such studies and allow new questions to be addressed.

Glycan-Glycan Interaction Determines Shigella Tropism toward Human T Lymphocytes

Direct interactions between bacterial and host glycans have been recently reported to be involved in the binding of pathogenic bacteria to host cells. In the case of Shigella, the Gram-negative enteroinvasive bacterium responsible for acute rectocolitis, such interactions contribute to bacterial adherence to epithelial cells. However, the role of glycans in the tropism of Shigella for immune cells whose glycosylation pattern varies depending on their activation state is unknown. We previously reported that Shigella targets activated, but not nonactivated, human CD4⁺ T lymphocytes. Here, we show that nonactivated CD4⁺ T lymphocytes can be turned into Shigella-targetable cells upon loading of their plasma membrane with sialylated glycosphingolipids (also termed gangliosides). The Shigella targeting profile of ganglioside-loaded nonactivated T cells is similar to that of activated T cells, with a predominance of injection of effectors from the type III secretion system (T3SS) not resulting in cell invasion. We demonstrate that gangliosides interact with the O-antigen polysaccharide moiety of lipopolysaccharide (LPS), the major bacterial surface antigen, thus promoting Shigella binding to CD4⁺ T cells. This binding step is critical for the subsequent injection of T3SS effectors, a step which we univocally demonstrate to be dependent on actin polymerization. Altogether, these findings highlight the critical role of glycan-glycan interactions in Shigella pathogenesis.

Glycosylation of host cell surface varies with species and location in the body, thus contributing to species specificity and tropism of microorganisms. Cross talk by Shigella, the Gram-negative enteroinvasive bacterium responsible for bacillary dysentery, with its exclusively human host has been extensively studied. However, the molecular determinants of the step of binding to host cells are poorly defined. Taking advantage of the observation that human-activated CD4⁺ T lymphocytes, but not nonactivated cells, are targets of Shigella, we succeeded in rendering the refractory cells susceptible to targeting upon loading of their plasma membrane with sialylated glycosphingolipids (gangliosides) that are abundantly present on activated cells. We show that interactions between the sugar polar part of gangliosides and the polysaccharide moiety of Shigella lipopolysaccharide (LPS) promote bacterial binding, which results in the injection of effectors via the type III secretion system. Whereas LPS interaction with gangliosides was proposed long ago and recently extended to a large variety of glycans, our findings reveal that such glycan-glycan interactions are critical for Shigella pathogenesis by driving selective interactions with host cells, including immune cells.

Development of a multiplex PCR assay for rapid virulence factor profiling of extraintestinal pathogenic Escherichia coli isolated from cattle

Virulence factor (VF) profiling is important for the control of extraintestinal pathogenic Escherichia coli (ExPEC) infection because VF prevalence is highly variable. We analyzed the VF profile of ExPEC isolated from cattle in Yamagata prefecture, Japan, 2000-2015 and developed a rapid VF profiling method using a multiplex PCR assay.

The trend of enteropathogenic Escherichia coli towards atypical multidrug resistant genotypes

The aim of this study was to investigate the prevalence of multidrug resistance (MDR) in atypical enteropathogenic Escherichia coli (EPEC) genotypes among 547 diarrheal children. All E. coli isolates with eae⁺stx1^-stx2^- genotypes included in this study and atypical property of EPEC was characterized by the absence of Bundle-forming pili (bfpA gene). Bacterial pathogens were detected in 70 patients (12.8%) among which atypical EPEC (5.3%) were the most common. The higher resistance rate was seen to tetracycline (70%), cotrimoxazole (60%) and nalidixic acid (53.3%) related to MDR phenotype in 63.3% of isolates. The presence of class 1 and 2 integrons was 30% and 6.6% with the dominance of dfrA, aadA gene cassettes among the isolates. Eleven out of 21 phenotypically tetracycline-resistant isolates (52.38%) harboured one or two tetracycline resistance genes (A-D) which shows the incapability of known data to reasonable tetracycline resistance phenotypes among EPEC isolates. A high level of genotypic diversity was seen among the isolates by Pulsed-field gel electrophoresis method which ranged from 89.7 to 29% and no clear correlation was obtained between tetracycline resistance or integron carriage and specific pulsotypes. In conclusion, the data presented here add to knowledge about the heterogeneous nature of MDR EPEC population in Iran which has a growing tendency towards atypical genotypes. The distribution of integrons among EPEC isolates in Iran is decreasing; although, the resistance gene content is almost stable through years.

Phylogenetic group distributions, virulence factors and antimicrobial resistance properties of uropathogenic Escherichia coli strains isolated from patients with urinary tract infections in South Korea

Urinary tract infections (UTIs) are one of the most common diseases by which humans seek medical help and are caused mainly by uropathogenic Escherichia coli (UPEC). Studying the virulence and antibiotic resistance of UPEC with respect to various phylogenetic groups is of utmost importance in developing new therapeutic agents. Thus, in this study, we analysed the virulence factors, antibiotic resistance and phylogenetic groups among various UPEC isolates from children with UTIs. The phylogenetic analysis revealed that majority of the strains responsible for UTIs belonged to the phylogenetic groups B2 and D. Of the 58 E. coli isolates, 79·31% belonged to group B2, 15·51% to group D, 3·44% to group A and 1·72% to B1. Simultaneously, the number of virulence factors and antibiotic resistance exhibited were also significantly high in groups B2 and D compared to other groups. Among the isolates, 44·8% were multidrug resistant and of that 73% belonged to the phylogenetic group B2, indicating the compatibility of antibiotic resistance and certain strains carrying virulence factor genes. The antibiotic resistance profiling of UPEC strains elucidates that the antimicrobial agents such as chloramphenicol, cefoxitin, cefepime, ceftazidime might still be used in the therapy for treating UTIs.

SIGNIFICANCE AND IMPACT OF THE STUDY

As the antibiotic resistance pattern of uropathogenic Escherichia coli varies depending on different geographical regions, the antibiotic resistance pattern from this study will help the physicians to effectively administer antibiotic therapy for urinary tract infections. In addition, the frequency of virulence factors and antibiotic resistance genes among various phylogenic groups could be effectively used to draw new targets for uropathogenic Escherichia coli antibiotic-independent therapies. The study emphasizes need of public awareness on multidrug resistance and for more prudent use of antimicrobials.

Molecular Epidemiology of Extraintestinal Pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC), the specialized E. coli strains that possess the ability to overcome or subvert host defenses and cause extraintestinal disease, are important pathogens in humans and certain animals. Molecular epidemiological analysis has led to an appreciation of ExPEC as being distinct from other E. coli (including intestinal pathogenic and commensal variants) and has offered insights into the ecology, evolution, reservoirs, transmission pathways, host-pathogen interactions, and pathogenetic mechanisms of ExPEC. Molecular epidemiological analysis also provides an essential complement to experimental assessment of virulence mechanisms. This chapter first reviews the basic conceptual and methodological underpinnings of the molecular epidemiological approach and then summarizes the main aspects of ExPEC that have been investigated using this approach.

Blood Groups in Infection and Host Susceptibility

Blood group antigens represent polymorphic traits inherited among individuals and populations. At present, there are 34 recognized human blood groups and hundreds of individual blood group antigens and alleles. Differences in blood group antigen expression can increase or decrease host susceptibility to many infections. Blood groups can play a direct role in infection by serving as receptors and/or coreceptors for microorganisms, parasites, and viruses. In addition, many blood group antigens facilitate intracellular uptake, signal transduction, or adhesion through the organization of membrane microdomains. Several blood groups can modify the innate immune response to infection. Several distinct phenotypes associated with increased host resistance to malaria are overrepresented in populations living in areas where malaria is endemic, as a result of evolutionary pressures. Microorganisms can also stimulate antibodies against blood group antigens, including ABO, T, and Kell. Finally, there is a symbiotic relationship between blood group expression and maturation of the gastrointestinal microbiome.

Pathogenesis of human diffusely adhering Escherichia coli expressing Afa/Dr adhesins (Afa/Dr DAEC): current insights and future challenges

The pathogenicity and clinical pertinence of diffusely adhering Escherichia coli expressing the Afa/Dr adhesins (Afa/Dr DAEC) in urinary tract infections (UTIs) and pregnancy complications are well established. In contrast, the implication of intestinal Afa/Dr DAEC in diarrhea is still under debate. These strains are age dependently involved in diarrhea in children, are apparently not involved in diarrhea in adults, and can also be asymptomatic intestinal microbiota strains in children and adult. This comprehensive review analyzes the epidemiology and diagnosis and highlights recent progress which has improved the understanding of Afa/Dr DAEC pathogenesis. Here, I summarize the roles of Afa/Dr DAEC virulence factors, including Afa/Dr adhesins, flagella, Sat toxin, and pks island products, in the development of specific mechanisms of pathogenicity. In intestinal epithelial polarized cells, the Afa/Dr adhesins trigger cell membrane receptor clustering and activation of the linked cell signaling pathways, promote structural and functional cell lesions and injuries in intestinal barrier, induce proinflammatory responses, create angiogenesis, instigate epithelial-mesenchymal transition-like events, and lead to pks-dependent DNA damage. UTI-associated Afa/Dr DAEC strains, following adhesin-membrane receptor cell interactions and activation of associated lipid raft-dependent cell signaling pathways, internalize in a microtubule-dependent manner within urinary tract epithelial cells, develop a particular intracellular lifestyle, and trigger a toxin-dependent cell detachment. In response to Afa/Dr DAEC infection, the host epithelial cells generate antibacterial defense responses. Finally, I discuss a hypothetical role of intestinal Afa/Dr DAEC strains that can act as "silent pathogens" with the capacity to emerge as "pathobionts" for the development of inflammatory bowel disease and intestinal carcinogenesis.

Virulence factors of uropathogenic E. coli and their interaction with the host

Urinary tract infections (UTIs) belong to the most common infectious diseases worldwide. The most frequently isolated pathogen from uncomplicated UTIs is Escherichia coli. To establish infection in the urinary tract, E. coli has to overcome several defence strategies of the host, including the urine flow, exfoliation of urothelial cells, endogenous antimicrobial factors and invading neutrophils. Thus, uropathogenic E. coli (UPEC) harbour a number of virulence and fitness factors enabling the bacterium to resist and overcome these different defence mechanisms. There is no particular factor which allows the identification of UPEC among the commensal faecal flora apart from the ability to enter the urinary tract and cause an infection. Many of potential virulence or fitness factors occur moreover with high redundancy. Fimbriae are inevitable for adherence to and invasion into the host cells; the type 1 pilus is an established virulence factor in UPEC and indispensable for successful infection of the urinary tract. Flagella and toxins promote bacterial dissemination, while different iron-acquisition systems allow bacterial survival in the iron-limited environment of the urinary tract. The immune response to UPEC is primarily mediated by toll-like receptors recognising lipopolysaccharide, flagella and other structures on the bacterial surface. UPEC have the capacity to subvert this immune response of the host by means of actively impacting on pro-inflammatory signalling pathways, or by physical masking of immunogenic structures. The large repertoire of bacterial virulence and fitness factors in combination with host-related differences results in a complex interaction between host and pathogen in the urinary tract.

Detection of virulence genes in Escherichia coli isolated from patients with cystitis and pyelonephritis

BACKGROUND

Uropathogenic Escherichia coli (UPEC) is a common cause of ascending urinary tract infections including cystitis and pyelonephritis. The purpose of this study was to investigate virulence genes among Escherichia coli isolated from patients with cystitis and pyelonephritis.

METHODS

Between December 2012 and June 2013, 150 E. coli isolates from hospitalized patients with pyelonephritis (n = 72) and cystitis (n=78) were collected at Shahid Beheshti Hospital in Kashan. A PCR assay was used to evaluate the presence of virulence genes including pap, hly, aer, sfa, cnf, afa, traT, and pathogenicity island (PAI) markers in isolates.

RESULTS

Of the total 150 UPEC isolates, 130 (86.7%) were found to carry the virulence genes studied. Nineteen different virulence patterns were identified. The most prevalent virulence pattern was UPEC including traT-PAI operons. The pap, traT, aer, hly, and PAI operons were more prevalent among patients with pyelonephritis than cystitis, and the sfa, afa, and cnf genes were not detected in any of the isolates.

CONCLUSIONS

Higher virulence gene diversity was found among pyelonephritis UPEC isolates in comparison to cystitis UPEC isolates, showing that UPEC strains that cause pyelonephritis need more virulence factors.

Colon cancer-associated B2 Escherichia coli colonize gut mucosa and promote cell proliferation

AIM

To provide further insight into the characterization of mucosa-associated Escherichia coli (E. coli) isolated from the colonic mucosa of cancer patients.

METHODS

Phylogroups and the presence of cyclomodulin-encoding genes of mucosa-associated E. coli from colon cancer and diverticulosis specimens were determined by PCR. Adhesion and invasion experiments were performed with I-407 intestinal epithelial cells using gentamicin protection assay. Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) expression in T84 intestinal epithelial cells was measured by enzyme-linked immunosorbent assay and by Western Blot. Gut colonization, inflammation and pro-carcinogenic potential were assessed in a chronic infection model using CEABAC10 transgenic mice. Cell proliferation was analyzed by real-time mRNA quantification of PCNA and immunohistochemistry staining of Ki67.

RESULTS

Analysis of mucosa-associated E. coli from colon cancer and diverticulosis specimens showed that whatever the origin of the E. coli strains, 86% of cyclomodulin-positive E. coli belonged to B2 phylogroup and most harbored polyketide synthase (pks) island, which encodes colibactin, and/or cytotoxic necrotizing factor (cnf) genes. In vitro assays using I-407 intestinal epithelial cells revealed that mucosa-associated B2 E. coli strains were poorly adherent and invasive. However, mucosa-associated B2 E. coli similarly to Crohn's disease-associated E. coli are able to induce CEACAM6 expression in T84 intestinal epithelial cells. In addition, in vivo experiments using a chronic infection model of CEACAM6 expressing mice showed that B2 E. coli strain 11G5 isolated from colon cancer is able to highly persist in the gut, and to induce colon inflammation, epithelial damages and cell proliferation.

CONCLUSION

In conclusion, these data bring new insights into the ability of E. coli isolated from patients with colon cancer to establish persistent colonization, exacerbate inflammation and trigger carcinogenesis.

Colonic mucosa-associated diffusely adherent afaC+ Escherichia coli expressing lpfA and pks are increased in inflammatory bowel disease and colon cancer

OBJECTIVE

Colonic mucosa-associated Escherichia coli are increased in Crohn's disease (CD) and colorectal cancer (CRC). They variously haemagglutinate, invade epithelial cell lines, replicate within macrophages, translocate across M (microfold) cells and damage DNA. We investigated genes responsible for these effects and their co-association in colonic mucosal isolates.

DESIGN

A fosmid library yielding 968 clones was prepared in E coli EPI300-T1 using DNA from a haemagglutinating CRC isolate, and resulting haemagglutinating clones were 454-pyrosequenced. PCR screening was performed on 281 colonic E coli isolates from inflammatory bowel disease (IBD) (35 patients), CRC (21) and controls (24; sporadic polyps or irritable bowel syndrome).

RESULTS

454-Pyrosequencing of fosmids from the haemagglutinating clones (n=8) identified the afimbrial adhesin afa-1 operon. Transfection of afa-1 into E coli K-12 predictably conferred diffuse adherence plus invasion of HEp-2 and I-407 epithelial cells, and upregulation of vascular endothelial growth factor. E coli expressing afaC were common in CRC (14/21, p=0.0009) and CD (9/14, p=0.005) but not ulcerative colitis (UC; 8/21) compared with controls (4/24). E coli expressing both afaC and lpfA (relevant to M-cell translocation) were common in CD (8/14, p=0.0019) and CRC (14/21, p=0.0001), but not UC (6/21) compared with controls (2/24). E coli expressing both afaC and pks (genotoxic) were common in CRC (11/21, p=0.0015) and UC (8/21, p=0.022), but not CD (4/14) compared with controls (2/24). All isolates expressed dsbA and htrA relevant to intra-macrophage replication, and 242/281 expressed fimH encoding type-1 fimbrial adhesin.

CONCLUSIONS

IBD and CRC commonly have colonic mucosal E coli that express genes that confer properties relevant to pathogenesis including M-cell translocation, angiogenesis and genotoxicity.

Interleukin-8 Secretion by Epithelial Cells Infected with Diffusely AdherentEscherichia coliPossessing Afa Adhesin-Coding Genes

Escherichia coli that adhere sparsely to human epithelial (HEp-2) cells are known as diffusely adherent E. coli(DAEC) and considered potentially diarrheagenic. The role of the afimbrial adhesive sheath (Afa)-identified originally as a uropathogenic factor-in diffuse adhesion is now understood. However, the role of DAEC in diarrheal disease remains controversial. Recently, ability to induce interleukin-8 (IL-8) secretion from intestinal epithelial cells has been suggested as one of the properties of enterovirulent bacteria. In this study, we examined whether DAEC strains possessing Afa genes induced IL-8 in cultures of human carcinoma epithelial cells (e.g., HEp-2, Caco-2, and T84). Nineteen afa-positive DAEC strains were examined for their ability to induce IL-8 secretion, and only 7 strains (37%; 7/19) induced IL-8 as much as enteroaggregative E. coli did. No marked differences in adhesion were observed between high and low inducers. Diffusive adhesiveness itself is unlikely to be sufficient to induce IL-8. All high inducers were motile and others were nonmotile. Additional stimulation by flagella may be required to cause high levels of chemokine induction. Motility or presence of flagella can be an important criterion to predict DAEC diarrheagenicity at clinical laboratories.

Epithelial Cells Secrete Interleukin-8 in Response to Adhesion and Invasion of Diffusely AdheringEscherichia coliLacking Afa/Dr Genes

Escherichia coli that sparsely adhere to human epithelial cells are known as diffusely adherent E. coli (DAEC), and the role of the Afa/Dr family of adhesins is now understood. Strains that do not possess Afa/Dr, however, comprise another group of DAEC, of which the pathogenicity remains unknown. The ability to induce interleukin-8 (IL-8) secretion from intestinal epithelial cells might be a feature of enterovirulent bacteria. We previously found that some Afa/Dr DAEC strains induce IL-8 by stimulating epithelial cells with flagella. The present study examines whether non-Afa/Dr DAEC can induce IL-8 in epithelial cells (HEp-2, INT407, and T84). Among 21 strains, 11 (52%; 11/21) induced as much IL-8 as high inducer strains of Afa/Dr DAEC. Adhesion did not significantly differ between high and low inducers; therefore diffuse adhesion alone is probably insufficient to induce IL-8. It was shown that IL-8 induction and the number of intracellular bacteria directly correlated. Wortmannin, an inhibitor of the phosphatidylinositol-3-phosphate kinase, reduced both intracellular bacteria and IL-8 secretion. Motile strains were significantly more prevalent among high (10/11) than low (4/10) inducers. However, 4 low invasive strains hardly induced IL-8 despite their motility. In conclusion, some non-Afa/Dr DAEC invoke the induction of high levels of inflammatory cytokines. Unlike Afa/Dr DAEC, however, non-Afa/Dr strains may require invasion to cause strong induction. These non-Afa/Dr high inducers can be enteropathogenic for the cytokine-inducing properties.

Recent advances in understanding enteric pathogenic Escherichia coli

Although Escherichia coli can be an innocuous resident of the gastrointestinal tract, it also has the pathogenic capacity to cause significant diarrheal and extraintestinal diseases. Pathogenic variants of E. coli (pathovars or pathotypes) cause much morbidity and mortality worldwide. Consequently, pathogenic E. coli is widely studied in humans, animals, food, and the environment. While there are many common features that these pathotypes employ to colonize the intestinal mucosa and cause disease, the course, onset, and complications vary significantly. Outbreaks are common in developed and developing countries, and they sometimes have fatal consequences. Many of these pathotypes are a major public health concern as they have low infectious doses and are transmitted through ubiquitous mediums, including food and water. The seriousness of pathogenic E. coli is exemplified by dedicated national and international surveillance programs that monitor and track outbreaks; unfortunately, this surveillance is often lacking in developing countries. While not all pathotypes carry the same public health profile, they all carry an enormous potential to cause disease and continue to present challenges to human health. This comprehensive review highlights recent advances in our understanding of the intestinal pathotypes of E. coli.

The AfaR small RNA controls expression of the AfaD-VIII invasin in pathogenic Escherichia coli strains

Pathogenic Escherichia coli strains carrying the afa-8 gene cluster are frequently associated with extra-intestinal infections in humans and animals. The afa-8 A to E genes determine the formation of an afimbrial adhesive sheath consisting of the AfaD-VIII invasin and the AfaE-VIII adhesin at the bacterial cell surface. This structure is thought to be required for host colonization. We characterized a new gene encoding the small RNA AfaR, which is transcribed in cis from the complementary strand of the 3' untranslated region of the afaD messenger RNA, within the afaD-afaE intercistronic region. AfaR is a trans-acting Hfq-dependent antisense small RNA that binds the 5' untranslated region of the afaD messenger RNA, initiating several ribonuclease E-dependent cleavages, thereby downregulating production of the AfaD-VIII invasin. AfaR transcription is dependent on σ(E), a member of the stress response family of extracytoplasmic alternative sigma factors. We found that the AfaR-dependent regulatory pathway was controlled by temperature, allowing the production of the AfaD-VIII invasin at temperatures above 37 °C. Our findings suggest that the entry of afa-8-positive pathogenic E. coli strains into epithelial cells is tightly regulated by the AfaR small RNA.

Distribution of uropathogenic virulence genes in Escherichia coli isolated from patients with urinary tract infection

BACKGROUND

Escherichia coli is the predominant pathogen causing urinary tract infection (UTI), the most common bacterial infectious disease encountered in clinical practice, accounting for significant morbidity and high medical costs. The severity of UTI produced by E. coli is due to the expression of a wide spectrum of virulence factors. In this study we evaluated the role of E. coli virulence determinants in the pathogenesis of UTI.

METHODS

A total of 90 uropathogenic E. coli strains were screened by PCR for the prevalence of seven virulence genes encoding type 1 fimbriae (fimH), pili associated with pyelonephritis (pap), S and F1C fimbriae (sfa and foc), afimbrial adhesins (afa), cytotoxic necrotizing factor (cnf), hemolysin (hly), and aerobactin (aer).

RESULTS

The prevalence of genes coding for fimbrial adhesive systems was 68% for fimH, 41% for pap, and 34% for sfa/foc. The operons coding for afa afimbrial adhesins were identified in 20% of strains. The hly and cnf genes coding for toxins were amplified in 19% and 3% of strains, respectively. A prevalence of 52% was found for the aer gene. The various combinations of detected genes were designated as virulence patterns. The strains isolated from hospitalized patients displayed a great diversity of gene associations compared to those isolated from ambulatory patients.

CONCLUSIONS

Our study showed that investigation of the bacterial pathogenicity associated with UTI may contribute to a better medical intervention.

Actin cytoskeleton manipulation by effector proteins secreted by diarrheagenic Escherichia coli pathotypes

The actin cytoskeleton is a dynamic structure necessary for cell and tissue organization, including the maintenance of epithelial barriers. Disruption of the epithelial barrier coincides with alterations of the actin cytoskeleton in several disease states. These disruptions primarily affect the paracellular space, which is normally regulated by tight junctions. Thereby, the actin cytoskeleton is a common and recurring target of bacterial virulence factors. In order to manipulate the actin cytoskeleton, bacteria secrete and inject toxins and effectors to hijack the host cell machinery, which interferes with host-cell pathways and with a number of actin binding proteins. An interesting model to study actin manipulation by bacterial effectors is Escherichia coli since due to its genome plasticity it has acquired diverse genetic mobile elements, which allow having different E. coli varieties in one bacterial species. These E. coli pathotypes, including intracellular and extracellular bacteria, interact with epithelial cells, and their interactions depend on a specific combination of virulence factors. In this paper we focus on E. coli effectors that mimic host cell proteins to manipulate the actin cytoskeleton. The study of bacterial effector-cytoskeleton interaction will contribute not only to the comprehension of the molecular causes of infectious diseases but also to increase our knowledge of cell biology.

Escherichia coli: a brief review of diarrheagenic pathotypes and their role in diarrheal diseases in Iran

Diarrheagenic Escherichia coli have developed different strategies for establishment of infection in their host. Understanding these pathogenic mechanisms has led to the development of specific diagnostic tools for identification and categorization of E. coli strains into different pathotypes. This review aims to provide an overview of the various categories of diarrheagenic Escherichia coli and the data obtained in Iran pertaining to these pathotypes.

Maternal/fetal mortality and fetal growth restriction: role of nitric oxide and virulence factors in intrauterine infection in rats

OBJECTIVE

The mechanism of infection-related deaths of pregnant rats and intrauterine growth restriction are not understood. We assessed whether nitric oxide (NO) has differential effects on infection with Escherichia coli Dr/Afa mutants that lack either AfaE or AfaD invasins.

STUDY DESIGN

Sprague-Dawley rats were infected intrauterinally with the clinical strain of E coli AfaE(+)D(+) or 1 of its isogenic mutants in the presence or absence of the NO synthesis inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). Maternal/fetal mortality rates, fetoplacental weight, and infection rates were evaluated.

RESULTS

Maternal and/or fetal death was associated with the presence of at least 1 virulence factor (AfaE(+)D(+)>AfaE(+)D(-)>AfaE(-)D(+)) and was increased by L-NAME treatment. The fetal and placental weights were lower than controls and were further reduced by L-NAME treatment.

CONCLUSION

These results demonstrate that NO enhanced AfaE- and AfaD-mediated virulence and plays an important role in Dr/Afa(+)E coli gestational tropism.

Spread of Escherichia coli O25b:H4-B2-ST131 producing CTX-M-15 and SHV-12 with high virulence gene content in Barcelona (Spain)

OBJECTIVES

The present study was carried out to evaluate the current prevalence of the clonal group O25b:H4-B2-ST131 among extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBLEC) collected in the Hospital Vall d'Hebron in Barcelona (Spain) with regard to other clonal groups and to characterize their genetic background.

METHODS

Ninety-four consecutive non-duplicate ESBLEC isolates collected from May to December 2008 were studied. ESBL enzymes, phylogenetic groups, serotypes, virulence genes, sequence types (STs) and PFGE profiles were determined. Results The most prevalent ESBLs were CTX-M-14 (47%), CTX-M-15 (26%) and SHV-12 (19%). Thirty (32%) of the 94 ESBLEC isolates belonged to the clonal group O25b:H4-B2-ST131 of which 19 (63%) carried the bla(CTX-M-15) gene and eight (27%) the bla(SHV-12) gene. Moreover, five additional clonal groups (O15/O25a:H1/HNM-D-ST393, O78:HNM-A-ST369, ONT:H21,42/HNM-B1-ST101, O9:H4-A-ST410 and O8:H19-B1-ST162) were detected among 16 isolates producing CTX-M-14 and SHV-12. The 30 ST131 isolates exhibited a significantly higher virulence score (mean number of virulence genes 9.60 versus 5.84) compared with the 64 non-ST131 isolates. In particular, the SHV-12-producing ST131 isolates showed the highest virulence score (range 8-13, mean score 11.75).

RESULTS

also revealed that the 30 ST131 isolates were distributed in five different groups according to their virulence, XbaI macrorestriction and resistance patterns.

CONCLUSIONS

We report for the first time the clonal spread of SHV-12-producing O25b:H4-B2-ST131 isolates characterized by high virulence gene content. Moreover, we describe the distribution of the ST131 isolates within different virulence groups.

Characterization and molecular epidemiology of extended-spectrum beta-lactamases in clinical isolates of Enterobacteriaceae in a Tunisian University Hospital

One hundred extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae were recovered from the intensive care unit and the urology ward of the University Hospital of Sahloul in Tunisia between May 2005 and May 2006. The majority of strains showed a high level of resistance to cefotaxime and ceftazidime. Double-disk synergy test and E-test strips were used to confirm production of ESBLs. The molecular analysis revealed that the majority of strains (91%) carried genes encoding CTX-M-15. SHV-12 and SHV-2a were produced, respectively, by 9% and 3% of the strains. Pulsed-field gel electrophoresis of ESBL-producing Klebsiella pneumoniae isolates revealed four different clonal groups and three for Escherichia coli, showing the absence of spread of any epidemic clone. The CTX-M-15 ESBL-producing E. coli of the major clonal group belong to the B2 phylogenetic group, to the sequence type 131, and has a high virulence potential. In conclusion, CTX-M-15 ESBLs accounted for the overwhelming majority of ESBL types among Enterobacteriaceae from our hospital. This study confirms the high rate of ESBLs in Tunisia and further demonstrates the worldwide spread of genes coding for CTX-M-15 enzymes in clinical isolates.

Type II Secretion in Escherichia coli

The type II secretion system (T2SS) is used by Escherichia coli and other gram-negative bacteria to translocate many proteins, including toxins and proteases, across the outer membrane of the cell and into the extracellular space. Depending on the bacterial species, between 12 and 15 genes have been identified that make up a T2SS operon. T2SSs are widespread among gram-negative bacteria, and most E. coli appear to possess one or two complete T2SS operons. Once expressed, the multiple protein components that form the T2S system are localized in both the inner and outer membranes, where they assemble into an apparatus that spans the cell envelope. This apparatus supports the secretion of numerous virulence factors; and therefore secretion via this pathway is regarded in many organisms as a major virulence mechanism. Here, we review several of the known E. coli T2S substrates that have proven to be critical for the survival and pathogenicity of these bacteria. Recent structural and biochemical information is also reviewed that has improved our current understanding of how the T2S apparatus functions; also reviewed is the role that individual proteins play in this complex system.

Multiplex real-time PCR for exhaustive detection of diarrhoeagenic Escherichia coli

AIMS

The source and routes of diarrhoeagenic Escherichia coli (DEC) have not been clarified because it is difficult to detect these organisms in samples with numerous coliform bacteria. We have developed multiplex real-time PCR assays for exhaustive detection of DEC.

METHODS AND RESULTS

Primers and TaqMan probes were designed to amplify and quantify one gene (eae, stx1, stx2, elt, est, virB, aggR, astA, and afaB) from each of seven pathotypes of DEC, in duplex or triplex reactions under the same PCR cycling conditions. Specificity was confirmed using 860 strains including 88 DEC strains. The fluorescence threshold cycle and DNA concentrations correlated with decision coefficients of more than 0.99. Subsequently, meat samples and enrichment broths were spiked with DEC and the assays used to detect the genes. The detection limits varied from 7.1 x 10(2) to 1.1 x 10(4) CFU ml(-1), depending on the target genes. All meat samples spiked with a variety of DEC (more than 10 CFU 10 g(-1)) were found to be positive by the method.

CONCLUSIONS

The present system allows for the efficient and simultaneous determination of various DEC pathotypes.

SIGNIFICANCE AND IMPACT OF THE STUDY

This system makes epidemiological investigations for DEC sensitive and quick, and is a useful tool to clarify the source and routes of DEC.

A phylogenetic group of Escherichia coli associated with active left-sided inflammatory bowel disease

Background

Escherichia coli have been found in increased numbers in tissues from patients with Inflammatory Bowel Disease (IBD) and adherent-invasive E. coli have been found in resected ileum from patients with Crohn's disesae. This study aimed to characterize possible differences in phylogenetic group (triplex PCR), extraintestinal pathogenic E. coli (ExPEC) genes and multilocus sequence type (MLST) between E. coli strains isolated from IBD patients with past or present involvement of the left side of the colon and from controls.

Results

Fecal samples were collected from 18 patients and from 10 healthy controls. Disease activity was evaluated by sigmoidoscopy. Interestingly, E. coli strains of the phylogenetic group B2 were cultured from 60% of patients with IBD compared to 11% of healthy controls (p < 0.05). Furthermore, when comparing the number of E. coli B2 strains with at least one positive ExPEC gene among different groups, 86% were found positive among active IBD patients, significantly more than 13% among inactive IBD patients (p < 0.05), and 11% among healthy controls (p < 0.05). The B2 phylogenetic group was found in a specific cluster based on MLST, but no further separation between E. coli strains associated with active compared to inactive IBD was achieved.

Conclusion

In conclusion, E. coli of the phylogenetic group B2 were isolated more frequently from IBD patients with past or present involvement of the left side of the colon compared to healthy controls, and B2 strains with ExPEC genes were found more frequently among IBD patients with active disease compared to patients with inactive disease.

Molecular epidemiology of Escherichia coli producing extended-spectrum {beta}-lactamases in Lugo (Spain): dissemination of clone O25b:H4-ST131 producing CTX-M-15

OBJECTIVES

Having shown that the Xeral-Calde Hospital in Lugo (Spain) has been concerned by Escherichia coli clone O25:H4-ST131 producing CTX-M-15 (Nicolas-Chanoine et al. J Antimicrob Chemother 2008; 61: 273-81), the present study was carried out to evaluate the prevalence of this clone among the extended-spectrum beta-lactamase (ESBL)-producing E. coli isolates and also to molecularly characterize the E. coli isolates producing ESBL other than CTX-M-15.

METHODS

In the first part of this study, 105 ESBL-producing E. coli isolates (February 2006 to March 2007) were characterized with regard to ESBL enzymes, serotypes, virulence genes, phylogenetic groups, multilocus sequence typing (MLST) and PFGE. In the second part of this study, 249 ESBL-producing E. coli isolates (April 2007 to May 2008) were investigated only for the detection of clone O25b:H4-ST131 producing CTX-M-15 using a triplex PCR developed in this study and based on the detection of the new operon afa FM955459 and the targets rfbO25b and 3' end of the bla(CTX-M-15) gene.

RESULTS

Of the 105 ESBL-producing E. coli isolates, 60 (57.1%) were positive for CTX-M-14, 23 (21.9%) for CTX-M-15, 10 (9.5%) for SHV-12 and 7 (6.7%) for CTX-M-32. Serotypes, virulence genes, phylogenetic groups and molecular typing by PFGE demonstrated high homogeneity within those producing CTX-M-15 and high diversity within E. coli producing CTX-M-14 and other ESBLs. By PFGE, CTX-M-15-producing E. coli isolates O25b:H4 belonging to the phylogenetic group B2 and MLST profile ST131 were grouped in the same cluster. The epidemic strain of clone O25b:H4-ST131 represented 23.1%, 22.5% and 20.0% of all ESBL-producing E. coli isolated in 2006, 2007 and 2008, respectively.

CONCLUSIONS

CTX-M-type ESBLs, primarily CTX-M-14 and CTX-M-15, have emerged as the predominant types of ESBL produced by E. coli isolates in Lugo. In view of the reported findings, long-term care facilities for elderly people may represent a significant reservoir for E. coli clone O25b:H4-ST131 producing CTX-M-15. The triplex PCR developed in this work will be useful for rapid and simple detection of this clone.

Role of deoxyribose catabolism in colonization of the murine intestine by pathogenic Escherichia coli strains

We previously suggested that the ability to metabolize deoxyribose, a phenotype encoded by the deoK operon, is associated with the pathogenic potential of Escherichia coli strains. Carbohydrate metabolism is thought to provide the nutritional support required for E. coli to colonize the intestine. We therefore investigated the role of deoxyribose catabolism in the colonization of the gut, which acts as a reservoir, by pathogenic E. coli strains. Molecular and biochemical characterization of 1,221 E. coli clones from various collections showed this biochemical trait to be common in the E. coli species (33.6%). However, multivariate analysis evidenced a higher prevalence of sugar-metabolizing E. coli clones in the stools of patients from countries in which intestinal diseases are endemic. Diarrhea processes frequently involve the destruction of intestinal epithelia, so it is plausible that such clones may be positively selected for in intestines containing abundant DNA, and consequently deoxyribose. Statistical analysis also indicated that symptomatic clinical disorders and the presence of virulence factors specific to extraintestinal pathogenic E. coli were significantly associated with an increased risk of biological samples and clones testing positive for deoxyribose. Using the streptomycin-treated-mouse model of intestinal colonization, we demonstrated the involvement of the deoK operon in gut colonization by two pathogenic isolates (one enteroaggregative and one uropathogenic strain). These results, indicating that deoxyribose availability promotes pathogenic E. coli growth during host colonization, suggest that the acquisition of this trait may be an evolutionary step enabling these pathogens to colonize and persist in the mammalian intestine.

Uropathogenic Escherichia coli AL511 requires flagellum to enter renal collecting duct cells

Escherichia coli is the leading cause of urinary tract infections, but the mechanisms governing renal colonization by this bacterium remain poorly understood. We investigated the ability of 13 E. coli strains isolated from the urine of patients with pyelonephritis and cystitis and normal stools to invade collecting duct cells, which constitute the first epithelium encountered by bacteria ascending from the bladder. The AL511 clinical isolate adhered to mouse collecting duct mpkCCD(cl4) cells, used as a model of renal cell invasion, and was able to enter and persist within these cells. Previous studies have shown that bacterial flagella play an important role in host urinary tract colonization, but the role of flagella in the interaction of E. coli with renal epithelial cells remains unclear. An analysis of the ability of E. coli AL511 mutants to invade renal cells showed that flagellin played a key role in bacterial entry. Both flagellum filament assembly and the motor proteins MotA and MotB appeared to be required for E. coli AL511 uptake into collecting duct cells. These findings indicate that pyelonephritis-associated E. coli strains may invade renal collecting duct cells and that flagellin may act as an invasin in this process.

Small-molecule type III secretion system inhibitors block assembly of the Shigella type III secreton

Type III secretion systems (T3SSs) are essential virulence devices for many gram-negative bacteria that are pathogenic for plants, animals, and humans. They serve to translocate virulence effector proteins directly into eukaryotic host cells. T3SSs are composed of a large cytoplasmic bulb and a transmembrane region into which a needle is embedded, protruding above the bacterial surface. The emerging antibiotic resistance of bacterial pathogens urges the development of novel strategies to fight bacterial infections. Therapeutics that rather than kill bacteria only attenuate their virulence may reduce the frequency or progress of resistance emergence. Recently, a group of salicylidene acylhydrazides were identified as inhibitors of T3SSs in Yersinia, Chlamydia, and Salmonella species. Here we show that these are also effective on the T3SS of Shigella flexneri, where they block all related forms of protein secretion so far known, as well as the epithelial cell invasion and induction of macrophage apoptosis usually demonstrated by this bacterium. Furthermore, we show the first evidence for the detrimental effect of these compounds on T3SS needle assembly, as demonstrated by increased numbers of T3S apparatuses without needles or with shorter needles. Therefore, the compounds generate a phenocopy of T3SS export apparatus mutants but with incomplete penetrance. We discuss why this would be sufficient to almost completely block the later secretion of effector proteins and how this begins to narrow the search for the molecular target of these compounds.

Uropathogenic Escherichia coli (UPEC) strains may carry virulence properties of diarrhoeagenic E. coli

To analyze whether Escherichia coli strains that cause urinary tract infections (UPEC) share virulence characteristics with the diarrheagenic E. coli (DEC) pathotypes and to recognize their genetic diversity, 225 UPEC strains were examined for the presence of various properties of DEC and UPEC (type of interaction with HeLa cells, serogroups and presence of 30 virulence genes). No correlation between adherence patterns and serogroups was observed. Forty-five serogroups were found, but 64% of the strains belonged to one of the 12 serogroups (O1, O2, O4, O6, O7, O14, O15, O18, O21, O25, O75, and O175) and carried UPEC virulence genes (pap, hly, aer, sfa, cnf). The DEC genes found were: aap, aatA, aggC, agg3C, aggR, astA, eae, ehly, iha, irp2, lpfA(O113), pet, pic, pilS, and shf. Sixteen strains presented aggregative adherence and/or the aatA sequence, which are characteristics of enteroaggregative E. coli (EAEC), one of the DEC pathotypes. In summary, certain UPEC strains may carry DEC virulence properties, mostly associated to the EAEC pathotype. This finding raises the possibility that at least some faecal EAEC strains might represent potential uropathogens. Alternatively, certain UPEC strains may have acquired EAEC properties, becoming a potential cause of diarrhoea.

Adherence, anti-adherence, and oligosaccharides preventing pathogens from sticking to the host

For many pathogenic bacteria, infections are initiated only after the organism has first adhered to the host cell surface. If adherence can be inhibited, then the subsequent infection can also be inhibited. This approach forms the basis of anti-adherence strategies, which have been devised to prevent a variety of bacterial infections. In this chapter, the molecular basis by which respiratory, urinary, and gastrointestinal tract pathogens adhere to host cells will be described. The five general types of anti-adherence agents will also be reviewed. The most well-studied are the receptor analogs, which include oligosaccharides produced synthetically or derived from natural sources, including milk, berries, and other plants. Their ability to inhibit pathogen adherence may lead to development of novel, food-grade anti-infective agents that are inexpensive and safe.

The solution structure of the invasive tip complex from Afa/Dr fibrils

Afa/Dr family of adhesins are produced by pathogenic Escherichia coli strains that are especially prevalent in chronic diarrhoeal and recurrent urinary tract infections. Most notably, they are found in up to 50% of cystitis cases in children and 30% of pyelonephritis in pregnant women. Afa/Dr adhesins are capped surface fibrils that mediate recognition of the host and subsequent bacterial internalization. Using the newly solved three-dimensional structure of the minimal invasive complex (AfaDE) combined with biochemical and cellular assays, we reveal the architecture of the fibrillar cap and identify a novel mode of synergistic integrin recognition.