Allelic variability of critical virulence genes (eae, bfpA and perA) in typical and atypical enteropathogenic Escherichia coli in Peruvian children

The Effect of Oral Iron Supplementation on Gut Microbial Composition: a Secondary Analysis of a Double-Blind, Randomized Controlled Trial among Cambodian Women of Reproductive Age

The World Health Organization recommends untargeted iron supplementation for women of reproductive age (WRA) in countries where anemia prevalence is greater than 40%, such as Cambodia. Iron supplements, however, often have poor bioavailability, so the majority remains unabsorbed in the colon. The gut houses many iron-dependent bacterial enteropathogens; thus, providing iron to individuals may be more harmful than helpful. We examined the effects of two oral iron supplements with differing bioavailability on the gut microbiomes in Cambodian WRA. This study is a secondary analysis of a double-blind, randomized controlled trial of oral iron supplementation in Cambodian WRA. For 12 weeks, participants received ferrous sulfate, ferrous bisglycinate, or placebo. Participants provided stool samples at baseline and 12 weeks. A subset of stool samples (n = 172), representing the three groups, were randomly selected for gut microbial analysis by 16S rRNA gene sequencing and targeted real-time PCR (qPCR). At baseline, 1% of women had iron-deficiency anemia. The most abundant gut phyla were Bacteroidota (45.7%) and Firmicutes (42.1%). Iron supplementation did not alter gut microbial diversity. Ferrous bisglycinate increased the relative abundance of Enterobacteriaceae, and there was a trend towards an increase in the relative abundance of Escherichia-Shigella. qPCR detected an increase in the enteropathogenic Escherichia coli (EPEC) virulence gene, bfpA, in the group that received ferrous sulfate. Thus, iron supplementation did not affect overall gut bacterial diversity in predominantly iron-replete Cambodian WRA, however, evidence does suggest an increase in relative abundance within the broad family Enterobacteriaceae associated with ferrous bisglycinate use. IMPORTANCE To the best of our knowledge, this is the first published study to characterize the effects of oral iron supplementation on the gut microbiomes of Cambodian WRA. Our study found that iron supplementation with ferrous bisglycinate increases the relative abundance of Enterobacteriaceae, which is a family of bacteria that includes many Gram-negative enteric pathogens like Salmonella, Shigella, and Escherichia coli. Using qPCR for additional analysis, we were able to detect genes associated with enteropathogenic E. coli, a type of diarrheagenic E. coli known to be present around the world, including water systems in Cambodia. The current WHO guidelines recommend blanket (untargeted) iron supplementation for Cambodian WRA despite a lack of studies in this population examining iron's effect on the gut microbiome. This study can facilitate future research that may inform evidence-based global practice and policy.

Molecular Study to Detect Escherichia coli in Diarrheic Children and its Antibiotic Resistance

Diarrheal diseases can lead to infections and cause morbidity and mortality in children. Diarrheagenic Escherichia coli (DEC) is an etiological agent, which is considered the major causative agent of diarrhea in children in some developing countries. The aims of this work were to estimate Escherichia coli (E. coli) causing diarrhea in children less than 5 years old, and to detect some biofilm virulence factors and the effect of some antibiotics. For the methodology, a total of 112 specimens were collected from children from two health centers, Al-Zahraa Teaching Hospital and Public Health Laboratory (located in Al-Kut city/ and the Wasit province in Iraq). All specimens were grown on simple and rich media. A total of 43 (38.4%) E. coli isolates were identified using different traditional methods, such as biochemical tests and 16S rRNA sequencing. Polymerase chain reaction (PCR) testing was used to detect some virulence factor genes that play an important role in the pathogenesis of diarrheic E. coli e.g., 16S rRNA, bfpA, and eaeA. In this study, several antibiotics were used to estimate the sensitivity and resistivity of E. coli isolates. A total of 43 isolates were fully identified as E. coli. These samples were used to detect the virulence factor genes, and 31 (72.1%) and 29 (29.4%) isolates carried bfpA and eaeA, respectively. The preponderance of E. coli isolates were completely resistant to penicillin 43 (100%). Additionally, 33 (76.7%) and 27 (62.8%) isolates were resistant to cephalothin and amoxycillin-clavulanic acid, respectively. Furthermore, the isolates of E. coli isolates showed different levels of sensitivity to antibiotics, including polymyxin B 40 (93%), norfloxacin 38 (88.4%), gentamycin 26 (60.4%), and meropenem 22 (51.2%). In conclusion, diarrheagenic E. coli isolates were the prevalent among diarrheic children. Most isolates showed varying results for the presence of virulence factors. In addition, all isolates were resistant to penicillin and sensitive to polymyxin B.

Genomic Characterization of Escherichia coli Isolates Belonging to a New Hybrid aEPEC/ExPEC Pathotype O153:H10-A-ST10 eae-beta1 Occurred in Meat, Poultry, Wildlife and Human Diarrheagenic Samples

Different surveillance studies (2005–2015) in northwest Spain revealed the presence of eae-positive isolates of Escherichia coli O153:H10 in meat for human consumption, poultry farm, wildlife and human diarrheagenic samples. The aim of this study was to explore the genetic and genomic relatedness between human and animal/meat isolates, as well as the mechanism of its persistence. We also wanted to know whether it was a geographically restricted lineage, or whether it was also reported elsewhere. Conventional typing showed that 32 isolates were O153:H10-A-ST10 fimH54, fimAv_MT78, traT and eae-beta1. Amongst these, 21 were CTX-M-32 or SHV-12 producers. The PFGE XbaI-macrorestriction comparison showed high similarity (>85%). The plasmidome analysis revealed a stable combination of IncF (F2:A-:B-), IncI1 (STunknown) and IncX1 plasmid types, together with non-conjugative Col-like plasmids. The core genome investigation based on the cgMLST scheme from EnteroBase proved close relatedness between isolates of human and animal origin. Our results demonstrate that a hybrid MDR aEPEC/ExPEC of the clonal group O153:H10-A-ST10 (CH11-54) is circulating in our region within different hosts, including wildlife. It seems implicated in human diarrhea via meat transmission, and in the spreading of ESBL genes (mainly of CTX-M-32 type). We found genomic evidence of a related hybrid aEPEC/ExPEC in at least one other country.

Virulence genes in Escherichia coli isolates from commercialized saltwater mussels Mytella guyanensis (Lamarck, 1819)

Abstract The isolation of Escherichia coli from food is a major concern. Pathogenic strains of these bacteria cause diseases which range from diarrhea to hemolytic-uremic syndrome. Therefore the virulence genes in E. coli isolates from the mussel ( Mytella guyanensis) commercialized in Cachoeira, Bahia, Brazil were investigated. Samples were purchased from four vendors: two from supermarkets and two from fair outlets. They were conditioned into isothermal boxes with reusable ice and transported to the laboratory for analysis. E. coli strains were isolated in eosin methylene blue agar, preserved in brain-heart infusion medium with 15% glycerol and stored at -20 °C, after microbiological analysis. Virulence genes in the isolated strains were identified by specific primers, with Polymerase Chain Reaction. Twenty-four isolates were obtained, with a prevalence of elt gene, typical from enterotoxigenic infection, in 75% of the isolates. The stx and bfpA genes, prevalent in enterohemorragic and enteropathogenic E. coli, respectively, were not detected. The occurrence of elt virulence-related gene in the E. coli isolates of Mytella guyanensis reveals urgent improvement in food processing, including good handling practices, adequate storage and cooking before consumption, to ensure consumer’s health.

Prevalence and Characterization of Atypical Enteropathogenic Escherichia coli Isolated from Retail Foods in China

Atypical enteropathogenic Escherichia coli (aEPEC) is an emerging pathogen that has been implicated in outbreaks of diarrhea worldwide. The objective of this study was to investigate the occurrence of aEPEC in retail foods at markets in the People's Republic of China and to characterize the isolates for virulence genes, intimin gene ( eae) subtypes, multilocus sequence types (STs), and antimicrobial susceptibility. From May 2014 to April 2015, 1,200 food samples were collected from retail markets in China, and 41 aEPEC isolates were detected in 2.75% (33 of 1,200) of the food samples. The virulence genes tir, katP, etpD, efa/lifA, ent, nleB, and nleE were commonly detected in these isolates. Nine eae subtypes were detected in the isolates, among which θ (23 isolates) and β1 (6 isolates) were the most prevalent. The 41 isolates were divided into 27 STs by multilocus sequence typing. ST752 and ST10 were the most prevalent. Antibiotic susceptibility testing revealed high resistance among isolates to streptomycin (87.80%), cephalothin (73.16%), ampicillin (51.22%), tetracycline (63.42%), trimethoprim-sulfamethoxazole (43.90%), and kanamycin (43.90%). Thirty isolates (73.17%) were resistant to at least three antibiotics, and 20 (53.66 %) were resistant to five or more antibiotics. Our results suggest that retail foods in markets are important sources of aEPEC. The presence of virulent and multidrug-resistant aEPEC in retail foods poses a potential threat to consumers. Surveillance of aEPEC contamination and prudent use of antibiotics is strongly recommended in China.

Characterization of enteropathogenic Escherichia coli of clinical origin from the pediatric population in Pakistan

BACKGROUND

Enteropathogenic Escherichia coli (EPEC) is one of the leading causes of watery diarrhea among children.

METHODS

In this study EPEC isolates from the pediatric population of Pakistan (2010-2012) were subjected to phylotyping, antibiotic susceptibility, extended-spectrum beta-lactamase (ESBL) profiling and evaluation of one representative strain from each panel of phylotypesin Galleria mellonella, infection model.

RESULTS

A total of 46/225 (20.4%) stool samples were positive for EPEC. Isolates mainly belong to D phylogroup (18, 39%) followed by nontypeable (10, 22%), B1 (9, 20%), B2 (8, 17%) and A (1, 2%). High resistance was observed for ampicillin (42, 91%), erythromycin (41, 89%), cefaclor (37, 80%), trimethoprim/sulfamethoxazole (36, 78%), tetracycline (36, 78%). Among nalidixic acid resistant isolates 13 (28%) showed presence of single nucleotide polymorphism (SNP) in parC (C330-T330) whereas 1 (2%) isolate showed gyrB (A660-T660) SNP. Furthermore, 27 (59%) isolates were ESBL producers. Representative isolates of phlyotypes A and B2 showed enhance killing of G. mellonella compared to ones belonging to phylotypes B1 and D.

CONCLUSIONS

Non-typeable EPEC strains were frequently observed. ESBL production in ESBL producers was found to be plasmid mediated. No significant association of antibiotic resistance profile with specific phylogroup of EPEC was found, however G. mellonella infection model differentiated representative phylotypes.

Diarrheagenic Escherichia coli

Most Escherichia coli strains live harmlessly in the intestines and rarely cause disease in healthy individuals. Nonetheless, a number of pathogenic strains can cause diarrhea or extraintestinal diseases both in healthy and immunocompromised individuals. Diarrheal illnesses are a severe public health problem and a major cause of morbidity and mortality in infants and young children, especially in developing countries. E. coli strains that cause diarrhea have evolved by acquiring, through horizontal gene transfer, a particular set of characteristics that have successfully persisted in the host. According to the group of virulence determinants acquired, specific combinations were formed determining the currently known E. coli pathotypes, which are collectively known as diarrheagenic E. coli. In this review, we have gathered information on current definitions, serotypes, lineages, virulence mechanisms, epidemiology, and diagnosis of the major diarrheagenic E. coli pathotypes.

Atypical enteropathogenic Escherichia coli as aetiologic agents of sporadic and outbreak-associated diarrhoea in Brazil

Enteropathogenic Escherichia coli (EPEC) are important agents of diarrhoea in industrialized as well as developing countries, such as Brazil. The hallmark of EPEC pathogenesis is the establishment of attaching and effacing lesions in enterocytes, in which pedestal-like structures are formed underneath adherent bacteria. EPEC are divided into two subgroups, typical (tEPEC) and atypical (aEPEC), based on the presence of the EPEC adherence factor plasmid in tEPEC and its absence in aEPEC. This study was designed to characterize 82 aEPEC isolates obtained from stool samples of diarrhoeic patients during 2012 and 2013 in Brazil. The majority of the aEPEC were assigned to the phylo-group B1 (48.8 %), and intimin subtypes θ (20.7 %), β1 (9.7 %) and λ (9.7 %) were the most prevalent among the isolates. The nleB and nleE genes were concomitantly detected in 32.9 % of the isolates, demonstrating the occurrence of the pathogenicity island O122 among them. The O157-plasmid genes (ehxA and/or espP) were detected in 7.3 % of the isolates, suggesting that some aEPEC could be derived from Shiga-toxin-producing E. coli that lost the stx genes while trafficking in the host. PFGE of 14 aEPEC of serotypes O2 : H16, O33 : H34, O39 : H9, O108 : H- and ONT : H19 isolated from five distinct outbreaks showed serotype-specific PFGE clusters, indicating a high degree of similarity among the isolates from the same event, thus highlighting these serotypes as potential aetiologic agents of diarrhoeal outbreaks in Brazil.

Genetic Diversity of Intimin Gene of Atypical Enteropathogenic Escherichia coli Isolated from Human, Animals and Raw Meats in China

Atypical enteropathogenic Escherichia coli (aEPEC) is considered to be an emerging enteropathogen that is more prevalent than typical EPEC in developing and developed countries. The major adherence factor, intimin, an outer membrane protein encoded by eae, plays a pivotal role in the pathogenesis of aEPEC. This study investigated the distribution and polymorphisms of intimin subtypes of 143 aEPEC strains from diarrheal patients, healthy carriers, animals, and raw meats in China. These aEPEC strains belonged to more than 71 different serotypes, which comprised 52 O serogroups and 24 H types. Sixty-eight different eae genotypes and 19 intimin subtypes were detected. Eighteen, eight, seven, and five intimin subtypes were identified from 86 diarrheal patients, 14 healthy carriers, 19 animals, and 24 raw meats strains, respectively. Intimin β1 was the most prevalent subtype in strains from diarrheal patients (34.88%) and animals (47.37%). There was a statistically significant difference in the distribution of eae-β1 between diarrheal patients and healthy carriers (P = 0.004). Intimin-θ was more predominant among raw meat strains (50%) than among diarrheal patients strains (12.79%, P = 0.0003), healthy carrier strains (7.14%, P = 0.007), or animal strains (15.79%, P = 0.020). The two predominant subtypes (eae-β1 and eae-θ) had considerable polymorphisms with no significant differences among the four sources. PFGE analysis revealed 119 distinct patterns and the strains were clustered into 11 groups with similarity indices ranging from 63% to 100%. These results suggest that in China, aEPEC strains from different sources are highly heterogeneous. Animals and raw meats are important sources of genetically diverse intimin-harboring aEPEC, which might serve as important transmission vehicles of these bacteria.

Identification of enteropathogenic Escherichia coli in children with acute diarrheic syndrome from Sucre State, Venezuela

INTRODUCTION

Diarrheagenic Escherichia coli is an important causative agent of acute diarrheic syndrome. 

OBJECTIVE

To identify clonal groups of enteropathogenic E. coli (EPEC), in 485 children with acute diarrhea aged 0 to 10 years attending health care centers in Arismendi, Benítez and Sucre municipalities, Sucre state, Venezuela, from March to December, 2011. 

MATERIALS AND METHODS

After obtaining the informed consent, stool samples were collected. Escherichia coli was identified using standard coproculture methods and serology with polyvalent and monovalent antisera. DNA was isolated, and eae (intimin) and bfpA (bundlin) genes were amplified through two multiplex polymerase chain reactions (PCR). 

RESULTS

The presence of bacterial infection was determined in 39.6% of coprocultures. The prevalence of E. coli was 54.7%; 82.9% of these isolates were positive by serology for the evaluated serogroups and serotypes, which were mostly identified in children between 0 and 2 years (37.9%); 48.6% of E. coli strains amplified the eae gene; of these, 58.8% were classified as typical EPEC (eae+ y bfp+). EPEC II was the most common serogroup (38.7%), with predominance of typical EPEC (60%). In positive strains for eae gene, the β intimin allele was the most frequently identified (74.5%). Only four strains with O157:H7 serotype were identified, which showed no PCR amplification of the eae and bfpA genes. 

CONCLUSION

This study showed the importance of molecular tests to identify diarrheagenic E. coli strains causing clinical conditions of varying severity.

High Frequency of Diarrheagenic Escherichia coli in HIV-Infected Patients and Patients with Thalassemia in Kerman, Iran

This study was conducted on patients with thalassemia and HIV-infected patients to determine the frequency of diarrheagenic Escherichia coli in Kerman, Iran. We analyzed 68 and 49 E coli isolates isolated from healthy fecal samples of patients with thalassemia and HIV-infected patients, respectively. The E coli isolates were studied using a multiplex polymerase chain reaction to identify the enterotoxigenic E coli (ETEC), enterohemorrhagic E coli (EHEC), and enteropathogenic E coli (EPEC) groups. Statistical analysis was carried out to determine the correlation of diarrheagenic E coli between HIV-infected patients and patients with thalassemia using Stata 11.2 software. The frequency of having at least 1 diarrheagenic E coli was more common in patients with thalassemia (67.64%) than in HIV-infected patients (57.14%; P = .25), including ETEC (67.64% versus 57.14%), EHEC (33.82% versus 26.53%), and EPEC (19.11% versus 16.32%). The results of this study indicate that ETEC, EHEC, and EPEC pathotypes are widespread among diarrheagenic E coli isolates in patients with thalassemia and HIV-infected patients.

Occurrence and Characterization of Enteropathogenic Escherichia coli (EPEC) in Retail Ready-to-Eat Foods in China

Enteropathogenic Escherichia coli (EPEC) is an important foodborne pathogen that potentially causes infant and adult diarrhea. The occurrence and characteristics of EPEC in retail ready-to-eat (RTE) foods have not been thoroughly investigated in China. This study aimed to investigate EPEC occurrence in retail RTE foods sold in the markets of China and to characterize the isolated EPEC by serotyping, virulence gene analyses, antibiotic susceptibility test, and molecular typing based on enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). From May 2012 to April 2013, 459 RTE food samples were collected from retail markets in 24 cities of China. E. coli in general, and EPEC specifically, were detected in 144 (31.4%) and 39 (8.5%) samples, respectively. Cold vegetable in sauce was the food type most frequently contaminated with EPEC (18.6%). Of 39 EPEC isolates, 38 were atypical EPEC (eae+) and 1 was typical EPEC (eae+bfpA+) by multiplex PCR assays. The virulence genes espA, espB, tir, and iha were detected in 12, 9, 2, and 1 of 39 isolates, respectively, while genes toxB, etpD, katP, and saa were not detected. O-antigen serotyping results showed that among 28 typeable isolates, the most common serotype was O119, followed by O26, O111, and O128. Many isolates were resistant to tetracycline (64.1%; 25/39), ampicillin (48.7%; 19/39), and trimethoprim/sulfamethoxazole (48.7%; 19/39). ERIC-PCR indicated high genetic diversity in EPEC strains, which classified 42 strains (39 isolates and 3 reference strains) into 32 different profiles with a discrimination index of 0.981. The findings of this study highlight the need for close surveillance of the RTE foods at the level of production, packaging, and storage to minimize risks of foodborne disease.

Comparative Genomics Provides Insight into the Diversity of the Attaching and Effacing Escherichia coli Virulence Plasmids

Attaching and effacing Escherichia coli (AEEC) strains are a genomically diverse group of diarrheagenic E. coli strains that are characterized by the presence of the locus of enterocyte effacement (LEE) genomic island, which encodes a type III secretion system that is essential to virulence. AEEC strains can be further classified as either enterohemorrhagic E. coli (EHEC), typical enteropathogenic E. coli (EPEC), or atypical EPEC, depending on the presence or absence of the Shiga toxin genes or bundle-forming pilus (BFP) genes. Recent AEEC genomic studies have focused on the diversity of the core genome, and less is known regarding the genetic diversity and relatedness of AEEC plasmids. Comparative genomic analyses in this study demonstrated genetic similarity among AEEC plasmid genes involved in plasmid replication conjugative transfer and maintenance, while the remainder of the plasmids had sequence variability. Investigation of the EPEC adherence factor (EAF) plasmids, which carry the BFP genes, demonstrated significant plasmid diversity even among isolates within the same phylogenomic lineage, suggesting that these EAF-like plasmids have undergone genetic modifications or have been lost and acquired multiple times. Global transcriptional analyses of the EPEC prototype isolate E2348/69 and two EAF plasmid mutants of this isolate demonstrated that the plasmid genes influence the expression of a number of chromosomal genes in addition to the LEE. This suggests that the genetic diversity of the EAF plasmids could contribute to differences in the global virulence regulons of EPEC isolates.

Characterization of the pathogenome and phylogenomic classification of enteropathogenic Escherichia coli of the O157:non-H7 serotypes

Escherichia coli of the O157 serogroup are comprised of a diverse collection of more than 100 O157:non-H7 serotypes that are found in the environment, animal reservoir and infected patients and some have been linked to severe outbreaks of human disease. Among these, the enteropathogenic E. coli O157:non-H7 serotypes carry virulence factors that are hallmarks of enterohemorrhagic E. coli, such as causing attaching and effacing lesions during human gastrointestinal tract infections. Given the shared virulence gene pool between O157:H7 and O157:non-H7 serotypes, our objective was to examine the prevalence of virulence traits of O157:non-H7 serotypes within and across their H-serotype and when compared to other E. coli pathovars. We sequenced six O157:non-H7 genomes complemented by four genomes from public repositories in an effort to determine their virulence state and genetic relatedness to the highly pathogenic enterohemorrhagic O157:H7 lineage and its ancestral O55:H7 serotype. Whole-genome-based phylogenomic analysis and molecular typing is indicative of a non-monophyletic origin of the heterogeneous O157:non-H7 serotypes that are only distantly related to the O157:H7 serotype. The availability of multiple genomes enables robust phylogenomic placement of these strains into their evolutionary context, and the assessment of the pathogenic potential of the O157:non-H7 strains in causing human disease.

Enteropathogenic Escherichia coli: foe or innocent bystander?

Enteropathogenic Escherichia coli (EPEC) remain one the most important pathogens infecting children and they are one of the main causes of persistent diarrhoea worldwide. Historically, typical EPEC (tEPEC), defined as those isolates with the attaching and effacement (A/E) genotype (eae(+)), which possess bfpA(+) and lack the stx(-) genes are found strongly associated with diarrhoeal cases. However, occurrence of atypical EPEC (aEPEC; eae(+)bfpA(-)stx(-)) in diarrhoeal and asymptomatic hosts has made investigators question the role of these pathogens in human disease. Current epidemiological data are helping to answer the question of whether EPEC is mainly a foe or an innocent bystander during infection.

Bowman-Birk inhibitor-like protein is secreted by sprouted pea seeds in response to induced colonization by enteropathogenic Escherichia coli

The interaction between the clinical isolate of enteropathogenic Escherichia coli (EPEC) SBANU8 and pea sprouts was compared with avirulent K 12. E. coli. This was carried out by repeated co-incubation with pea sprouts for 5 days, and the protein profile of the culture supernatant was analyzed by single and two-dimensional electrophoresis. Mass spectrometry analysis led to the identification of two serine protease inhibitors including a Bowman-Birk-type protein secreted by pea sprouts in response to clinical isolate. Expression of the E. coli intimin gene involved in animal host colonization and virulence was studied by reverse transcription polymerase chain reaction. Expression of this gene was high in SBANU8 when co-incubated with pea sprouts. The present study gives baseline data on the molecular level interactions of EPEC and pea sprouts, which are needed to design the outbreak control strategies.

Prevalence and antibiotic resistance profiles of diarrheagenic Escherichia coli strains isolated from food items in northwestern Mexico

Diarrheogenic Escherichia coli (DEC) strains are an important cause of intestinal syndromes in the developing world mainly affecting children. DEC strains often infect tourists from developed countries traveling to Mexico, causing so-called "traveler diarrhea". DEC strains are typically transmitted by contaminated food and water; however, the prevalence of these strains in food items that are produced, consumed and sometimes exported in northwestern Mexico has not been evaluated. In this study, we conducted a large microbiological survey of DEC strains in 5162 food items and beverages consumed throughout Sinaloa state during 2008 and 2009. We developed a panel of eight sequential PCR reactions that detected the presence of all DEC categories, including typical or atypical variants. Thermotolerant coliforms (also known as fecal coliforms) and E. coli were detected by conventional bacteriology in 13.4% (692/5162) and 7.92% (409/5162) of food items, respectively. Among 409 E. coli isolates, 13.6% (56/409) belonged to DEC strains. Dairy products (2.8%) were the most contaminated with DEC, while DEC strains were not detected in beverages and ice samples. The pathogenic type that was most commonly isolated was EPEC (78.5%), followed by EAEC (10.7%), STEC (8.9%) and ETEC (1.7%). EHEC, DAEC and EIEC strains were not detected. Approximately 80% of EPEC and EAEC strains were classified as atypical variants; they did not adhere to a culture of HEp-2 cell. Of the isolated DEC strains, 66% showed resistance to at least one commonly prescribed antibiotic. In conclusion, the presence of DEC strains in food items and beverages available in northwestern Mexico is low and may not represent a threat for the general population or those traveling to tourist areas.

Intimin subtyping of atypical enteropathogenic Escherichia coli isolated from children with and without diarrhea: a possible temporal shift in the distribution of intimin alleles

Intimins of atypical EPEC strains from children with and without diarrhea were genotyped. κ was not found and β was the most common. η- and ζ-alleles prevailed in strains from children without diarrhea and ι-allele among children older than 13 months. ε-allele emerged in 2006 and was the most common in 2007.

Genetic diversity of locus of enterocyte effacement genes of enteropathogenic Escherichia coli isolated from Peruvian children

The aim of this study was to determine the frequency and allele associations of locus of enterocyte effacement encoded esp and tir genes among 181 enteropathogenic Escherichia coli (EPEC) strains (90 diarrhoea-associated and 91 controls) isolated from Peruvian children under 18 months of age. We analysed espA, espB, espD and tir alleles by PCR-RFLP. EPEC strains were isolated with higher frequency from healthy controls (91/424, 21.7%) than from diarrhoeal samples (90/936, 9.6%) (P<0.001); 28.9% of diarrhoeal and 17.6% of control samples were typical EPEC (tEPEC). The distribution of espA alleles (alpha, beta, beta2 and gamma) and espD alleles (alpha, beta, gamma and a new variant, espD-N1) between tEPEC and atypical EPEC (aEPEC) was significantly different (P<0.05). espD-alpha was more common among acute episodes (P<0.05). espB typing resulted in five alleles (alpha, beta, gamma and two new sub-alleles, espB-alpha2 and espB-alpha3), while tir-beta and tir-gamma2 were the most common intimin receptor subtypes. Seventy-two combinations of espA, espB, espD and tir alleles were found; the most prevalent combination was espA-beta, espB-beta, espD-beta, tir-beta (34/181 strains), which was more frequent among tEPEC strains (P<0.05). Our findings indicate that there is a high degree of heterogeneity among EPEC strains isolated from Peruvian children and that aEPEC and tEPEC variants cluster.

Enteropathogenic escherichia coli infection in children

PURPOSE OF REVIEW

Enteropathogenic Escherichia coli (EPEC) is an important diarrheal pathogen of young children. As the diagnosis of EPEC is now based mainly on molecular criteria, there has been an important change in its prevalence. The purpose of this study is to review the current epidemiology of EPEC infection and the new insights into its physiopathology.

RECENT FINDINGS

Recent epidemiological studies indicate that atypical EPEC (aEPEC) is more prevalent than typical EPEC (tEPEC) in both developed and developing countries, and that aEPEC is important in both pediatric endemic diarrhea and diarrhea outbreaks. Therefore, it is important to further characterize the pathogenicity of these emerging strains. The virulence mechanisms and physiopathology of the attaching and effacing lesion (A/E) and the type three secretion-system (T3SS) are complex but well studied. A/E strains use their pool of locus of enterocyte effacement (LEE)-encoded and non-LEE-encoded effector proteins to subvert and modulate cellular and barrier properties of the host. However, the exact mechanisms of diarrhea in EPEC infection are not completely understood.

SUMMARY

Remarkable progress has been made to identify virulence determinants required to mediate the pathogenesis of EPEC. However, fast, easy, and inexpensive diagnostic methods are needed in order to define optimal treatment and prevention for children in endemic areas.

Quantitative real-time polymerase chain reaction for enteropathogenic Escherichia coli: a tool for investigation of asymptomatic versus symptomatic infections

BACKGROUND

Enteropathogenic Escherichia coli (EPEC) strains are pediatric pathogens commonly isolated from both healthy and sick children with diarrhea in areas of endemicity. The aim of this study was to compare the bacterial load of EPEC isolated from stool samples from children with and without diarrhea to determine whether bacterial load might be a useful tool for further study of this phenomenon.

METHODS

EPEC was detected by polymerase chain reaction (PCR) of colonies isolated on MacConkey plates from 53 diarrheal and 90 healthy children aged <2 years. DNA was isolated from stool samples by cetyltrimethylammonium bromide extraction. To standardize quantification by quantitative real-time PCR (qRT-PCR), the correlation between fluorescence threshold cycle and copy number of the intimin gene of EPEC E2348/69 was determined.

RESULTS

The detection limit of qRT-PCR was 5 bacteria/mg stool. The geometric mean load in diarrhea was 299 bacteria/mg (95% confidence interval [CI], 77-1164 bacteria/mg), compared with 29 bacteria/mg (95% CI, 10-87 bacteria/mg) in control subjects (P = .016). Bacterial load was significantly higher in children with diarrhea than in control subjects among children <12 months of age (178 vs 5 bacteria/mg; P = .006) and among children with EPEC as the sole pathogen (463 vs 24 bacteria/mg; P = .006).

CONCLUSIONS

EPEC load measured by qRT-PCR is higher in diarrheal than in healthy children. qRT-PCR may be useful to study the relationship between disease and colonization in settings of endemicity.