Quinolone-resistant Escherichia coli O127a:K63 serotype with an extended-spectrum-beta-lactamase phenotype from a food poisoning outbreak in China

Molecular and Genomic Analysis of the Virulence Factors and Potential Transmission of Hybrid Enteropathogenic and Enterotoxigenic Escherichia coli (EPEC/ETEC) Strains Isolated in South Korea

Hybrid strains Escherichia coli acquires genetic characteristics from multiple pathotypes and is speculated to be more virulent; however, understanding their pathogenicity is elusive. Here, we performed genome-based characterization of the hybrid of enteropathogenic (EPEC) and enterotoxigenic E. coli (ETEC), the strains that cause diarrhea and mortality in children. The virulence genes in the strains isolated from different sources in the South Korea were identified, and their phylogenetic positions were analyzed. The EPEC/ETEC hybrid strains harbored eae and est encoding E. coli attaching and effacing lesions and heat-stable enterotoxins of EPEC and ETEC, respectively. Genome-wide phylogeny revealed that all hybrids (n = 6) were closely related to EPEC strains, implying the potential acquisition of ETEC virulence genes during ETEC/EPEC hybrid emergence. The hybrids represented diverse serotypes (O153:H19 (n = 3), O49:H10 (n = 2), and O71:H19 (n = 1)) and sequence types (ST546, n = 4; ST785, n = 2). Furthermore, heat-stable toxin-encoding plasmids possessing estA and various other virulence genes and transporters, including nleH2, hlyA, hlyB, hlyC, hlyD, espC, espP, phage endopeptidase Rz, and phage holin, were identified. These findings provide insights into understanding the pathogenicity of EPEC/ETEC hybrid strains and may aid in comparative studies, virulence characterization, and understanding evolutionary biology.

Molecular analysis of enteropathogenic Escherichia coli (EPEC) isolates from healthy food-producing animals and humans with diarrhoea

Enteropathogenic Escherichia coli (EPEC) is a pathogen associated with acute diarrhoea in humans. To determine whether EPEC isolated from healthy food-producing animals possesses the same virulence gene repertoire as EPEC isolated from human with diarrhoea, we compared six typical EPEC (tEPEC) and 20 atypical EPEC (aEPEC) from humans with diarrhoea and 42 aEPEC from healthy animals (swine, sheep and buffaloes), using pulsed-field gel electrophoresis (PFGE), virulence markers, serotyping and subtyping of eae and tir genes. We found that human and animal isolates shared virulence genes, including nleB, nleE and nleF, which were associated with human diarrhoea. Serogroups and serotypes identified in isolates of food-producing animals such as O26:H11, O128:H2, O76:H7, O103, O108, O111 and O145, have previously been implicated in human disease. The subtypes eae and tir were also shared between human and animal isolates, being eae-γ1 and eae-β1 the most prevalent in both groups, while the most common tir subtypes were α and β. Despite PFGE analysis demonstrating that EPEC strains are heterogeneous and there was no prevalent clone identified, EPEC isolated from humans and food-producing animals shared some characteristics, such as virulence genes associated with human diarrhoea, indicating that food-producing animals could play a role as reservoirs for those genes.

Quantitative analysis and virulence phenotypes of atypical enteropathogenic Escherichia coli (EPEC) acquired from diarrheal stool samples from a Midwest US hospital

Infectious diarrhea causes approximately 179 million illnesses annually in the US. Multiplex PCR assays for enteric pathogens detect enteropathogenic Escherichia coli (EPEC) in 12-29% of diarrheal stool samples from all age groups in developed nations. The aim of this study was to isolate and characterize EPEC from diarrhea samples identified as EPEC positive by BioFire Gastrointestinal Panel (GIP). EPEC is the second most common GIP-detected pathogen, equally present in sole and mixed infections peaking during summer months. EPEC bacterial load is higher in samples with additional pathogens. EPEC-GIP-positive stool samples were cultured on MacConkey II agar and analyzed by colony PCR for eaeA and bfpA to identify and classify EPEC isolates as typical (tEPEC) or atypical (aEPEC). EPEC were not recovered from the majority of stool samples with only 61 isolates obtained from 277 samples; most were aEPEC from adults. bfpA-mRNA was severely diminished in 3 of 4 bfpA-positive isolates. HeLa and SKCO-15 epithelial cells were infected with EPEC isolates and virulence-associated phenotypes, including adherence pattern, attachment level, pedestal formation, and tight junction disruption, were assessed. All aEPEC adherence patterns were represented with diffuse adherence predominating. Attachment rates of isolates adhering with defined adherence patterns were higher than tEPEC lacking bfpA (ΔbfpA). The majority of isolates formpedestals. All but one isolate initially increases but ultimately decreases transepithelial electrical resistance of SKCO-15 monolayers, similar to ΔbfpA. Most isolates severely disrupt occludin; ZO-1 disruption is variable. Most aEPEC isolates induce more robust virulence-phenotypes in vitro than ΔbfpA, but less than tEPEC-E2348/69.

Comparative genomic analysis provides insight into the phylogeny and virulence of atypical enteropathogenic Escherichia coli strains from Brazil

Background

Atypical enteropathogenic Escherichia coli (aEPEC) are one of the most frequent intestinal E. coli pathotypes isolated from diarrheal patients in Brazil. Isolates of aEPEC contain the locus of enterocyte effacement, but lack the genes of the bundle-forming pilus of typical EPEC, and the Shiga toxin of enterohemorrhagic E. coli (EHEC). The objective of this study was to evaluate the phylogeny and the gene content of Brazilian aEPEC genomes compared to a global aEPEC collection.

Methodology

Single nucleotide polymorphism (SNP)-based phylogenomic analysis was used to compare 106 sequenced Brazilian aEPEC with 221 aEPEC obtained from other geographic origins. Additionally, Large-Scale BLAST Score Ratio was used to determine the shared versus unique gene content of the aEPEC studied.

Principal Findings

Phylogenomic analysis demonstrated the 106 Brazilian aEPEC were present in phylogroups B1 (47.2%, 50/106), B2 (23.6%, 25/106), A (22.6%, 24/106), and E (6.6%, 7/106). Identification of EPEC and EHEC phylogenomic lineages demonstrated that 42.5% (45/106) of the Brazilian aEPEC were in four of the previously defined lineages: EPEC10 (17.9%, 19/106), EPEC9 (10.4%, 11/106), EHEC2 (7.5%, 8/106) and EPEC7 (6.6%, 7/106). Interestingly, an additional 28.3% (30/106) of the Brazilian aEPEC were identified in five novel lineages: EPEC11 (14.2%, 15/106), EPEC12 (4.7%, 5/106), EPEC13 (1.9%, 2/106), EPEC14 (5.7%, 6/106) and EPEC15 (1.9%, 2/106). We identified 246 genes that were more frequent among the aEPEC isolates from Brazil compared to the global aEPEC collection, including espG2, espT and espC (P<0.001). Moreover, the nleF gene was more frequently identified among Brazilian aEPEC isolates obtained from diarrheagenic patients when compared to healthy subjects (69.7% vs 41.2%, P<0.05).

Conclusion

The current study demonstrates significant genomic diversity among aEPEC from Brazil, with the identification of Brazilian aEPEC isolates to five novel EPEC lineages. The greater prevalence of some virulence genes among Brazilian aEPEC genomes could be important to the specific virulence strategies used by aEPEC in Brazil to cause diarrheal disease.

Atypical EPEC (aEPEC) is one of the most frequent diarrheagenic Escherichia coli pathotypes isolated from patients in Brazil and is associated with diarrheal outbreaks. This study is the first to sequence the genomes of a collection of aEPEC isolates from a South American country, Brazil, and compare their phylogenetic relationships and gene content with a global collection of aEPEC. This approach identified Brazilian aEPEC genomes in previously characterized EPEC/EHEC phylogenomic lineages and resulted in the identification of five novel EPEC phylogenomic lineages, designated EPEC11 to EPEC15. We also observed that virulence genes, such as espG2, espT and espC were more frequently identified among the Brazilian aEPEC genomes, demonstrating potential differences in the virulence repertoire of this pathogen in Brazil.

The Complete Genome of the Atypical Enteropathogenic Escherichia coli Archetype Isolate E110019 Highlights a Role for Plasmids in Dissemination of the Type III Secreted Effector EspT

Enteropathogenic Escherichia coli (EPEC) is a leading cause of moderate to severe diarrhea among young children in developing countries, and EPEC isolates can be subdivided into two groups. Typical EPEC (tEPEC) bacteria are characterized by the presence of both the locus of enterocyte effacement (LEE) and the plasmid-encoded bundle-forming pilus (BFP), which are involved in adherence and translocation of type III effectors into the host cells. Atypical EPEC (aEPEC) bacteria also contain the LEE but lack the BFP. In the current report, we describe the complete genome of outbreak-associated aEPEC isolate E110019, which carries four plasmids. Comparative genomic analysis demonstrated that the type III secreted effector EspT gene, an autotransporter gene, a hemolysin gene, and putative fimbrial genes are all carried on plasmids. Further investigation of 65 espT-containing E. coli genomes demonstrated that different espT alleles are associated with multiple plasmids that differ in their overall gene content from the E110019 espT-containing plasmid. EspT has been previously described with respect to its role in the ability of E110019 to invade host cells. While other type III secreted effectors of E. coli have been identified on insertion elements and prophages of the chromosome, we demonstrated in the current study that the espT gene is located on multiple unique plasmids. These findings highlight a role of plasmids in dissemination of a unique E. coli type III secreted effector that is involved in host invasion and severe diarrheal illness.

Diversity of strategies used by atypical enteropathogenic Escherichia coli to induce attaching and effacing lesion in epithelial cells

PURPOSE

This study aimed to characterize 82 atypical enteropathogenic Escherichia coli (aEPEC) isolates, obtained from patients with diarrhea in Brazil, regarding their adherence patterns on HeLa cells and attaching and effacing (AE) lesion pathways.

METHODOLOGY

The adherence and fluorescence-actin staining (FAS) assays were performed using HeLa cells. AE lesion pathways were determined through the detection of tyrosine residue 474 (Y474) phosphorylation in the Tir protein, after its translocation to host cells, and by PCR assays for tir genotyping and detection of Tir-cytoskeleton coupling protein (tccP) genes.

RESULTS

Regarding the adherence pattern, determined in the presence of d-mannose, 12 isolates (14.6 %) showed the localized adherence (LA)-like pattern, 3 (3.7  %) the aggregative adherence pattern and 4 (4.9  %) a hybrid LA/diffuse adherence pattern. In addition, 36 (43.9  %) isolates displayed an undefined adherence, and 26 (31.7  %) were non-adherent (NA), while one (1.2 %) caused cell detachment. Among the 26 NA aEPEC isolates, 11 showed a type 1 pilus-dependent adherence in assays performed without d-mannose, while 15 remained NA. Forty-eight (58.5 %) aEPEC were able to trigger F-actin accumulation underneath adherent bacteria (FAS-positive), which is an important feature of AE lesions. The majority (58.3 %) of these used the Tir-Nck pathway, while 39.6  % may use both Tir-Nck and Tir-TccP pathways to induce AE lesions.

CONCLUSION

Our results reveal the diversity of strategies used by aEPEC isolates to interact with and damage epithelial host cells, thereby causing diarrheal diseases.

Characteristics of diarrheagenic Escherichia coli among children under 5 years of age with acute diarrhea: a hospital based study

BACKGROUND

Diarrhea is the leading infectious cause of childhood morbidity and mortality. Among bacterial agents, diarrheagenic Escherichia coli (DEC) is the major causal agent of childhood diarrhea in developing countries, particularly in children under the age of 5 years. Here, we performed a hospital-based prospective study to explore the pathotype distribution, epidemiological characteristics and antibiotic resistance patterns of DEC from < 5-year-old diarrheal children.

METHODS

Between August 2015 and September 2016, 684 stool samples were collected from children (< 5 years old) with acute diarrhea. All samples were cultured and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and biochemical tests. PCR was used for subtyping, and enteropathogenic E. coli (EPEC) isolates were identified simultaneously with serology. Furthermore, antimicrobial sensitivity tests and sequencing of antibiotic resistance-related genes were conducted.

RESULTS

DEC strains were identified in 7.9% of the 684 stool samples. Among them, the most commonly detected pathotype was EPEC (50.0% of DEC), of which 77.8% were classified as atypical EPEC (aEPEC). Age and seasonal distribution revealed that DEC tended to infect younger children and to occur in summer/autumn periods. Multidrug-resistant DEC isolates were 66.7%; resistance rates to ampicillin, co-trimoxazole, cefazolin, cefuroxime, cefotaxime, and ciprofloxacin were ≥ 50%. Among 5 carbapenem-resistant DEC, 60.0% were positive for carbapenemase genes (2 blaNDM-1 and 1 blaKPC-2). Among 30 cephalosporin-resistant DEC, 93.3% were positive for extended-spectrum β-lactamase (ESBL) genes, with blaTEM-1 and blaCTX-M-55 being the most common types. However, no gyrA or gyrB genes were detected in 16 quinolone-resistant isolates. Notably, aEPEC, which has not received much attention before, also exhibited high rates of drug resistance (81.0%, 66.7%, and 14.3% for ampicillin, co-trimoxazole , and carbapenem resistance, respectively).

CONCLUSIONS

EPEC was the most frequent DEC pathotype in acute diarrheal children, with aEPEC emerging as a dominant diarrheal agent in central China. Most DEC strains were multidrug-resistant, making even ciprofloxacin unsuitable for empiric treatment against DEC infection. Among carbapenem-resistant DEC strains, those harboring blaNDM-1 and blaKPC-2 were the main causal agents. blaTEM-1 and blaCTX-M-55 were the major genetic determinants associated with high levels of cephalosporin resistance.

Application of ImmunoScore Model for the Differentiation between Active Tuberculosis and Latent Tuberculosis Infection as Well as Monitoring Anti-tuberculosis Therapy

Tuberculosis (TB) is a leading global public health problem. To achieve the end TB strategy, non-invasive markers for diagnosis and treatment monitoring of TB disease are urgently needed, especially in high-endemic countries such as China. Interferon-gamma release assays (IGRAs) and tuberculin skin test (TST), frequently used immunological methods for TB detection, are intrinsically unable to discriminate active tuberculosis (ATB) from latent tuberculosis infection (LTBI). Thus, the specificity of these methods in the diagnosis of ATB is dependent upon the local prevalence of LTBI. The pathogen-detecting methods such as acid-fast staining and culture, all have limitations in clinical application. ImmunoScore (IS) is a new promising prognostic tool which was commonly used in tumor. However, the importance of host immunity has also been demonstrated in TB pathogenesis, which implies the possibility of using IS model for ATB diagnosis and therapy monitoring. In the present study, we focused on the performance of IS model in the differentiation between ATB and LTBI and in treatment monitoring of TB disease. We have totally screened five immunological markers (four non-specific markers and one TB-specific marker) and successfully established IS model by using Lasso logistic regression analysis. As expected, the IS model can effectively distinguish ATB from LTBI (with a sensitivity of 95.7% and a specificity of 92.1%) and also has potential value in the treatment monitoring of TB disease.

Clinical features and molecular epidemiology of diarrheagenic Escherichia coli pathotypes identified by fecal gastrointestinal multiplex nucleic acid amplification in patients with cancer and diarrhea

Diarrheagenic Escherichia coli (DEC) pathotypes with differing epidemiology and clinical features, are known causes of disease with worldwide occurrence. At a major cancer center in the U.S., we studied patients with cancer and diarrhea for whom a GI Biofire FilmArray multiplex GI panel (BFM) was performed. An enteropathogen was identified in 382 of 2017 (19%) samples distributed across 311 patients. Of these, 60/311(19%) were positive for DEC. Patients receiving hematopoietic stem cell transplants (HSCT) 29/60 (48%) or with a hematologic malignancy 17/60 (28%) accounted for the majority of DEC cases. Enteropathogenic E. coli (EPEC, n=35 [58%]), enteroaggregative E. coli (EAEC, n=10 [17%]) and Shiga toxin producing E. coli (STEC, n=3 [5%]) were the most common DEC identified and peaked in the summer months. Stool cultures confirmed infections in 6/10 (60%) EAEC (five typical AggR⁺), and EPEC was recovered in 8/35 (22%) samples (all atypical eaeA⁺, bfp^-). DEC was identified in 22 cases (37%) that developed diarrhea >48hours after admission suggesting health care acquisition. Chronic infections were found in 2 EPEC and 1 EAEC cases that were tested at 1month or beyond with shedding that ranged from 58 to >125days. Two patients that underwent hematopoietic stem cell transplantation carried EAEC strains resistant to multiple antibiotics including fluoroquinolones and expressed extended spectrum beta lactamases. While in some instances BFM results were not verified in culture and could represent false positives, DEC pathotypes, especially EPEC and EAEC, caused chronic infections with antimicrobial-resistant strains in a subset of immunosuppressed cancer patients.

High Prevalence of Virulence Genes in Specific Genotypes of Atypical Enteropathogenic Escherichia coli

Atypical enteropathogenic Escherichia coli (aEPEC) strains are emerging enteropathogens that have been detected worldwide. A collection of 228 aEPEC strains (121 from diarrheal patients, 27 from healthy carriers, 47 from animals and 33 from raw meats) were investigated for serotypes, virulence gene profiles and phylogenetic relationships. Sixty-six O serogroups were identified. Serogroup O51 was the most prevalent, followed by O119, O26 and O76. For the 20 virulence genes detected, statistically significant differences were observed in the overall prevalence of efa1 (lifA), nleB, nleE, set/ent, paa, and ehxA genes among strains from diarrheal patients, healthy carriers, animals and raw meats, respectively. Strains from diarrheal patients had significantly higher levels of efa1 (lifA) (29.8 vs. 0%, P = 0.0002), nleB (41.3 vs. 7.4%, P = 0.0004), nleE (43.8 vs. 7.4%, P = 0.0002) and set/ent (41.3 vs. 7.4%, P = 0.0004) genes than strains obtained from healthy carriers. The paa gene was identified more often in isolates from raw meats (63.6 vs. 14.8%, P < 0.0001), animals (42.6 vs. 14.8%, P < 0.0122), and diarrheal patients (36.4 vs. 14.8%, P < 0.0225) than in strains obtained from healthy carriers. The ehxA gene was detected more frequently in strains from raw meats than in strains from diarrheal patients (27.3 vs. 2.5%, P = 0.0000) and healthy carriers (27.3 vs. 7.4%, P = 0.0474). The phylogenetic marker, yjaA, was more frequently observed in strains among healthy carriers than in diarrheal patient strains. Among the 228 aEPEC strains, 79 sequence types (STs) were identified. The prominent STs, which comprised strains carrying the four OI-122 genes and lpfA, were ST40, ST328, and ST29. Overall, the results indicate that aEPEC strains isolated in China are highly heterogeneous. aEPEC strains that are potentially more pathogenic appear to be related to specific STs or clonal complexes and serotypes. The high prevalence of diarrhea-associated genes in animal or raw meat strains suggests a zoonotic transmission pathway for potentially human pathogenic aEPEC.

Prevalence, antimicrobial resistance and multiple-locus variable-number tandem-repeat analysis profiles of diarrheagenic Escherichia coli isolated from different retail foods

Diarrheagenic E. coli (DEC) isolates were recovered from local retail markets and the Osaka Municipal Central Wholesale Market in Japan. Retail food samples were collected for analysis in Osaka Japan from 2005 to 2008 and consisted of 32 beef, 28 pork, 20 poultry, 136 fish, 66 fruits and vegetables and 51 ready-to-eat (RTE) food samples. A total of 82 DEC strains were recovered from 64 (19%) food samples with the highest prevalence in poultry (100%, 20/20), followed by pork (54%, 15/28), beef (28%, 9/32), fruits and vegetables (12%, 8/66), fish (6.6%, 9/136) and RTE foods (5.9%, 3/51). Most of the strains belonged to E. coli possessing the enteroaggregative E. coli (EAEC) heat-stable enterotoxin 1 (EAST1) gene (EAST1EC; n=62, P<0.0001) and enteropathogenic E. coli (EPEC; n=16, P<0.01), whereas only 1 strain belonged to Shiga toxin-producing E. coli (STEC), 1 to EAEC and 2 to enterotoxigenic E. coli (ETEC) strains. Of the 82 DEC isolates, 22 O and 13H serogroups were detected, including some specific serogroups (O91, O103, O115, O119, O126, and O157) which have been associated with human diarrheal infections. Phylogenetic group A and B1 were predominant among the DEC isolates. Antimicrobial resistance to tetracycline was most common (49%), followed by nalidixic acid (28%), ampicillin (24%), sulfamethoxazole/trimethoprim (20%), and cephalothin (18%). All isolates were susceptible to aztreonam. Of the resistant strains, 44% (22/50) demonstrated resistance to >3 antimicrobial agents. Isolates resistant to >5 antimicrobials were only found in the meat samples, while isolates from the fruits and vegetables as well as RTE foods showed resistance to only 1 or 2 antimicrobial agents. Sixty one percent of EAST1EC, 56% of EPEC and all of the EAEC and ETEC were resistant to at least 1 antimicrobial agent. Multiple-locus variable-number tandem repeat analysis (MLVA) was used in this study for genotyping of DEC. The 82 isolates collected for this study showed 77 distinct MLVA profiles located among 3 branches. The Simpson's Index of Diversity (D) was 99.9% at its highest. The high diversity of these food strains would suggest their originating from a variety of sources and environments. In conclusion, retail food samples in Japan were contaminated with DEC; EAST1EC, a putative DEC, were detected at high rates in poultry, pork and beef. Isolates resistant to >3 antimicrobials were found only in raw meat and fish. Food animals may act as the reservoir for multi-resistant bacteria. Due to the finding that nearly 1/3 of EAST1EC strains were resistant to >3 antimicrobials, additional surveillance for EAST1EC should be initiated.

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.

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.

Travel-associated faecal colonization with ESBL-producing Enterobacteriaceae: incidence and risk factors

OBJECTIVES

To study the acquisition of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE) among the faecal flora during travel, with a focus on risk factors, antibiotic susceptibility and ESBL-encoding genes.

METHODS

An observational prospective multicentre cohort study of individuals attending vaccination clinics in south-east Sweden was performed, in which the submission of faecal samples and questionnaires before and after travelling outside Scandinavia was requested. Faecal samples were screened for ESBL-PE by culturing on ChromID ESBL and an in-house method. ESBL-PE was confirmed by phenotypic and genotypic methods. Susceptibility testing was performed with the Etest. Individuals who acquired ESBL-PE during travel (travel-associated carriers) were compared with non-carriers regarding risk factors, and unadjusted and adjusted ORs after manual stepwise elimination were calculated using logistic regression.

RESULTS

Of 262 enrolled individuals, 2.4% were colonized before travel. Among 226 evaluable participants, ESBL-PE was detected in the post-travel samples from 68 (30%) travellers. The most important risk factor in the final model was the geographic area visited: Indian subcontinent (OR 24.8, P < 0.001), Asia (OR 8.63, P < 0.001) and Africa north of the equator (OR 4.94, P = 0.002). Age and gastrointestinal symptoms also affected the risk significantly. Multiresistance was seen in 77 (66%) of the ESBL-PE isolates, predominantly a combination of reduced susceptibility to third-generation cephalosporins, trimethoprim/sulfamethoxazole and aminoglycosides. The most common species and ESBL-encoding gene were Escherichia coli (90%) and CTX-M (73%), respectively.

CONCLUSION

Acquisition of multiresistant ESBL-PE among the faecal flora during international travel is common. The geographical area visited has the highest impact on ESBL-PE acquisition.