Prevalence and characteristics of intimin- and Shiga toxin-producing Escherichia coli from gulls, pigeons and broilers in Finland

Characterization of Escherichia coli strains producing Shiga Toxin 2f subtype from domestic Pigeon

Shiga toxin-producing Escherichia coli (STEC) can cause mild diarrhea even severe hemolytic uremic syndrome (HUS). Shiga toxin (Stx) is the primary virulence factor. Two Stx types and several subtypes have been identified. STEC strains encoding stx2f (Stx2f-STECs) are frequently identified from pigeons. Stx2f was initially considered to be associated with mild symptoms, more recently Stx2f-STECs have been isolated from HUS cases, indicating their pathogenic potential. Here, we investigated the prevalence of Stx2f-STECs among domestic pigeons in two regions in China, characterized the strains using whole-genome sequencing (WGS), and assessed the Stx2f transcriptions. Thirty-two Stx2f-STECs (4.36%) were culture-positive out of 734 fecal samples (one strain per sample). No other stx subtype-containing strain was isolated. Four serotypes and two sequence types were determined, and a novel sequence type ST15057 was identified. All strains harbored the E. coli attaching and effacing gene eae. Two types of Stx2f prophages were assigned. Stx2f-STECs showed variable Stx transcription levels induced by mitomycin C. Whole genome single-nucleotide polymorphism (wgSNP) analysis revealed different genetic backgrounds between pigeon-derived strains and those from diarrheal or HUS patients. In contrast, pigeon-derived Stx2f-STECs from diverse regions exhibited genetic similarity. Our study reports the prevalence and characteristics of Stx2f-STECs from pigeons in China. The pigeon-derived strains might pose low public health risk.

Antimicrobial Susceptibility and Molecular Identification of Antibiotic Resistance Enteric Bacteria Isolated From Pigeon Feces in the City of Jeddah, Saudi Arabia

Background Due to their potential to carry a wide range of bacteria, pigeon feces may contribute to the spreading of infectious diseases in urban settings.  Objective This study analyzed the presence of enteric bacteria from pigeon feces in Jeddah and their antimicrobial susceptibility and described the molecular characteristics of the carbapenem resistance genes it produced. Method Two hundred twenty-five pigeon feces specimens were collected from eight parks in Jeddah. Conventional microbiology techniques were employed to identify the isolated bacteria, and the automated Vitek2® system (bioMérieux, Marcy-l'Étoile, Lyon, France) provided additional confirmation. Kirby-Bauer disk diffusion method was utilized to screen for antimicrobial resistance. Only 50 antibiotic-resistance isolates further underwent molecular diagnosis for testing groups of carbapenems-encoding genes (blaNDM, blaSIM, and blaAIM), using multiplex polymerase chain reaction (PCR).  Result Of the 50 antibiotic-resistant isolates, 28% (14/50) were Klebsiella pneumoniae, 24% (12/50) were Enterobacter cloacae, and 48% (24/50) were Escherichia coli. Ninety percent (90%) of the isolates showed resistance to cefuroxime, 56% to gentamicin, 52% to amoxicillin/clavulanic acid, and 100% to meropenem. NDM beta-lactamase was the most often discovered gene (26%) and was followed by AIM beta-lactamase (5%) Conclusion According to this study, there may be a chance for resistant K. pneumoniae, E. cloacae, and E. coli to spread amongst several hosts within the same area. Consequently, to prevent the continued occurrence and dissemination of resistant strains among other hosts in the same location, it is essential to monitor the AMR (antimicrobial resistance) of E. coli, E. cloacae, and K. pneumoniae from pigeons.

A Comprehensive Review on Shiga Toxin Subtypes and Their Niche-Related Distribution Characteristics in Shiga-Toxin-Producing E. coli and Other Bacterial Hosts

Shiga toxin (Stx), the main virulence factor of Shiga-toxin-producing E. coli (STEC), was first discovered in Shigella dysenteriae strains. While several other bacterial species have since been reported to produce Stx, STEC poses the most significant risk to human health due to its widespread prevalence across various animal hosts that have close contact with human populations. Based on its biochemical and molecular characteristics, Shiga toxin can be grouped into two types, Stx1 and Stx2, among which a variety of variants and subtypes have been identified in various bacteria and host species. Interestingly, the different Stx subtypes appear to vary in their host distribution characteristics and in the severity of diseases that they are associated with. As such, this review provides a comprehensive overview on the bacterial species that have been recorded to possess stx genes to date, with a specific focus on the various Stx subtype variants discovered in STEC, their prevalence in certain host species, and their disease-related characteristics. This review provides a better understanding of the Stx subtypes and highlights the need for rapid and accurate approaches to toxin subtyping for the proper evaluation of the health risks associated with Shiga-toxin-related bacterial food contamination and human infections.

Pathogenicity assessment of Shiga toxin-producing Escherichia coli strains isolated from wild birds in a major agricultural region in California

Shiga toxin-producing Escherichia coli (STEC) consists of diverse strains differing in genetic make-up and virulence potential. To better understand the pathogenicity potential of STEC carried by the wildlife, three STEC and one E. coli strains isolated from wild birds near a major agricultural region in California were selected for comparative pathogenomic analyses. Three American crow (Corvus brachyrhynchos) strains, RM9088, RM9513, and RM10410, belonging to phylogroup A with serotypes O109:H48, O9:H30, and O113:H4, respectively, and a red-winged blackbird (Agelaius phoeniceus) strain RM14516 in phylogroup D with serotype O17:H18, were examined. Shiga toxin genes were identified in RM9088 (stx1a), RM10410 (stx1a + stx2d), and RM14516 (stx2a). Unlike STEC O157:H7 strain EDL933, none of the avian STEC strains harbored the pathogenicity islands OI-122, OI-57, and the locus of enterocyte effacement, therefore the type III secretion system biogenesis genes and related effector genes were absent in the three avian STEC genomes. Interestingly, all avian STEC strains exhibited greater (RM9088 and RM14516) or comparable (RM10410) cytotoxicity levels compared with EDL933. Comparative pathogenomic analyses revealed that RM9088 harbored numerous genes encoding toxins, toxins delivery systems, and adherence factors, including heat-labile enterotoxin, serine protease autotransporter toxin Pic, type VI secretion systems, protein adhesin Paa, fimbrial adhesin K88, and colonization factor antigen I. RM9088 also harbored a 36-Kb high pathogenicity island, which is related to iron acquisition and pathogenicity in Yersinia spp. Strain RM14516 carried an acid fitness island like the one in EDL933, containing a nine gene cluster involved in iron acquisition. Genes encoding extracellular serine protease EspP, subtilase cytotoxin, F1C fimbriae, and inverse autotransporter adhesin IatC were only detected in RM14516, and genes encoding serine protease autotransporter EspI and P fimbriae were only identified in RM10410. Although all curli genes were present in avian STEC strains, production of curli fimbriae was only detected for RM9088 and RM14516. Consistently, strong, moderate, and little biofilms were observed for RM9088, RM14516, and RM10410, respectively. Our study revealed novel combinations of virulence factors in two avian strains, which exhibited high level of cytotoxicity and strong biofilm formation. Comparative pathogenomics is powerful in assessing pathogenicity and health risk of STEC strains.

Genotypic and Phenotypic Characterization of Pathogenic Escherichia coli, Salmonella spp., and Campylobacter spp., in Free-Living Birds in Mainland Portugal

Birds are potential carriers of pathogens affecting humans and agriculture. Aiming to evaluate the occurrence of the top three most important foodborne pathogens in free-living birds in Portugal, we investigated 108 individual fecal samples from free-living birds and one pooled sample of gull feces (n = 50) for the presence of Escherichia coli (pathogenic and non-pathogenic), Salmonella spp. and Campylobacter spp. Virulence- and antimicrobial resistance- (AMR) associated genes were detected by PCR and Whole-Genome Sequencing (WGS), and phenotypic (serotyping and AMR profiles) characterization was performed. Overall, 8.9% of samples tested positive for pathogenic E. coli, 2.8% for Salmonella spp., and 9.9% for Campylobacter spp. AMR was performed on all pathogenic isolates and in a fraction of non-pathogenic E. coli, being detected in 25.9% of them. Ten of the tested E. coli isolates were multidrug-resistant (MDR), and seven of them were Extended-spectrum β-lactamase (ESBL) producers. Among Salmonella (n = 3) and Campylobacter (n = 9), only one strain of C. jejuni was identified as MDR. Most of the identified serotypes/sequence types had already been found to be associated with human disease. These results show that free-living birds in Portugal may act as carriers of foodborne pathogens linked to human disease, some of them resistant to critically important antimicrobials.

Prevalence and Characterization of Shiga Toxin Producing Escherichia coli Isolated from Animal Feed in Croatia

A survey on prevalence and number of Shiga toxin-producing Escherichia (E.) coli (STEC) in animal feed was carried out over a period of nine years in the Republic of Croatia. A total of 1688 feed samples were collected from feed factories and poultry farms. Analysis included two standard procedures: sample enrichment and (a) immunomagnetic separation and plating on two selective media; or (b) plating on two selective media. Confirmation of STEC included morphological examination, biochemical tests, serotyping, and polymerase chain reaction. Morphological and biochemical characterization revealed 629 E. coli strains. Further serological screening method revealed 78 STEC and EPEC serotypes, while only 27 strains were confirmed as STEC with PCR. All positive samples (1.6%) originated from poultry farms and contained combination of virulence genes: eaeA, stx1, and/or stx2. Since the presence of stx (especially stx2) and eae are identified as risk factors for development of severe diseases in humans, results of this survey indicate that avian sources of STEC infections might be one of those "undefined sources" of human illnesses. Further research is necessary for evaluation of risks posed by contaminated feed, poultry, and environment.

High Frequency of Multidrug-Resistant (MDR) Atypical Enteropathogenic Escherichia coli (aEPEC) in Broilers in Hungary

Escherichia coli (EC) strains belong to several pathotypes capable of infecting both humans and animals. Some of them have zoonotic potential and can sporadically cause epidemic outbreaks. Our aim was to screen for the distribution of these pathotypes in broilers and their related products. Therefore, E. coli strains were isolated (n = 118) from poultry intestine (n = 57), carcass (n = 57), and wastewater (n = 4) samples from one slaughterhouse with own reared poultry source and the National Reference Laboratory (NRL) poultry E. coli collection (n = 170) from the year 2017 was also studied. All 288 E. coli strains were screened by PCR for pathotype-specific genes stx, eae, st-lt, aggR, ipaH, and for further EPEC-specific virulence genes (bfp, EAF, tir, perA, ler). Altogether 35 atypical enteropathogenic E. coli (aEPEC) strains from the slaughterhouse and 48 aEPEC strains from the NRL collection were found. Regarding the phylogenetic groups of aEPEC, all four main groups were represented but there was a shift toward the B2 group (25%) as compared with the non-EPEC isolates (3%). The aEPEC isolates belonged to serogroups O14, O108, and O45. Multidrug resistance (MDR) was abundant in aEPEC strains (80 out of 83 aEPEC) with a diverse resistance pattern (n = 56). Our results of this study indicate that the high frequency of aEPEC in broilers and on their carcass surface, with frequent MDR to several antibiotic groups, raises the possibility that these strains pose a zoonotic risk to humans.

A scoping review on the prevalence of Shiga-toxigenic Escherichia coli in wild animal species

Zoonotic pathogens constitute the major source (60.3%) of emerging infectious diseases. Previous studies have investigated the prevalence of Shiga-toxigenic Escherichia coli (STEC) among wild animal species, but comprehensive data are needed to assess the role that these animals have in the transmission of STEC infections to the human population via faecal contamination of the environment, agri-food or water chain. Due to the nature of these microorganisms in which this human-animal-environment interface plays a relevant role on the disease's dynamics, a "One Health" approach is needed to prevent and control the worldwide spread. The aim of this study was to review the published research on the prevalence of STEC in wildlife. The search was performed using several online databases consisting of three blocks of specific search terms covering pathogen, type of study and population. Two reviewers applied the inclusion and exclusion criteria to screening and eligibility phases. Two hundred and twenty-five abstracts were screened for relevance, and 72 were included for data analysis. Most studies (77.8%) investigated the prevalence of STEC in ruminants and urban birds. Their role in transmitting the pathogen to humans, other animals and the agri-food chain is potentiated by the peculiar biological characteristics in ruminants and improved adaptation of urban birds to urban environments. The popularity of convenience and voluntary response sampling may be due to the lack of human-made boundaries on the wild animal species' habitat and having some samples from hunted-harvested animals. To our knowledge, this is the first comprehensive review on STEC prevalence in wild animal species from studies conducted across the globe. We recommend that future research includes and compares samples from varying origins (i.e., human, animal, environment and food) and applies a "One Health" approach to the emerging challenges that STEC poses to public health.

Zoonotic Agents in Feral Pigeons (Columba livia) from Costa Rica: Possible Improvements to Diminish Contagion Risks

Most studies on zoonotic agents in pigeons have been conducted in the Palearctic region, but the scarcity of data is notorious in the Neotropical region, where these birds can breed all year around and are in close contact with humans. In this study, we used a combination of culture-dependent and culture-independent methods to identify infectious agents in 141 fecal samples from pigeons collected at four urban parks from Costa Rica. Of these we identified 34 positive samples for Salmonella enterica subsp. enterica serovar Braenderup (24.1%), 13 for Chlamydophila psittaci (9.2%), 9 for enteropathogenic Escherichia coli (6.4% eaeA, 0% stx-1 and 0% stx-2), and 2 for Campylobacter jejuni (1.4%). These populations of pigeons pose low risk for healthy adult humans, however, they may pose a health risk to immunocompromised patients or children. This study provides scientific data, which can be incorporated into educational programs aiming to reverse the public attitude toward pigeon feeding and to rationally justify population control efforts.

Genotyping of virulent Escherichia coli obtained from poultry and poultry farm workers using enterobacterial repetitive intergenic consensus-polymerase chain reaction

Aim

The aim of this study was to characterize virulent Escherichia coli isolated from different poultry species and poultry farm workers using enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) genotyping.

Materials and Methods

Fecal swabs from different poultry species (n=150) and poultry farm workers (n=15) were analyzed for E. coli and screened for virulence genes (stx1, stx2, eaeA, and hlyA) by multiplex PCR. Virulent E. coli was serotyped based on their "O" antigen and then genotyped using ERIC-PCR.

Results

A total of 134 E. coli isolates (122/150 from poultry and 12/15 from farm workers) were recovered. Virulence genes were detected in a total of 12 isolates. Serological typing of the 12 virulent E. coli revealed nine different serotypes (O2, O49, O60, O63, O83, O101, O120, UT, and Rough). ERIC-PCR genotyping allowed discrimination of 12 virulent E. coli isolates into 11 ERIC-PCR genotypes. The numerical index of discrimination was 0.999.

Conclusion

Our findings provide information about the wide genetic diversity and discrimination of virulent E. coli in apparently healthy poultry and poultry farm workers of Andhra Pradesh (India) based on their genotype.

Characterization and zoonotic impact of Shiga toxin producing Escherichia coli in some wild bird species

Aim:

Wild birds are considered silent vectors of some zoonotic water and food borne pathogens of public health significance. Owing to the importance of Shiga toxin producing Escherichia coli (STEC) as the most pathogenic among the emerging diarrheagenic E. coli groups that can infect man; the present study was designed to detect the occurrence of STEC among wild birds in Egypt.

Materials and Methods:

A total of 177 intestinal content swab samples originating from five wild bird species were investigated for the presence of E. coli and STEC by standard culture methods. Suspect STEC isolates were further characterized by serotyping, random amplified polymorphic DNA polymerase chain reaction (RAPD PCR), antimicrobial resistance pattern and PCR detection of stx₁, stx₂, and eae genes.

Results:

A total of 30 suspect STEC isolates from 30 positive birds’ samples were detected and identified on STEC CHROMagar (semi-captive pigeons, 15; house crows, 8; cattle egrets, 3; moorhens, 2; and house teals, 2). 25 isolates were grouped into 13 serogroups (O:20, O:25, O:26, O:27, O:63, O:78, O:111, O:114, O:125, O:128, O:142, O:153, and O:158), while five were rough strains. The distribution of STEC virulence genes among wild birds was as follows: 16 birds carried stx₁ gene only (nine pigeons [28.1%], six crows [7.1%], and one cattle egret [5.6%]). Stx₁ and stx₂ genes together were detected in four birds (one cattle egret [5.6%], two moorhens [6.1%], and one house teal, [10%]). Only one pigeon (3.1%) possessed the three alleles. Disk diffusion test results showed that cefixime was the most effective against STEC serotypes with (93.3%) sensitivity, followed by gentamycin (56.7%), and amoxicillin (50%). On the other hand, all the recovered STEC isolates were resistant to cefotaxime, doxycycline, cephalothin, and sulfisoxazole. RAPD fingerprinting using primers OPA-2 and OPA-9 showed that STEC isolates were heterogeneous; they yielded 30 and 27 different clusters, respectively.

Conclusions:

Wild birds carry STEC and may add to the contamination of the surrounding environment.

ISOLATION AND MOLECULAR IDENTIFICATION OF POTENTIALLY PATHOGENIC Escherichia coli AND Campylobacter jejuni IN FERAL PIGEONS FROM AN URBAN AREA IN THE CITY OF LIMA, PERU

Feral pigeons (Columbia livia) live in close contact with humans and other animals. They can transmit potentially pathogenic and zoonotic agents. The objective of this study was to isolate and detect strains of diarrheagenic Escherichia coli and Campylobacter jejuni of urban feral pigeons from an area of Lima, Peru. Fresh dropping samples from urban parks were collected for microbiological isolation of E. coli strains in selective agar, and Campylobacter by filtration method. Molecular identification of diarrheagenic pathotypes of E.coli and Campylobacter jejuni was performed by PCR. Twenty-two parks were sampled and 16 colonies of Campylobacter spp. were isolated. The 100% of isolates were identified as Campylobacter jejuni. Furthermore, 102 colonies of E. coliwere isolated and the 5.88% resulted as Enteropathogenic (EPEC) type and 0.98% as Shiga toxin-producing E. coli (STEC). The urban feral pigeons of Lima in Peru can act as a reservoir or carriers of zoonotic potentially pathogenic enteric agents.

Isolation of atypical enteropathogenic Escherichia coli from chicken and chicken-derived products

Atypical enteropathogenic Escherichia coli (EPEC) strains from chicken and chicken-derived products were isolated and characterised. The strains presented a wide variety of serotypes, some have been reported in other animal species (O2:H40, O5:H40) and in children with diarrhoea (O8:H-). Most of the strains carried intimin β. The results indicate that chicken and chicken products are important sources of atypical EPEC strains that could be associated with human disease, and highlight the need to improve hygiene practices in chicken slaughtering and meat handling.

Linking fecal bacteria in rivers to landscape, geochemical, and hydrologic factors and sources at the basin scale

Linking fecal indicator bacteria concentrations in large mixed-use watersheds back to diffuse human sources, such as septic systems, has met limited success. In this study, 64 rivers that drain 84% of Michigan's Lower Peninsula were sampled under baseflow conditions for Escherichia coli, Bacteroides thetaiotaomicron (a human source-tracking marker), landscape characteristics, and geochemical and hydrologic variables. E. coli and B. thetaiotaomicron were routinely detected in sampled rivers and an E. coli reference level was defined (1.4 log10 most probable number⋅100 mL(-1)). Using classification and regression tree analysis and demographic estimates of wastewater treatments per watershed, septic systems seem to be the primary driver of fecal bacteria levels. In particular, watersheds with more than 1,621 septic systems exhibited significantly higher concentrations of B. thetaiotaomicron. This information is vital for evaluating water quality and health implications, determining the impacts of septic systems on watersheds, and improving management decisions for locating, constructing, and maintaining on-site wastewater treatment systems.

Virulence genes, antibiotic resistance and integrons in Escherichia coli strains isolated from synanthropic birds from Spain

The aim of this study was to determine the presence of virulence genes and antibiotic resistance profiles in 164 Escherichia coli strains isolated from birds (feral pigeons, hybrid ducks, house sparrows and spotless starlings) inhabiting urban and rural environments. A total of eight atypical enteropathogenic E. coli strains were identified: one in a house sparrow, four in feral pigeons and three in spotless starlings. Antibiotic resistance was present in 32.9% (54) of E. coli strains. The dominant type of resistance was to tetracycline (21.3%), ampicillin (19.5%) and sulfamethoxazole (18.9%). Five isolates had class 1 integrons containing gene cassettes encoding for dihydrofolate reductase A (dfrA) and aminoglycoside adenyltransferase A (aadA), one in a feral pigeon and four in spotless starlings. To our knowledge, the present study constitutes the first detection of virulence genes from E. coli in spotless starlings and house sparrows, and is also the first identification worldwide of integrons containing antibiotic resistance gene cassettes in E. coli strains from spotless starlings and pigeons.

Molecular characterization, genetic diversity and antibacterial susceptibility of Escherichia coli encoding Shiga toxin 2f in domestic pigeons

This study aimed to evaluate prevalence, characteristics, genotypic diversity and antibacterial susceptibility of Escherichia coli encoding Shiga toxin 2f in domestic pigeons in different provinces of Iran. A total of 117 faecal samples were collected from pigeons and were subjected to molecular detection of stx2f. In total, 20, 25·8, 21·4 and 9% of pigeons from Tehran, Ferdows, Garmsar and Babol cities carried stx2f+ isolates, respectively. Of the 460 E. coli isolates examined, 43 were stx2f+ and most also carried eae (95·3%) and astA (97·7%) genes. Some of the stx2f+ isolates harboured cnf (9·3%), but all were negative for stx1, stx2 (other subtypes) and ehly. Most Strains (90%) were assigned to B1 phylogroup and possessed Intimin-β. Fingerprinting of the stx2f+ isolates using either enterobacterial repetitive intergenic consensus sequences (ERIC) or random amplified polymorphic DNA (RAPD)-polymerase chain reaction revealed seven distinct profiles by each method, with one prevailing (65·1 and 46·5%, respectively). By the combination of methods, 10 profiles were recognized. Ten isolates from different profiles were shown to belong to O20, O78 and O115 serogroups, and eight were 100% identical in the stx2f gene sequence. The strains were consistently resistant to amoxicillin and lincospectin and commonly resistant to tetracycline (88·4%) and doxycycline (74·4%). Overall, the results indicate a limited degree of genetic diversity in stx2f-harbouring E. coli from pigeons. Significance and impact of the study: Carriage of stx2f gene tends to be underreported in pigeon Escherichia coli isolates because most routine genetic and phenotypic tests cannot efficiently target this gene or detect the toxin. Nevertheless, pigeons frequently carry E. coli strains that are stx2f-positive, and this situation is not limited to any distinct geographical area. The current results suggest that genetic background of stx2f-encoding E. coli is distinct from most Shiga toxin-producing E. coli strains. However, the factors that contribute to host preferences and pathogenicity remain unclear. These findings have public health significance that should be addressed in future research.

[Characterization of enteropathogenic Escherichia coli (EPEC) strains isolated during the chicken slaughtering process]

In Argentina, EPEC is one of the most prevalent agents isolated from children with diarrhea. Because contamination with this pathotype could occur during slaughter, the aim of this study was to isolate and characterize EPEC strains obtained from live animals (cloacae), eviscerated carcasses, washed carcasses and water from chillers. Twenty nine isolates of atypical EPEC were characterized. These isolates presented a wide variety of serotypes, some of which (O2:H40, O8:H19 and O108:H9) had been reported in other animal species. Serotype O45:H8, previously isolated from children with diarrhea was also found. Isolates of serotypes O2:H40, O108:H9 and O123:H32 were detected at different stages of the slaughtering process, suggesting that the process is not adequately performed. This latter fact highlights the importance of reinforcing control and hygienic measures at different stages of the chicken slaughtering process in order to reduce microbial contamination.

Isolation and characteristics of Shiga toxin 2f-producing Escherichia coli among pigeons in Kyushu, Japan

An increasing number of Shiga toxin 2f-producing Escherichia coli (STEC2f) infections in humans are being reported in Europe, and pigeons have been suggested as a reservoir for the pathogen. In Japan, there is very little information regarding carriage of STEC2f by pigeons, prompting the need for further investigation. We collected 549 samples of pigeon droppings from 14 locations in Kyushu, Japan, to isolate STEC2f and to investigate characteristics of the isolates. Shiga toxin stx 2f gene fragments were detected by PCR in 16 (2.9%) of the 549 dropping samples across four of the 14 locations. We obtained 23 STEC2f-isolates from seven of the original samples and from three pigeon dropping samples collected in an additional sampling experiment (from a total of seven locations across both sampling periods). Genotypic and phenotypic characteristics were then examined for selected isolates from each of 10 samples with pulsed-field gel electrophoresis profiles. Eight of the stx 2f gene fragments sequenced in this study were homologous to others that were identified in Europe. Some isolates also contained virulence-related genes, including lpfA O26, irp 2, and fyuA, and all of the 10 selected isolates maintained the eae, astA, and cdt genes. Moreover, five of the 10 selected isolates contained sfpA, a gene that is restricted to Shiga toxin-producing E. coli O165:H2 and sorbitol-fermenting Shiga toxin-producing E. coli O157:NM. We document serotypes O152:HNM, O128:HNM, and O145:H34 as STEC2f, which agrees with previous studies on pigeons and humans. Interestingly, O119:H21 was newly described as STEC2f. O145:H34, with sequence type 722, was described in a German study in humans and was also isolated in the current study. These results revealed that Japanese zoonotic STEC2f strains harboring several virulence-related factors may be of the same clonal complexes as some European strains. These findings provide useful information for public health-related disease management strategies in Japan.

Occurrence of diarrheagenic virulence genes and genetic diversity in Escherichia coli isolates from fecal material of various avian hosts in British Columbia, Canada

Contamination of surface water by fecal microorganisms originating from human and nonhuman sources is a public health concern. In the present study, Escherichia coli isolates (n = 412) from the feces of various avian host sources were screened for various virulence genes: stx1 and stx2 (Shiga toxin-producing E. coli [STEC]), eae (enteropathogenic E. coli [EPEC]), est-h, est-p, and elt (encoding heat-stable toxin [ST] variants STh and STp and heat-labile toxin [LT], respectively) (enterotoxigenic E. coli [ETEC]), and ipaH (enteroinvasive E. coli [EIEC]). None of the isolates were found to be positive for stx1, while 23% (n = 93) were positive for only stx2, representing STEC, and 15% (n = 63) were positive for only eae, representing EPEC. In addition, five strains obtained from pheasant were positive for both stx2 and eae and were confirmed as non-O157 by using an E. coli O157 rfb (rfbO157) TaqMan assay. Isolates positive for the virulence genes associated with ETEC and EIEC were not detected in any of the hosts. The repetitive element palindromic PCR (rep-PCR) fingerprint analysis identified 143 unique fingerprints, with an overall Shannon diversity index of 2.36. Multivariate analysis of variance (MANOVA) showed that the majority of the STEC and EPEC isolates were genotypically distinct from nonpathogenic E. coli and clustered independently. MANOVA analysis also revealed spatial variation among the E. coli isolates, since the majority of the isolates clustered according to the sampling locations. Although the presence of virulence genes alone cannot be used to determine the pathogenicity of strains, results from this study show that potentially pathogenic STEC and EPEC strains can be found in some of the avian hosts studied and may contaminate surface water and potentially impact human health.

Assessment of virulence factors characteristic of human Escherichia coli pathotypes and antimicrobial resistance in O157:H7 and non-O157:H7 isolates from livestock in Spain

The distribution of virulence factors (VFs) typical of diarrheagenic Escherichia coli and the antimicrobial resistance (AMR) profiles were assessed in 780 isolates from healthy pigs, broilers, and cattle from Spain. VF distribution was broader than expected, although at low prevalence for most genes, with AMR being linked mainly to host species.

Prevalence and characteristics of intimin-producing Escherichia coli strains isolated from healthy chickens in Korea

Virulent Escherichia coli strains have commonly been associated with diarrheal illness in humans and animals. Typical enteropathogenic Escherichia coli (EPEC) with intimin gene (eaeA) and E. coli adherence factor plasmid, or atypical EPEC with only eaeA have been implicated in human cases. In the present study, we investigated the prevalence of virulence-associated genes including eaeA in the E. coli strains isolated from cloacal specimens of 184 chicken flocks in 7 provinces in Korea between 2009 and 2010. When 7 virulence genes (VT1, VT2, LT, and ST for enterotoxigenic E. coli; eaeA and bfpA for enteropathogenic E. coli; and aggR for enteroaggregative E. coli) were screened by multiplex PCR, a total of 30 E. coli strains carrying only the eaeA gene were detected from 184 flocks that were identified as atypical enteropathogenic Escherichia coli (aEPEC). The aEPEC strains were analyzed by eae subtyping, phylogenetic grouping PCR, and serotyping. Twelve (40%) of 30 aEPEC strains possessed an eae-β subtype, followed by θ (30%), ε (16.7%), and β1 (13.3%). Eight (26.7%) of 30 aEPEC strains were designated into the phylogenetic group A. Two (6.7%) and 3 (10%) aEPEC strains were classified into the phylogenetic group B2 and D, respectively. A total of 15 (50%) aEPEC strains were serotyped to groups O24, O25, O26, O71, O80, O103, and O157, and the remaining strains were nontypeable. In analyzing the genetic diversity among the 30 aEPEC isolates by the pulsed-field gel electrophoresis method with XbaI-digestion, the pulsed-field gel electrophoresis profiling produced 20 different patterns, but isolates within the same group did not show clear geographic or breed relationships. Our data indicate that healthy chickens may constitute an important natural reservoir of aEPEC strains, and suggest that transmission to humans could not be excluded.

Identification of shiga toxin and intimin genes in Escherichia coli detected from canary (Serinus canaria domestica)

The pathogenicity of enterohemorrhagic Escherichia coli (EHEC) strains is, in large part, due to shiga toxin (Stx) genes (Stx1 and Stx2) and/or intimin (eae) gene. The purpose of this study was to analyze the role of domestic canaries (Serinus canaria domestica) as a reservoir of Stx and intimin producing strains of E. coli. For this study, a total of 50 cloacal swabs were collected from 50 healthy domestic canaries. Cloacal swabs were cultured and tested using standard methods of microbiology. After primary identification of E. coli, DNA was extracted and polymerase chain reaction was performed using specific primers for Stx1, Stx2 and eae genes. In this study, three of 50 samples were found to be Stx2 positive. In the present study, nine (18%) of 50 canaries tested were positive for eae gene. Only 2% of total canaries tested were positive for simultaneous Stx and eae genes. By considering the presence of Stx genes in E. coli isolated from cloacal contents of canary, this hypothesis expressed that the canaries may be the carriers of virulence genes that can risk human health. Canary was considered to be a reservoir of Stx and intimin genes and make these birds important vehicles for the spread of zoonosis infection.

Prevalence of diarrheagenic Escherichia coli virulence genes in the feces of slaughtered cattle, chickens, and pigs in Burkina Faso

We investigated the prevalence of the virulence genes specific for five major pathogroups of diarrheagenic Escherichia coli (DEC) in primary cultures from feces of animals slaughtered for human consumption in Burkina Faso. For the study, 704 feces samples were collected from cattle (n = 304), chickens (n = 350), and pigs (n = 50) during carcass processing. The presence of the virulence-associated genes in the mixed bacterial cultures was assessed using 16-plex polymerase chain reaction (PCR). Virulence genes indicating presence of DEC were detected in 48% of the cattle, 48% of the chicken, and 68% of the pig feces samples. Virulence genes specific for different DECs were detected in the following percentages of the cattle, chicken, and pig feces samples: Shiga toxin-producing E. coli (STEC) in 37%, 6%, and 30%; enteropathogenic E. coli (EPEC) in 8%, 37%, and 32%; enterotoxigenic E. coli (ETEC) in 4%, 5%, and 18%; and enteroaggregative E. coli (EAEC) in 7%, 6%, and 32%. Enteroinvasive E. coli (EIEC) virulence genes were detected in 1% of chicken feces samples only. The study was the first of its kind in Burkina Faso and revealed the common occurrence of the diarrheal virulence genes in feces of food animals. This indicates that food animals are reservoirs of DEC that may contaminate meat because of the defective slaughter and storage conditions and pose a health risk to the consumers in Burkina Faso.

A Survey for Escherichia coli Virulence Factors in Asymptomatic Free-Ranging Parrots

Parrots in captivity are frequently affected by Escherichia coli (E. coli) infections. The objective of this study was to collect information on the carrier state for E. coli pathotypes in asymptomatic free-ranging parrots. Cloacal swabs were collected from nestlings of Hyacinth, Lear's macaws and Blue-fronted Amazon parrots and tested by polymerase chain reaction (PCR) for virulence factors commonly found in enteropathogenic, avian pathogenic, and uropathogenic E. coli strains. In total, 44 samples were cultured and E. coli isolates were yielded, from which DNA was extracted and processed by PCR. Genes commonly found in APEC isolates from Blue-fronted Amazon parrots and Hyacinth macaws were expressed in 14 of these 44 samples. One atypical EPEC isolate was obtained from a sample from Lear's macaw. The most commonly found gene was the increased serum survival (iss) gene. This is the first report, that describes such pathotypes in asymptomatic free-living parrots. The findings of this study suggest the presence of a stable host/parasite relationship at the time of the sampling brings a new understanding to the role that E. coli plays in captive and wild parrots. Such information can be used to improve husbandry protocols as well as help conservation efforts of free-living populations.

Enteropathogenic Escherichia coli contamination at different stages of the chicken slaughtering process

Enteropathogenic Escherichia coli is a foodborne pathogen that produces potentially fatal infant diarrhea, noticeably in developing countries. The aim of this study was to detect EPEC contamination by PCR at different stages of the chicken slaughtering process. We collected swabs from chicken cloacae and washed carcasses (external and visceral cavity) during the slaughtering process in 3 sampling occasions. Unwashed eviscerated carcasses were also sampled (at the visceral cavity) in the second and third sampling occasions. Enteropathogenic Escherichia coli was detected in 6 to 28% of cloacal samples, 39 and 56% of unwashed eviscerated carcasses, and 4 to 58% of washed carcasses. None of the samples were positive for bfpA, suggesting contamination with atypical EPEC. The detection of EPEC at different stages of the chicken slaughtering process showed that the proportion of contaminated samples remained or even increased during processing. In addition, the high proportion of contaminated carcasses during chicken processing represents a risk for the consumers and a challenge to improve procedures for those working in the sanitary control service.

Identification of shiga toxin and intimin coding genes in Escherichia coli isolates from pigeons (Columba livia) in relation to phylotypes and antibiotic resistance patterns

Shiga toxin-producing Escherichia coli (STEC) strains are responsible for outbreaks of human intestinal diseases worldwide. Pigeons are distributed in public areas and are potential reservoirs for pathogenic bacteria. One hundred fifty-four fresh fecal samples were obtained from trapped pigeons in southeast of Iran and were cultured for isolation of E. coli. The isolates were examined to determine the prevalence of stx1, stx2, and eae genes, antimicrobial resistance, and their phylotypes. The confirmed E. coli isolates (138) belong to four phylogenetic groups: A (54.34%), B1 (34.05%), B2 (3.62%), and D (7.79%). Thirteen (9.42%) isolates were positive for one of the examined genes. Eight isolates (5.79%) were positive for eae, four (2.89%) for stx2, and one isolate (1.44%) for stx1 gene. Phylotyping assays showed that eight eae-positive isolates fall into three phylogroups; A (three isolates), B1 (three isolates), and D (two isolates), whereas four stx2-positive isolates belonged to the A (three isolates) and D (one isolate) groups. The stx1-positive isolate belonged to phylogroup A. One hundred six isolates (76.81%) showed resistance to at least one of the selected antibacterial agents. The maximum resistance rate was against oxytetracycline (73.91%), and the minimum was against flumequine (2.17%). Twenty different patterns of drug resistance were observed. According to the results, pigeons could be considered as carriers of STEC strains. However, E. coli isolates of pigeon feces increase the potential of these birds to act as a reservoir of multiple antibiotic resistant bacteria.

Cattle, weather and water: mapping Escherichia coli O157:H7 infections in humans in England and Scotland

Entero-haemorrhagic Escherichia coli O157:H7 is a zoonotic pathogen, responsible for a relatively small number of food poisoning and illness outbreaks each year, when compared with other food-borne bacteria capable of causing infections in the population. Nevertheless, E. coli O157:H7 is a bacterial pathogen associated with severe human illnesses including bloody diarrhoea and haemolytic uremic syndrome occurring in both outbreak and sporadic settings. In England and Wales approximately 1% of all laboratory-confirmed cases of food poisoning are the result of E. coli O157:H7; however, in Scotland this figure increases to 3%. When the size of the population is taken into account and the rate of E. coli O157:H7 confirmed cases per 100,000 population is examined, the rate of E. coli 0157:H7 infections in Scotland is much greater than England and Wales. The routes of transmission have changed over time, with new routes of transmission such as farm visits emerging. The prevalence of E. coli O157:H7 has a seasonal dependency, with greater faecal shedding of the organism in the warmer months; this is directly mirrored in the increased reporting of E. coli O157:H7 infection among hospitalized patients. This review attempts to suggest why this phenomenon occurs, paying particular attention to weather, animal movement and private water supplies.

Biofilm formation by and multicellular behavior of Escherichia coli O55:H7, an atypical enteropathogenic strain

Enteropathogenic Escherichia coli (EPEC) is an important causal agent of diarrheal illness throughout the world. Nevertheless, researchers have only recently begun to explore its capacity to form biofilms. Strain O55:H7 (DMS9) is a clinical isolate belonging to the atypical EPEC (aEPEC) group, which displays a high degree of genetic relatedness to enterohemorrhagic E. coli. Strain DMS9 formed a robust biofilm on an abiotic surface at 26 degrees C, but not at 37 degrees C. It also formed a dense pellicle at the air-liquid interface and developed a red, rough, and dry (RDAR) morphotype on Congo red agar. Unlike a previously described E. coli O157:H7 strain, the aEPEC strain seems to express cellulose. Transposon mutagenesis was used to identify biofilm-deficient mutants. One of the mutants was inactivated in the csgFG genes, required for assembly and secretion of curli fimbriae, while a second mutant had a mutation in crl, a thermosensitive global regulator that modulates sigma(S) activity and downstream expression of curli and cellulose. The two mutants were deficient in their biofilm formation capabilities and did not form a pellicle at the air-liquid interface. Unlike in Salmonella, the csgFG mutant in aEPEC completely lost the RDAR phenotype, while the crl mutant displayed a unique RDAR "pizza"-like morphotype. Genetic complementation of the two mutants resulted in restoration of the wild-type phenotype. This report is the first to describe and analyze a multicellular behavior in aEPEC and support a major role for curli and the crl regulator in biofilm development at low temperatures corresponding to the nonmammalian host environment.

Diarrheagenic Escherichia coli strains recovered from urban pigeons (Columba livia) in Brazil and their antimicrobial susceptibility patterns

Urban pigeons (Columba livia) come into close contact with humans and animals, and may contribute to the spread of infectious agents. These may include human pathogens such as diarrheagenic Escherichia coli strains, which are able to survive in pigeon feces, thus creating potential for human exposure and infection. Our objectives were to determine the occurrence of diarrheagenic E. coli strains in fresh feces from urban pigeons and their drug susceptibility patterns. E. coli strains were isolated from 100 fresh feces samples and presumptive phenotypic species identification was carried out, confirmed by amplification of specific 16S ribosomal RNA encoding DNA. Multiplex PCR was performed to characterize pathogenic strains. Drug susceptibility patterns were determined by the agar dilution method. Enteroinvasive E. coli, Shiga toxin-producing E. coli, enteropathogenic E. coli, and enterotoxigenic E. coli were detected at an overall rate of 12.1%. Among the isolated E. coli strains, 62.1% were susceptible to all tested drugs, whereas 37.9% were resistant to at least one of the antimicrobials tested. Amikacin was the less effective drug (36.8% resistance), followed by ampicillin (7.8%). No resistance was detected to gentamicin, ceftriaxone, and ceftazidime and almost all the isolates were susceptible to ampicillin-sulbactam (98.4%), levofloxacin (97.8%), and trimethoprim-sulfamethoxazole (96.1%). Since these pigeons may harbor multidrug-resistant pathogens, their presence in an urban environment could be an important component of infection spread, with impact on public health.

Isolation of atypical enteropathogenic Escherichia coli and Shiga toxin 1 and 2f-producing Escherichia coli from avian species in India

AIMS

To study the prevalence and characterize atypical enteropathogenic Escherichia coli (EPEC) and Shiga toxin producing E. coli (STEC) in avian species in India.

METHODS AND RESULTS

Two hundred and twelve faecal samples collected from 62 chickens, 50 ducks and 100 pigeons were investigated for the presence of stx(1), stx(2), eae and ehxA virulence genes by multiplex PCR. In all, 42 E. coli isolates (25 chicken, 2 duck and 15 pigeon) possessed at least one virulence gene. Out of these, nine (4.24%) isolates were STEC and 33 (15.56%) were EPEC. All isolates from duck and chicken were EPEC while among 15 pigeon isolates nine (60%) were STEC and six (40%) were EPEC. Among the STEC isolates four each carried stx(1) or stx(2) and one possessed both stx(1) and stx(2). Subtype analysis of stx revealed the presence of stx(2f) in four STEC isolates. None of the STEC isolates carried stx(1c), stx(2c), stx(2d) or stx(2e). Isolates carrying stx(2f) demonstrated vero cell toxicity. One each belonged to serogroup O17 and O78, while one was rough and the other untypeable. All EPEC isolates were atypical as they lacked bfpA. This appears to be the first report of detection of stx(2f) from India.

CONCLUSIONS

The study established the presence of stx(1) and stx(2f) containing E. coli in pigeons and atypical EPEC in poultry in India. Pigeons might serve as vectors for transmission of STEC to environment and humans.

SIGNIFICANCE AND IMPACT OF THE STUDY

Taking into account the close contact between fanciers and pigeons, these findings warrant a more critical appraisal of these zoonotic pathogens in pigeons and humans.

Risk factors for the occurrence ofEscherichia colivirulence geneseae,stx1andstx2in wild bird populations

Shiga toxin-producingEscherichia coli(STEC) can cause serious disease in human beings. Ruminants are considered to be the main reservoir of human STEC infections. However, STEC have also been isolated from other domestic animals, wild mammals and birds. We describe a cross-sectional study of wild birds in northern England to determine the prevalence ofE. coli-containing genes that encode Shiga toxins (stx1and stx2) and intimin (eae), important virulence determinants of STEC associated with human disease. Multivariable logistic regression analysis identified unique risk factors for the occurrence of each virulence gene in wild bird populations. The results of our study indicate that while wild birds are unlikely to be direct sources of STEC infections, they do represent a potential reservoir of virulence genes. This, coupled with their ability to act as long-distance vectors of STEC, means that wild birds have the potential to influence the spread and evolution of STEC.

Escherichia coli encoding Shiga toxin 2f as an emerging human pathogen

Escherichia coli harbouring the stx2f gene have been previously reported in pigeons. Here we demonstrate the presence of this allele in human diarrhoeagenic E. coli strains originally classified as atypical enteropathogenic E. coli (aEPEC). Thirty-two stx2f-positive E. coli serotyped as O63:H6, O128:H2, O132:H34, O145:H34, and O178:H7 were found to belong to a large number of clonal groups due to their different MLST-, PFGE- and virulence patterns. The appearance of various stx2f-positive clonal lineages among E. coli reveals emerging clinical significance. Therefore, it seems to be prudent to include stx2f into the diagnostic scope employed for laboratory investigation of enteric infections.

Prevalence and characteristics of eae- and stx-positive strains of Escherichia coli from wild birds in the immediate environment of Tokyo Bay

The prevalence and characteristics of eae- and stx-positive Escherichia coli strains in wild birds in the immediate environment of Tokyo Bay, Japan, was examined using cloacal swab samples taken from 447 birds belonging to 62 species. PCR screening showed that the prevalences of stx- and eae-positive strains of Escherichia coli were 5% (23/447) and 25% (113/447), respectively. Four strains of stx(2f)-positive E. coli were isolated from two feral pigeons, an oriental turtle dove and a barn swallow. In contrast, 39 eae-positive E. coli strains were isolated, and most of the strains possessed a subtype of intimin that is classified as a minor group of human intimins, such as intimin upsilon, kappa, and mu. Moreover, these strains did not possess any of the other pathogenic genes tested, such as stxs, ehxA, bfp, or irp. Thus, wild birds were considered to be a reservoir of atypical enteropathogenic E. coli.

Relationship between phylogenetic groups, genotypic clusters, and virulence gene profiles of Escherichia coli strains from diverse human and animal sources

Escherichia coli strains in water may originate from various sources, including humans, farm and wild animals, waterfowl, and pets. However, potential human health hazards associated with E. coli strains present in various animal hosts are not well known. In this study, E. coli strains from diverse human and animal sources in Minnesota and western Wisconsin were analyzed for the presence of genes coding for virulence factors by using multiplex PCR and biochemical reactions. Of the 1,531 isolates examined, 31 (2%) were found to be Shiga toxin-producing E. coli (STEC) strains. The majority of these strains, which were initially isolated from the ruminants sheep, goats, and deer, carried the stx(1c) and/or stx(2d), ehxA, and saa genes and belonged to E. coli phylogenetic group B1, indicating that they most likely do not cause severe human diseases. All the STEC strains, however, lacked eae. In contrast, 26 (1.7%) of the E. coli isolates examined were found to be potential enteropathogenic E. coli (EPEC) strains and consisted of several intimin subtypes that were distributed among various human and animal hosts. The EPEC strains belonged to all four phylogenetic groups examined, suggesting that EPEC strains were relatively widespread in terms of host animals and genetic background. Atypical EPEC strains, which carried an EPEC adherence factor plasmid, were identified among E. coli strains from humans and deer. DNA fingerprint analyses, done using the horizontal, fluorophore-enhanced repetitive-element, palindromic PCR technique, indicated that the STEC, potential EPEC, and non-STEC ehxA-positive E. coli strains were genotypically distinct and clustered independently. However, some of the potential EPEC isolates were genotypically indistinguishable from nonpathogenic E. coli strains. Our results revealed that potential human health hazards associated with pathogenic E. coli strains varied among the animal hosts that we examined and that some animal species may harbor a greater number of potential pathogenic strains than other animal species.

Presence of Shiga toxin-producing Escherichia coli O157:H7 in living layer hens

AIMS

To evaluate the presence of Shiga toxin-producing strains of Escherichia coli (STEC) of the O157:H7 serotype in living layer hens so as to analyse the role of this avian species as potential reservoir.

METHODS AND RESULTS

Cloacal swabs were collected between November 2004 and November 2005 from four intensive management layer hen farms and analysed for STEC O157:H7 by immunomagnetic separation methods and multiplex polymerase chain reaction for stx1 and/or stx2, the E. coli attaching and effacing (eae) and hly genes. STEC was detected in 26 of the 720 samples.

CONCLUSIONS

The layer hens analysed were shown to carry STEC O157:H7. The presence of this bacterium in living layer hen farms investigated did not result in any detectable increase in gastrointestinal disease in this species.

SIGNIFICANCE AND IMPACT OF THE STUDY

Living layer hens are a novel potential reservoir of E. coli O157:H7.

Escherichia coli O157:H7 in environments of culture-positive cattle

Outbreaks of Escherichia coli O157:H7 disease associated with animal exhibits have been reported with increasing frequency. Transmission can occur through contact with contaminated haircoats, bedding, farm structures, or water. We investigated the distribution and survival of E. coli O157:H7 in the immediate environments of individually housed, experimentally inoculated cattle by systematically culturing feed, bedding, water, haircoat, and feed bunk walls for E. coli O157:H7 for 3 months. Cedar chip bedding was the most frequently culture-positive environmental sample tested (27/96 or 28.15%). Among these, 12 (44.0%) of positive bedding samples were collected when the penned animal was fecal culture negative. Survival of E. coli O157:H7 in experimentally inoculated cedar chip bedding and in grass hay feed was determined at different temperatures. Survival was longest in feed at room temperature (60 days), but bacterial counts decreased over time. The possibility that urine plays a role in the environmental survival of E. coli O157:H7 was investigated. Cedar chip bedding moistened with sterile water or bovine urine was inoculated with E. coli O157:H7. Bedding moistened with urine supported growth of E. coli O157:H7, whereas inoculated bedding moistened with only water yielded decreasing numbers of bacteria over time. The findings that environmental samples were frequently positive for E. coli O157:H7 at times when animals were culture negative and that urine provided a substrate for E. coli O157:H7 growth have implications for understanding the on-farm ecology of this pathogen and for the safety of ruminant animal exhibits, particularly petting zoos and farms where children may enter animal pens.

A national surveillance of Shiga toxin-producing Escherichia coli in food-producing animals in Japan

To assess the public health risk, the prevalence and anti-microbial resistance of Shiga toxin-producing Escherichia coli (STEC) among food-producing animals were studied throughout Japan. Faecal samples were collected from healthy animals of 272 cattle, 179 pigs, and 158 broilers on 596 farms in all 47 Japanese prefectures. STEC were isolated from 62 (23%) cattle and 32 (14%) pig samples but from no chicken samples. Of the bovine isolates, 19 belonged to serotypes frequently implicated in human disease (O157:H7/non-motile (NM)/H not typeable, O26:NM/H11/H21/H not typeable, O113:H21, and O145:NM). The eae genes were observed in 37% of bovine isolates; among them one O145:NM and all four O157 isolates possessed eae-gamma1, and one O145:NM, one O103:H11, and all five O26 isolates possessed eae-beta1 gene. Among the swine isolates, stx2e were dominant, and serotypes frequently implicated in human diseases or eae-positive isolates were not observed. Bovine isolates showed less anti-microbial resistance, but six isolates of 26:NM/H11 and O145:NM were multi-resistant and may need careful monitoring. Swine isolates showed various resistance patterns; chloramphenicol resistance patterns were more common than in bovine isolates. This first national study of STEC in the Japanese veterinary field should aid our understanding of Japan's STEC status.

Attaching-effacing bacteria in animals

Enteric bacteria with a demonstrable or potential ability to form attaching-effacing lesions, so-called attaching-effacing (AE) bacteria, have been found in the intestinal tracts of a wide variety of warm-blooded animal species, including man. In some host species, for example cattle, pigs, rabbits and human beings, attaching-effacing Escherichia coli (AEEC) have an established role as enteropathogens. In other host species, AE bacteria are of less certain significance. With continuing advances in the detection and typing of AE strains, the importance of these bacteria for many hosts is likely to become clearer. The pathogenic effects of AE bacteria result from adhesion to the intestinal mucosa by a variety of mechanisms, culminating in the formation of the characteristic intimate adhesion of the AE lesion. The ability to induce AE lesions is mediated by the co-ordinated expression of some 40 bacterial genes organized within a so-called pathogenicity island, known as the "Locus for Enterocyte Effacement". It is also believed that the production of bacterial toxins, principally Vero toxins, is a significant virulence factor for some AEEC strains. Recent areas of research into AE bacteria include: the use of Citrobacter rodentium to model human AEEC disease; quorum-sensing mechanisms used by AEEC to modulate virulence gene expression; and the potential role of adhesion in the persistent colonization of the intestine by AE bacteria. This review of AE bacteria covers their molecular biology, their occurrence in various animal species, and the diagnosis, pathology and clinical aspects of animal diseases with which they are associated. Reference is made to human pathogens where appropriate. The focus is mainly on natural colonization and disease, but complementary experimental data are also included.