Verotoxin-producing Escherichia coli (VTEC), enteropathogenic E. coli (EPEC) and necrotoxigenic E. coli (NTEC) isolated from healthy cattle in Spain

Detection and analysis of Shiga toxin producing and enteropathogenic Escherichia coli in cattle from Tierra del Fuego, Argentina

Shiga toxin producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) are pathovars that affect mainly infants' health. Cattle are the main reservoir of STEC. Uremic hemolytic syndrome and diarrheas can be found at high rates in Tierra del Fuego (TDF). This study aimed to establish the prevalence of STEC and EPEC in cattle at slaughterhouses in TDF and to analyze the isolated strains. Out of 194 samples from two slaughterhouses, STEC prevalence was 15%, and EPEC prevalence was 5%. Twenty-seven STEC strains and one EPEC were isolated. The most prevalent STEC serotypes were O185:H19 (7), O185:H7 (6), and O178:H19 (5). There were no STEC eae + strains (AE-STEC) or serogroup O157 detected in this study. The prevalent genotype was stx2c (10/27) followed by stx1a/stx2hb (4/27). Fourteen percent of the strains presented at least one stx non-typeable subtype (4/27). Shiga toxin production was detected in 25/27 STEC strains. The prevalent module for the Locus of Adhesion and Autoaggregation (LAA) island was module III (7/27). EPEC strain was categorized as atypical and with the ability to cause A/E lesion. The ehxA gene was present in 16/28 strains, 12 of which were capable of producing hemolysis. No hybrid strains were detected in this work. Antimicrobial susceptibility tests showed that all strains were resistant to ampicillin and 20/28 were resistant to aminoglycosides. No statistical differences could be seen in the detection of STEC or EPEC either by slaughterhouse location or by production system (extensive grass or feedlot). The rate of STEC detection was lower than the one reported for the rest of Argentina. STEC/EPEC relation was 3 to 1. This is the first study on cattle from TDF as reservoir for strains that are potentially pathogenic to humans.

First Report of OXA-48 and IMP Genes Among Extended-Spectrum Beta-Lactamase-Producing Escherichia coli Isolates from Diarrheic Calves in Tunisia

Antimicrobial resistance is one of the most serious threats to human and animal health. Evidence suggests that the overuse of antimicrobial agents in animal production has led to the emergence and dissemination of multidrug-resistant isolates. The objective of this study was to assess the rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in calf feces and to characterize their resistance genes for antibiotics like beta-lactams and colistin, but also to determine their virulence genes. Fecal samples were collected from 100 diarrheic calves in the region of Bizerte, Tunisia. After isolation, E. coli isolates were screened for antimicrobial resistance against 21 antibiotics by the disc diffusion method. Characterization of β-lactamase genes and determination of associated resistance genes were performed by polymerase chain reaction. Among 71 E. coli isolates, 26 (36.6%) strains were ESBL-producing. Most of these isolates were multidrug-resistant (92.3%) and the most prevalent beta-lactamase genes detected were bla_CTX-M (n = 26), bla_SHV (n = 11), and bla_TEM (n = 8), whereas only 1 isolate carried the bla_CMY gene. In addition, resistance to carbapenems was detected in two isolates; one of them harbored both bla_OXA-48 and bla_IMP genes and the other isolate carried only the bla_IMP gene. Several resistance genes were identified for the first time in Tunisia from cases of diarrheic calves. Furthermore, to the best of our knowledge, this is the first report of detection and identification of carbapenem resistance genes and virulence genes from calves in North Africa. A high occurrence of antimicrobial resistance of E. coli recovered from fecal samples of calves with diarrhea was observed, highlighting the need for prudent use of antimicrobial agents in veterinary medicine to decrease the incidence of multidrug-resistant bacteria for both animals and humans.

Virulence potential of faecal <i>Escherichia coli</i> strains isolated from healthy cows and calves on farms in Perm Krai

Cattle are a reservoir of pathogenic and potentially pathogenic Escherichia coli (E. coli) strains, which can pose a threat to human and animal health. The aim of the study was to evaluate the occurrence of 22 virulence-associated genes (VAGs), as well as the prevalence of antimicrobial drug resistance and three different bla-genes among 49 E. coli strains isolated from healthy cattle. The presence of VAGs that are common among diarrheagenic E. coli (DEC) strains and/or extraintestinal pathogenic E. coli (ExPEC) strains was determined by amplifying specific gene sequences by PCR. The following VAGs associated with DEC were found: east1 in 24.5 % of the studied E. coli strains, estI in 10.2 %, ehxA in 8.2 %, stx2 in 6.1 %, eltA in 4.1 %, estII and stx1 in 2.0 % of the studied strains. The prevalence of ExPEC VAGs was: fimH – 91.8 %, afa/draBC – 61.2 %, iutA – 44.9 %, flu – 32.7 %, sfaDE and hlyF – 30.6 %, iroN – 22.4 %, ompT and papC – 20.4 %, kpsMTII and hlyA – 18.4 %, iss – 14.3 %, usp – 2.0 %, cnf1 and iha were not detected among the studied strains. Based on the found co-occurrence of VAGs “classical”, hetero-pathogenic and hybrid-pathogenic E. coli strains were found. E. coli strains isolated from cows had a higher diarrheagenic potential, whereas E. coli strains isolated from calves more frequently contained genes associated with the ExPEC pathotype. Among the studied E. coli strains, 77.6 % were resistant to ampicillin, 49.0 % to tetracycline, 20.4 % to chloramphenicol, 16.3 % to cefoperazone, 16.3 % to ceftriaxone, 16.3 % to aztreonam, 14.3 % to cefepime, 10.2 % to norfloxacin, 10.2 % to ciprofloxacin, 6.1 % to levofloxacin and 2.0 % to gentamicin. All strains were sensitive to meropenem and amikacin. 32.7 % of the studied E. coli strains were found to be multidrug resistant, as they were resistant to at least three groups of antibiotics. With PCR, the blaTEM, blaSHV, and blaCTX-M genes were detected in 100, 31.6, and 26.3 %, respectively, of strains resistant to at least one of the beta-lactam antibiotics. Thus, it was shown that the studied faecal E. coli of healthy cows and calves had a high hetero-pathogenic potential, therefore in the future molecular genetic characterization of these bacteria shall be an important part of the epizootic monitoring.

A systematic review and meta-analysis of published literature on prevalence of non-O157 Shiga toxin-producing Escherichia coli serogroups (O26, O45, O103, O111, O121, and O145) and virulence genes in feces, hides, and carcasses of pre- and peri-harvest cattle worldwide

OBJECTIVE

The objective of this study was to summarize peer-reviewed literature on the prevalence and concentration of non-O157 STEC (O26, O45, O103, O111, O121, and O145) serogroups and virulence genes (stx and eae) in fecal, hide, and carcass samples in pre- and peri-harvest cattle worldwide, using a systematic review of the literature and meta-analyses.

DATA SYNTHESIS

Seventy articles were eligible for meta-analysis inclusion; data from 65 articles were subjected to random-effects meta-analysis models to yield fecal prevalence estimates. Meta-regression models were built to explore variables contributing to the between-study heterogeneity.

RESULTS

Worldwide pooled non-O157 serogroup, STEC, and EHEC fecal prevalence estimates (95% confidence interval) were 4.7% (3.4-6.3%), 0.7% (0.5-0.8%), and 1.0% (0.8-1.1%), respectively. Fecal prevalence estimates significantly differed by geographic region (P < 0.01) for each outcome classification. Meta-regression analyses identified region, cattle type, and specimen type as factors that contribute to heterogeneity for worldwide fecal prevalence estimates.

CONCLUSIONS

The prevalence of these global foodborne pathogens in the cattle reservoir is widespread and highly variable by region. The scarcity of prevalence and concentration data for hide and carcass matrices identifies a large data gap in the literature as these are the closest proxies for potential beef contamination at harvest.

Literature Review: Coinfection in Young Ruminant Livestock-Cryptosporidium spp. and Its Companions

The protozoan Cryptosporidium parvum is one of the major causative pathogens of diarrhoea in young ruminants; therefore, it causes economic losses and impairs animal welfare. Besides C. parvum, there are many other non-infectious and infectious factors, such as rotavirus, Escherichia coli, and Giardia duodenalis, which may lead to diarrhoeic disease in young livestock. Often, more than one infectious agent is detected in affected animals. Little is known about the interactions bet-ween simultaneously occurring pathogens and their potential effects on the course of disease. In this review, a brief overview about pathogens associated with diarrhoea in young ruminants is presented. Furthermore, information about coinfections involving Cryptosporidium is provided.

Comparative Whole Genome Analysis of Escherichia coli O157:H7 Isolates From Feedlot Cattle to Identify Genotypes Associated With the Presence and Absence of stx Genes

A comparative whole genome analysis was performed on three newly sequenced Escherichia coli O157:H7 strains with different stx profiles, previously isolated from feedlot cattle [C1-010 (stx1-, stx2c+), C1-057 (stx-), and C1-067 (stx1+, stx2a+)], as well as five foodborne outbreak strains and six stx-negative strains from NCBI. Phylogenomic analysis demonstrated that the stx2c-carrying C1-010 and stx-negative C1-057 strains were grouped with the six NCBI stx-negative E. coli O157:H7 strains in Cluster 1, whereas the stx2a-carrying C1-067 and five foodborne outbreak strains were clustered together in Cluster 2. Based on different clusters, we selected the three newly sequenced strains, one stx2a-carrying strain, and the six NCBI stx-negative strains and identify their prophages at the stx insertion sites. All stx-carrying prophages contained both the three Red recombination genes (exo, bet, gam) and their repressor cI. On the other hand, the majority of the stx-negative prophages carried only the three Red recombination genes, but their repressor cI was absent. In the absence of the repressor cI, the consistent expression of the Red recombination genes in prophages might result in more frequent gene exchanges, potentially increasing the probability of the acquisition of stx genes. We further investigated each of the 10 selected E. coli O157:H7 strains for their respective unique metabolic pathway genes. Seven unique metabolic pathway genes in the two stx2a-carrying strains and one in the single stx2c-carrying and seven stx-negative strains were found to be associated with an upstream insertion sequence 629 within a conserved region among these strains. The presence of more unique metabolic pathway genes in stx2a-carrying E. coli O157:H7 strains may potentially increase their competitiveness in complex environments, such as feedlot cattle. For the stx2c-carrying and stx-negative E. coli O157:H7 strains, the fact that they were grouped into the same phylogenomic cluster and had the same unique metabolic pathway genes suggested that they may also share closely related evolutionary pathways. As a consequence, gene exchange between them is more likely to occur. Results from this study could potentially serve as a basis to help develop strategies to reduce the prevalence of pathogenic E. coli O157:H7 in livestock and downstream food production environments.

Raccoons (Procyon lotor) in the Madrid region of Spain are carriers of antimicrobial-resistant Escherichia coli and enteropathogenic E. coli

The role of wildlife in the epidemiology of antimicrobial resistance is unclear. Raccoons in North America can carry a variety of enteric bacteria, with associated antimicrobial resistance, that could infect humans and livestock. The potential for raccoons to carry these bacteria in Europe, where they are an invasive species, has not been explored. Our objectives were to determine the prevalence of Escherichia coli with associated antimicrobial resistance in raccoons from the Madrid region of Spain and to determine whether they are carriers of potential human pathogens, including verotoxin-producing E. coli (VTEC) and enteropathogenic E. coli (EPEC). In total, we tested 237 E. coli isolates from the faeces of 83 euthanized raccoons for susceptibility to 14 antimicrobial agents and the presence of VTEC and EPEC. Antimicrobial resistance to at least one antimicrobial was detected in the faeces of 51% (42/83; 95% CI, 40.1-61.1) of the raccoons tested. A high percentage of raccoons carried, in their faeces, E. coli isolates resistant to ampicillin (33%), streptomycin (33%), tetracycline (30%), sulphafurazole (31%) and trimethoprim-sulphamethoxazole (23%). We detected one isolate of extended-spectrum β-lactamase-producing E. coli from the faeces of one raccoon. We detected VTEC in the faeces of one raccoon, and EPEC in the faeces of 12% (10/83) of the raccoons. Of the raccoons that carried EPEC in their faeces, 60% (6/10) carried EPEC isolates that exhibited characteristics associated with pathogenicity in humans. Raccoons in Madrid can carry pathogenic and antimicrobial-resistant E. coli in their faeces and may be a risk to public health because of their potential to contaminate food and the environment with their faeces.

Multi-Year Persistence of Verotoxigenic Escherichia coli (VTEC) in a Closed Canadian Beef Herd: A Cohort Study

In this study, fecal samples were collected from a closed beef herd in Alberta, Canada from 2012 to 2015. To limit serotype bias, which was observed in enrichment broth cultures, Verotoxigenic Escherichia coli (VTEC) were isolated directly from samples using a hydrophobic grid-membrane filter verotoxin immunoblot assay. Overall VTEC isolation rates were similar for three different cohorts of yearling heifers on both an annual (68.5 to 71.8%) and seasonal basis (67.3 to 76.0%). Across all three cohorts, O139:H19 (37.1% of VTEC-positive samples), O22:H8 (15.8%) and O?(O108):H8 (15.4%) were among the most prevalent serotypes. However, isolation rates for serotypes O139:H19, O130:H38, O6:H34, O91:H21, and O113:H21 differed significantly between cohort-years, as did isolation rates for some serotypes within a single heifer cohort. There was a high level of VTEC serotype diversity with an average of 4.3 serotypes isolated per heifer and 65.8% of the heifers classified as "persistent shedders" of VTEC based on the criteria of >50% of samples positive and ≥4 consecutive samples positive. Only 26.8% (90/336) of the VTEC isolates from yearling heifers belonged to the human disease-associated seropathotypes A (O157:H7), B (O26:H11, O111:NM), and C (O22:H8, O91:H21, O113:H21, O137:H41, O2:H6). Conversely, seropathotypes B (O26:NM, O111:NM) and C (O91:H21, O2:H29) strains were dominant (76.0%, 19/25) among VTEC isolates from month-old calves from this herd. Among VTEC from heifers, carriage rates of vt1, vt2, vt1+vt2, eae, and hlyA were 10.7, 20.8, 68.5, 3.9, and 88.7%, respectively. The adhesin gene saa was present in 82.7% of heifer strains but absent from all of 13 eae+ve strains (from serotypes/intimin types O157:H7/γ1, O26:H11/β1, O111:NM/θ, O84:H2/ζ, and O182:H25/ζ). Phylogenetic relationships inferred from wgMLST and pan genome-derived core SNP analysis showed that strains clustered by phylotype and serotype. Further, VTEC strains of the same serotype usually shared the same suite of antibiotic resistance and virulence genes, suggesting the circulation of dominant clones within this distinct herd. This study provides insight into the diverse and dynamic nature of VTEC populations within groups of cattle and points to a broad spectrum of human health risks associated with these E. coli strains.

Inhibition of the lethality of Shiga-like toxin-1 by functional gold nanoparticles

Escherichia coli O157:H7 is a pathogen, which can generate Shiga-like toxins (SLTs) and cause hemolytic-uremic syndrome. Foodborne illness outbreaks caused by E. coli O157:H7 have become a global issue. Since SLTs are quite toxic, effective medicines that can reduce the damage caused by SLTs should be explored. SLTs consist of a single A and five B subunits, which can inhibit ribosome activity for protein synthesis and bind with the cell membrane of host cells, respectively. Pigeon ovalbumin (POA), i.e. a glycoprotein, is abundant in pigeon egg white (PEW) proteins. The structure of POA contains Gal-α(1→4)-Gal-β(1→4)-GlcNAc ligands, which have binding affinity toward the B subunit in SLT type-1 (SLT-1B). POA immobilized gold nanoparticles (POA-Au NPs) can be generated by reacting PEW proteins with aqueous tetrachloroauric acid in one-pot. The generated POA-Au NPs have been demonstrated to have selective trapping-capacity toward SLT-1B previously. Herein, we explore that POA-Au NPs can be used as protective agents to neutralize the toxicity of SLT-1 in SLT-1-infected model cells. The results show that the cells can be completely rescued when a sufficient amount of POA-Au NPs is used to treat the SLT-1-infected cells within 1 h.

Selective Detection of Shiga-like Toxin 1 from Complex Samples Using Pigeon Ovalbumin Functionalized Gold Nanoparticles as Affinity Probes

Escherichia coli O157:H7 is a foodborne pathogen. This bacterial strain can generate Shiga-like toxins (SLTs), which can cause serious sickness and even death. Thus, it is important to develop effective and sensitive methods that can be used to rapidly identify the presence of SLTs from complex samples. Pigeon egg white (PEW) contains abundant glycoproteins, including pigeon ovalbumin (POA) (∼60%). POA possesses Gal-α(1→4)-Gal-β(1→4)-GlcNAc termini, which can recognize the B subunits in SLT type 1 (SLT-1B). Thus, POA is a suitable probe for trapping SLT-1B. In this work, we used PEW proteins as starting materials to react with aqueous tetrachloroauric acid for generation of PEW-protein-immobilized gold nanoparticles (AuNPs@PEW) via one-pot reactions. We demonstrated that the generated AuNPs@PEW were mainly dominated by POA-immobilized Au NPs. The as-prepared AuNPs@PEW were used as affinity probes to selectively probe SLT-1B from complex cell lysates derived from E. coli O157:H7. The selective trapping step can be completed within ∼90 s under microwave heating (power = 450 W) to enrich sufficient SLT-1B for matrix-assisted laser desorption/ionization (MALDI) mass spectrometric analysis. Furthermore, this approach can be used to detect SLT-1B at a concentration as low as ∼40 pM. The feasibility of using the proposed method to selectively detect SLT-1B from ham contaminated by E. coli O157:H7 was also demonstrated.

Detection of virulence-associated genes characteristic of intestinal Escherichia coli pathotypes, including the enterohemorrhagic/enteroaggregative O104:H4, in bovines from Germany and Spain

Cattle are reservoirs of enterohemorrhagic Escherichia coli; however, their role in the epidemiology of other pathogenic E. coli remains undefined. A new set of quantitative real-time PCR assays for the direct detection and quantification of nine virulence-associated genes (VAGs) characteristic of the most important human E. coli pathotypes and four serotype-related genes (wzxO104 , fliCH4 , rbfO157 , fliCH7 ) that can be used as a surveillance tool for detection of pathogenic strains was developed. A total of 970 cattle fecal samples were collected in slaughterhouses in Germany and Spain, pooled into 134 samples and analyzed with this tool. stx1, eae and invA were more prevalent in Spanish samples whereas bfpA, stx2, ehxA, elt, est and the rbfO157 /fliCH7 combination were observed in similar proportions in both countries. Genes characteristic of the hybrid O104:H4 strain of the 2011 German outbreak (stx2/aggR/wzxO104 /fliCH4 ) were simultaneously detected in six fecal pools from one German abattoir located near the outbreak epicenter. Although no isolate harboring the full stx2/aggR/wzxO104 /fliCH4 combination was cultured, sequencing of the aggR positive PCR products revealed 100% homology to the aggR from the outbreak strain. Concomitant detection by this direct approach of VAGs from a novel human pathogenic E. coli strain in cattle samples implies that the E. coli gene pool in these animals can be implicated in de novo formation of such highly-virulent strains. The application of this set of qPCRs in surveillance studies could be an efficient early-warning tool for the emergence of zoonotic E. coli in livestock.

Magnetic Nanoparticle-Based Platform for Characterization of Shiga-like Toxin 1 from Complex Samples

Foodborne illness outbreaks resulting from contamination of Escherichia coli O157:H7 remain a serious concern in food safety. E. coli O157:H7 can cause bloody diarrhea, hemolytic uremic syndrome, or even death. The pathogenicity of E. coli O157:H7 is mainly caused by the expression of Shiga-like toxins (SLTs), i.e., SLT-1 and SLT-2. SLTs are pentamers composed of a single A and five B subunits. In this study, we propose a magnetic nanoparticle (MNP)-based platform to rapidly identify SLT-1 from the complex cell lysate of E. coli O157:H7. The core of the MNPs is made of iron oxide, whereas the surface of the core is coated with a thin layer of alumina (Fe3O4@Al2O3 MNPs). The Fe3O4@Al2O3 MNPs are functionalized with pigeon ovalbumin (POA), which contains Gal-α(1→4)-Gal-β(1→4)-GlcNAc termini that can bind SLT-1B selectively. Furthermore, POA is a phosphate protein. Thus, it can be easily immobilized on the surface of the Fe3O4@Al2O3 MNPs through aluminum phosphate chelation under microwave heating within 1.5 min. The generated POA-Fe3O4@Al2O3 MNPs are capable of effectively enriching SLT-1B from complex cell lysates simply by pipetting 20 μL of the sample in and out of the tip in a vial for ∼1 min. To release SLT-1 from the MNPs, Gal-α(1→4)-Gal disaccharides were used for displacement. The released target species are sufficient to be identified by matrix-assisted laser desorption/ionization mass spectrometry. Although the sample volume used in this approach is small (20 μL) and the enrichment time is short (1 min), the selectivity of this approach toward SLT-1B is quite good. We have demonstrated the effectiveness of this approach for rapid determination of the presence of SLT-1 from complex cell lysates and ham/juice samples based on the detection of SLT-1B.

Occurrence and characterization of Shiga toxin-producing Escherichia coli O157:H7 and other non-sorbitol-fermenting E. coli in cattle and humans in urban areas of Morogoro, Tanzania

Escherichia coli strains such as Shiga toxin-producing E. coli (STEC), enteropathogenic E. coli, enterotoxigenic, attaching, and effacing E. coli, and enteroinvasive E. coli cause diarrhea in humans. Although other serotypes exist, the most commonly reported STEC in outbreaks is O157:H7. A cross-sectional study was conducted to isolate and characterize non-sorbitol-fermenting (NSF) E. coli O157:H7 from urban and periurban livestock settings of Morogoro, Tanzania. Human stool, cattle feces, and soil and water samples were collected. Observations and questionnaire interview studies were used to gather information about cattle and manure management practices in the study area. E. coli were isolated on sorbitol MacConkey agar and characterized by conventional biochemical tests. Out of 1049 samples, 143 (13.7%) yielded NSF E. coli. Serological and antimicrobial tests and molecular typing were performed to NSF E. coli isolates. These procedures detected 10 (7%) pathogenic E. coli including STEC (n=7), enteropathogenic E. coli (EPEC) (n=2), and attaching and effacing E. coli (A/EEC) (n=1) strains. The STEC strains had the ability to produce VT1 and different VT2 toxin subtypes that caused cytopathic effects on Vero cells. The prevalence of STEC in cattle was 1.6%, out of which 0.9% was serotype O157:H7 and the overall prevalence of diarrheagenic E. coli in cattle was 2.2%. The serotypes O157:H7, O142:H34, O113:H21, O+:H-, O+:H16, and O25:H4 were identified. One ESBL-producing isolate showed the MLST type ST131. To our knowledge, this is the first finding in Tanzania of this recently emerged worldwide pandemic clonal group, causing widespread antimicrobial-resistant infections, and adds knowledge of the geographical distribution of ST131. Cattle manure was indiscriminately deposited within residential areas, and there was direct contact between humans and cattle feces during manure handling. Cattle and manure management practices expose humans, animals, and the environment to pathogenic E. coli and other manure-borne pathogens. Therefore, there is a need to improve manure management practices in urban and periurban areas to prevent pathogen spread and associated human health risks.

Distribution of Escherichia coli strains harbouring Shiga toxin-producing E. coli (STEC)-associated virulence factors (stx1, stx2, eae, ehxA) from very young calves in the North Island of New Zealand

The objective of this study was to determine the distribution of Shiga toxin-producing Escherichia coli (STEC) virulence markers (stx1, stx2, eae, ehxA) in E. coli strains isolated from young calves aged fewer than 7 days (bobby calves). In total, 299 recto-anal mucosal swabs were collected from animals at two slaughter plants and inoculated onto tryptone bile X-glucuronide and sorbitol MacConkey agar supplemented with cefixime and potassium tellurite. Isolates were analysed using multiplex polymerase chain reaction to detect stx1, stx2, eae and ehxA genes. The most common combination of virulence markers were eae, ehxA (n = 35) followed by eae (n = 9). In total, STEC and atypical enteropathogenic E. coli (aEPEC) were isolated from 8/299 (2·6%) and 37/299 (12·3%) calves, respectively. All the isolates could be assigned to 15 genotype clusters with >70% similarity cut-off using XbaI pulsed-field gel electrophoresis. It may be concluded that healthy calves from the dairy industry are asymptomatic carriers of a diverse population of STEC and aEPEC in New Zealand.

Antimicrobial Activity of Trifoliate Orange (Poncirus trifoliate) Seed Extracts on Gram-Negative Food-borne Pathogens

Trifoliate orange seed extracts (TSEs) were prepared from different solvents, water (TW), ethanol (TE), and n-hexane (TH), and assessed for their antimicrobial activities against six gram-negative food-borne pathogens (Escherichia coli KCTC 1039, Escherichia coli O157:H7 ATCC 43895, Salmonella Enteritidis ATCC 3311, Salmonella Typhimurium KCCM 11862, Shigella sonnei KCTC 2518, and Vibrio parahaemolyticus ATCC 17802). Among the tested TSEs, TE and TH showed a slight inhibition activity on V. parahaemolyticus ATCC 17802, but a good growth inhibition activity on Sal. Typhimurium KCCM 11862. TH and TE showed steady growth inhibition activity with increasing growth time after 6 hr when compared to the control (p<0.05). From these results, we confirmed the possibility of TH and TE as antimicrobial materials.

Occurrence, virulence genes and antibiotic resistance of enteropathogenic Escherichia coli (EPEC) from twelve bovine farms in the north-east of Ireland

Cattle faecal samples (n = 480) were collected from a cluster of 12 farms, and PCR screened for the presence of the intimin gene (eae). Positive samples were cultured, and colonies were examined for the presence of eae and verocytotoxin (vtx) genes. Colonies which were positive for the intimin gene and negative for the verocytotoxin genes were further screened using PCR for a range of virulence factors including bfpA, espA, espB, tir ehxA, toxB, etpD, katP, saa, iha, lpfAO157/OI-141 and lpfAO157/OI-154. Of the 480 faecal samples, 5.8% (28/480) were PCR positive, and one isolate was obtained from each. All 28 isolates obtained were bfpA negative and therefore atypical EPEC (aEPEC). The serotypes detected included O2:H27, O8:H36, O15:H2, O49:H+, O84:H28, O105:H7 and O132:H34 but half of the isolates could not be serogrouped using currently available antisera. Twenty-two (79%) of the isolates carried the tir gene but only 25% were espB positive, and all other virulence genes tested for were scarce or absent. Several isolates showed intermediate resistance to ciprofloxacin, kanamycin, nalidixic acid, minocycline and tetracycline; full resistance to nalidixic acid or tetracycline with one isolate (O-:H8) displaying resistance to aminoglycosides (kanamycin and streptomycin), quinolones (nalidixic acid) and sulphonamides. This study provides further evidence that cattle are a potential source of aEPEC and add to the very limited data currently available on virulence genes and antibiotic resistance in this pathogenic E. coli group in animals.

Characterization of enterotoxigenic E. coli (ETEC), Shiga-toxin producing E. coli (STEC) and necrotoxigenic E. coli (NTEC) isolated from diarrhoeic Mediterranean water buffalo calves (Bubalus bubalis)

Two hundred and twenty Escherichia coli isolates from 314 Mediterranean water buffalo calves less than 4 weeks old affected by severe diarrhoea with a lethal outcome were characterized for the presence of the virulence factors LT, ST, Stx1, Stx2, haemolysins, intimin, CNF1, CNF2, CDT-I, CDT-II, CDT-III, CDT-IV, and F17-related fimbriae (F17a, F17b, F17c, F17d). The prevalence of ETEC, STEC and NTEC were 1.8%, 6.8% and 20.9%, respectively. The ETEC isolates were all LT-positive and ST-negative. The STEC isolates were all Stx and intimin-positive, with Stx1 (80%) more frequent than Stx2 (27%). The NTEC isolates were all CNF and Hly-positive, with CNF2 (83%) more frequent than CNF1 (22%). Susceptibility assays to 11 antimicrobials displayed high rates of resistance (>30%) to antimicrobials tested. These data show that the most prevalent strains in diarrhoeic water buffalo calves were NTEC, mostly CNF2 and HlyA-positive, with strong associations CNF2/CDT-III and CNF2/F17c.

Antimicrobial resistance and prevalence of virulence factor genes in fecal Escherichia coli of Holstein calves fed milk with and without antimicrobials

Diarrhea in calves has a significant effect on the dairy industry. A common management practice for preventing or decreasing the effects of such disease in preweaned calves is by the use of antimicrobials in milk or milk replacer. In this study, Escherichia coli antimicrobial resistance in fecal samples collected from calves 2 to 8 d of age that had or had not received antimicrobials in the milk and that had or had not signs of diarrhea by inspection of fecal consistency were investigated. Specifically, resistance of E. coli isolates to individual antimicrobials, multiresistance patterns, and presence of virulence factors were analyzed. Escherichia coli isolates were tested for susceptibility to 12 antimicrobials by use of a Kirby-Bauer disk diffusion assay. The study was conducted at 3 farms, 1 administering growth-promoting antimicrobials (GPA) in the milk and 2 not using GPA in the milk (NGPA). All isolates were susceptible to ciprofloxacin and cefepime. From the total isolates tested, 84% (n=251) were resistant to at least 2 antimicrobials and 81% (n=251) were resistant to 3 or more antimicrobials. When antimicrobial resistance was compared between GPA and NGPA, it was observed that the GPA group had higher odds of antimicrobial resistance for most of the individual antimicrobials tested. No significant correlation of virulence factors in GPA or NGPA and diarrheic or non-diarrheic (control) fecal samples was found. Of the 32 virulence factors evaluated, 21 were detected in the study population; the incidence of only 1 virulence factor was statistically significant in each of the diarrheic status (diarrheic or non-diarrheic) and treatment status (NGPA or GPA) groups. Phylogenetic analysis based on the nucleotide sequence of the DNA gyrase gene (gyrB) from 31 fecal E. coli isolates revealed 3 main clades.

Tracking verocytotoxigenic Escherichia coli O157, O26, O111, O103 and O145 in Irish cattle

The purpose of this study was to investigate carriage and transfer of verocytotoxigenic Escherichia coli (VTEC) O157, O26, O111, O103 and O145 from faeces and hide to dressed carcasses of Irish cattle as well as establishing the virulence potential of VTEC carried by these cattle. Individual cattle was tracked and faecal samples, hide and carcass (pre-evisceration and post-wash) swabs were analysed for verotoxin (vt1 and vt2) genes using a duplex real-time PCR assay. Positive samples were screened for the five serogroups of interest by real-time PCR. Isolates were recovered from PCR positive samples using immunomagnetic separation and confirmed by latex agglutination and PCR. Isolates were subject to a virulence screen (vt1, vt2, eaeA and hlyA) by PCR. Isolates carrying vt genes were examined by Pulsed-Field Gel Electrophoresis (PFGE). Of the VTEC isolated, E. coli O157 was the most frequently recovered from hide (17.6%), faeces (2.3%) and pre-evisceration/post-wash carcass (0.7%) samples. VTEC O26 was isolated from 0.2% of hide swabs and 1.5% of faeces samples. VTEC O145 was isolated from 0.7% of faeces samples. VTEC O26 and VTEC O145 were not recovered from carcass swabs. Non-VTEC O103 was recovered from all sample types (27.1% hide, 8.5% faeces, 5.5% pre-evisceration carcass, 2.2% post-wash carcass), with 0.2% of hide swabs and 1.0% of faeces samples found to be positive for VTEC O103 isolates. E. coli O111 was not detected in any samples. For the four serogroups recovered, the direct transfer from hide to carcass was not observed. This study shows that while VTEC O157 are being carried by cattle presented for slaughter in Ireland, a number of other verotoxin producing strains are beginning to emerge.

Subtilase cytotoxin-coding genes in verotoxin-producing Escherichia coli strains from sheep and goats differ from those from cattle

Subtilase cytotoxin (SubAB) from verotoxin (VT)-producing Escherichia coli (VTEC) strains was first described in the 98NK2 strain and has been associated with human disease. However, SubAB has recently been found in two VT-negative E. coli strains (ED 591 and ED 32). SubAB is encoded by two closely linked, cotranscribed genes (subA and subB). In this study, we investigated the presence of subAB genes in 52 VTEC strains isolated from cattle and 209 strains from small ruminants, using PCR. Most (91.9%) VTEC strains from sheep and goats and 25% of the strains from healthy cattle possessed subAB genes. The presence of subAB in a high percentage of the VTEC strains from small ruminants might increase the pathogenicity of these strains for human beings. Some differences in the results of PCRs and in the association with some virulence genes suggested the existence of different variants of subAB. We therefore sequenced the subA gene in 12 strains and showed that the subA gene in most of the subAB-positive VTEC strains from cattle was almost identical (about 99%) to that in the 98NK2 strain, while the subA gene in most of the subAB-positive VTEC strains from small ruminants was almost identical to that in the ED 591 strain. We propose the terms subAB1 to describe the SubAB-coding genes resembling that in the 98NK2 strain and subAB2 to describe those resembling that in the ED 591 strain.

ESCHERICHIA COLI, PRODUTORAS DE SHIGATOXINAS DETECTADAS EM FEZES DE BOVINOS LEITEIROS

RESUMO Este trabalho teve como objetivo determinar a prevalência de Escherichia coli produtoras de Shigatoxinas (STEC) e E. coli dos sorogrupos O157, O111 e O113 em rebanhos leiteiros do Município de Jaboticabal, SP, Brasil. A presença de sequências gênicas stx1, stx2e eae foi detectada pela reação em cadeia da polimerase (PCR) em amostras de fezes. Todas as amostras stx e eae positivas foram submetidas a uma nova reação de PCR para detecção das sequências rfb O157, O111 e O113. Observou-se uma alta prevalência (72,16%) de sequências stx nas fezes dos bovinos, sendo que o perfil genotípico encontrado com maior frequência foi o stx1 associado à stx2. Os coeficientes de prevalência das sequências rfb O157, O111 e O113 foram, respectivamente, 14,77%, 0,2% e 30,83%. Animais de todos os rebanhos (100%) apresentaram em suas fezes STEC e E. coli O113 e os sorogrupos O157 e O111 foram observados em 60,0% e 10,0% dos rebanhos, respectivamente. Concluiu-se que a alta prevalência de STEC detectada em rebanho leiteiro evidenciada nas fezes de bovinos desempenham um papel importante na contaminação ambiental e podem oferecerrisco de agravo à saúde pública.

The structure of the antigenic O-polysaccharide in the lipopolysaccharide of enterohaemorrhagic Escherichia coli serotype O71:H12

The antigenic O-polysaccharide component of the lipopolysaccharide produced by Escherichia coli serotype O71:H12 was analyzed by chemical composition, nuclear magnetic spectroscopy, and Smith-type periodate oxidation methods. It was determined to be a partially O-acetylated unbranched polymer of a repeating tetrasaccharide unit composed of L-rhamnose, D-galactose, 2-acetamido-2-deoxy-D-galactose, and 3-acetamido-3-deoxy-D-quinovose (1:1:1:1) residues having the following structure: [structure: see text]

Rapid microarray-based genotyping of enterohemorrhagic Escherichia coli serotype O156:H25/H-/Hnt isolates from cattle and clonal relationship analysis

Since enterohemorrhagic Escherichia coli (EHEC) isolates of serogroup O156 have been obtained from human diarrhea patients and asymptomatic carriers, we studied cattle as a potential reservoir for these bacteria. E. coli isolates serotyped by agglutination as O156:H25/H-/Hnt strains (n = 32) were isolated from three cattle farms during a period of 21 months and characterized by rapid microarray-based genotyping. The serotyping by agglutination of the O156 isolates was not confirmed in some cases by the results of DNA-based serotyping as only 25 of the 32 isolates were conclusively identified as O156:H25. In the multilocus sequence typing (MLST) analysis, all EHEC O156:H25 isolates were characterized as sequence type 300 (ST300) and ST688, which differ by a single-nucleotide exchange in the purA gene. Oligonucleotide microarrays allow simultaneous detection of a wider range of EHEC-associated and other E. coli virulence markers than other methods. All O156:H25 isolates showed a wide spectrum of virulence factors typical for EHEC. The stx(1) genes combined with the EHEC hlyA (hlyA(EHEC)) gene, the eae gene of the zeta subtype, as well as numerous other virulence markers were present in all EHEC O156:H25 strains. The behavior of eight different cluster groups, including four that were EHEC O156:H25, was monitored in space and time. Variations in the O156 cluster groups were detected. The results of the cluster analysis suggest that some O156:H25 strains had the genetic potential for a long persistence in the host and on the farm, while other strains did not. As judged by their pattern of virulence markers, E. coli O156:H25 isolates of bovine origin may represent a considerable risk for human infection. Our results showed that the miniaturized E. coli oligonucleotide arrays are an excellent tool for the rapid detection of a large number of virulence markers.

Association of Vt1C with Verotoxin-Producing Escherichia Coli from Goats and Sheep

A total of 232 verotoxin 1 (VT1)-positive, VT-producing Escherichia coli (VTEC) strains isolated from goats, sheep, and cattle were analyzed for the presence of the vt1c gene by polymerase chain reaction. One hundred and forty of the 144 (97.2%) caprine strains and 55 of the 63 (87.3%) ovine strains possessed the vt1c gene. In contrast, the gene was not detected in any of the 25 bovine strains. These results show that the vt1c gene is found in caprine VTEC strains and confirm that gene is associated with ovine VTEC strains.

Characteristics and virulence genes of Escherichia coli isolated from septicemic calves in southeast of Iran

Virulence factors are associated with the capacity of E. coli strains to cause intestinal and extraintestinal infections. Thirty one E. coli isolates were obtained from heart blood or internal organs of septicemic calves. The O serogroups of isolates were determined. PCR assays were performed to determine the phylogenetic groups and presence of specific virulence genes. Fourteen (45.16%) isolates belonged to seven O serogroups (O8, O15, O20, O45, O78, O101 and O103) and 17 (54.83%) isolates were O-nontypeable. E. coli isolates fall into three phylogenetic groups included 15 isolates belonged to B1, 9 to A and 7 to D phylogenetic groups. Nineteen (61.29%) isolates exhibited at least one of the virulence genes. F17 family (5 isolates f17b, 3 isolates f17c, 1 isolate f17a) genes and aerobactin encoding gene of iucD (5 isolates) were the two most prevalent virulence genes. Three isolates were positive for cnf2 and cdtIII genes in combination and they were O-nontypeable. AfaE-VIII, CS31A gene (clpG) and hemolysin encoding gene (hly) were detected in 3, 4 and 3 isolates respectively. None of the isolates contained the ipaH sequences and the genes encoding fimbria (F5, F41, S, P), AfaI adesin, toxins (LT-I, ST-I, SLT-I, SLT-II, CNF1 and CDT-IV) and intimin.

The studies on the aetiology of diarrhoea in neonatal calves and determination of virulence gene markers of Escherichia coli strains by multiplex PCR

The purpose of this study was to determine aetiological agents of diarrhoea in neonatal calves and to investigate virulence gene markers of Escherichia coli strains isolated from calves by multiplex polymerase chain reaction (PCR). Eighty‐two diarrhoeic calves and 18 healthy calves were used as subjects. Faeces were taken from the rectums of all the calves and were subjected to bacterial culture. Antigen enzyme‐linked immunosorbent assay (ELISA) was performed to detect rotavirus, coronavirus and E. coli K99 in faeces of all the calves. A multiplex PCR was used to characterize E. coli strains in all the calves. Escherichia coli was isolated from 37 faeces samples, Enterococcus ssp. was isolated from 22 faeces samples and Salmonella was isolated from one faeces sample in diarrhoeic calves. Furthermore, only E. coli was isolated from all 18 faeces samples of healthy calves. Of the 37 E. coli isolated from diarrhoeic calves, K99 (18.9%), F41 (18.9%), heat‐stable enterotoxin a (STa) (18.9%), Shiga toxin 1 (Stx1; 13.5%) and Shiga toxin 2 (Stx2; 5.4%) and intimin (8.1%) genes were identified by multiplex PCR. Of the 18 E. coli isolated from healthy calves, K99 (16.6%) and intimin (55.5%) genes were identified by PCR. A total of 15 rotavirus, 11 coronavirus and 11 E. coli K99 were detected in diarrhoeic calves by the antigen ELISA. As a result, this study shows that rotavirus, coronavirus, E. coli and Enterococcus ssp. were determined to play a role in the aetiology of diarrhoea in the neonatal calves. K99, F41, STa, Stx1 and Stx2 were found as the most common virulence gene markers of E. coli strains isolated from calves with diarrhoea. Multiplex PCR may be useful for characterization of E. coli isolated from calves.

Phylogenetic background, virulence gene profiles, and genomic diversity in commensal Escherichia coli isolated from ten mammal species living in one zoo

Three hundred commensal Escherichia coli recovered from healthy herbivorous, carnivorous, and omnivorous mammals from one zoo were characterized for their phylogenetic origin, intestinal virulence gene (VG) prevalence, and genomic diversity. The phylogenetic structure of the E. coli (groups A, B1, B2, and D) from the herbivores was homogenous, with a prevailing representation of group B1. In the carnivores and omnivores, the phylogenetic diversity was species specific with a higher representation of group A compared to the herbivores. Of 16 intestinal VGs in the whole set, 8 were detected and they formed 13 VG profiles. In the herbivores, all the VG-positive isolates belonged to group B1 and harboured the genes eaeA, eastI, ehxA, stx1, and stx2, which separately or in combination formed 8 VG profiles. In the carnivores and omnivores, the VG-positive isolates frequently belonged to group A and harboured the estI and estII genes or a combination of eastI and estI, forming three VG profiles. Single genes cnf2, in group B2, and eastI, in group D, were found. Similarity analysis of pulsed-field gel electrophoresis (PFGE) patterns revealed closer relatedness between the isolates from carnivores and omnivores than those from herbivores. The comparison between the prevalence of phylogenetic groups and the phylogenetic origin of VG-positive isolates in the examined E. coli suggested, that E. coli from group B1 in herbivores and E. coli from group A rather than B1 in carnivores and omnivores are "best adapted" to the host organism. The groups revealed different preferences in the acquisition and maintenance of intestinal VGs.

Variants of eae and stx genes of atypical enteropathogenic Escherichia coli and non-O157 Shiga toxin-producing Escherichia coli from calves

AIMS

To determine the subtypes of stx and eae genes of Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic Escherichia coli (EPEC) from calves and to ascertain the typical and atypical nature of EPEC.

METHODS AND RESULTS

One hundred and eighty-seven faecal samples from 134 diarrhoeic and 53 healthy calves were investigated for the presence of stx, eae and ehxA virulence genes by polymerase chain reaction and enzyme-linked immunosorbent assay. Subtype analysis of stx(1) exhibited stx(1c) in 13 (31.70%) isolates, while that of stx(2) revealed stx(2c) in eight (24.24%) and stx(2d) in two (6.06%) isolates. Subtyping of eae gene showed the presence of eae-beta, eae-eta and eae-zeta in two, three and four isolates respectively. None of the E. coli isolates possessed stx(2e), stx(2f), eae-alpha, eae-delta, eae-epsilon and eae-xi. All EPEC isolates were atypical.

CONCLUSIONS

stx(1), stx(1c), stx(2), stx(2c), stx(2d), eae-beta, eae-eta and eae-zeta subtypes are prevalent in STEC and EPEC isolates in India.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first subtype analysis of stx(2) and eae genes of animal E. coli isolates in India and emphasizes the need to investigate their transmission to humans.

Antibiotic resistance and molecular epidemiology of Escherichia coli O26, O103 and O145 shed by two cohorts of Scottish beef cattle

OBJECTIVES

The aim of this study was to identify the profile of antibiotic resistance among E. coli O26, O103 and O145 in two cohorts of Scottish beef cattle on two farms and to determine whether there is an association between resistant phenotypes and the genotypic PFGE patterns to suggest clonality among resistant strains.

METHODS

MICs of 11 antibiotics for 297 E. coli O26, 152 E. coli O103 and 13 E. coli O145 were determined. Isolates were screened for the presence integrons 1 and 2 and the virulence factors stx1, stx2, eaeA and ehxA by PCR with specific primers. PFGE subtyping was performed after digestion with XbaI endonuclease.

RESULTS

Among E. coli O26, O103 and O145 there were four, four and one isolates, respectively, that harboured a class 1 integron. A class 2 integron was detected in only one O145 isolate. Diversity in PFGE patterns was higher among E. coli O103 and O145 strains compared with the O26 serotype; and PFGE demonstrated 13, 27 and 6 different patterns among O26, O103 and O145 isolates, respectively. Selective PFGE types that harboured virulence factors were widespread among the cattle population throughout the sampling period. There were multiply resistant isolates that were of similar PFGE patterns.

CONCLUSIONS

The dissemination and persistence of certain PFGE genotypes among the cattle population was evident in this study. Certain resistance phenotypes, especially among E. coli O26 isolates, were associated with distinct PFGE clones.

Serotypes and analysis of distribution of Shiga toxin-producingEscherichia colifrom cattle and sheep in the lower North Island, New Zealand

AIMS

To serotype a subset of Shiga toxin-producing Escherichia coli (STEC) isolates from cattle and sheep to determine whether any corresponding serotypes have been implicated in human diarrhoeal disease, both in New Zealand and worldwide, and to examine the distribution of STEC and enteropathogenic Escherichia coli (EPEC) amongst cattle (calves, heifers and dairy) and sheep (lambs, rams and ewes), to assess whether carriage of identified bacterial genotypes may be associated with a particular age of animal.

METHODS

Recto-anal mucosal swabs (RAMS) were taken from 91 calves, 24 heifers and 72 dairy cattle, and 46 lambs, 50 ewes and 36 rams, from four sites in the Manawatu and Rangitikei regions of New Zealand. Strains of E. coli selected from primary isolation plates were subjected to a multiplex polymerase chain reaction (PCR), to determine the presence of Shiga toxin genes (stx1 and stx2) and the E. coli attaching and effacing gene (eae).

RESULTS

Overall, 186/319 (58.3%) animals sampled were positive for stx1, stx2, or eae isolates. More sheep (43.9%) were stx1-positive than cattle (2.7%; p = 0.036), and amongst sheep more lambs and ewes were stx1-positive than rams (p = 0.036). Amongst cattle, more calves and heifers were eae-positive than dairy cows (p = 0.030). Two or more different STEC were isolated from at least 28 (9%) animals (three cattle and 25 sheep), based on their stx/eae genotype. Enterohaemolysin genes were found in 39/51 (76%) isolates serotyped. Twenty-one different serotypes were detected, including O5:H-, O9:H51, O26:H11, O84:H-/H2 and O149:H8 from cattle, and O26:H11, O65:H-, O75:H8, O84:H-, O91:H-, O128:H2 and O174:H8 from sheep; O84:H-, O26:H11, O5:H-, O91:H- and O128:H2 serotypes have been associated with human disease.

CONCLUSIONS

If nationally representative, this study confirms that cattle and sheep in New Zealand may be a major reservoir of STEC serotypes that have been recognised as causative agents of diarrhoeal disease in humans. Distribution of STEC and EPEC in cattle and sheep indicates that direct contact with, in particular, calves or their faeces, or exposure to environments cross contaminated with ruminant faeces, may represent an increased risk factor for human disease in New Zealand.

The prevalence of Shiga toxin-producingEscherichia coliin cattle and sheep in the lower North Island, New Zealand

AIM

To genotype Escherichia coli cultured from the faeces of healthy cattle and sheep in the lower North Island, in order to investigate the possible role of ruminants as a reservoir for Shiga toxin-producing E. coli (STEC) in New Zealand.

METHODS

A total of 952 strains of E. coli were isolated on selective media, from faecal swabs from 319 animals (187 cattle and 132 sheep) from four sites in the Manawatu and Rangitikei regions of New Zealand. A multiplex polymerase chain reaction (PCR) was used to genotype the E. coli isolates, using amplification of Shiga toxin genes (stx1 and stx2) and the E. coli attaching and effacing gene (eae).

RESULTS

Isolates of E. coli were cultured from swabs from 178/187 (95.2%) cattle and all 132 (100%) sheep. Ninety-nine (10.4%) of the isolates were stx1 only, 83 (8.7%) stx2 only, 33 (3.5%) stx1 and stx2, 23 (2.4%) stx1 and eae, one (0.1%) stx2 and eae, and 115 (12.1%) were eae only. Overall, 51 (27.3%) cattle and 87 (65.9%) sheep were stx-positive, whereas 69 (36.9%) cattle and 36 (27.3%) sheep were eae-positive.

CONCLUSIONS

Both healthy cattle and sheep are asymptomatic reservoirs of STEC in New Zealand. Direct contact with cattle and sheep or consumption of water or foodstuffs contaminated with cattle of sheep faeces may represent a significant source of infection for humans.

Inactivation of Listeria innocua in milk and orange juice by ultrahigh-pressure homogenization

The aim of this work was to evaluate the bactericidal efficacy of ultrahigh-pressure homogenization (UHPH) against Listeria innocua ATCC 33090 inoculated into milk and orange juice. We also intended to study the effect of inlet temperature on the lethality and production of sublethal injuries in this microorganism and its ability to survive, repair, and grow in refrigerated storage after UHPH treatment. Samples of ultrahigh-temperature whole milk and ultrahigh-temperature orange juice inoculated at a concentration of approximately 7.0 log (CFU per milliliter) were immediately pressurized at 300 MPa on the primary homogenizing valve and at 30 MPa on the secondary valve, with inlet temperatures of 6.0 +/- 1.0 degrees C and 20 +/- 1.0 degrees C. L. innocua viable counts and injured cells were measured 2 h after UHPH treatment and after 3, 6, and 9 days of storage at 4 degrees C for milk and after 3, 6, 9, 12, 15, 18, and 21 days of storage at 4 degrees C for orange juice. Both the inlet temperature and the food matrix influenced significantly (P < 0.05) the inactivation of L. innocua, which was higher in whole milk at the 20 degrees C inlet temperature. The UHPH treatment caused few or no sublethal injuries in L. innocua. During storage at 4 degrees C after treatments, counts increased by approximately 2 logarithmic units from day 0 to 9 in whole milk, whereas in orange juice counts diminished by approximately 2.5 logarithmic units from day 0 to 18.

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.

Naturally acquired attaching and effacing Escherichia coli in sheep

In a series of experiments involving the inoculation of sheep with Escherichia coli O157:H7, and subsequent detailed histopathological examination of the intestinal mucosa, attaching-effacing (AE) lesions formed by elements of the natural flora were observed in 18% of animals. These incidental AE lesions typically were small and sparse, and were not associated with clinical disease. It was possible to identify further some of the lesional bacteria, revealing that E. coli O115 had formed lesions in one of the seven affected animals, and similarly E. coli O26 had formed some of the lesions in another. As AE strains, source flocks, housing and feed sources were diverse, a common source of lesion-forming bacteria appears to be unlikely. It is postulated that subclinical AE lesions are a mechanism of persistence of AE bacteria in sheep.

Detection of the saa gene in verotoxin-producing Escherichia coli from ruminants

A total of 163 verotoxin-producing Escherichia coli (VTEC) strains isolated from diarrheic and healthy cattle, sheep, and goats were analyzed for the presence of the saa gene by polymerase chain reaction. Seventeen (45.9%) and 5 (29.4%) of the VTEC isolated from healthy cattle and diarrheic calves, respectively, had the saa gene. None of the saa-positive strains carried the eae gene, but 20 of the 22 saa positive were ehxA positive. In contrast with cattle VTEC, none of the VTEC isolated from small ruminants were saa positive. These results show that the saa gene is commonly associated with bovine eae-negative VTEC strains but not with ovine or caprine VTEC strains.

Invited Review: Prevalence of Shiga Toxin-Producing Escherichia coli in Dairy Cattle and Their Products

The main objective of this review was to assess the role of dairy cattle and their products in human infections with Shiga toxin-producing Escherichia coli (STEC). A large number of STEC strains (e.g., members of the serogroups O26, O91, O103, O111, O118, O145, and O166) have caused major outbreaks and sporadic cases of human illnesses that have ranged from mild diarrhea to the life-threatening hemolytic uremic syndrome. These illnesses were traced to O157 and non-O157 STEC. In most cases, STEC infection was attributed to consumption of ground beef or dairy products that were contaminated with cattle feces. Thus, dairy cattle are considered reservoirs of STEC and can impose a significant health risk to humans. The global nature of food supply suggests that safety concerns with beef and dairy foods will continue and the challenges facing the dairy industry will increase at the production and processing levels. In this review, published reports on STEC in dairy cattle and their products were evaluated to achieve the following specific objectives: 1) to assemble a database on human infections with STEC from dairy cattle, 2) to assess prevalence of STEC in dairy cattle, and 3) to determine the health risks associated with STEC strains from dairy cattle. The latter objective is critically important, as many dairy STEC isolates are known to be of high virulence. Fecal testing of dairy cattle worldwide showed wide ranges of prevalence rates for O157 (0.2 to 48.8%) and non-O157 STEC (0.4 to 74.0%). Of the 193 STEC serotypes of dairy cattle origin, 24 have been isolated from patients with hemolytic uremic syndrome. Such risks emphasize the importance and the need to develop long-term strategies to assure safety of foods from dairy cattle.