Tilapia Lake Virus (TiLV) from Vietnam is genetically distantly related to TiLV strains from other countries.

Tilapia Lake Virus (TiLV) is reported as a threat to tilapia aquaculture in 16 countries on four continents with outbreaks causing up to 90% mortality. This research is one of the first studies on TiLVs from Vietnam. We propagated successfully one TiLV isolate HB196-VN-2020 from a diseased tilapia sample using an E-11 cell line and evaluated its virulence in two different weights of red hybrid tilapia and three serial 10-fold diluted viral titers. Smaller fish (4.5 ± 1.98 g) were proved to be more susceptible to TiLV infection at the viral titre of 9.1 × 105 TCID50 fish-1 than larger fish (20.8 ± 7.5 g) with the mortalities of 92.5% and 12.5%, respectively. Reassortant detection analysis revealed seven potential reassortment events among 23 TiLV genomes, indicating the mixed infection of multiple TiLV isolates at the farms and the fish movement among different regions. Seven maximum likelihood phylogenetic trees based on the individual segments or the concatenated coding regions of some segments showed the genetically distant relationship of the Southern Vietnamese isolate RIA2-VN-2019 with the 21 reference isolates, and suggest the different origins of two Vietnamese TiLV isolates (RIA2-VN-2019 and HB196-VN-2020). However, additional sequences from various sampling locations and times are required to better understand the impacts of genetic diversity and reassortments on the evolution, migration and natural selection of TiLVs in Vietnam and other countries.

Functional differentiation and scalable production of renal proximal tubular epithelial cells from human pluripotent stem cells in a dynamic culture system.

OBJECTIVE: To provide a standardized protocol for large-scale production of proximal tubular epithelial cells (PTEC) generated from human pluripotent stem cells (hPSC). METHODS: The hPSC were expanded and differentiated into PTEC on matrix-coated alginate beads in an automated levitating fluidic platform bioLevitator. Differentiation efficacy was evaluated by immunofluorescence staining and flow cytometry, ultrastructure visualized by electron microscopy. Active reabsorption by PTEC was investigated by glucose, albumin, organic anions and cations uptake assays. Finally, the response to cisplatin-treatment was assessed to check the potential use of PTEC to model drug-induced nephrotoxicity. RESULTS: hPSC expansion and PTEC differentiation could be performed directly on matrix-coated alginate beads in suspension bioreactors. Renal precursors arose 4 days post hPSC differentiation and PTEC after 8 days with 80% efficiency, with a 10-fold expansion from hPSC in 24 days. PTEC on beads, exhibited microvilli and clear apico-basal localization of markers. Functionality of PTECs was confirmed by uptake of glucose, albumin, organic anions and cations and expression of KIM-1 after Cisplatin treatment. CONCLUSION: We demonstrate the efficient expansion of hPSC, controlled differentiation to renal progenitors and further specification to polarized tubular epithelial cells. This is the first report employing biolevitation and matrix-coated beads in a completely defined medium for the scalable and potentially automatable production of functional human PTEC.

Aeromonas hydrophila ST251 and Aeromonas dhakensis are major emerging pathogens of striped catfish in Vietnam.

Introduction: Aeromonads are ubiquitous in aquatic environments and several species are opportunistic pathogens of fish. Disease losses caused by motile Aeromonas species, particularly Aeromonas hydrophila, can be challenging in intensive aquaculture, such as at striped catfish (Pangasianodon hypophthalmus) farms in Vietnam. Outbreaks require antibiotic treatments, but their application is undesirable due to risks posed by resistance. Vaccines are an attractive prophylactic and they must protect against the prevalent strains responsible for ongoing outbreaks. Methods: This present study aimed to characterize A. hydrophila strains associated with mortalities in striped catfish culture in the Mekong Delta by a polyphasic genotyping approach, with a view to developing more effective vaccines. Results: During 2013-2019, 345 presumptive Aeromonas spp. isolates were collected at farms in eight provinces. Repetitive element sequence-based PCR, multi-locus sequence typing and whole-genome sequencing revealed most of the suspected 202 A. hydrophila isolates to belong to ST656 (n = 151), which corresponds to the closely-related species Aeromonas dhakensis, with a lesser proportion belonging to ST251 (n = 51), a hypervirulent lineage (vAh) of A. hydrophila already causing concern in global aquaculture. The A. dhakensis ST656 and vAh ST251 isolates from outbreaks possessed unique gene sets compared to published A. dhakensis and vAh ST251 genomes, including antibiotic-resistance genes. The sharing of resistance determinants to sulphonamides (sul1) and trimethoprim (dfrA1) suggests similar selection pressures acting on A. dhakensis ST656 and vAh ST251 lineages. The earliest isolate (a vAh ST251 from 2013) lacked most resistance genes, suggesting relatively recent acquisition and selection, and this underscores the need to reduce antibiotics use where possible to prolong their effectiveness. A novel PCR assay was designed and validated to distinguish A. dhakensis and vAh ST251 strains. Discussion: This present study highlights for the first time A. dhakensis, a zoonotic species that can cause fatal human infection, to be an emerging pathogen in aquaculture in Vietnam, with widespread distribution in recent outbreaks of motile Aeromonas septicaemia in striped catfish. It also confirms vAh ST251 to have been present in the Mekong Delta since at least 2013. Appropriate isolates of A. dhakensis and vAh should be included in vaccines to prevent outbreaks and reduce the threat posed by antibiotic resistance.

A systematic review of potential screening biomarkers for active TB disease.

INTRODUCTION: The standard TB Four Symptom Screen does not meet the World Health Organization (WHO) ideal screening criteria for having greater than 90% sensitivity to identify active TB disease, regardless of HIV status. To identify novel screening biomarkers for active TB, we performed a systematic review of any cohort or case-control study reporting associations between screening biomarkers and active TB disease. METHODS: We searched PubMed and Embase for articles published before October 10, 2021. We included studies from high or medium tuberculosis burden countries. We excluded articles focusing on C-reactive protein and lipoarabinomannan. For all included biomarkers, we calculated sensitivity, specificity and 95% confidence intervals, and assessed study quality using a tool adapted from the QUADAS-2 risk of bias. RESULTS: From 8,062 abstracts screened, we included 79 articles. The articles described 302 unique biomarkers, including host antibodies, host proteins, TB antigens, microRNAs, whole blood gene PCRs, and combinations of biomarkers. Of these, 23 biomarkers had sensitivity greater than 90% and specificity greater than 70%, meeting WHO criteria for an ideal screening test. Among the eleven biomarkers described in people living with HIV, only one had a sensitivity greater than 90% and specificity greater than 70% for active TB. CONCLUSION: Further evaluation of biomarkers of active TB should be pursued to accelerate identification of TB disease.

Moral decision making under modafinil: a randomized placebo-controlled double-blind crossover fMRI study.

RATIONALE: Modafinil is increasingly used by healthy humans as a neuroenhancer in order to improve cognitive functioning. Research on the effects of modafinil on cognition yielded most consistent findings for complex tasks relying on the prefrontal cortex (PFC). OBJECTIVES: The present randomized placebo-controlled double-blind crossover study aimed to investigate the effect of a single dose of modafinil (200 mg) on everyday moral decision making and its neural correlates, which have been linked to the ventro- and dorsomedial PFC. METHODS: Healthy male study participants were presented with short stories describing everyday moral or neutral dilemmas. Each moral dilemma required a decision between a personal desire and a moral standard, while the neutral dilemmas required decisions between two personal desires. The participants underwent this task twice, once under the influence of modafinil and once under placebo. Brain activity associated with the processing of the dilemmas was assessed by means of functional magnetic resonance imaging. RESULTS: For the processing of moral vs. neutral dilemmas, activations were found in a network of brain regions linked to social cognitive processes including, among others, the bilateral medial PFC, the insula, and the precuneus. Modafinil was found to increase the number of moral decisions and had no effect on brain activity associated with dilemma processing. Exploratory analyses revealed reduced response-locked activity in the dorsomedial PFC for moral compared to neutral dilemmas under modafinil, but not under placebo. CONCLUSIONS: The results are discussed in terms of altered predictions of others' emotional states under modafinil, possibly due to higher processing efficiency.

Efficacy of a polyvalent injectable vaccine against Flavobacterium psychrophilum administered to rainbow trout (Oncorhynchus mykiss L.).

Flavobacterium psychrophilum is one of the most important pathogens affecting cultured rainbow trout (Oncorhynchus mykiss). Recent information from UK salmonid farms showed country-wide distribution of genetically and serologically divergent clones, which has hampered the development of a vaccine for rainbow trout fry syndrome. The current study assessed the efficacy of an injectable polyvalent vaccine containing formalin-inactivated F. psychrophilum in rainbow trout. The vaccine was formulated with an oil adjuvant (Montanide ISA 760VG) or formalin-killed cells alone. Duplicate groups of trout (60 ± 13 g) were given phosphate-buffered saline or vaccine formulated with Montanide by intra-peritoneal (i.p.) injection and challenged by intra-muscular (i.m.) injection with a homologous and a heterologous isolate of F. psychrophilum at 525 degree days post-vaccination (dd pv). Significant protection was achieved in vaccinated fish (p = 0.0001, RPS 76% homologous, 88% heterologous). Efficacy of the adjuvanted vaccine was also demonstrated by heterologous challenge at 1155 dd pv resulting in 100% protection, whereas survival in the un-adjuvanted group was not significantly different from control fish. Levels of specific antibody at 1155 dd pv, as measured by ELISA, were significantly higher in the fish vaccinated with adjuvant when compared with unvaccinated fish.

Genetic and serological diversity of Flavobacterium psychrophilum isolates from salmonids in United Kingdom.

Flavobacterium psychrophilum is one of the most important bacterial pathogens affecting cultured rainbow trout (Oncorhynchus mykiss) and is increasingly causing problems in Atlantic salmon (Salmo salar L.) hatcheries. Little is known about the heterogeneity of F. psychrophilum isolates on UK salmonid farms. A total of 315 F. psychrophilum isolates, 293 of which were collected from 27 sites within the UK, were characterised using four genotyping methods and a serotyping scheme. A high strain diversity was identified among the isolates with 54 pulsotypes, ten (GTG)5-PCR types, two 16S rRNA allele lineages, seven plasmid profiles and three serotypes. Seven PFGE groups and 27 singletons were formed at a band similarity of 80%. PFGE group P (n=75) was found to be numerically predominant in eight sites within the UK. Two major PFGE clusters and 13 outliers were found at the band similarity of 40%. The predominant profileobserved within the F. psychrophilum isolates examined was PFGE cluster II - (GTG)5-PCR type r1-16S rRNA lineage II - serotype Th (70/156 isolates examined, 45%). Co-existence of genetically and serologically heterogeneous isolates within each farm was detected, confounding the ability to control RTFS outbreaks. The occurrence over time (up to 11 years) of F. psychrophilum pulsotypes in three representative sites (Scot I, Scot III and Scot V) within Scotland was examined, potentially providing important epidemiological data for farm management and the development of site-specific vaccines.

Detection of the florfenicol resistance gene floR in Chryseobacterium isolates from rainbow trout. Exception to the general rule?

Bacteria from the family Flavobacteriaceae often show low susceptibility to antibiotics. With the exception of two Chryseobacterium spp. isolates that were positive for the florfenicol resistance gene floR, no clinical resistance genes were identified by microarray in 36 Flavobacteriaceae isolates from salmonid fish that could grow in ≥ 4 mg/L florfenicol. Whole genome sequence analysis of the floR positive isolates revealed the presence of a region that contained the antimicrobial resistance genes floR, a tet(X) tetracycline resistance gene, a streptothricin resistance gene and a chloramphenicol acetyltransferase gene. In silico analysis of 377 published genomes for Flavobacteriaceae isolates from a range of sources confirmed that well-characterised resistance gene cassettes were not widely distributed in bacteria from this group. Efflux pump-mediated decreased susceptibility to a range of antimicrobials was confirmed in both floR positive isolates using an efflux pump inhibitor (phenylalanine-arginine ß-naphthylamide) assay. The floR isolates possessed putative virulence factors, including production of siderophores and haemolysins, and were mildly pathogenic in rainbow trout. Results support the suggestion that, despite the detection of floR, susceptibility to antimicrobials in Flavobacteriaceae is mostly mediated via intrinsic mechanisms rather than the horizontally acquired resistance genes more normally associated with Gram-negative bacterial pathogens such as Enterobacteriaceae.

Toward Ending the Guessing Game: Study of the Formation of Nanostructures Using In Situ Liquid Transmission Electron Microscopy.

The field of synthetic nanochemistry has grown tremendously in the past three decades since the discovery of nonaqueous synthesis of monodispersed particles. Almost all classes of materials, from II-VI semiconductor to metal, alloy, and metal oxide can now be prepared in various sizes and shapes. One major challenge has been the development of a technique for direct real-time recording of data during the formation of nanostructures in liquid reaction media where nucleation and growth occur. A viable solution finally arrived with the recent development of static and flow liquid cells for transmission electron microscopy (TEM). This Perspective will showcase a few selected examples in this rapidly growing area, with a focus on using the new capabilities of liquid TEM (LTEM) for quantitative study of nucleation and growth, as well as shape formation of nanocrystals in solution. A discussion on future direction is also presented.

Thermo-responsiveness and tunable optical properties of asymmetric polystyrene/PNIPAM-gold composite particles.

Environmentally responsive polystyrene/poly (N-isopropylacrylamide)-gold composite particles are successfully synthesized via a Pickering emulsion polymerization method. It is found that the core-shell and asymmetric structured particles are simultaneously formed during the polymerization. Compared with the core-shell structured composite particles, the asymmetric particles have a higher thermo-responsiveness as a result of differences in morphology and formation mechanism. For asymmetric composite particles, an increase in N-isopropylacrylamide (NIPAAM) content leads to more significant size variation upon temperature changes. From rheology measurements, the viscosity of asymmetric particles suspension greatly decreases as temperature is increased above the lower critical solution temperature (LCST). The large size decrease in asymmetric composite particles gives rise to a significant scattering intensity increase, as a result of increased refractive index contrast between the PNIPAM content and surrounding water. The resulting size decrease also leads to tunable surface plasmon resonance properties.

Assessment of the performance of automated focimeters in the measurement of single vision spectacle lenses.

BACKGROUND: The accuracy and precision of any instrument should not be taken for granted. While there is an international standard for checking focimeters, there is no report of any study on their performance. METHOD: A sample set of 51 focimeters (11 brands), were used to measure the spherical power of a set of lenses and the prismatic power of two lenses complying with ISO 9342-1:2005 and other calibrated prismatic lenses and the spherical power of some grey filters. RESULTS: The mean measured spherical power corresponded very closely with the calibrated values; however, the spread of results was substantial and 10 focimeters did not comply with ISO 8598:1996. The measurement of prism was much more accurate and precise and all the focimeters complied easily. With the grey filters, about one-third of the focimeters either showed erratic reading or an error with the equivalent of category 4 sunglasses. On the other hand, nine focimeters had stable and accurate reading on a filter with a luminous transmittance of 0.5 per cent. CONCLUSIONS: These results confirm that, in common with all other measurement instruments, there is a need to ensure that a focimeter is reading accurately and precisely over the range of refractive powers and luminous transmittances. The accurate and precise performance of an automated focimeter over its working life cannot be assumed. Checking before purchase with a set of calibrated lenses and some dark sunglass tints will indicate the suitability of a focimeter. Routine checking with the calibrated lenses will inform the users if a focimeter continues to indicate accurately.

Core-shell and asymmetric polystyrene-gold composite particles via one-step Pickering emulsion polymerization.

Core-shell structured polystyrene-gold composite particles are synthesized from one-step Pickering emulsion polymerization. The surface coverage of the core-shell composite particles is improved with increasing gold nanoparticle (AuNP) hydrophobicity and concentration. At high surface coverage, the AuNPs exhibit an ordered hexagonal pattern, likely due to electrostatic repulsion during the emulsion polymerization process. In addition to core-shell structured polystyrene-gold composite particles, an intriguing observation is that at low AuNP concentrations, asymmetric polystyrene-gold nanocomposite particles are simultaneously formed, where a single gold nanoparticle is attached onto each polystyrene particle. It is found that these asymmetric particles are formed via a "seeded-growth" mechanism. The core-shell and asymmetric polystyrene-gold composite particles prove to be efficient catalysts as they successfully catalyze the Rhodamine B reduction reaction with stable performance and show high recyclability as catalysts.

Efficient transformation of grease to biodiesel using highly active and easily recyclable magnetic nanobiocatalyst aggregates.

Green and efficient production of biodiesel (FAME) from waste grease containing high amount of free fatty acid (FFA) was achieved by using novel magnetic nanobiocatalyst aggregates (MNA). Thermomyces lanuginosus Lipase (TLL) and Candida antarctica Lipase B (CALB) were covalently immobilized on core-shell structured iron oxide magnetic nanoparticle (80 nm), respectively, followed by freeze-dry to give MNA (13-17 µm) with high yield (80-89%) and high enzyme loading (61 mg TLL or 22 mg CALB per gram MNA). MNA TL showed the best performance among immobilized enzymes known thus for the production of FAME from grease (17 wt.% FFA) with methanol, giving 99% yield in 12 h (3.3 wt.% catalyst). MNA TL was easily separated under magnetic field and reused, retaining 88% productivity in 11th cycle. MNA CA converted >97% FFA in grease (17 wt.% FFA) to FAME in 12 h (0.45 wt.% catalyst), being useful in two-step transformation of grease to biodiesel.

Impact resistance and prescription compliance with AS/NZS 1337.6:2010.

BACKGROUND: Australian/New Zealand Standard 1337.6 deals with prescription eye protection and has been in place since 2007. There have been many standards marking licences granted since then. The issue of the worst-case situations for assessment in a certification scheme, in particular -1.50 m(-1) lenses, has been the subject of discussion in Standards Australia/Standards New Zealand Committee SF-006. Given that a body of data from testing exists, this was explored to advise the Committee. METHODS: Data from testing 40 sets of prescription eye protectors were analysed retrospectively for compliance with the impact and refractive power requirements in 2010-11. The testing had been carried out according to the methods of AS/NZS 1337.6:2007 under the terms and conditions of the accreditation of the Optics & Radiometry Laboratory by the National Association of Testing Authorities. RESULTS: No eye protector failed the low-impact resistance test. Failure rates of 1.6 per cent (two of the 40 sets) to the medium impact test and 1.6 per cent (three of the sets) to the medium impact test in the elevated temperature stability test were seen. These are too small for useful statistical analysis. Only -1.50 m(-1) lenses were in all failing sets and these lenses were over-represented in the failures and borderlines, especially compared with the +1.50 D lenses. Failures in prismatic power were equally distributed over all prescriptions. This over-representation of -1.50 m(-1) lenses was not related to the ocular/lens material or to the company manufacturing the eye protectors. CONCLUSIONS: The proposal is made that glazing lenses tightly to ensure they are retained in the frame on impact may result in unwanted refractive power in those lenses most prone to flex. These data support the proposal that -1.50 m(-1) lenses should form part of a worst-case testing regime in a certification scheme.

Efficient production of biodiesel from waste grease: one-pot esterification and transesterification with tandem lipases.

A novel concept and efficient method for producing biodiesel (FAME) from grease (15-40wt% free fatty acid, FFA) were developed by using tandem lipases for one-pot esterification of FFA and transesterification of triglyceride with methanol in a solvent-free system. Combining immobilized Candida antarctica lipase B (CALB) (Novozyme 435) favoring the esterification and immobilized Thermomyces lanuginosus lipase (TLL) (Lipozyme TLIM) preferring the transesterification at 2:8 (wt/wt) gave FAME in 80% yield, being better than that with Novozyme 435 or Lipozyme TLIM. Recombinant Escherichia coli (Calb/Tll) co-expressing CALB and TLL was engineered as a more efficient tandem-lipases system. Using wet or dry cells (4wt%) gave FAME in 87% or 95% yield, which is much better than that with E. coli cells expressing either CALB or TLL alone. Cells of E. coli (Calb/Tll) were recycled for five times and retained 75% productivity, thus being practical for producing biodiesel from grease.

Whole-cell based solvent-free system for one-pot production of biodiesel from waste grease.

A whole-cell based solvent-free system was developed for efficient conversion of waste grease to biodiesel via one-pot esterification and transesterification. By isolation and screening of lipase-producing strains from soil, Serratia marcescens YXJ-1002 was discovered for the biotransformation of grease to biodiesel. The lipase (SML) from this strain was cloned and expressed in Escherichia coli as an intracellular enzyme, showing 6 times higher whole-cell based hydrolysis activity than that of wild type strain. The recombinant cells were used for biodiesel production from waste grease in one-pot reactions containing no solvent with the addition of methanol in several small portions, and 97% yield of biodiesel (FAME) was achieved under optimized conditions. In addition, the whole-cell biocatalysts showed excellent reusability, retaining 74% productivity after 4 cycles. The developed system, biocatalyst, and process enable the efficient, low-cost, and green production of biodiesel from waste grease, providing with a potential industrial application.

Reversible clustering of magnetic nanobiocatalysts for high-performance biocatalysis and easy catalyst recycling.

Reversible clusters of nanobiocatalysts are developed via non-covalent interaction among enzyme-bound iron oxide magnetic nanoparticles. Dissociation of the clusters by shaking during biotransformation enables high catalytic performance, and re-clustering by stopping shaking after reaction allows for easy magnetic separation. The novel concept is demonstrated with alcohol dehydrogenase RDR for the enantioselective reduction of 7-methoxy-2-tetralone.

Prescription compliance in ophthalmic lenses.

PURPOSE: Tolerances required for ophthalmic lenses are set down in national and international standards. It appears that the compliance of manufactured lenses has not been reported previously. Assembling a statistical quantity of lenses of a single prescription is usually an expensive process. It was, secondary to a lens impact study, possible to assemble a large number of plano lenses. In the assessment of the fracture velocity of lenses approximately 20 plano lenses of each material and thickness are required. Prior to using lenses for the impact study, they were checked for prescription. The results of the prescription measurements are reported here and the results of the impact study are reported in a separate paper. METHODS: Using an automated focimeter, 679 plano lenses in stock thickness, typical occupational eye protector thickness and up to 3.5 mm thick were measured. There were 21 combinations of material/thickness/coating from seven suppliers. The power was evaluated against Australian Standard 2228.1-1992, as the lenses were supplied in Australia. The permitted tolerances are ±0.09 D sphere and ±0.06 D cylinder. RESULTS: When assessed for material/thickness/coating combination, failure rates varied from <0.0001 per cent to 77.5 per cent (with a further 17.3 per cent classified as borderline, because they were within the uncertainty of measurement of the required limit). Grouped by supplier, the failure rates ranged from <0.0001 per cent to 7.6 per cent (with a further 12.3 per cent borderline). To improve understanding of the result, it may be easier to quote the figures without considering uncertainties. When assessed by supplier, the failure rate varies from <0.0001 per cent to 12.6 per cent. CONCLUSIONS: Compliance of plano lenses should be among the easiest of tasks for a laboratory. While we know of no defined or required acceptance rates for prescription lenses, a failure rate for a laboratory of 12.6 per cent, which includes a failure rate of 88 per cent in 2.8 mm thick refractive index = 1.53 hard coated lenses (n = 20) cannot be considered satisfactory and is a strong indication of a failure to check lenses before they leave the laboratory.

Occurrence of Perkinsus olseni in the Venus clam Protothaca jedoensis in Korean waters.

This is the first report of the occurrence of Perkinsus olseni in the Venus clam Protothaca jedoensis off the western and southern coasts of South Korea. Histological observations revealed Perkinsus-like organisms in the mantle, gills, digestive tubules, and gonad. Haemocytic infiltration and tissue necrosis were also observed in heavily infected clams. Hypnospore formation of the Perkinsus-like organism was confirmed with Ray's fluid thioglycollate medium assay (RFTM). When incubated in filtered and aerated seawater, the hypnospore gave rise to cell division and subsequently discharged hundreds of motile zoospores. Genus- and species-specific polymerase chain reaction (PCR) assays and the DNA sequences of the internal transcribed spacer region (ITS) of the Perkinsus sp. isolated from the Venus clam were identical to those of P. olseni reported from the Manila clam Venerupis (=Ruditapes)philippinarum. Based on the DNA sequences and microscopic data, the Perkinsus-like pathogen isolated from P. jedoensis was identified as P. olseni, which parasitizes the Manila clam in European and Asian waters and Haliotis rubra (abalone) in Australian waters. The prevalence and infection intensity of a clam population collected from Yosu, Korea, was determined using RFTM and Choi's 2M NaOH digestion technique. The intensities averaged 10,768 and 7438 Perkinsus cells per gram tissue in 2003 and 2004, and the prevalence ranged from 37.0 to 53.9%, respectively.

Prevalence, risk factors, O serogroups, and virulence profiles of Shiga toxin-producing bacteria from cattle production environments.

Shiga toxin (Stx)-producing bacteria are important human pathogens that have been linked with cattle and associated food products. We recovered Stx-producing bacteria from 27.5% of cattle, 6.8% of water, and 2.3% of wildlife samples from a cattle production area during an 11-month period. Positive samples were found during every month and on 98% of sampling days. We recovered isolates from all cattle operations sampled, and prevalence within operations ranged from approximately 5 to 33%. Cattle prevalence was associated with the presence of Stx-producing bacteria in water and the production group and environment of cattle, with an interaction between production group and environment. Odds of recovering isolates from cattle were highest for groups of adult cows and their unweaned calves in pasture environments. Overall, 49 O serogroups were identified from 527 isolates. Seventy of the isolates contained virulence genes that encoded intimin and enterohemorrhagic Escherichia coli hemolysin. These were serogroups O111, O157, O109, O103, O145, O172, O84, O26, O108, O117, O126, O159, O5, O69, O74, O98, and O-rough. Our results suggest that the prevalence of Stx-producing bacteria can be relatively high in cattle, and associated factors may not be entirely similar to those reported for serotype O157:H7. Although Stx-producing bacteria were frequently detected, the strains may not be equally pathogenic for humans given the wide variety of serogroups and virulence genes. However, focusing on O157:H7 in food safety and surveillance programs may allow other Stx-producing bacteria, which appear to be widespread in cattle, to go undetected.