Oil and gas extraction in the western United States generates significant volumes of produced water (PW) that is typically injected into deep disposal wells. Recently, crop irrigation has emerged as an attractive PW reuse option, but the impact on plant immune response is not known. In this study, we conducted a 3-month greenhouse pot study. Spring wheat (Triticum aestivum) was irrigated 3 times a week with 150 mL (∼80–100% of soil water holding capacity) with one of four irrigation treatments: tap water control, 10% PW dilution, 50% PW dilution, and salt water (NaCl50) control containing the same amount of total dissolved solids as PW50 to determine the effect on disease resistance. The wheat leaves were inoculated with either bacterial or fungal pathogens and changes in pathogenesis-related PR-1 and PR-5 gene expression were measured from the leaf tissue. PW50 experienced the largest relative suppression of PR-1 and PR-5 gene expression compared to noninfected wheat, followed by PW10, NaCl50, and the tap water control. A combination of PW contaminants (boron, total petroleum hydrocarbons, and NaCl) are likely reducing PR-gene expression by reallocating metabolic resources to fight abiotic stresses, which then makes it more challenging for the plants to produce PR genes to fight pathogens. This study provides the first evidence that plant disease resistance is reduced due to irrigation with reused PW, which could have negative implications for food security.

The purpose of this study was to investigate the difference in expression of fatty acid biosynthesis genes and survival of different serotypes of Salmonella when incubated in a low‐water‐activity (aw) food over a 14‐day period. Stationary cells of five strains of Salmonella enterica belonging to 3 different serovars (Typhimurium ATCC 2486, Enteritidis H4267, Tennessee ARI‐33, Tennessee S13952 and Tennessee K4643) were inoculated into granular sugar (aW = 0·50) and held aerobically over a 14‐day period at 25°C. Survival was determined by enumerating colonies on TSA and XLT‐4 plates at 0, 1, 3, 5, 7 and 14 days. Correspondingly, gene expression was evaluated for three selected genes involved in fatty acid biosynthesis and modification (fabA, fabD and cfa). After 14 days of incubation, the population was reduced from 2·29 to 3·36 log for all five strains. Salmonella Tennessee ARI‐33 and Salm. Tennessee K4643 displayed greater survival than Salm. Typhimurium and Salm. Enteritidis. The increased expression of the cfa gene (involved in cyclopropane fatty acid biosynthesis) over 14 days was found associated with strains with a lower survival rate. The fabA gene (involved in unsaturated fatty acid biosynthesis) was observed up‐regulated for all strains for at least one sampling time and for Salm. Tennessee ARI‐33 for all time points tested, suggesting its potential role in enhancing Salmonella survival in low awfoods. SIGNIFICANCE AND IMPACT OF THE STUDY: Numerous outbreaks of salmonellosis associated with low‐water‐activity foods have been reported. Therefore, the adaptive mechanisms utilized by Salmonella to survive in low‐water‐activity foods for prolonged periods of time need to be better understood. The results in this study showed that low‐water‐activity environments increase expression of gene fabA, which is involved in unsaturated fatty acid biosynthesis of Salmonella, while the increased expression of cfa, associated with cyclopropane fatty acid synthesis, was associated with decreased survival over 14 days.

Pejerrey, Odontesthes bonariensis, is an euryhaline fish of commercial importance in Argentina. This work aimed to determine if water salinity affects the expression of genes involved in somatic growth (gh; ghr-I; ghr-II; igf-I), lipid metabolism (Δ6-desaturase) and food intake (nucb2/nesfatin-1). First, we identified the full-length cDNA sequences of Δ6-desaturase (involved in lipid metabolism) and nesfatin-1 (an anorexigen). Then, pejerrey juveniles were reared during 8weeks in three different water salinity conditions: 2.5g/L (S2.5), 15g/L (S15) and 30g/L (S30) of NaCl. Brain, pituitary, liver and muscle samples were collected in order to analyze mRNA expression. The expression of gh and ghr-II mRNAs increased in the pituitary of fish reared at S2.5 and S30 compared with the S15 group. The expression of ghr-I was higher in the liver of S30 group compared to S2.5 and S15. Igf-I mRNA expression in liver increased with the increment of water salinity, while it decreased in the muscle of S15 and S30 groups. Δ6-desaturase expression increased in S2.5 group compared to S15 in both liver and muscle. S30 caused a decrease in the Δ6-desaturase expression in liver compared to S15. The S30 treatment produced an increase in nucb2/nesfatin-1 mRNA expression in the brain and liver compared to S2.5 and S15. The changes in gene expression observed could help pejerrey perform better during salinity challenges. The S30 condition would likely promote pejerrey somatic growth in the long term.

Diarrheagenic E. coli (DEC) has been implicated in foodborne outbreaks worldwide and have been associated with childhood stunting in the absence of diarrhoea. Infection is extraordinarily common, but the routes of transmission have not been determined. Therefore, determining the most prevalent pathotypes in food and environmental sources may help provide better guidance to various stakeholders in ensuring food safety and public health and advancing understanding of the epidemiology of enteric disease. We characterized 205 E. coli strains previously isolated from producer distributor bulk milk (PDBM)(118), irrigation water (48), irrigated lettuce (29) and street vendor coleslaw (10) in South Africa. Enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC) and diffusely adherent E. coli (DAEC) were sought. We used PCR and partial gene sequencing for all 205 strains while 46 out of 205 that showed poor resolution were subsequently characterized using cell adherence (HeLa cells).PCR and partial gene sequencing of aatA and/or aaiC genes confirmed EAEC (2%, 5 out of 205) as the only pathotype. Phylogenetic analysis of sequenced EAEC strains with E. coli strains in GenBank showing ≥80% nucleotide sequence similarity based on possession of aaiC and aatA generated distinct clusters of strains separated predominantly based on their source of isolation (food source or human stool) suggesting a potential role of virulence genes in source tracking. EAEC 24%, 11 out of 46 strains (PDBM = 15%, irrigation water = 7%, irrigated lettuce = 2%) was similarly the predominant pathotype followed by strains showing invasiveness to HeLa cells, 4%, 2 out of 46 (PDBM = 2%, irrigated lettuce = 2%), among stains characterized using cell adherence.Therefore, EAEC may be the leading cause of DEC associated food and water-borne enteric infection in South Africa. Additionally, solely using molecular based methods targeting virulence gene determinants may underestimate prevalence, especially among heterogeneous pathogens such as EAEC.

Cyclospora cayetanensis is a coccidian parasite that causes diarrheal illness outbreaks worldwide. The development of new laboratory methods for detection of C. cayetanensis is of critical importance because of the high potential for environmental samples to be contaminated with a myriad of microorganisms, adversely impacting the specificity when testing samples from various sources using a single molecular assay. In this study, a new sequencing-based method was designed targeting a specific fragment of C. cayetanensis cytochrome oxidase gene and developed as a complementary method to the TaqMan qPCR present in the U.S. FDA BAM Chapter 19b and Chapter 19c. The comparative results between the new PCR protocol and the qPCR for detection of C. cayetanensis in food and water samples provided similar results in both matrices with the same seeding level. The target region and primers in the protocol discussed in this study contain sufficient Cyclospora-specific sequence fidelity as observed by sequence comparison with other Eimeriidae species. The sequence of the PCR product appears to represent a robust target for identifying C. cayetanensis on samples from different sources. Such a sensitive method for detection of C. cayetanensis would add to the target repertoire of qPCR-based screening strategies for food and water samples.

A rapid and sensitive assay was developed for detection of small numbers of Campylobacter jejuni and Campylobacter coil cells in environmental water, sewage, and food samples. Water and sewage samples were filtered, and the filters were enriched overnight in a nonselective medium. The enrichment cultures were prepared for PCR by a rapid and simple procedure consisting of centrifugation, proteinase K treatment, and boiling. A seminested PCR based on specific amplification of the intergenic sequence between the two Campylobacter flagellin genes, flaA and flaB, was performed, and the PCR products were visualized by agarose gel electrophoresis. The assay allowed us to detect 3 to 15 CFU of C. jejuni per 100 ml in water samples containing a background flora consisting of up to 8,700 heterotrophic organisms per ml and 10,000 CFU of coliform bacteria per 100 ml. Dilution of the enriched cultures 1:10 with sterile broth prior to the PCR was sometimes necessary to obtain positive results. The assay was also conducted with food samples analyzed with or without overnight enrichment. As few as less than or equal to 3 CFU per g of food could be detected with samples subjected to overnight enrichment, while variable results were obtained for samples analyzed without prior enrichment. This rapid and sensitive nested PCR assay provides a useful tool for specific detection of C. jejuni or C. coli in drinking water, as well as environmental water, sewage, and food samples containing high levels of background organisms.

Failing to initiate first feeding during the transition from endogenous nutrition to exogenous feeding will lead to starvation of fish larvae. However, little is known about the mechanism of first feeding selection of fish. Golden mandarin fish larvae (3 d after hatch, 2.05 ± 0.03 mg) were fed with four different foods for 7 d, including the following: M – Megalobrama amblycephala (prey fish larvae as natural food); S – surimi of M. amblycephala; A – Artemia (zooplankton); and MA –mixed M. amblycephala with Artemia (mixed food). Larvae fed with the mixed food achieved an appropriate balance between high survival and good growth through elevating the expression of growth genes (GH, IGF‐I, and IGF‐II) and fatty acid synthesis genes (FAD and ELO). Growth performance of fish fed with MA reared at different salinities (0, 5, and 10 ppt) was examined. The salinity of 5 ppt produced the best growth performance of the three salinity levels tested. Fish larvae adapted to high‐ or low‐salinity environments through increasing the expression of lipolysis genes (HSL, LPL, and HL). Therefore, both food type and salinity affect the growth, survival, and lipometabolism of golden mandarin fish larvae during initial feeding stage, and mixed food and 5 ppt salinity improved its survival and growth.