Salmonella is a major foodborne pathogen that causes foodborne disease in humans through consumption of contaminated foods, especially those of animal origin. Multiple Salmonella strains are antibiotic-resistant due to the common use of antibiotics in farm animals, including broiler farms. In this study, an alternative strategy using phage-based treatment was evaluated against Salmonella isolated from the broiler production. The prevalence of Salmonella spp. showed up to 46.2 and 44.4% in bedding samples from the broiler farms located in eastern and southern Thailand, respectively. Overall, 21 samples (36.2%) were positive for Salmonella and eight serovars were recovered from cloacal swabs, bedding materials (rice husk), and boot swabs collected from five farms. Up to 20 Salmonella phages were isolated from seven water samples from wastewater treatment ponds, a river, and a natural reservoir in Songkhla province. Isolated phages were investigated, as well as their lysis ability on eight target Salmonella serovars derived from broiler farms, five foodborne outbreak-related serovars, and 10 multidrug-resistant (MDR) serovars. All phages showed a strong lytic ability against five serovars of Salmonella derived from broiler farms including Kentucky, Saintpaul, Schwarzengrund, Corvalis, and Typhimurium; three foodborne outbreak serovars including Enteritidis, Typhimurium, and Virchow; and eight MDR serovars including Agona, Albany, Give, Kentucky, Typhimurium, Schwarzengrund, Singapore, and Weltevreden. Three phages with the highest lysis potential including vB_SenS_WP109, vB_SenS_WP110, and vB_SenP_WP128 were selected for a phage cocktail preparation. Overall, a phage cocktail could reduce Salmonella counts by 2.2–2.8 log units at 6 h of treatment. Moreover, Salmonella did not develop a resistant pattern after being treated with a phage cocktail. Findings here suggest that a phage cocktail is an effective biocontrol to combat Salmonella derived from broiler production chain, other serovars linked to foodborne outbreaks, and MDR serovars.
Trypanosoma evansi infection, or surra, is currently affecting various species of animals, especially water buffaloes. Since diagnosis is an important aspect of surra control, development of novel diagnostic antigens is of interest to implement and improve the currently utilized methods. Our study evaluated the tandem repeat antigen TeGM6-4r in T. evansi antibody detection in water buffaloes. TeGM6-4r-based ELISA was performed with 20 positive and 8 negative controls and 484 field samples from water buffaloes in Northern Vietnam. To examine cross-reactivity, sera from Japanese cattle that had been experimentally infected with Theileria orientalis (n=10), Babesia bovis (n=3), Babesia bigemina (n=7) and Trypanosoma theileri (n=59) were included in the study. The sensitivity of the test was 80%. TeGM6-4r did not react with Theileria or Babesia infected sera, however it showed cross reactivity with 11/59 T. theileri infected samples. The reference test, CATT/T. evansi also reacted with 3/59 T. theileri infected sera. The lysate antigen-based ELISA reacted with 4/59 T. theileri, 9/10 Theileria and 3/10 Babesia infected sera. In contrast, TeGM6-4r-based ELISA was 86.3% sensitive and 58.3% specific in the screening of field samples. The average seroprevalence of T. evansi infection among water buffaloes in Northern Vietnam was 27.1% by CATT/T. evansi and 53.7% by TeGM6-4r. Seroprevalence in the five surveyed provinces ranged from 17.4% to 39.8% in the reference test, and 47.3% to 67.3% in the recombinant antigen based test. The finding indicated that the disease is still widely endemic in the area and that surveillance programs need to be carried out regularly to better control surra. We proposed TeGM6-4r as a useful serodiagnostic antigen for the detection and epidemiological surveillance of T. evansi infection among water buffaloes.
Salmonella is an important foodborne pathogen, which is often found on chicken meat and various sites in wet markets in Southeast Asia, thus requiring close monitoring for effective control measures. In this study, 130 samples from chicken meat, environment, and wastewater from three chicken meat stalls at a wet market were tested for Salmonella spp. For stall A, B, and C, 20 (44.4%), 8 (17.4%), and 9 (23.1%) samples were positive for Salmonella, respectively. In this study, Salmonella was often detected on working tables, scales, cutting board, knives, and bucket, suggesting important food contact equipment that typically links to the presence of Salmonella at local stalls or retails. This equipment should be emphasized for the improved control measures to minimize Salmonella contamination. Using the nine virulence genes (sipB, prgH, spaN, orgA, tolC, sitC, sifA, cdtB, and sopB, pattern IV (sifA and cdtB negative) was a predominant pattern. Most Salmonella isolates (n = 42) were resistant to tetracycline, but none showed resistance to ceftriaxone. Data suggest potential sources of Salmonella, including chicken and several environmental sites at a wet market. This could be of a public health concern as multiple patterns of virulence genes and multidrug resistance were observed. Practical applications Salmonella spp. are commonly found on chicken meat sold at a retail level and, commonly in Southeast Asia, at wet markets where chicken carcasses are processed. This could be a typical source of Salmonella contamination, thus requiring close monitoring for effective control measures. Information obtained from this study reported the distribution and characteristics regarding the presence of virulence genes and antibiotic resistance. This will help effective implementation for ensuring food safety at the wet markets. This is also a useful tool for market management to further minimize the spread of some Salmonella isolates shown to be multidrug resistance that is found in chicken and several environmental sites at a wet market.
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