The effects of feed supplementation with the approved antimicrobial agents bambermycin, penicillin, salinomycin, and bacitracin or a combination of salinomycin plus bacitracin were evaluated for the incidence and distribution of antibiotic resistance in 197 commensal Escherichia coli isolates from broiler chickens over 35 days. All isolates showed some degree of multiple antibiotic resistance. Resistance to tetracycline (68.5%), amoxicillin (61.4%), ceftiofur (51.3%), spectinomycin (47.2%), and sulfonamides (42%) was most frequent. The levels of resistance to streptomycin, chloramphenicol, and gentamicin were 33.5, 35.5, and 25.3%, respectively. The overall resistance levels decreased from day 7 to day 35 (P < 0.001). Comparing treatments, the levels of resistance to ceftiofur, spectinomycin, and gentamicin (except for resistance to bacitracin treatment) were significantly higher in isolates from chickens receiving feed supplemented with salinomycin than from the other feeds (P < 0.001). Using a DNA microarray analysis capable of detecting commonly found antimicrobial resistance genes, we characterized 104 tetracycline-resistant E. coli isolates from 7-to 28-day-old chickens fed different growth promoters. Results showed a decrease in the incidence of isolates harboring tet(B), bla TEM , sulI, and aadA and class 1 integron from days 7 to 35 (P < 0.01). Of the 84 tetracycline-ceftiofur-resistant E. coli isolates, 76 (90.5%) were positive for bla CMY-2 . The proportions of isolates positive for sulI, aadA, and integron class 1 were significantly higher in salinomycin-treated chickens than in the control or other treatment groups (P < 0.05). These data demonstrate that multiantibiotic-resistant E. coli isolates can be found in broiler chickens regardless of the antimicrobial growth promoters used. However, the phenotype and the distribution of resistance determinants in E. coli can be modulated by feed supplementation with some of the antimicrobial agents used in broiler chicken production.

The impact of feed supplementation with bambermycin, monensin, narasin, virginiamycin, chlortetracycline, penicillin, salinomycin, and bacitracin on the distribution of Escherichia coli pathotypes in broiler chickens was investigated using an E. coli virulence DNA microarray. Among 256 E. coli isolates examined, 59 (23%) were classified as potentially extraintestinal pathogenic E. coli (ExPEC), while 197 (77%) were considered commensal. Except for chlortetracycline treatment, the pathotype distribution was not significantly different among treatments (P > 0.05). Within the 59 ExPEC isolates, 44 (75%) were determined to be potentially avian pathogenic E. coli (APEC), with the remaining 15 (25%) considered potentially "other" ExPEC isolates. The distribution within phylogenetic groups showed that 52 (88%) of the ExPEC isolates belonged to groups B2 and D, with the majority of APEC isolates classified as group D and most commensal isolates (170, 86%) as group A or B1. Indirect assessment of the presence of the virulence plasmid pAPEC-O2-ColV showed a strong association of the plasmid with APEC isolates. Among the 256 isolates, 224 (88%) possessed at least one antimicrobial resistance gene, with nearly half (107, 42%) showing multiple resistance genes. The majority of resistance genes were distributed among commensal isolates. Considering that the simultaneous detection of antimicrobial resistance tet(A), sulI, and bla TEM genes and the integron class I indicated a potential presence of the resistance pAPEC-O2-R plasmid, the results revealed that 35 (14%) of the isolates, all commensals, possessed this multigene resistance plasmid. The virulence plasmid was never found in combination with the antimicrobial resistance plasmid. The presence of the ColV plasmid or the combination of iss and tsh genes in the majority of APEC isolates supports the notion that when found together, the plasmid, iss, and tsh serve as good markers for APEC. These data indicate that different resistant E. coli pathotypes can be found in broiler chickens and that the distribution of such pathotypes and certain virulence determinants could be modulated by antimicrobial agent feed supplementation.

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Extraction of secondary metabolites from St. Lawrence Estuary edible seaweeds – Saccharina longicruris, Ascophyllum nodosum and Ulva lactuca – was carried out by pressurized liquid extraction using ethanol. The antioxidant potential of extracts was evaluated through DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) radical scavenging, oxygen radical absorbance capacity and ferric reducing antioxidant power assays, and the antibacterial activity was tested against food spoilage bacteria: Escherichia coli, Micrococcus luteus and Brochothrix thermosphacta. Of all seaweed extracts, A. nodosum exhibited the highest phenolic and carotenoid contents, 50.2 mg GAE/g and 85 μg/g, respectively. A. nodosum also displayed the best DPPH scavenging activity, EC50 10.4 μg/mL, and best capacity to reduce ferric ion, 677.2 μmol TE/g dry weight at a concentration of 100 μg/mL. U. lactuca extracts showed the highest growth inhibition of E. coli, 69.5%; M. luteus, 61.4%; and B. thermosphacta, 21.4%. These findings suggest a high potential of St. Lawrence Estuary seaweed extracts for application in the food industry. Practical Applications Food producers, food industries, governments and consumers are aware of the importance to look into effective preventive measures in food quality and food safety fields. The decay of foods is caused by physical, chemical and biological factors, which leads to the loss of the organoleptic characteristics and consumer safety. Natural extracts combining both antioxidant and antibacterial activities can be used for further applications in reducing food spoilage and prolonging food shelf life. The majority of natural extracts could be approved as Generally Recognized As Safe (GRAS). St. Lawrence Estuary seaweed extracts possess high potential for application in the food industry using pressurized liquid extraction (PLE) method, which was selected for extraction efficiency purposes. In addition, production of seaweeds extracts using approved food‐grade ethanol solvent by PLE method involves, on an industrial scale, cost savings.