P a g e | 1 P a g e | 2 ABSTRACT Only few studies concerning Shiga toxin-producing E. coli (STEC) detection in coastal environments and bivalves have been reported and there have been no reported outbreaks by STEC from bivalves in the world.The aim of this thesis was to investigate the occurrence of STEC in Norwegian bivalves, and to characterize potential STEC isolates obtained from the samples.To improve our understanding of STEC, the occurrence was investigated in 269 bivalves collected from harvesting areas along the Norwegian coast in 2016/17. Microbial enrichment of the samples followed by DNA extraction with subsequent screening of STEC-associated genes was performed as described in ISO/TS -13136. Real-time PCR assays were conducted for genes encoding Shiga toxin (stx1 and stx2), intimin (eae) and the five major serogroups of concern (O157, O26, O111, O145 and O103). The screening results revealed the presence of the virulence genes (eae and stx) in 19 of the 269 samples. These 19 samples were selected for isolation of STEC. Colonies obtained from enrichment were screened for presence of stx and positive isolates were further characterized to determine their serotype and virulence profile. For two samples, automated immuno-magnetic separation (AIMS) was performed to facilitate isolation of STEC associated serogroups.Presumptive positive colonies from different serogroups were isolated by AIMS and the serogroup O157 was confirmed by real-time PCR but lacked the virulence genes. A total of three samples from 269 analyzed harbored STEC isolates, therefore, there seems to be a low risk of human infection by STEC in Norwegian bivalves.
The use of bacteriophages as biocontrol agents to control Salmonella in food production has gained popularity over the last two decades. Previously, our laboratory demonstrated that bacteriophages can be direct fed to limit Salmonella colonization and transmission in pigs. Here, we characterized the bacteriophages in our treatment cocktail in terms of lytic spectrum, growth kinetics, survivability under various conditions, and genomic sequencing. PCR-based fingerprinting indicated that 9 of the 10 phages, while related, were distinct isolates. Single-step growth kinetics analysis determined that the eclipse periods, latent periods, and burst sizes averaged 21.5 min, 31.5 min, and 43.3 particles, respectively. The viability of the phages was measured after exposure to various pH ranges, temperatures, digestive enzymes, UV light, and chlorinated water. Temperatures greater than 87.5°C, pH of <2.0, UV light (302 and 365 nm), and chlorinated water (500 ppm) inactivated the tested phages. Only select bacteriophages, however, were affected by incubation at temperatures of ≤75.0°C or pH of 4.0 to 10.0. Genomic sequencing of the phage with the broadest spectrum in the collection (effectively lysed all four Salmonella serovars tested), vB_SalM_SJ2, revealed it to belong to the Viunalikevirus genus of the Myoviridae family. Of the 197 predicted open reading frames, no toxin-associated, lysogenic, Salmonella virulence, or antimicrobial resistance genes were identified. Taken together, these data indicate that phages, as biologicals, may require some manner of protection (e.g., microencapsulation) to remain viable under various physiological and manufacturing conditions. In addition, based on its ability to effectively lyse diverse Salmonella serovars, phage vB_SalM-SJ2 could be further developed as an important biocontrol agent in various aspects of food production when the exact serovar or strain of contaminating Salmonella is not yet known.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.