Occurrence of Salmonella-Specific Bacteriophages in Swine Feces Collected from Commercial Farms

Food and Feed Safety Research Unit, Agricultural Research Service, U.S. Department of Agriculture, College Station, Texas 77845, USA.
Foodborne Pathogens and Disease (Impact Factor: 1.91). 03/2010; 7(7):851-6. DOI: 10.1089/fpd.2009.0512
Source: PubMed


Salmonella is one of the leading causes of human foodborne illness and is associated with swine production. Bacteriophages are naturally occurring viruses that prey on bacteria and have been suggested as a potential intervention strategy to reduce Salmonella levels in food animals on the farm and in the lairage period. If phages are to be used to improve food safety, then we must understand the incidence and natural ecology of both phages and their hosts in the intestinal environment. This study investigates the incidence of phages that are active against Salmonella spp. in the feces of commercial finishing swine. Fecal samples (n = 60) were collected from each of 10 commercial swine finishing operations. Samples were collected from 10 randomly selected pens throughout each operation; a total of 600 fecal samples were collected. Salmonella spp. were found in 7.3% (44/600) of the fecal samples. Bacteriophages were isolated from fecal samples through two parallel methods: (1) initial enrichment in Salmonella Typhimurium; (2) initial enrichment in Escherichia coli B (an indicator strain), followed by direct spot testing against Salmonella Typhimurium. Bacteriophages active against Salmonella Typhimurium were isolated from 1% (6/600) of the individual fecal samples when initially enriched in Salmonella Typhimurium, but E. coli B-killing phages were isolated from 48.3% (290/600) of the fecal samples and only two of these phages infected Salmonella Typhimurium on secondary plating. Collectively, our results indicate that bacteriophages are widespread in commercial swine, but those capable of killing Salmonella Typhimurium may be present at relatively low population levels. These results indicate that phages (predator) populations may vary along with Salmonella (prey) populations; and that phages could potentially be used as a food safety pathogen reduction strategy in swine.

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    • "However, while a large body of data exists on the Salmonella serovar diversity associated with human and animal disease (e.g., CDC Salmonella Annual Summary and WHO Global Salm-Surv (Galanis et al., 2006; CDC, 2009)), our understanding of Salmonella phage diversity and the role of phages in the ecology and serovar diversity of Salmonella is still limited. Some studies have though shown considerable diversity among Salmonella phages isolated from swine effluent lagoons, human sewage, and swine and poultry feces (Andreatti Filho et al., 2007; Callaway et al., 2010; McLaughlin et al., 2006). One study reported isolation of phages representing different phage families and numerous different host ranges from 26 samples collected from 26 different sites (e.g., broiler farms, abattoirs, and waste water plants) in southern England (Atterbury et al., 2007). "
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    ABSTRACT: Salmonella is an animal and human pathogen of worldwide concern. Surveillance programs indicate that the incidence of Salmonella serovars fluctuates over time. While bacteriophages are likely to play a role in driving microbial diversity, our understanding of the ecology and diversity of Salmonella phages is limited. Here we report the isolation of Salmonella phages from manure samples from 13 dairy farms with a history of Salmonella presence. Salmonella phages were isolated from 10 of the 13 farms; overall 108 phage isolates were obtained on serovar Newport, Typhimurium, Dublin, Kentucky, Anatum, Mbandaka, and Cerro hosts. Host range characterization found that 51% of phage isolates had a narrow host range, while 49% showed a broad host range. The phage isolates represented 65 lysis profiles; genome size profiling of 94 phage isolates allowed for classification of phage isolates into 11 groups with subsequent restriction fragment length polymorphism analysis showing considerable variation within a given group. Our data not only show an abundance of diverse Salmonella phage isolates in dairy farms, but also show that phage isolates that lyse the most common serovars causing salmonellosis in cattle are frequently obtained, suggesting that phages may play an important role in the ecology of Salmonella on dairy farms.
    Full-text · Article · Dec 2013 · Food Microbiology
    • "Phages have also been isolated capable of infecting Salmonella strains that are associated with food-borne illnesses, including Salmonella enterica Typhimurium, albeit with low frequency and with narrow host ranges, which will limit their use as pre-harvest biocontrol agents[9]. In contrast, phages recognizing TolC as their receptor can prevent adherence of Salmonella serovars to their host[10 ]. "

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