Occurrence of Salmonella-Specific Bacteriophages in Swine Feces Collected from Commercial Farms
ABSTRACT 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.
SourceAvailable from: Kitiya Vongkamjan[Show abstract] [Hide abstract]
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.Food Microbiology 12/2013; 36(2):275-85. DOI:10.1016/j.fm.2013.06.014 · 3.37 Impact Factor
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ABSTRACT: The use of bacteriophages is considered as a viable alternative to chemical antimicrobials against foodborne pathogens. The objective of this study was to develop a collection of lytic bacteriophages which will be able to infect different pathogenic Salmonella enterica serovars. Phages were isolated from animal feces and sewage samples, purified, characterized morphologically and by DNA fingerprinting, and host ranges were determined. Spot test and efficiency of plaquing (EOP) data indicated that two phages, SEA1 and SEA2 had the broadest host range against Salmonella among all isolated phages. SEA2 was highly efficient to infect S. Typhimurium DT104 (0.5–1 EOP value). Only phage SSA1 was able to infect S. Montevideo. Transmission electron microscopy (TEM) revealed the phages in the collection were mostly (4 out of 6) Siphoviridae, while SEA1 and SEA2 were Myoviridae T4-like phages. SEA1 and SEA2 had the largest genome sizes in the collection, 190 and 170 kb, respectively. Pulsed field gel electrophoresis (PFGE) analysis demonstrated distinct digestion profiles with EcoRI for phages SSA1, STD3, STE3 and STF1. However, SEA1 and SEA2 shared a similar restriction enzyme (RE) digestion pattern with same morphotype, but distinct profiles in lysing Salmonella strains. These anti-Salmonella phages were highly host specific with few exceptions of lytic phages that were able to infect a wide variety of Salmonella. These phages have potential for use in applications controlling Salmonella on different matrices.Food Control 04/2014; 38:67–74. DOI:10.1016/j.foodcont.2013.09.064 · 2.82 Impact Factor
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ABSTRACT: Abstract Foodborne illness due to Salmonella-contaminated pork products is an important public health problem, causing significant economic losses worldwide. The use of bacteriophages is a potential intervention tool that has attracted interest for the control of foodborne pathogens. The objective of this study was to detect the presence of Salmonella in commercial pig farms and to isolate specific autochthonous bacteriophages against Salmonella Typhimurium, to characterize them and to evaluate their lytic capacity against Salmonella Typhimurium in vivo and in vitro. Salmonella was isolated on 50% (4/8) of the farms, with serotype Typhimurium being the most prevalent, detected in 48.2% of samples (13/27). The isolated Salmonella Typhimurium bacteriophages belong to the Podoviridae family, were active against serotypes Abony, Enteritidis, Typhi, and Typhimurium, but not against serotypes Arizonae, Cholerasuis, Gallinarum, and Pullorum. In in vitro tests, bacteriophage at 10(7) PFU/mL and 10(9) PFU/mL significantly reduced (p<0.05) Salmonella Typhimurium counts in 1.6 and 2.5 log10 colony-forming units (CFU)/mL, respectively, after 24 h. Before the in vivo treatment with bacteriophages, Salmonella was identified in 93.3% (28/30) of the fecal samples from the pigs inoculated with 10(6) CFU/mL, and only in 56.6% (17/30) after the treatment consisting of oral administration of the pool of the bacteriophages after the fasting period, simulating a common preslaughter practice. These results indicate that the pool of bacteriophages administered was capable of reducing the colonization of Salmonella in pigs.Foodborne Pathogens and Disease 05/2014; 11(8). DOI:10.1089/fpd.2013.1600 · 2.09 Impact Factor