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J. Environ. Qual
Vol. 35, No. xx, 2006; Pages: 522–528

Isolation of Salmonella Bacteriophages from Swine Effluent Lagoons

M. R. McLaughlin,* M. F. Balaa, J. Sims, and R. King

United States Department of Agriculture, Agricultural Research Service, Waste Management and
Forage Research Unit, Mississippi State, MS 39762.


Bacteriophages (phages) associated with Salmonella were collected from nine swine manure lagoons in Mississippi. Phages were isolated by an enrichment protocol or directly from effluent. For enrichment, chloroform-treated samples were filtered (0.22 m) and selectively enriched by adding a cocktail of Salmonella strains in trypticase soy broth. After overnight incubation at 35oC, chloroform was added and samples stored at 5oC. Enriched samples were tested by double agar layer (DAL) plaque assay against individual Salmonella isolates. Phage titers of 2.9 x108 to 2.1 x109 plaque forming units (pfu) per mL were produced, but estimation of phage titers in lagoons was not possible. For direct isolation, effluent was clarified by centrifugation, filtered (0.22 m), and used in DAL plaque assays to select single-plaque isolates for 15 Salmonella strains. Plaque counts varied among Salmonella strains and lagoons. The most sensitive strain for direct phage recovery was ATCC 13311. Phage titers estimated by direct isolation with ATCC 13311 ranged among lagoons from 12 to 148 pfu per mL. In limited host range tests, 66 isolates recovered by the enrichment protocol produced plaques only on Enteritidis and Typhimurium strains of Salmonella and none produced plaques on lagoon isolates of Citrobacter, Escherichia, Proteus, Providencia, or Serratia. Electron microscopy (EM) showed purified enrichment isolates had Podoviridae morphology (tailless 50- nm icosahedral heads with tail spikes). Electron microscopy of clarified concentrated effluent showed 5.5:1 tailless to tailed phages. The isolated phages have potential as typing reagents, specific indicators, and biocontrol agents of Salmonella.

Keywords:Bacteriophages,Salmonella,Salmonellastrains,Citrobacter,Escherichia,Proteus, Providencia,Serratia,Salmonella Bacteriophages,pathogens.

Corresponding author:

E-mail: mmclaughlin@msa-msstate.ars. usda.gov

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