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Title: Characterization of Salmonella bacteriophages isolated from swine lagoon effluent

item McLaughlin, Michael

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2007
Publication Date: 1/1/2008
Citation: McLaughlin, M.R., King, R. 2008. Characterization of Salmonella bacteriophages isolated from swine lagoon effluent. Current Microbiology. 56:208-213.

Interpretive Summary: Phages, viruses that infect bacteria, are of scientific and commercial interest for use in biocontrol of harmful bacteria. Before phages can be applied to biocontrol, however, characteristics of the phages must be determined, such as how to culture them, their relatedness to other phages, the types of bacteria they infect, whether the infections kill the bacteria, and if so, whether new phages are produced that are capable of infecting and killing more bacteria. In the work reported here, these characteristics were determined for four new phages that had been collected from a swine manure lagoon in a previous study. The lagoon phages rapidly infected and killed some, but not all strains of Salmonella tested, and the infections produced 100-200 fold increases in progeny phage. Additional tests showed the four lagoon phages to be similar to each other, but distinct from two other well-characterized Salmonella phages. These results are being used by scientists to formulate new phage treatments for control of Salmonella in animal manure management systems. Successful application of this type of control would reduce Salmonella on animal production farms, thus reducing potential contamination at processing plants and ultimately benefiting all consumers of animal agricultural food products.

Technical Abstract: Four Salmonella bacteriophages originally isolated from swine lagoon effluent were further characterized. Their differences and similarities to known phages and to each other and their potential for biocontrol of Salmonella were assessed. In host inoculation spot tests the lagoon phages produced similar reactions in reference Salmonella hosts, but slightly different reactions in lagoon Salmonella isolates, several of which were resistant to infection by the lagoon phages. The phages were purified through CsCl gradients and used to produce phage-specific antisera for serological tests and DNA for restriction enzyme digest analysis. The four phages were indistinguishable from each other in agarose gel immunodiffusion and infectivity neutralization serological tests and in restriction digest analysis, but were clearly distinct from Salmonella phages P22 and Felix 01. Analysis of single step growth curves for the four phages at 35ºC showed latent periods of 15-20 min and a range of relatively high burst sizes from 100 to 230, a potential benefit in biocontrol applications. The four phages were concluded to be very similar to each other and likely isolates or strains of a common ancestor, but different from P22 and Felix 01.