|Donoghue, Ann - Annie|
Submitted to: Food Safety Consortium Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 9/30/2003
Publication Date: 10/2/2003
Citation: Bielke, L.R., Higgins, S.E., Guenther, K.L., Nava, G.M., Tellez, G.I., Donoghue, D.J., Donoghue, A.M., Hargis, B.M. 2003. Salmonella host range of bacteriophages which exhibit increased host range. [CD-ROM]. Food Safety Consortium Proceedings. Interpretive Summary:
Technical Abstract: Conventionally, bacteriophages (phages) are presented as viruses capable of amplifcation only in a narrow range of closely-related bacteria. We selected phages with the ability to infect more than one bacterial genus. Initially, wild-type phages were selected by ability to form plaques in Salmonella enteritidis (SE) agar overlays. For determination of host specificity, a pool of 44 combined isolates of phages were evaluated for ability to propagate in individual non-pathogenic enteric bacterial isolates. After incubation in suspension culture, phage titer (pfu) was determined by incubation of serial dilutions of the phage mixture in tryptic soy agar (TSA) overlay with SE. In 2 separate experiments phage was combined with each bacterial isolate and tryptic soy broth (1:3:5, respectively). This mixture was incubated, sterile filtered, and recombined using the above ratio with fresh bacterial culture and media for 4 sequential passes, and the resulting phage titer was determined using SE. One Klebsiella and 3 different Escherichia isolates, successfully amplified some phage(s) from the SE-selected phage pool. Resulting plaques were then reisolated and passed in their respective enteric bacterial isolate. Amplification in each species was confirmed by the formation of increased pfu's in a TSA overlay with the enteric (alternative host) bacteria. In a subsequent study, 2 selected wide-host-range phages were evaluated for ability to amplify in 10 different Salmonella isolates (different serovars) by amplification in broth culture. Phage A had the ability to amplify in 6 different Salmonella serovars and Phage B had the ability to amplify in 2 different Salmonella serovars. These experiments suggest that phage host range is not always genera-restricted, and that selection of subpopulations of phages, capable of amplification in alternative genera, may provide a tool for selection of broad host-range phages for the pathogen of interest. Ongoing studies are evaluating the potential for more phylogenetically distant non-pathogenic isolates to support replication of Salmonella phages, which may allow improved safety for bacteriophage application to poultry.