Journal of Pure and Applied MicrobiologyVol. 8 No. Special Edition Nov. 2014

A Lytic Bacteriophage with Potential for Inactivation of a Fish Pathogenic Streptococcus agalactiae

Parichat Phumkhachorn and Pongsak Rattanachaikunsopon

Department of Biological Science, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand.

Received on 10 September 2014 and accepted on 28 October 2014



Bacteriophage S14 specific to Streptococcus agalactiae PS01, a fish pathogenic strain, was isolated from fish pond water. It was a lytic bacteriophage that could lyse all four strains of S. agalactiae used in this study. It was tolerant to high temperature (up to 70°C), to a wide range of pH (3-11), and to antimicrobial chemicals commonly used in aquaculture. One-step growth curve showed that the bacteriophage had latent and burst periods of 40 and 160, respectively and burst size of 145 PFU/infected cell. Transmission electron microscopy reveals that the bacteriophage had an icosahedral head of 52 ± 4.6 nm in diameter and a noncontractile tail of 12 ± 0.4 nm in width and 210 ± 11.8 nm in length. Its nucleic acid was double stranded DNA because it was digested by EcoRI, but not by RnaA and nuclease S1. Based on its morphology and genome, the bacteriophage S14 was likely to be a member of the family Siphoviridae. This study showed that bacteriophage S14 had specificity, host range and stability favoring its use as a therapeutic agent against S. agalactiae infection in aquaculture.

Keywords : Bacteriophage, fish pathogen, Streptococcus agalactiae.