Location: Aquatic Animal Health Research
Title: Nile Tilapia Infectivity by Genomically Diverse Streptoccocus agalactiae Isolates from Multiple Hosts Authors
Submitted to: World Aquaculture Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 23, 2009
Publication Date: March 1, 2010
Citation: Evans, J.J., Klesius, P.H., Pasnik, D.J., Garcia, J.C., Shoemaker, C.A. 2010. Nile Tilapia Infectivity by Genomically Diverse Streptoccocus agalactiae Isolates from Multiple Hosts. World Aquaculture Society. Aquaculture 2010. March 1-5, 2010 San Diego, California. pg 312. Technical Abstract: Streptococcus agalactiae, Lancefield group B Streptococcus (GBS), is recognized for causing cattle mastitis, human neonatal meningitis, and fish meningo-encephalitis. We investigated the genomic diversity of GBS isolates from different phylogenetic hosts and geographical regions using serological typing and multilocus sequence typing (MLST). Studies were also conducted on infectivity of fish, dolphin, bovine and human GBS isolates in Nile tilapia, Oreochromis niloticus. A previously unreported fish capsular serotype, Ia, was discovered for tilapia isolates from Brazil, Israel and the U.S.A, and mullet, seabream and dolphin isolates from Kuwait. Sequence typing of isolates produced six sequence types (ST-7, ST-257, ST-258, ST-259, ST-260 and ST-261), the latter five ST’s unique to the GBS MLST database. Kuwait GBS fish and dolphin isolates shared the same sequence type and capsular serotype as human GBS strains from Japan (Ia, ST-7). Kuwait isolates (ST-7) and tilapia GBS (non-ST-7) isolates from Brazil, Israel, Honduras and the U.S.A. represent two distinct genetic populations, the latter unrelated to bovine and human GBS. In infectivity studies, tilapia GBS isolates and isolates from mullet, seabream, dolphin, and humans caused experimental disease signs and mortality in Nile tilapia. Bovine GBS isolates were not infective to Nile tilapia. Results suggest that 1) GBS isolates from different aquatic animals irrespective of serotype and MLST type and 2) mammalian GBS isolates of the same serotype and MLST are capable of infecting tilapia.