Molecular characterization and virulence gene profiling of pathogenic Streptococcus agalactiae populations from tilapia ( Oreochromis sp.) farms in Thailand.
Streptococcus spp. were recovered from diseased tilapia in Thailand during 2009-2010 ( n = 33), and were also continually collected from environmental samples (sediment and water) from tilapia farms for 9 months in 2011 ( n = 25). The relative percent recovery of streptococci from environmental samples was 13-67%. All streptococcal isolates were identified as S. agalactiae (group B streptococci [GBS]) by a species-specific polymerase chain reaction. In molecular characterization assays, 4 genotypic categories comprised of 1) molecular serotypes, 2) the infB allele, 3) virulence gene profiling patterns ( cylE, hylB, scpB, lmb, cspA, dltA, fbsA, fbsB, bibA, gap, and pili backbone-encoded genes), and 4) randomly amplified polymorphic DNA (RAPD) fingerprinting patterns, were used to describe the genotypic diversity of the GBS isolates. There was only 1 isolate identified as molecular serotype III, while the others were serotype Ia. Most GBS serotype Ia isolates had an identical infB allele and virulence gene profiling patterns, but a large diversity was established by RAPD analysis with diversity tending to be geographically dependent. Experimental infection of Nile tilapia ( Oreochromis niloticus) revealed that the GBS serotype III isolate was nonpathogenic in the fish, while all 5 serotype Ia isolates (3 fish and 2 environmental isolates) were pathogenic, with a median lethal dose of 6.25-7.56 log10colony-forming units. In conclusion, GBS isolates from tilapia farms in Thailand showed a large genetic diversity, which was associated with the geographical origins of the bacteria.
Departments of Veterinary Microbiology (Kayansamruaj, Rodkhum) Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Departments of Veterinary Pathology (Pirarat), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Laboratories of Fish Health Management (Katagiri) Tokyo University of Marine Science and Technology, Tokyo, Japan.|Laboratories of Genome Science (Hirono), Tokyo University of Marine Science and Technology, Tokyo, Japan.
Pattanapon
P
Kayansamruaj
Departments of Veterinary Microbiology (Kayansamruaj, Rodkhum) Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Departments of Veterinary Pathology (Pirarat), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Laboratories of Fish Health Management (Katagiri) Tokyo University of Marine Science and Technology, Tokyo, Japan.|Laboratories of Genome Science (Hirono), Tokyo University of Marine Science and Technology, Tokyo, Japan.
Nopadon
N
Pirarat
Departments of Veterinary Microbiology (Kayansamruaj, Rodkhum) Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Departments of Veterinary Pathology (Pirarat), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Laboratories of Fish Health Management (Katagiri) Tokyo University of Marine Science and Technology, Tokyo, Japan.|Laboratories of Genome Science (Hirono), Tokyo University of Marine Science and Technology, Tokyo, Japan.
Takayuki
T
Katagiri
Departments of Veterinary Microbiology (Kayansamruaj, Rodkhum) Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Departments of Veterinary Pathology (Pirarat), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Laboratories of Fish Health Management (Katagiri) Tokyo University of Marine Science and Technology, Tokyo, Japan.|Laboratories of Genome Science (Hirono), Tokyo University of Marine Science and Technology, Tokyo, Japan.
Ikuo
I
Hirono
Departments of Veterinary Microbiology (Kayansamruaj, Rodkhum) Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Departments of Veterinary Pathology (Pirarat), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.|Laboratories of Fish Health Management (Katagiri) Tokyo University of Marine Science and Technology, Tokyo, Japan.|Laboratories of Genome Science (Hirono), Tokyo University of Marine Science and Technology, Tokyo, Japan.
Channarong
C
Rodkhum
D000818:Animals; D017756:Aquaculture; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D023681:Cichlids; D005393:Fish Diseases / Q000382:microbiology*; D014644:Genetic Variation; D005838:Genotype; D039881:Prokaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D065288:Serogroup; D013290:Streptococcal Infections / Q000382:microbiology / Q000662:veterinary*; D013292:Streptococcus agalactiae / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D013785:Thailand; D014774:Virulence
D001426:Bacterial Proteins; D039881:Prokaryotic Initiation Factor-2
Genetic diversity; Streptococcus agalactiae; molecular characteristic; tilapia; virulence gene profiling.