Pandemic strains of O3:K6 Vibrio parahaemolyticus in the aquatic environment of Bangladesh.
A total of 1500 environmental strains of Vibrio parahaemolyticus, isolated from the aquatic environment of Bangladesh, were screened for the presence of a major V. parahaemolyticus virulence factor, the thermostable direct haemolysin (tdh) gene, by the colony blot hybridization method using a digoxigenin-labeled tdh gene probe. Of 1500 strains, 5 carried the tdh sequence, which was further confirmed by PCR using primers specific for the tdh gene. Examination by PCR confirmed that the 5 strains were V. parahaemolyticus and lacked the thermostable direct haemolysin-related haemolysin (trh) gene, the alternative major virulence gene known to be absent in pandemic strains. All 5 strains gave positive Kanagawa phenomenon reaction with characteristic beta-haemolysis on Wagatsuma agar medium. Southern blot analysis of the HindIII-digested chromosomal DNA demonstrated, in all 5 strains, the presence of 2 tdh genes common to strains positive for Kanagawa phenomenon. However, the 5 strains were found to belong to 3 different serotypes (O3:K29, O4:K37, and O3:K6). The 2 with pandemic serotype O3:K6 gave positive results in group-specific PCR and ORF8 PCR assays, characteristics unique to the pandemic clone. Clonal variations among the 5 isolates were analyzed by comparing RAPD and ribotyping patterns. Results showed different patterns for the 3 serotypes, but the pattern was identical among the O3:K6 strains. This is the first report on the isolation of pandemic O3:K6 strains of V. parahaemolyticus from the aquatic environment of Bangladesh.
Islam
M Sirajul
MS
International Centre for Diarrhoeal Disease Research, Bangladesh, GPO 128, Dhaka 1000, Bangladesh. sislam@icddrb.org
Tasmin
Rizwana
R
Khan
Sirajul Islam
SI
Bakht
Habibul Bari Mahmud
HB
Mahmood
Zahid Hayat
ZH
Rahman
M Ziaur
MZ
Bhuiyan
Nurul Amin
NA
Nishibuchi
Mitsuaki
M
Nair
G Balakrish
GB
Sack
R Bradley
RB
Huq
Anwar
A
Colwell
Rita R
RR
Sack
David A
DA
D001427:Bacterial Toxins / Q000235:genetics; D001459:Bangladesh; D015139:Blotting, Southern; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000032:analysis; D018628:Gene Dosage; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000235:genetics; D017720:Molecular Epidemiology; D009693:Nucleic Acid Hybridization; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D019105:Random Amplified Polymorphic DNA Technique; D021521:Ribotyping; D012703:Serotyping; D014736:Vibrio parahaemolyticus / Q000235:genetics* / Q000302:isolation & purification*; D014871:Water Microbiology
D001427:Bacterial Toxins; D004269:DNA, Bacterial; D006460:Hemolysin Proteins; C068489:thermostable direct hemolysin