Epidemiology and Infection



Clonal dissemination of Vibrio parahaemolyticus displaying similar DNA fingerprint but belonging to two different serovars (O3[ratio]K6 and O4[ratio]K68) in Thailand and India


N. R. CHOWDHURY a1, S. CHAKRABORTY a1, B. EAMPOKALAP a2, W. CHAICUMPA a3, M. CHONGSA-NGUAN a3, P. MOOLASART a2, R. MITRA a1, T. RAMAMURTHY a1, S. K. BHATTACHARYA a1, M. NISHIBUCHI a4, Y. TAKEDA a5 and G. BALAKRISH NAIR a1c1
a1 National Institute of Cholera and Enteric Diseases, Calcutta, India
a2 Bamrasnaradura Infectious Diseases Hospital, Nonthaburi Province, Thailand
a3 Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand
a4 Center for Southeast Asian Studies, Kyoto University, Kyoto, Japan
a5 National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan

Abstract

Active surveillance of Vibrio parahaemolyticus infection among hospitalized patients in Calcutta, India, showed the appearance of the O4[ratio]K68 serovar for the first time in March 1998 alongside the continued predominant incidence of the O3[ratio]K6 serovar. Strains belonging to both these serovars have been reported to possess pandemic potential. The genomes of O3[ratio]K6 and O4[ratio]K68 strains and for comparison, non-O3[ratio]K6 and non-O4[ratio]K68 strains isolated from two different countries, India and Thailand, were examined by different molecular techniques to determine their relatedness. The O3[ratio]K6 and O4[ratio]K68 strains from Calcutta and Bangkok carried the tdh gene but not the trh gene. Characterization of representative strains of these two serovars by ribotyping and by arbitrarily primed-polymerase chain reaction (AP-PCR) showed that the isolates had identical ribotype and DNA fingerprint. Pulsed-field gel electrophoresis (PFGE) performed with the same set of strains yielded nearly similar restriction fragment length polymorphism (RFLP) patterns for the O3[ratio]K6 and O4[ratio]K68 isolates from Calcutta and Thailand. Phylogenetic analysis of the NotI RFLP showed that the O3[ratio]K6 and O4[ratio]K68 strains formed a cluster with 78–91% similarity thus indicating close genetic relationship between the two different serovars isolated during the same time-frame but from widely separated geographical regions. The non-O3[ratio]K6 and non-O4[ratio]K68, in contrast, showed different ribotype, AP-PCR and PFGE patterns.

(Accepted March 20 2000)


Correspondence:
c1 Author for correspondence: National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Scheme XM, Beliaghata, Calcutta – 700010, India.


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