Characterization of Vibrio Cholerae O1 Isolated During 2001-2004 by Variable Number of Tandem Repeat (VNTR) Typing

ABSTRACT

Vibrio cholerae causes severe secretory diarrhoea. The cholera infection remains a major problem of public health worldwide particularly in developing countries including Thailand. Variable numbers of tandem repeats (VNTRs) has been increasingly used as molecular markers for typing various bacteria. As it is PCR-based, this method provides more rapidity and reproducibility, lower intensive labor and less cost compared to other molecular techniques. This study was aimed to examine allelic diversity of variable number of tandem repeats (VNTRs) of V. cholerae O1 El Tor Inaba strains isolated from different regions of Thailand during 2001-2004 using the VNTR typing method. Ten loci of tandem repeats were selected and used for differentiating the isolates. The results of VNTR typing showed that the most potential marker for distinguishing the strains was at designated locus VC2_7. This locus showed variation of 5 alleles and Polymorphic Information Content (PIC) was 0.48. The other loci generated 1-2 alleles with a very low PIC value (0.095). The copy number of VNTRs among the strains from an outbreak in Songkla province isolated in the year 2001 (n=34) and other sporadic cases isolated during 2001-2004 except one isolate from Chaiyapum province revealed that it was genetically closely related. It was suggested that these close strains were most likely from the same origin and there was possibly low mutation rate of tandem repeats among the Inaba strains.