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.
ABSTRACT
Fruits of <I>Brucea javanica</I> (L.) Merr. (“Ratchadad” in Thai) and roots of <I>Eurycoma longifolia</I> Jack (“Plalaipeag” in Thai) are used as traditional medicines for the treatment of malarial fever. Ethanol, methanol, ethyl acetate, ethyl alcohol and aqueous extracts were tested against the multidrug-resistant <I>Plasmodium falciparum</I> strain K1. Ethanol and methanol-ethanol extracts, together with methanol residue, from fruits of <I>B. javanica</I> (L.) Merr. showed the highest antiplasmodial activities with IC<SUB>50</SUB> values of 0.5 ± 0.3, 0.3 ± 0.1 and 0.3 ± 0.05 Μg⁄mL, respectively, comparable to the IC<SUB>50</SUB> values of chloroquine (0.17 ± 0.02 Μg⁄mL) and quinine (0.3 ± 0.1 Μg⁄mL). Similarly, ethanol and methanol-ethanol extracts of roots of <I>E. longifolia</I> Jack showed higher activities than those of the other solvent extracts, but their activities were about 10-fold lower than those of extracts from <I>B. javanica</I> (L.) Merr. fruit. In drug combination tests, <I>B. javanica</I> (L.) Merr. and <I>E. longifolia</I> Jack extracts did not appear to antagonize antiplasmodial activity of chloroquine and quinine. Not only well-known quassinoid glycosides but also coumarins and flavonoids identified by thin-layer chromatography in ethanol and methanol-ethanol extracts and in methanol residue of <I>B. javanica</I> (L.) Merr fruit and <I>E. longifolia</I> roots may be responsible for the antimalarial activity. Taken together, our extraction conditions provided extracts containing novel active compounds that did not antagonize the inhibitory effects of the two widely used antimalarials. This finding could lend support to the future discovery of active antimalaria compounds of <I>Brucea javanica</I> (L.) Merr. and <I>Eurycoma longifolia</I> Jack as drugs for the treatment of malaria that could be employed as drug combinations in order to delay the onset of parasite drug resistance.