Variable number tandem repeat analysis of Mycobacterium bovis isolates from Gyeonggi-do, Korea

Abstract

Bovine tuberculosis (TB) is a major zoonosis that's caused by Mycobacterium bovis (M. bovis). Being able to detect M. bovis is important to control bovine TB. We applied a molecular technique, the variable number tandem repeat (VNTR) typing method, to identify and distinguish the M. bovis isolates from Gyeonggi-do, Korea. From 2003 to 2004, 59 M. bovis clinical strains were isolated from dairy cattle in Gyeonggi-do, Korea, and these cattle had tuberculosis- like lesions. Twenty-four published MIRUVNTR markers were applied to the M. bovis isolates and ten of them showed allelic diversity. The most discriminatory locus for the M. bovis isolates in Korea was QUB 3336 (h = 0.64). QUB 26 and MIRU 31 also showed high discriminative power (h = 0.35). The allelic diversity by the combination of all VNTR loci was 0.86. Six loci (MIRU 31, ETR-A and QUB-18, -26, -3232, -3336) displayed valuable allelic diversity. Twelve genotypes were identified from the 59 M. bovis isolates that originated from 20 cattle farms that were dispersed throughout the region of Gyenggi-do. Two genotypes [designation index (d.i.) = e, g] showed the highest prevalence (20% of the total farms). For the multiple outbreaks on three farms, two successive outbreaks were caused by the same genotype at two farms. Interestingly, the third outbreak at one farm was caused by both a new genotype and a previous genotype. In conclusion, this study suggests that MIRU-VNTR typing is useful to identify and distinguish the M. bovis isolates from Gyeonggi-do, Korea.

Fig. 1

The geographical origin of the M. bovis strains isolated from cattle are aligned with the corresponding VNTR genotype. A capital letter indicates the cattle farm. A lower-case letter indicates the genotypes of the M. bovis strains at each cattle farm and the number in parenthesis indicates the number of outbreaks of the genotype of the M. bovis isolates.

Fig. 2

PCR products of the various M. bovis isolates with using primers that amplify QUB3336. Lane M: 100 bp DNA ladder, lane 1-12 and lanes 15-26: M. bovis isolates, lanes 13 and 27: M. tuberculosis H37Rv, lanes 14 and 28: negative controls.