Restriction fragment length polymorphism analysis of Mycobacterium tuberculosis isolated from countries in the western pacific region

Abstract

A total of 422 Mycobacterium tuberculosis isolates from eight countries were subjected to IS6110 and IS1081 DNA fingerprinting by means of restriction fragment analysis to characterize M. tuberculosis strains from each country. Chinese, Mongolian, Hong Kong, Filipino, and Korean isolates had comparatively more copies of IS6110 (proportion with eight or more copies; 95% +/- 5%), while Thai, Malaysian, and Vietnamese isolates had fewer copies (proportion with eight or more copies, 60% +/- 4%). We found a number of novel IS1081 types in this study. One IS1081 type was present in 56% of Filipino isolates, had a specific 6.6-kb PvuII fragment in its IS6110 DNA fingerprint, and was termed the "Filipino family." The IS1081 types of Thai isolates had interposing characteristics between the characteristics of northeastern Asian and southeastern Asian IS1081 types. A 1.3-kb single-copy IS6110 fragment was found only in Vietnamese M. tuberculosis isolates. Although M. tuberculosis isolates from each country had comparatively similar characteristics depending on the classification factor, each country's isolates showed characteristic DNA fingerprints and differed slightly from the isolates from the other countries in either the mode number of IS6110 copies or the distribution of IS1081 types.

FIG. 1

Comparison of IS6110-based DNA fingerprints of M. tuberculosis strains isolated from the WPR.

FIG. 2

IS6110 DNA fingerprints of M. tuberculosis strains isolated from the Philippines. Most strains showed similar patterns because of the common 4.4-, 2.8-, 2.3-, and 2.0-kb fragments. Strains containing a 6.6-kb fragment by IS6110 fingerprinting were classified as type J. Lane 1, M. tuberculosis H37Rv. Numbers on the left are in kilobases.

FIG. 3

Clusters of Vietnamese M. tuberculosis strains (strains V1 to V14) hybridized with IS6110 (A), IS1081 (B), and PGRS (C). Clusters of isolates with the same IS6110 fingerprints were typed as VA (V1 to V10), VB (V11 and V12), or VC (V13 and V14). Four strains of type VA with a 1.3-kb PvuII fragment, two strains of type VB with a 1.5-kb fragment, and two strains of type VC were differentiated with the PGRS probe. Numbers on the left are in kilobases.

FIG. 4

Various types of IS1081 DNA fingerprints of M. tuberculosis isolated from the WPR. The type F IS1081 fingerprint was not detected in this study, but novel IS1081 types were found: J and K types in the Philippines, M and N types in Malaysia, and O and P types in Vietnam. Numbers on the left are in kilobases.

FIG. 5

Clusters of Korean M. tuberculosis strains hybridized with IS6110 (A), IS1081 (B), and PGRS (C). Clusters of patients infected with isolates with the same IS6110 fingerprints were typed as KA (patients K1 to K4), KB (patients K5 and K6), KC (patients K7 and K8), KD (patients K9 and K10), KE (patients K11 to K13), and KF (patients K14 to K15). Two strains from patients in cluster type KF were discriminated with the PGRS probe. Numbers on the left are in kilobases.

FIG. 6

Geographical distribution of patients in six Korean IS6110 clusters (clusters KA and KF). The patients in cluster type KD contracted TB by household contact while those in KB contracted TB by neighborhood contact.