Application of Mycobacterial Interspersed Repetitive Unit Typing to Manitoba Tuberculosis Cases: Can Restriction Fragment Length Polymorphism Be Forgotten?

Abstract

Since 1993, all Mycobacterium tuberculosis isolates recovered in the province of Manitoba, Canada, have been genotyped by the standard IS6110-restriction fragment length polymorphism (RFLP) method for routine surveillance, prevention, and control purposes. To date, our laboratory has collected 1,290 isolates, from which we have identified approximately 390 unique fingerprint patterns or "types." Although the standard method is well known for being a lengthy and labor-intensive procedure, a more efficient alternative for typing tuberculosis isolates, the mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) method, has recently gained acceptance. Consequently, all isolates acquired in 2003 (n ‫؍‬ 126) were typed by both methods in order to determine the utility of replacing the RFLP method with MIRU typing for all future isolates. Application of Hunter's discriminatory index to the available study population showed that the MIRU method was close in discriminatory power (D) to the RFLP method (D MIRU ‫؍‬ 0.831 to 0.984 versus D RFLP ‫؍‬ 0.821 to 0.997). Clustering of isolates by using MIRU data correlated with RFLP-derived clustering, lending useful information for either an investigation or confirmation of an incidence of recent transmission. In addition, it was determined that each predominant RFLP type in Manitoba had a corresponding, recognizable MIRU type. It is conceivable that in the future RFLP typing can be replaced with MIRU for real-time, ongoing tuberculosis surveillance in the province.

Prospective Universal Application of Mycobacterial Interspersed Repetitive-Unit-Variable-Number Tandem-Repeat Genotyping To CharacterizeMycobacterium tuberculosisIsolates for Fast Identification of Clustered and Orphan Cases

“…MIRU-VNTR genotyping has been reported to identify as many clustered cases as RFLP genotyping (27), which led MIRU-VNTR-based genotyping to be chosen for the epidemiological survey in different institutions (5,8). However, in our study, MIRU-VNTR genotyping clustered isolates in a higher proportion than did RFLP genotyping.…”

Evaluation of the Selected 12-locus MIRU for Genotyping Beijing Family Mycobacterium tuberculosis in Korea

“…MIRU-VNTR genotyping based on a 12-loci set (MIRU-12) has been evaluated in several studies in different settings. Some authors have found it to show a discriminatory power equivalent to that of RFLP and have considered it an alternative to IS6110-RFLP for epidemiological purposes [4][5][6][7] . However, other authors have found limitations in its discriminatory power and incomplete correlation with the RFLP analysis [8][9][10] , indicating that MIRU analysis should be combined with an additional genotyping method [10][11][12][13] .…”

Assessment of an Optimized Mycobacterial Interspersed Repetitive- Unit-Variable-Number Tandem-Repeat Typing System Combined with Spoligotyping for Population-Based Molecular Epidemiology Studies of Tuberculosis

“…Among the different described sets of MIRU-VNTR loci (8,10,14,17,20,22,27), a system based on 12 loci (15,25,27), is now the most widely used in clinical mycobacteriology (see, for example, reference 1) and for local outbreak investigation (11). Genotypes based on these 12 loci are highly stable among epidemiologically linked isolates but sufficiently diverse to generate a resolution approaching that of IS6110-RFLP in some sets of isolates from low-incidence settings or from diverse geographic origins (2,15,25).…”