The discriminatory power of each VNTR and all 6
VNTRs combined was measured by Simpson’s Index of
Diversity (D). The highest D value was 0.957 and was
recorded for vca0283. Except for vca0283 and vca0171, all
D values were lower than previously reported. Our focus
on 7th pandemic isolates which have been shown to be
highly homogeneous may have contributed to these lower
D values. VNTR vc1457 had the lowest D value of 0.437,
which was lower than previously reported (D value = 0.58)
[16]. The combined D value of 7th pandemic isolates for
all 6 VNTRs in this study was 0.995. We also calculated D
values from previous studies by excluding MLVA data of
environmental and non-7th pandemic isolates [19-22] and
found that the D values were similar and ranged from
0.962 to 0.990 [19-22], when only 7th pandemic isolates
were analysed. Analysis using the two most variable
VNTRs, vca0171 and vca0283, produced comparable D
values, which could potentially reduce the need to use the
other markers. This would be particularly useful in outbreak
situations where there is limited time and resources
available to type isolates. However, typing the isolates in
this study using only