[Multilocus variable-number tandem-repeat analysis for molecular subtypes of Shigella isolates in Beijing].
OBJECTIVE
Selecting variable-number tandem-repeat (VNTR) loci for different serogroups of Shigella spp to explore and establish multilocus variable-number tandem-repeat analysis (MLVA) method, in order to study the molecular characteristic of the isolated strains.


METHODS
Of the Shigella strains found by dysentery surveillance in Beijing from 2001 to 2009, 180 strains were selected for this study, according to the number and serotypes of the surveillant strains, at the ratio of 15%; including 50 strains of Shigella sonnei and 130 strains of Shigella flexneri. After screening the polymorphism of the 18 VNTR loci, 10 VNTR loci (sh1-sh10) were retained and constructed three groups of multi-PCR methods to detect all he 180 strains and analyze MLVA molecular subtypes using capillary segments.


RESULTS
A range of 2 to 11 alleles were found on the 10 VNTR loci among the 180 Shigella strains, with a diversity index value between 0.158 and 0.766. The 10 loci showed diversity in different serogroups, such as only one allele found in sh6 of Shigella flexneri, sh2 and sh3 of Shigella sonnei individually. The isolated 180 strains were divided into 84 MLVA subtypes, with a resolution ratio D value at 0.967 (95%CI: 0.956 - 0.978). The 130 strains of Shigella flexneri were divided into 63 subtypes, named as TF001-TF063; among which TF001, TF002 and TF 005 were the dominant subtypes, accounting to 17, 16 and 15 strains respectively. The 50 strains of Shigella sonnei were divided into 21 subtypes, named as TS001-TS021; among which TS002 (14 strains) and TS001 (7 strains) were the dominant subtypes.


CONCLUSIONS
MLVA subtyping method including 10 VNTR loci was preliminarily developed. The MLVA cluster analysis revealed that the subtypes of Shigella strains isolated in Beijing were diverse, and suggested the possibility of multiple-clone source.
Department of Infectious and Endemic Diseases Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China.
Mei
M
Qu
Xin
X
Zhang
Ying
Y
Huang
Gui-rong
GR
Liu
Zhi-gang
ZG
Cui
Xi-tai
XT
Li
Lei
L
Jia
Fang
F
Huang
Biao
B
Kan
Quan-yi
QY
Wang
D000483:Alleles; D015373:Bacterial Typing Techniques / Q000379:methods; D002681:China; D004269:DNA, Bacterial / Q000235:genetics; D005838:Genotype; D018598:Minisatellite Repeats; D011110:Polymorphism, Genetic; D012760:Shigella / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
D004269:DNA, Bacterial