Similarly, significant level of linkage disequilibrium was observed on analysis of MLRT data. The I A and I S A values were 3.357 and 0.672 respectively, and differed significantly (p < 0.001) from zero. Simpson's diversity index (DI) for MLEE and MLRT was 0.98 and 0.77 respectively. Table 4 Multilocus linkage disequilibrium analysis of Y. enterocolitica biovar 1A strains Method Mean no. of alleles per locus Mean PND-1186 genetic diversity (H) V E* V O* I A I S A P† 95% critical value for V O MLEE 7.5 0.566 ± 0.088 1.234 1.990 0.613 0.128 < 0.001 1.378 MLRT 3.2

0.441 ± 0.048 1.409 6.149 3.357 0.672 < 0.001 1.573 *: Calculated as described by Maynard Smith et al [35]. V E: expected variance, V O: observed variance, I A: Index of association, I S A: Standardized index of association. †: Probability of observing V O/V E ratio as or MK-8931 in vivo more than that found in the original data calculated with 1,000 Monte Carlo randomizations. Discussion Indexing allelic variations

in sets of housekeeping genes provides a good measure of overall genetic heterogeneity in populations of microorganisms [21]. Methods based on this principle such as MLEE, MLRT and MLST (multilocus sequence typing) provide good insight into the genetic relationships among strains. In the present study, selleckchem we used MLEE and MLRT to assess the genetic relationships among 81 strains of Y. enterocolitica biovar 1A isolated from clinical and non-clinical sources. MLEE clustered Y. enterocolitica biovar 1A into four groups. A close analysis of data presented by Dolina and Peduzzi [23] who studied human, animal and aquatic strains of Y. enterocolitica isolated from Switzerland by MLEE, revealed that 51 biovar 1A strains clustered into two major groups, although minor clusters having one and six isolates each were also observed. Another study that used fluorescent amplified fragment length polymorphism (FAFLP) also clustered biovar 1A strains into two groups: one group comprised of biovar 1A strains; while a very few biovar 1A strains clustered with atypical pathogenic

biovars constituting the second group [39]. Further study by comparative genomic DNA microarray however showed that these biovar 1A strains constituted a single group [4]. Other studies using rep-PCR genotyping [17], 16S-23S IGS and gyrB RFLP [18], and MLVA [19] have also clustered biovar 1A strains into two clonal groups. MLEE revealed a total of 62 electrophoretic types (ETs) among 81 biovar 1A strains and showed high degree of discrimination (DI = 0.98). Studies of allelic variation by MLEE also revealed sufficient genetic diversity (H = 0.566) among strains of Y. enterocolitica biovar 1A. Similar genetic diversity was also reported in previous MLEE studies on Y. enterocolitica [22, 23]. In the present study however, based on the number of distinct ETs generated, the clinical serotype O:6,30 and O:6,30-6,31 isolates were shown to be heterogeneous with mean genetic diversities (H) of 0.514 ± 0.