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To analyze the genetic evolution and bacterial type changes of Yersinia enterocolitica in the Ningxia area between year 1984 and 2011.A total of 296 strains of Yersinia enterocolitica was collected from diarrhea patients, pig, rodents, sheep and dogs between year 1984 and 2011. The serotype, biotype, ail, ystA, ystB, yadA, virF and other toxic genes were detected. The PFGE subtypes of serotype O:3 and O:9 strains and the cluster features were analyzed.Out of 296 Yersinia enterocolitica strains, pig was the main host, accounting for 65.20% (193/296), followed by rodents, accounting for 32.43% (96/296). Serotype and biotype had their own respective dominant types in different periods. During 1984 and 1985, 2 strains of serotype O:3 and 3 strains of serotype O:9 were isolated, all belonged to biotype 3. Because of lack of strains, there were no obvious dominant types found. Between 1997 and 1999, 177 strains of serotype O:9 Yersinia enterocolitica were isolated as the dominant strain; and there were 178 strains of biotype 2 Yersinia enterocolitica were found. During 2007 and 2011, 54 strains of serotype O:3 Yersinia enterocolitica were isolated as dominant strain; followed by 26 strains of serotype O:5. There were separately 44 and 59 strains of biotype 1A and biotype 3. The PCR test divided the 248 strains into 4 types, including pathogenic strains as type I (ail(+), ystA(+), ystB(-), yadA(+), virF(+)). The PFGE divided the serotype O:3 into 12 types, in which K6GN11C30021 and K6GN11C30012 were the dominant types, accounting for 63.64% (42/66). The serotype O:9 were divided into 14 types, in which K6GN11C90010, K6GN11C90008, K6GN11C30018 and K6GN11C90003 were the dominant types, accounting for 89.01% (162/182).The different serotypes of isolated strains in Ningxia district showed different dominant bacteria in different periods; while the biotypes also changed with serotypes. The Yersinia enterocolitica isolated from different years showed great variation.

To investigate the distribution of virulent genes of Yersinia enterocolitica (Y. enterocolitica) in Ningxia Hui autonomous region and the characteristics of the molecular patterns of Y. enterocolitica.283 strains of Y. enterocolitica were isolated in Ningxia Hui autonomous region between year 1997 and 2010. The genes ail, ystA, ystB, yadA and virF were analyzed by PCR method; the chromosomal DNA of Y. enterocolitica was digested by restriction endonucleases NotI and processed by pulsed-field gel electrophoreses (PFGE); and then the cluster analysis were conducted by BioNumeric computer software towards the above results.Of all, 209 strains of serotypes O:3 and O:9 Y.enterocolitica showed positive virulence of genes ail, ystA, yadA and virF; 97.6% (204/209) of which, the ystB virulence were negative. The virulence of all genes in serotype O:8 and serum-unclassified strains were negative. 9 out of 11 strains of serotype O:5 Y. enterocolitica showed negative virulence of the above five genes. By PFGE, according to the NotI Macrorestriction Map on chromosomal DNA, the 29 strains of serotype O:3 Y. enterocolitica were divided into 12 PFGE patterns, 2 of which were dominant patterns which could be found in over 5 strains; and the 180 strains of serotype O:9 Y. enterocolitica were divided into 13 patterns, 4 of which were dominant patterns which existed in over 10 strains; which were isolated individually from pigs and house mouse, pigs and dogs as well as pigs and wild rabbits.Y.enterocolitica serotypes O:3 and O:9 were pathogenic in Ningxia, and serotype O:3 becomes predominant gradually. O:5, O:8 and serum-unclassified serotypes were non-pathogenic.