| In this work, molecular typing of Salmonella in partial areas of China was carried out to study the prevalence of Salmonella and the variation of its pathogen pectrum, which would benefit the establishment of molecular typing database of Salmonella, and improve the capability of the detection, prevention and control towards Salmonella.From January 2009 to March 2011, 191 suspected Salmonella strains in diarrhea were collected from the provinces of Nanjing, Beijing, Guangzhou, Jinan, Shenyang and Xinjiang, and their serotypes were identified. The results showed that 191 strains of Salmonella could be divided into 28 serotypes, which were mostly in the range of A ~ F groups except for eight strains (S. wandsworth) belonging to Q group. The dominant serotype was S. enteritidis (29.7%), followed by S. Newport(1.6%), S. kentucky(2.6%), S. albany(3.1%), S. mbandaka(3.1%), S. Litchfield(2.1%), S. montevideo(0.5%), S. stanley(2.6%)and S. cambridge(0.5%)and S. wandsworth(4.2%). View from the time distribution, the number of Salmonella strains collected increased from May to September, but keeps stable from November to the next April. View from the population distribution, the range of their age was from 10 to 80,among which ,the proportion aged 21-30 was up to 30%. Ninety six strains collected from Nanjing could be divided into 18 serotypes, and the dominant serotype was S. enteritidis ( 27.1%), followed by S. Newport(1.0%), S. Montevideo(1.0%), S. mbandaka(6.3%), S. Wandsworth(8.3%). Twenty five strains collected from Beijing could be divided into 10 serotypes, among which the dominant was S. enteritidis (24.0%), followed by S. Kentucky(20.0%). Twenty two isolates collected from Guangzhou could be divided into 7 serotypes: the dominant serotype was S.enteritidis (36.4%), followed S. albany(22.7%).Eighteen strains collected from Jinan could be divided into 4 serotypes, the dominant serotype was S. infantis (66.7%). Eighteen strains collected from Shenyang could be divided into 7 serotypes, the dominant serotype was S. enteritidis (58.3%). Eleven strains collected from Xinjiang could be divided into 4 serotypes: the dominant serotype was S. enteritidis (72.7%), followed by S. albany(9.1%).The resistance of 54 strains of S. enteritidis was studied using 14 kinds of widely used antibiotic and PCR amplification towards the genes of gyrA and parC. The results showed that 94.4% (51/54) of the strains have the resistance in different degrees including the resistance to nalidixic acid, and, to be concerned, that 19 strains were resistant to fluoroquinolones or third generation cephalosporins. The multiple drug resistance(MDR) rate was 70.4% (42/54). Fifty four strains all had mutations in Quinolone Resistance Determining Region (QRDR) of gyrA gene, and the dominant mutation patterns were Asp87â†'Tyr, Gly133â†'Glu (31.5%). The newly discovered point mutations were Ser27â†'Asn, Cys28â†'Gly outside the QRDR and Gly133â†'Glu in QRDR, but did not cause the increase of resistance. Only three strains had mutations of parC gene.Thirty three sequences types (STs) were identified among the 185 strains by using MLST analysis including seven housekeeping genes. The dominant ST was ST11 (29.7%). Two new STs, ST1498 and ST1499, were found. The same serotype generally has the same ST, except for S. typhimurium, S. paratyphiB, S. newport and S. choleraesuis, which showed high genetic variation. Ninety six strains of Salmonella from Nanjing generated 21 STs, including the ST1498 with the dominant ST of ST11 (27.1%); The dominant ST in Beijing was ST11 (24.0%). Twenty two strains of Salmonella in Guangzhou generated 8 STs with the dominant ST of ST11 (36.4%); Eighteen strains in Jinan were divided into five STs. with the dominant ST of ST32 (66.7%); Twelve strains of Salmonella in Shenyang were divided into 5 STs with the dominant ST of ST11 (58.3%); Eleven strains of Salmonella in Xinjiang region were divided into 4 STs with the dominant ST of ST11(72.7%). Genetic evolution diagram of 33 STs was made in the software of Bionumerics Version 6.0 , and the results indicated that ST19 might be the founder of the other STs, and that ST214 had the closest relationship with ST1498 , and that ST33 had the closest relationship with ST1499 .Ninety eight PFGE patterns were identified among 185 strains by using PFGE analysis, and the dominant PFGE pattern was PT84 , and the strains with the same serotype usually had the same PFGE pattern or gathered together, but some serotypes varied greatly, such as S. choleraesuis, S. senfternberg, S. enteritidis. 185 strains were divided into 8 clusters by cluster analysis , in which the dominant clusters were A1and E2. The PFGE patterns and dominant PFGE pattern in different regions were not compeletely accordant. The dominant PFGE pattern in Beijing was PT78, and that in Jinan was PT09, and that in other regions was PT84. Continuous surveillance for the dominant PFGE pattern, dominant cluster and the strains with high genetic variation should be enhanced.The results of MLVA analysis about six VNTR locis indicated that, 78 VNTR genotypes were generated among 124 strains of Salmonella , with the dominant type V73 accounting for 14.5% (18/124), which were S. enteritidis. Thirty nine genotypes were generated among 54 strains in Nanjing , with the dominant type V73 accounting for 9.4%; Sixteen VNTR genotypes were generated among 22 strains in Beijing , Each genotype contained no more than two strains; Eighteen strains in Guangzhou were divided into 11 VNTR genotypes, with the dominant type V73 accounting for 33.3%; Ten genotypes were generated among 15 strains in Jinan , with the dominant type V50 accounting for 26.7%; Four genotypes were generated among 10 strains in Xinjiang, with the dominant type V73, accounting for 50.0%; Five genotypes were generated among 5 strains in Shenyang , and each genotype contained no more than one strain. 124 strains of Salmonella were divided into 4 major clusters, among which cluster B was the dominant , accounted for 32.3% (40/124), contained strains of S.enteritidis, followed by the cluster A1 , accounted for 27.4% (34/124) .Strains with the same serotype were not all had the same VNTR genotypes, but generally gathered together. The 78 VNTR genotypes were analyzed by Bionumerics (Version6.0) software to create phylogenetic tree, and the results showed that 6 branchs were generated among 78 VNTR genotypes , in which Branch B dominated with 71.8% (56/78), followed by Branch C accounted for 19.2% (15/78), S. enteritidis were all in Branch C. Generally strains with the same serotypes were in the same genetic branch, but some strains of exceptions, S. mbandaka, S. choleraesuis, S. litchfield, S. infantis presented highly variation with the same serotypes in different genetic branches. MLVA generated 78 VNTR genotypes, PFGE generated 62 PFGE patterns, MLST generated 33 STs, In three molecular typing method, MLVA has the highest resolution.The prevalence of Salmonella in some areas of China had the dominant serotype S. enteritidis, but the emergence of rare serotypes was a major challenge to the detection, prevention and control to this pathogen. The strains of S. enteritidis were resistant to nalidixic acid, which was due to the most common gyrA gene mutations related to more serious and multiple drug resistance. 19 strains of S. enteritidis were found to be fluoroquinolone-resistant or third generation cephalosporins-resistant, which should be paid more attention in clinical, veterinary and animal husbandry departments. The ST11 was the dominant ST of 185 strains of Salmonella, and ST19 might be other ST's parents . The results of PFGE and MLVA demonstrated that the source of Salmonella isolated from diarrhea in the parts of China was of polyclonal, but some genotypes and clusters were of the dominant. Surveillance and epidemiological investigation should be enhanced towards the major epidemic strains, cloning and highly varied strains, which would benefit the prevention and control of the infectious diseases of Salmonella in China. |
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