[Technic study on multilocus sequence typing system of Salmonella enteritidis].
OBJECTIVE
To characterize different Salmonella enterica Enteritidis isolates through multilocus sequence typing (MLST) system, a molecular epidemiologic analysis method was established.


METHODS
Internal fragments of six housekeeping genes, thrA, purE, sucA, aroC, hemD and dnaN and a unique gene of S. Enteritidis were amplified and sequenced to develop the MLST method. Eighteen S. Enteritidis food isolates with unique serotype were studied and the data were analyzed by the Sequener 4.0 software. The genetic relationship of the isolates was estimated, and the DNA sequence diversity was also studied between S. Enteritidis and S. Typhimurium LT2.


RESULTS
A poor DNA sequence diversity among S. Enteritidis 50041 and 18 S. Enteritidis isolates in all six housekeeping genes were found. The number of variable sites per gene ranged from 1 to 6 nucleotides between S. Typhimurium LT2 and S. Enteritidis. Furthermore, S. Enteritidis 50041 and 18 S. Enteritidis isolates contained a mutation at C182T in SdfI in comparison with to the sequence in the GenBank. Our study showed that the MLST had poor discrimination power among S. Enteritidis isolates.


CONCLUSIONS
The MLST techniques should only be used to differentiate Salmonella isolates with different serotypes, it could not study the molecular epidemiological relationship of the isolates with the same serotype.
Li
Yanjun
Y
Institute of Nutrition and Food Safety, China CDC, Beijing 100021, China.
Ji
Rong
R
Wang
Yuping
Y
Jiang
Tao
T
D005516:Food Microbiology; D005798:Genes, Bacterial; D012477:Salmonella enteritidis / Q000145:classification* / Q000235:genetics*; D017422:Sequence Analysis, DNA / Q000379:methods; D012703:Serotyping / Q000379:methods*