Multilocus Sequence Typing Applied In Infant Formula Enterobacter Sakazakii Identification And Traceability Application Sources

Enterobacter sakazakii (E.sakazakii) is an independent and new genus of enterobacterium,namely Cronohactergen.nov, which had the characteristics of acid-resistant,resistant to dry and osmotic pressure,hence,it is liable and widespread to survival in the food and environment. If infected with the bacterium,people were prone to get diseases such as meningitis,enterocolitis and sepsis,especially the newborn population in the low immunity,its mortality rate above 50%,which may be related to its antibiotic resistance and drug-resistance and increase the difficulty of the clinical treatment. Currently,microbiologists were unknown about its original source of contamination,but the death case reports suggested the main infection channel about E.sakazakii was closely related to infant formula. Therefore,studying molecular classification,identification and traceability of E.sakazakii is a great significance for infant formula factories to monitor,warn early and control of E.sakazakii.E.sakazakii can’t be identified to species by traditional molecular classification methods such as random amplified polymorphic DNA markers (RAPD),and its less recognizable and repeatability,even easily confused. Multiple-locus sequence typing (MLST),is a high efficient and fast classification method which developed rapidly in recent years,can clearly distinguish the difference of each gene of E.sakazakii. This research use the plate method to detect and separate E.sakazakii and use API20E to identify Esakazakiifrom 12000 infant formulas,in order to know its pollution situation in the production environment of infant formulas. Results found that 61 samples were detected by E.sakazakii among the 12000 samples. To isolate 24 strains from the representative infant formulas,and to identify E.sakazakii by API20E reagent,and to classify them by the MLST method,and found them including 22 E.sakazakii strains of ST classification:19 strains were C.sakazakii,2 strains were C.turicensis and 1 strains was C.dublinensis. It can be clearly identify the evolutionary relationships and genetic relationship by building the evolutionary tree,and to determine well the type and trace its source.