| In order to understand the contamination of cronobacter in food and raw materials,214 samples were detected.Enterobacter sakazakii chromogenic agar,fusA gene sequence analysis and matrix assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS)were used for identification.It showed that the detection rate of positive samples(16 / 214)was 7.5%.17 isolates were isolated from oats,flour,starch,unsterilized egg salad,vermicelli and spices.Isolates were identified as cronobacter by mass spectrometry.Fus A housekeeping gene analysis identified isolates to species level,including 15 strains of C.sakazakii,1 strain of C.malonaticus,1 strain of C.dublinensis.Multilocus sequence typing of 13 isolates had been completed,and 4 isolates had not been completed due to individual genes.The typing results showed that there were4 strains of ST4,2 strains of ST475,each ST of ST12/ST17/ST163/ST438/ST40/ST226 and ST733 had 1 strain.In Pub MLST database,ST4 and ST12 have clear pathogenicity,while ST40 and ST17 have clinical isolates but no pathogenic information.Therefore,7 isolates in this study may have potential pathogenicity.Pub MLST database analysis showed that the number of Cronobacter isolates in China was relatively large,accounting for 39.3%.The isolates were mainly food isolates,with few clinical strains.Its clear pathogenic information was quite different from that of European and American countries.Only a few chinese strains like ST256,ST60 and ST83 had been associated with neonatal meningitis.The pathogenic strains in European and American were mainly distributed in ST4,ST1,ST12 and ST7.Twelve antibiotics were used to determine the susceptibility of the isolates.All strains were resistant to vancomycin,while 4/17 strains to amoxicillin,ampicillin and sulfamethoxazole,3/17 to cefazolin,2/17 to tetracycline,1/17 to chloramphenicol and kanamycin.17 isolates could survive at 50??65?,but there were some differences. |
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