Multilocus Sequence Typing of Bacillus cereus Isolates from the Processing Environment of Powdered Infant Formula

Multilocus sequence typing(MLST)was used to analyze the diversity and phylogenetic relationship of Bacillus cereus strains isolated from the processing environment of infant formula milk powder. The results indicated that 84 Bacillus cereus strains were divided into 24 sequence types(ST),including ST-24,ST-26,ST-32,ST-62,ST-144,ST-374,ST-999,ST-1119,ST-1243,ST-1284,ST-1333,ST-1334,ST-1335,ST-1336,ST-1337,ST-1338,ST-1339,ST-1340,ST-1341,ST-1342,ST-1343,ST-1344,ST-1345 and ST-1347. ST-999(22.62%),ST-1343(15.48%),ST-1335(7.14%)and ST-1345(7.14%)were the predominant STs. Three new alleles,pur-242,pyc-198,ilv-276 and 14 new STs,ST-1333,ST-1334,ST-1335,ST-1336,ST-1337,ST-1338,ST-1339,ST-1340,ST-1341,ST-1342,ST-1343,ST-1344,ST-1345 and ST-1347,were found in this study. Phylogenetic analysis revealed the diversity of Bacillus cereus group from the processing environment and showed that 24 STs were close to B. cereus,B. anthracis and B. thuringiensis,and they were far from the other eight species.