Abstract: In the present study, we analyzed the genetic diversity of Bacillus cereus isolated from the production line of goat milk-based infant formula, and we compared their gene sequences with published sequences of isolates from milk products, aiming to detect the specific sequence types of the isolates in this study, which will provide useful information for further research on pathogenesis, prevalence, traceability, prevention and control. A total of 350 B. cereus isolates were obtained in this study, which had been subtyped to 12 clusters (42 isolates) by random amplification of polymorphic DNA (RAPD). The multiple locus sequence typing (MLST) profiles for 42 isolates were conducted based on the house-keeping genes glpF, gmk, ilvD, pta, pur, pycA, and tpi. The clonal complexes for these isolates were analyzed by the online Burst (n-4). The results showed that 42 isolates were detected and classified into 7 sequence types: ST-770 (4.8%, 2/42), ST-1000 (71.4%, 30/42), ST-1084 (9.5%, 4/42), ST-1348 (2.4%, 1/42), ST-1349 (2.4%, 1/42), ST-1350 (2.4%, 1/42) and ST-1351 (7.1%, 3/42). Clonal complexes 205, 142, 23, and two groups (ST-770 and ST-1351) were detected as well as two singletons (3L33 with ST-1349 and 3L47 with ST-1350). Four novel STs (ST-1348, ST-1349, ST-1350, and ST-1351) and four novel alleles (glp-253, glp-254, ilv-277 and pyc-199) were found.

Key words: Bacillus cereus, goat milk-based infant formula, multiple locus sequence typing (MLST), sequence type (ST)