Multilocus sequence typing of Cronobacter sakazakii isolated from low water activity foods

Multilocus sequence typing (MLST) is a method for the molecular characterization of microorganisms and was used to characterize the genus Cronobacter. This technique assigns a sequence type (ST) by comparing the nucleotide sequence of seven housekeeping genes of the bacterium. In addition, clonal complexes (CC) of the isolates are assigned according to the combination of the seven alleles of the genes. These data are available in an international open-access database and can be used for molecular studies around the globe. The aim of this study was to characterize C. sakazakii strains isolated from low water activity food with functional activity by MLST. Sixteen isolates were obtained from granola, chia (Salvia hispanica) and flaxseed (Linum usitatissimum) samples (seeds and flours). Sanger sequencing of seven housekeeping genes was performed in each isolate. Nucleotide sequences were analyzed in Bioedit software and PubMLST Cronobacter database, and ST and CC of the strains were assigned. High genetic diversity was observed; sixteen strains belonged to nine different STs and five CCs. ST 1 was the most prevalent, with 4 isolates, followed by ST40, ST184, ST308 and ST745, with two isolates in each ST. STs 233, 384, 587 and 618 had one isolate. ST1 and ST40 are highly documented sequence types in the database, with 466 and 75 records until September 2023, not including these isolates. The remaining STs are poorly isolated around the world. These results demonstrate the high diversity of C. sakazakii, which strains of the same sequence type are spread in distant areas, and this information is important in monitoring the emergence of new strains of this pathogen.