Cytotoxicity profile ofCronobacterspecies isolated from food and clinical specimens in Brazil

Aims The objective of this study was to evaluate the cytotoxic activity ofCronobacterstrains isolated from foods (n = 50) and clinical samples (n = 6) in Brazil and genotype selected strains (n = 18) using multi-locus sequence typing (MLST) Methods and Results The cytotoxic activity ofC. sakazakii(n = 29),C. dublinensis(n = 13),C. malonaticus(n = 6),C. turicensis(n = 6) andC. muytjensii(n = 2) was screened using Vero, RK13, Hep2c, NCTC clone 929 and BHK-21 cell lines. SelectedCronobacterstrains were assigned toC. sakazakiiST 21,C. turicensisST 252,C. sakazakiiST 647, and three newly assigned STs:C. turicensisSTs 738-740. The maximum death caused by non-heat-treated filtrates was 20 center dot 4, 86 center dot 2, 47 center dot 0 and 84 center dot 0%, in Vero, RK13, Hep2c and NCTC clone 929 cells, respectively. These were caused byC. sakazakiistrains C291 and C292 (ST 494) which had been isolated during neonatalCronobactermeningitis infection, and C110 (ST 395) isolated from flaxseed flour. Thermal treatment (100 degrees C/20 min) significantly reduced the cytotoxicity activity in NCTC clone 929 and Vero cells (P <= 2 x 10(-6)), but not in RK13 (P = 0 center dot 12) and Hep2c (P = 0 center dot 85), indicating the cytotoxin(s) were probably proteinaceous. Electron microscopy revealed that cytotoxic compounds fromC. sakazakiiinduced several cell death characteristics, including loss of cell-cell contact, microvilli reduction and cellular lysis. Autophagic vacuoles and mitochondrial damage were the most common ultrastructural features observed. Conclusions: It was concluded thatCronobacterstrains, especiallyC. sakazakii, could produce heat-labile cytotoxic compounds in cell filtrates. Significance and Impact of the Study This study providing insights into the pathogenesis of theCronobactergenus. Cytotoxins were identified in excreted filtrates ofC. sakazakiistrains isolated from food and clinical specimens. The presence ofCronobacterstrains that can produce cytotoxins in foods can be a potential threat to human health and highlight the need for high levels of hygiene.

Automated summary

This study evaluated the cytotoxic activity of Cronobacter strains isolated from foods and clinical samples in Brazil, and identified some strains capable of producing cytotoxins.