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Aims: The objective of this study was to evaluate the cytotoxic activity of Cronobacter strains 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 of C. sakazakii (n = 29), C. dublinensis (n = 13), C. malonaticus (n = 6), C. turicensis (n = 6) and C. muytjensii (n = 2) was screened using Vero, RK13, Hep2c, NCTC clone 929 and BHK‐21 cell lines. Selected Cronobacter strains were assigned to C. sakazakii ST 21, C. turicensis ST 252, C. sakazakii ST 647, and three newly assigned STs: C. turicensis STs 738–740. The maximum death caused by non‐heat‐treated filtrates was 20·4, 86·2, 47·0 and 84·0%, in Vero, RK13, Hep2c and NCTC clone 929 cells, respectively. These were caused by C. sakazakii strains C291 and C292 (ST 494) which had been isolated during neonatal Cronobacter meningitis infection, and C110 (ST 395) isolated from flaxseed flour. Thermal treatment (100°C/20 min) significantly reduced the cytotoxicity activity in NCTC clone 929 and Vero cells (P ≤ 2 × 10−6), but not in RK13 (P = 0·12) and Hep2c (P = 0·85), indicating the cytotoxin(s) were probably proteinaceous. Electron microscopy revealed that cytotoxic compounds from C. sakazakii induced 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 that Cronobacter strains, especially C. sakazakii, could produce heat‐labile cytotoxic compounds in cell filtrates. Significance and Impact of the Study: This study providing insights into the pathogenesis of the Cronobacter genus. Cytotoxins were identified in excreted filtrates of C. sakazakii strains isolated from food and clinical specimens. The presence of Cronobacter strains that can produce cytotoxins in foods can be a potential threat to human health and highlight the need for high levels of hygiene. [ABSTRACT FROM AUTHOR]

Cronobacter infections of infants are commonly regarded as due to the ingestion of contaminated feed. The aim of this study was to determine the occurrence of Cronobacter, total coliforms and Escherichia coli in different brands of natural mineral waters as sold in 20 l returnable bottles in Rio de Janeiro, Brazil. The quantification of total coliforms and E. coli was performed by Most Probable Number. The detection of Cronobacter was as according to the ISO 22964:2017 and Bacteriological Analytical Manual/FDA. Molecular characterization of Cronobacter isolates was performed by real‐time PCR and by multi‐locus sequence typing. The antibiotic susceptibility profile was determined and biofilm production was evaluated in polystyrene microplates. Total coliforms and E. coli were detected in 13 (39·4%) and 2 (6·1%) of the 33 lots analysed respectively, and were considered unsatisfactory for human consumption according to Brazilian law. One (3·0%) lot showed contamination by C. malonaticus ST440 (Cronobacter MLST Databases accession no. ID 2646). The strain was susceptible to all (n = 13) antibiotics tested and only formed a weak biofilm. Since there is a high consumption of natural mineral waters by elderly and immunosuppressed persons, epidemiological surveillance agencies should be aware of the risk that these waters may represent for these groups. Significance and Impact of the Study: Cronobacter malonaticus ST440 was isolated from 20 l bottled drinking natural mineral waters sold in markets in Rio de Janeiro State, Brazil, and can be a potential threat to human health, particularly for neonates. Thirteen lots (39·4%) were unsatisfactory for human consumption due to the presence of total coliforms and/or Escherichia coli. Significance and Impact of the Study: Cronobacter malonaticus ST440 was isolated from 20 l bottled drinking natural mineral waters sold in markets in Rio de Janeiro State, Brazil, and can be a potential threat to human health, particularly for neonates. Thirteen lots (39·4%) were unsatisfactory for human consumption due to the presence of total coliforms and/or Escherichia coli. [ABSTRACT FROM AUTHOR]