Significance and Impact of the study: This study characterized Cronobacter strains isolated from powdered infant formulae and weaning foods by biotyping and multilocus sequence typing. The later method was shown to be more discriminative and suitable for both species identification and subtyping. Low level (0Á9%) of Cronobacter positivity was observed in 916 samples. Multiple sequence types were observed among strains isolated from the same food product. This highlights that multiple isolates from each single sample should be analysed in epidemiological studies, since more than one genetic subtype may be present. Thirteen Cronobacter strains were isolated from more than 900 powdered infant formulae, milk-based and cereal-based powdered weaning food products. The strains were assigned to five biogroups and ten multilocus sequence typing (MLST) sequence types. In total, twelve strains were identified as Cronobacter sakazakii and one strain as Cronobacter dublinensis. Multiple strains originated from parallel isolation were obtained in three samples and the variability between strains from the same food was observed twice. The results are in agreement with the hypothesis that the Cronobacter contamination detected in infant powdered food is low and originating in various accidental sources.
Cronobacter spp. are opportunistic pathogenic bacteria that are responsible for severe infections in neonates. Powdered infant formula was confirmed to be the source in some cases. Bacteriophages offer a safe means for eliminating this pathogen. In the present study, we investigated the growth parameters and genome organization of a new bacteriophage, Dev2, isolated from sewage. The Dev2 phage contains DNA with a length of 39 kb and belongs to the T7 branch of the subfamily Autographivirinae, with the highest degree of identity to the phage K1F. The host specificity of Dev2 is limited to C. turicensis strains of the CT O:1 serotype. With a lower efficiency, this phage also infects some Salmonella and E. coli strains. The Dev2 phage can inactivate sensitive Cronobacter strains in reconstituted milk formula. The results obtained in this study are an important prerequisite for application of Dev2 in food control.
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