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Published on: February 13, 2015
Identification and characterization of Cronobacter strains isolated from powdered infant foods
A Gičová1, M Oriešková, L Oslanecová
1Public Health Authority of the Slovak Republic, Bratislava, Slovakia.
Insights
Cronobacter bacteria contamination in infant formula is low, with most strains identified as Cronobacter sakazakii. Multilocus sequence typing (MLST) proved effective for differentiating strains found in powdered infant foods.
Area of Science:
- Food Microbiology
- Bacterial Pathogenesis
- Public Health
Background:
- Cronobacter spp. (formerly Enterobacter sakazakii) cause rare but severe infections in vulnerable infants.
- Surveillance of Cronobacter in infant foods is crucial for public health protection.
Purpose of the Study:
- To characterize Cronobacter strains isolated from powdered infant foods in Slovakia.
- To evaluate the prevalence and genetic diversity of Cronobacter in these products.
Main Methods:
- Analysis of over 900 powdered infant food samples using ISO/TS 22964:2006.
- Confirmation of positive strains using quantitative PCR (qPCR).
- Biotyping and multilocus sequence typing (MLST) for strain characterization.
Main Results:
- Thirteen Cronobacter strains were isolated, with 12 identified as Cronobacter sakazakii and one as Cronobacter dublinensis.
- Five biogroups and ten MLST sequence types were identified among the isolates.
- A low positivity rate of 0.9% was observed, with evidence of multiple genetic subtypes within single food samples.
Conclusions:
- Cronobacter contamination in powdered infant foods is generally low and likely from diverse sources.
- MLST is a highly discriminative method for species identification and subtyping of Cronobacter.
- Epidemiological studies should analyze multiple isolates per sample due to potential genetic variability.
Unlabelled:
Cronobacter spp. (formerly Enterobacter sakazakii) is responsible for rare but fatal cases of infection in neonates and immunocompromised infants. The aim of our study was to characterize Cronobacter strains isolated from powdered infant foods in Public Health Authority of the Slovak Republic in 2009-2010. Powdered infant food products have been analysed using currently available standard method ISO/TS 22964: 2006 for the detection of Cronobacter spp. complemented with qPCR confirmation of positive strains. 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.
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 (0·9%) 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.
