Isolation, molecular and phenotypic characterization of Cronobacter spp. in ready-to-eat salads and foods from Japanese cuisine commercialized in Brazil

Abstract

The aim of this study was to detect Cronobacter from 30 samples of ready-to-eat (RTE) salads and 30 foods from Japanese cuisine as commercially available in Brazil. The detection of Cronobacter was as according to the ISO standard 22964:2017. The isolates were phenotypically characterized by Vitek 2.0 and the antibiotic susceptibility profile was determined using the standardized agar disc diffusion method. Molecular characterization was accomplished by real-time PCR targeting dnaG gene, multiplex-PCR targeting cgcA gene, and fusA allele sequencing. Twenty-seven samples (45.0%) contained Cronobacter, 14 (23.3%) samples of foods from Japanese cuisine and 13 (21.7%) samples of RTE salads. Twenty-nine unique Cronobacter isolates were selected from the 27 positive samples and were identified as C. sakazakii (n = 18), C. malonaticus (n = 8), and C. dublinensis (n = 3). A high genetic diversity was observed, with 29 Cronobacter strains being assigned to 11 different fusA alleles, a ratio of 2.6 strains by fusA allele was found. The cgcA multiplex-PCR failed to identify many of the Cronobacter isolates at the species level. Four (13.8%) Cronobacter isolates were resistant to one or more antibiotics tested (n = 12). The presence of Cronobacter in RTE foods could be a potential threat to human health and highlights the need for high levels of hygiene, particularly when preparing food for elderly, immunosuppressed persons or adults with prior underlying pathology. Epidemiological surveillance agencies should be aware of the risk that these RTE foods may represent, for these groups.