Detection, antibiotic susceptibility and biofilm formation of Cronobacter spp. from various foods in Korea

Cronobacter spp. are emerging food-borne pathogens and can lead to serious developmental aftereffects and death in infants. Foods contaminated with Cronobacter spp. may pose a high risk to infants or weak individuals. In Korea, 353 various types of foods were examined for the prevalence of Cronobacter spp. Isolates were confirmed by targeting the ompA gene and the tRNA-23s rRNA intergenic region using VITEK and PCR. The results of a 16S rDNA gene sequence analysis showed 58 isolates of Cronobacter sakazakii, 2 isolates of Cronobacter muytjensii, and 6 isolates of Cronobacter dublinensis. The isolates were found to be susceptible to 4 antibiotics on performing agar disk diffusion. C. sakazakii isolates were susceptible to ampicillin(98.2%), tetracycline(98.2%), and chloramphenicol(96.6%) but resistant to streptomycin(12.0%). C. muytjensii and C. dublinensis isolates were susceptible to ampicillin, tetracycline and chloramphenicol. Biofilm formation by microtiter plate assay varied greatly between different Cronobacter spp. isolates. Cronobacter spp. isolates were frequently detected in various foods, and the most prevalent strain was C. sakazakii. Cronobacter spp. isolates did not seem to differ in terms of antibiotic susceptibility and biofilm formation.