Molecular Typing and Drug Resistance of Cronobacter spp. in Commercial Formula Rice Flour Products for Infants and Young Children
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Abstract:
To understand the contamination, molecular typing and drug resistance of Cronobacter spp. in formula rice flour products for infants and young children, the formula products from six different manufacturers and brands with different ingredients were collected in the markets of Guangxi city for isolation of Kronobacter, and fusA gene amplification, sequencing and MLST database comparative analysis. The molecular typing of the isolates was detected by pulsed field gel electrophoresis (PFGE), and the minimal inhibitory concentration (Minimal Inhibitory Concentrations, MICs) of the isolates against 8 common antibiotics was analyzed by the broth microdilution method. Two hundred sixty-eight samples of formula rice flour products were collected and 32 strains of Cronobacter spp. were isolated, with the detection rate as 11.94%. The strain identification results showed 32 isolated strains, including 22 strains of C. sakazakii, 6 strains of C. malonaticus, 3 strains of C. dublinensis and 1 strain of C. muytjensii. The contamination of the formula rice flour products with different ingredients differed significantly, with those ingredients fortified with Huailian or fruits and vegetable having the highest contamination rates (17.78% and 15.38%, respectively). PFGE analysis showed that 32 strains were divided into 32 different molecular types, with the similarity in the range of 61.20%~92.30%. All the isolates were sensitive to ciprofloxacin, gentamycin and cefotaxime, with some (6.25%~43.75%) being moderately sensitive to chloramphenicol,tetracycline, trimethoprim/sulfamethoxazole, cefoxitin and nalidixic acid, and two being resistant to chloramphenicol. The results showed a certain degree of contamination of Cronobacter spp. in the formula rice flour products, especially those fortified with nutrients. The source of contaminated Cronobacter spp. is broad, with some strains from the formula rice flour products being moderately sensitive or even resistant to some antibiotics, indicating that the sensitivity of Cronobacter spp. to antibiotics was on a weakening trend.
