Cronobacter spp. in Commercial Powdered Infant Formula Collected From Nine Provinces in China: Prevalence, Genotype, Biofilm Formation, and Antibiotic Susceptibility

Abstract

The purpose of this study was to investigate the prevalence of <i>Cronobacter</i> spp. in commercial powdered infant formula (PIF) from nine provinces in China from March 2018 to September 2020, and to reveal the genotype, biofilm-forming ability, and antibiotic susceptibility of these isolates. A total of 27 <i>Cronobacter</i> strains, consisting of 22 <i>Cronobacter sakazakii</i> strains, 3 <i>Cronobacter malonaticus</i> strains, 1 <i>Cronobacter turicensis</i> strain, and 1 <i>Cronobacter dublinensis</i> strain, were isolated from 3,600 commercial PIF samples with a prevalence rate of 0.75%. Compared with the other 8 provinces, PIF from Shaanxi province had a higher prevalence rate (1.25%) of <i>Cronobacter</i> spp. These isolates were divided into 14 sequence types (STs), and 6 <i>Cronobacter</i> serotypes. The main <i>Cronobacter</i> STs were ST4, ST1, and ST64, and the dominant <i>Cronobacter</i> serotype was <i>C. sakazakii</i> serotype O2. Approximately 88.89% of <i>Cronobacter</i> isolates had a strong ability (OD₅₉₅ > 1) to form biofilms on tinplate, among which the strains with ST4 were more dominant. All isolates were susceptible to ampicillin-sulbactam, ceftriaxone, cefotaxime, sulfadiazine, sulfadoxine, trimethoprim-sulfamethoxazole, gentamicin, tetracycline, ciprofloxacin, and colistin, while 55.56 and 96.30% isolates were resistant to cephalothin and vancomycin, respectively. Taken together, our findings highlighted the contamination status and characterization of <i>Cronobacter</i> spp. in commercial PIF from nine provinces of China, and provided guidance for the effective prevention and control of this pathogen in the production of PIF.