Prevalence and Molecular and Antimicrobial Characteristics of Cronobacter spp. Isolated From Raw Vegetables in China

Abstract

Cronobacter spp. is a foodborne pathogen that causes life-threatening and invasive diseases, such as necrotizing enterocolitis, meningitis, and sepsis. In this study, we aimed to investigate the prevalence, molecular characteristics and antimicrobial resistance of Cronobacter spp. in raw vegetables marketed in China. Based on dietary habits in China, 403 raw vegetables that could be eaten without additional cooking were collected. Of the 403 samples tested, 122 (30.27%) were positive for Cronobacter spp., and the contamination levels exceeded 110 most probable number (MPN)/g for 16.39% (20/122) of the samples. Coriander samples had the highest contamination rate of 52.81%, and the MPN values of 19.15% of positive coriander samples exceeded 100 MPN/g. Eleven serotypes were identified among 171 isolates, with Cronobacter sakazakii serogroup O1 (41 isolates) being the dominant serotype. Molecular characterization indicated that there was quite high genetic diversity in Cronobacter spp., and multilocus sequence typing analyses yielded 106 sequence types (STs), 55 of which were newly identified. Notably, the most prevalent ST (eight isolates) was C. malonaticus ST60, which appeared in a recent clinical infectious disease study in China. Five C. sakazakii ST4, seven C. malonaticus ST7, and three C. sakazakii ST8 confirmed as pathogenic STs in other countries were also detected in this study. Furthermore, all isolates were susceptible to amikacin, amoxicillin-clavulanic, cefepime, ciprofloxacin, and imipenem, but some isolates exhibited a high ratio of resistance to cephalothin (59.65%). In this study, the high contamination rate and the detection of pathogenic and new STs in raw vegetables indicated potential hazards to customers. To the best of our knowledge, this is the first report to provide valuable information on the contamination status of Cronobacter spp. in vegetables that can be eaten raw in China.

Prevalence, Virulence Feature, Antibiotic Resistance and MLST Typing of Bacillus cereus Isolated From Retail Aquatic Products in China

“…According to the report of Ling et al (2018), we also divided China into seven regions ( Supplementary Figure S1). Of the 147 STs, 11 STs (7.48%) were detected in three or more regions.…”

Prevalence, Antibiotic Susceptibility, and Molecular Characterization of Cronobacter spp. Isolated From Edible Mushrooms in China

“…Quantitative detection was conducted by an isolation and enrichment method according to the National Food Safety Standard of China Food microbiological examination: Enterobacter sakazakii (GB 4789.40-2010; National Standard of the People's Republic of China, 2010) for powdered infant formula (PIF), as described previously, with some modifications (Xu et al, 2015; Ling et al, 2018). We modified the method based on the analysis of PIF to mushroom for Cronobacter .…”

“…Neighbor-joining trees were constructed based on the seven MLST loci (concatenated length of 3,036 bp) of the Cronobacter spp. using MEGA (version 5.05) as previous study (Ling et al, 2018).…”

“…isolates were determined by antimicrobial dilution and disk susceptibility testing using Mueller-Hinton agar (Huankai, Guangzhou, China), following the protocols of the Clinical and Laboratory Standards Institute (Jorgensen, 2015). Sixteen antimicrobials (AMs) (Oxoid, Hampshire, United Kingdom) recommended for Enterobacteriaceae were tested, as previously reported (Ling et al, 2018).…”

Occurrence of Cronobacter Spp. in Ready‐to‐Eat Vegetable Products, Frozen Vegetables, and Sprouts Examined Using Cultivation and Real‐Time PCR Methods

“…Recently, vegetables were also identified as one of the most common sources of Cronobacter spp. contamination in China (Ling et al., ). In that study, Cronobacter spp.…”