Identification and Characterization of Cronobacter Strains Isolated from Environmental Samples.

As an emerging food-borne pathogen, Cronobacter species are ubiquitous in the food and environment. In order to know the characteristics of Cronobacter spp. from the environment, we isolated Cronobacter spp. from soil and water, and then studied the molecular typing and antibiotic resistance characteristics of these isolates. In 2016, 141 soil and water samples were collected from farms and Riverside Park in Beijing. Isolates were identified by real-time PCR, 16s rRNA sequencing, and whole-genome sequencing. Molecular subtyping of these isolates was characterized by pulsed-field gel electrophoresis, multilocus sequence typing (MLST), and antibiotic susceptibility tests. Cronobacter species were classified based on fusA sequencing. Twenty-two samples (15.60%) contained Cronobacter spp., and four species were detected, i.e., C. dubliniensis (n = 10), C. sakazakii (n = 6), C. turicensis (n = 4), and C. malonaticus (n = 2). For MLST, 12 types (ST519-ST525, ST533-ST537) were newly identified, indicating high diversity. Most isolates (68.18%) showed resistance to cefazolin. Siccibacter turicensis and Cronobacter both with blue-green colonies on selective media should be respectively identified. Apparently, major Cronobacter species in soil and water samples differed from those in food. Molecular subtyping showed that the environment could not be excluded as a source of Cronobacter infection. The resistance to cefazolin of most isolates indicated natural resistance.