Occurrence, Molecular Characterization, and Antibiotic Resistance of Cronobacter sakazakii in Goat Milk-Based Infant Formula from Shaanxi Province, China.

This study aimed to investigate the prevalence of Cronobacter sakazakii in goat milk-based infant formula (GIF) collected from Shaanxi Province, China, and reveal the molecular characterization and antibiotic resistance profile of these isolates. A total of 750 GIF samples were collected from the retail markets in 5 cities in Shaanxi Province from February 2019 to February 2021. Molecular characterization was investigated using multilocus sequence typing and O-antigen serotyping. Antibiotic resistance of C. sakazakii isolates was assessed using antimicrobial susceptibility testing. Thirty-two strains of C. sakazakii were isolated from GIF samples with a prevalence rate of 4.27% and were divided into 16 sequence types (STs); among them, ST4 (6/32, 18.75%) and ST21 (5/32, 15.63%) were dominant. Five C. sakazakii serotypes (O2, O1, O7, O4, and O3) were detected, and C. sakazakii serotype O2 (15/32, 46.88%) was the main. Of the 21 antimicrobials, isolates showed higher resistance against cephalothin (87.5%), amoxicillin (25%), azithromycin (18.75%), oxytetracycline (18.75%), ampicillin (12.5%), and streptomycin (12.5%). In addition, three isolates were found to be resistant to three antimicrobials. These findings revealed the potential epidemiological risk and characterization of C. sakazakii in GIF from Shaanxi Province, China, and provided reference data for the effective prevention and control of C. sakazakii in powdered infant formula.

Antibacterial Effect of Chrysanthemum Buds' Crude Extract Against Salmonella Typhimurium and Potential Application in Cooked Chicken.

The objective of this study was to clarify the antibacterial activity and mechanism of Chrysanthemum buds' crude extract (CBCE) against Salmonella Typhimurium, and explore the potential application in cooked chicken. The zone of inhibition (ZI), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were used to assess the in vitro antibacterial activity of CBCE against Salmonella Typhimurium. The antibacterial mechanism was elucidated by revealing the changes in intracellular adenosine 5'-triphosphate (ATP) concentration, membrane potential, content of biomacromolecule, and cell morphology. Furthermore, the effect of CBCE on the counts of Salmonella Typhimurium and color of cooked chicken during storage was studied. The results showed that the ZI, MIC, and MBC of CBCE against Salmonella Typhimurium were 12.9 ± 0.53-13.6 ± 0.14 mm, 40, and 80 mg/mL, respectively. In the process of inhibiting Salmonella Typhimurium by CBCE, the reduction of intracellular ATP concentration, cell membrane depolarization, leakage of protein and nucleic acid, and destruction of cell morphology were observed. Moreover, after treatments with CBCE, the growth of Salmonella Typhimurium in cooked chicken was significantly inhibited (p < 0.05) compared with the control group. No significant differences (p > 0.05) in lightness (L*), redness (a*), and yellowness (b*) values of cooked chicken were found between untreated and treated samples, as well as the color of cooked chicken treated with CBCE did not change significantly (p > 0.05) during the six days of storage. Overall, our findings suggested that CBCE exhibited the antibacterial effect against Salmonella Typhimurium, and had the potential to be used as a natural food preservative for the control of Salmonella Typhimurium in chicken products.