Epidemic Characteristics and Resistance of Salmonella Isolates from A Dairy in Chengdu City
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Abstract:
Samples were collected from a large dairy farm in Chengdu city to study the epidemic characteristics and resistance of Salmonella isolates. Strains of Salmonella were isolated, identified, and seroptyped. Drug susceptibility, virulence, drug resistance, and disinfectant resistance genes were tested. Minimum inhibitory concentrations (MIC) to commonly used disinfectants and effective sterilization temperatures were also determined. A total of 700 samples were collected; 16 strains of Salmonella and four serotypes were isolated (six strains of Salmonella enteritidis, six strains of S. paratyphoid A, three strains of S. typhimurium, and one strain of S. infantis). All strains were sensitive to ceftazidime, levofloxacin, and imipenem. Twenty four drug resistance genes were detected, and the highest detection rate was noted for tetB (93.75%), followed by that of aaC4 (75.00%). There were 12 virulence genes detected, and the highest detection rate was observed for sipA (62.50%); qacEΔ1 showed the highest detection rate of the disinfectant genes (56.25%). The MIC values of 16 Salmonella strains against nine different disinfectants were generally one to three times higher than the recommended concentrations from the manufacturers. The 100% sterilization temperatures of the strains in whole and skim milk were 64.00 ℃ and 63.50 ℃, respectively. The isolated strains of Salmonella on this dairy farm were resistant to some disinfectants, but could be effectively controlled at 64.00 ℃. It is recommended that dairy farms strengthen the prevention and control of Salmonella and the use of disinfectants should be standardized. Key words:
