Serotype and drug resistance of Salmonella isolates of human and food sources in Fujian province, 1984–2016

ObjectiveTo study the drug resistance characteristics and serotype spectrum of Salmonella isolates from human and food sources in Fujian province.

MethodsBy using the methods and materials of Salmonella serotyping recommend by WHO, a retrospective serotype identification was conducted for the Salmonella strains of clinical, health carrier and food sources in Fujian from 1984 to 2016. The resistance of the strains to 10 antibiotics was tested with disk diffusion method. Chi-square test was used to analyze categorical variables.

ResultsA total of 1 406 Salmonella strains of human and food sources were re-identified by the reference laboratory, including 17 serogroups in 16 clinical isolates, 9 isolates from healthy carriers and 8 food source isolates. S. Typhi, Paratyphi A and Choleraesuis were identified as invasive serotypes of infection. In addition to S. Typhi, Paratyphi A and B, the non-typhoidal Salmonella strains were confirmed to have 65 serotypes in 49 clinical isolates, 46 isolates from healthy carriers and 27 food source isolates. The top five serotypes of non-typhoidal Salmonella were S. Typhimurium, S. Enteritidis, S. Derby, S. Stanley and S. Weltevreden, while the predominant serotypes of clinical isolates were S. Typhimurium, S. Enteritidis, S. Stanley, S. Choleraesuis and S. Derby. Five human serotypes and 3 food source serotypes were isolated for the first time in China. The distribution of serogroups, serotypes and antibiotic resistance spectrum of Salmonella spp. of the isolates from healthy carriers were similar to those of food source isolates, and their multidrug resistance (MDR) rates were significantly lower than that of Salmonella spp. of clinical isolates (χ²＝191.675, P＜0.001). Resistant rates to ciprofloxacin and the third-generation cephalosporin in Salmonella from patients were less than 10%, but MDR rate was high (51.00%). S. Paratyphi A and S. Typhimurium, S. Enteritidis were the representatives of isolates with higher level drug resistance or MDR in S. Typhi/Paratyphi and non-typhoidal Salmonella, respectively.

ConclusionSalmonellae of human source had a wider variety of biological diversity compared with Salmonellae of food source in Fujian, and the antibiotic resistance rate of Salmonellae of human source was higher than that of Salmonellae of food source. It is suggested to strengthen the prevention and control of the outbreak of invasive infectious diseases and behavioral and ecological infectious diseases.