Objective To understand the serological type, molecular type and drug resistance of Salmonella in Nanping, Fujian province, in recent years, and provide technical guidance for the tracing of foodborne diseases caused by Salmonella and the rational clinical use of antibiotics.
Methods The samples collected were tested according to “National standard for food safety microbiological test for Salmonella” (GB 4789.4－2016) and “Foodborne disease surveillance work manual”. Salmonella was identified by isolation and biochemical test. Pulsed field gel electrophoresis (PFGE) was conducted to analyze the strains’ genetic relation and micro-broth dilution method was used to test the drug resistance of the strains.
Results The 55 Salmonella strains belonged to 21 serotypes, with Salmonella Enterica and Salmonella Typhimurium predominating, accounting for 30.90% and 29.09%, respectively. Nineteen serotypes of Salmonella were isolated from food samples and 4 serotypes from foodborne disease cases. The PFGE bands of the strains were polymorphic with 13 band types. The band similarity ranged from 37.29% to 100.00%, with an overall similarity of 63.77%. Different PFGE band types could be found in the same serotype. Salmonella had high resistance to ampicillin, nalidixic acid and sulfisoxazole with resistance rates of 67.27%, 65.45% and 54.55%, respectively. They were sensitive to three generations of cephalosporins (ceftazidime, cefoxitin), gentamicin and azithromycin. A total of 30 different drug resistance profiles were found in 55 Salmonella strains, with ampicillin-nalidixic acid predominating (47.27%, 26/55), and the main serotypes included Salmonella Enterica and Salmonella Typhimurium.
Conclusion Salmonella serotypes in foods in Nanping were diverse. The strains isolated from foods and food-borne disease cases had high and diverse resistance rates to 15 antibiotics, and more than half of the strains were multi-drug resistant, to which close attention needs to be paid.
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