Identification of drug resistance genes and drug resistance analysis of Salmonella in the duck farm environment of Zhanjiang, China

This study investigated and identified the distribution of drug resistance genes in feces, soil, and water of duck farms in Zhanjiang, China, and analyzed the drug resistance of Salmonella in the duck farm environment. PCR was used to assess the distribution of 25 resistance genes that are common in the duck farm environment. The isolation, biochemical identification, PCR identification of Salmonella, and the minimum inhibitory concentration (MIC) of 22 drugs were measured by micro-broth double dilution. In water, 25 drug resistance genes were detected, 24 in soil, and 23 in feces. Among them, the detection rate of the aadA1 gene in soil reached 100%, 13 drug resistance genes had a detection rate above 80%, and five species had a detection rate below 50%. In water, the detection rate of the floR and aadA1 genes was 100%, 12 drug resistance genes had a detection rate above 80%, and eight genes had a detection rate below 50%. In feces, nine drug resistance genes had a detection rate of 100%, nine genes had a detection rate above 80%, and one gene had a detection rate below 50%. In addition, 92 strains of Salmonella were isolated and identified, and their resistance rate to nine drugs was as high as 100%. All isolated Salmonella can tolerate at least nine drugs, 55.43% (51/92) of the strains can tolerate more than 16 drugs, and 4.35% (4/92) of the strains were resistant to up to 21 drugs. In conclusion, the present experiment suggested that drug resistance genes were ubiquitous in the duck farm environment in Zhanjiang and that these drug resistance genes may spread horizontally between feces, soil, and water. Moreover, drug resistance and multi-drug resistance were found for 92 isolated Salmonella strains from the duck farm environment. The government should consequently strengthen the regulation of antimicrobial drug use in duck farms.