Prevalence, biosecurity factor, and antimicrobial susceptibility analysis of Salmonella species isolated from commercial duck farms in Korea

Abstract

Duck meat consumption in South Korea has increased in recent years, but no standard about duck farm-specific biosecurity and hygiene guidelines have yet been established. We here investigated Salmonella contamination levels in duck farms to evaluate biosecurity and hygiene practices. We collected 1,116 environmental samples from 31 duck farms in Jeonnam Province, South Korea. The Salmonella-positive farm rate dramatically increased, from 22.6 to 71.0%, on introduction of ducklings. As the ducklings aged 4-6 wk, the positive rate slightly decreased to 64.5%. The Salmonella detection rate on each sampled surface, such as the feed pan (34.4%), wall (33.9%), litter (32.3%), and nipples (24.2%), was highest at 3 wk of age. The most frequently detected Salmonella serovars were Salmonella London (22.2%), Salmonella Albany (21.6%), Salmonella Bareilly (17.0%), and Salmonella Indiana (16.5%). Implementation of cleaning and disinfection procedures, rodent control, and metal house walls significantly lowered the prevalence of Salmonella (P < 0.001, P < 0.01, and P < 0.05, respectively). A high proportion of Salmonella isolates exhibited antimicrobial resistance: 100 and 62.9% exhibited resistance to erythromycin and nalidixic acid, respectively. Furthermore, a majority of S. Albany and all Salmonella Enteritidis isolates were multidrug resistant. These results indicate the level of Salmonella contamination in duck farm environments in Korea is high. Good biosecurity and hygiene practices are the most effective measures for controlling Salmonella contamination.

Keywords: Salmonella; antimicrobial resistance; biosecurity factor; duck; prevalence.

Figure 1

Salmonella isolation rate from various sampling sites at 3 time points. The fluctuation in the Salmonella isolation rate at each time point and sampling site is shown as the Salmonella positivity rate (A) and the number of positive samples (B).

Figure 2

Salmonella serotype frequency (n = 194). All Salmonella isolates were assigned to 10 serovars. The proportion (%) of each serovar is illustrated as a donut pie chart.

Figure 3

Antibiotic resistance rate of Salmonella isolates. The antibiotic resistance rate (%) of Salmonella isolates is presented as a bar graph. Abbreviations: A, ampicillin; Amc, amoxicillin/clavulanic acid; An, amikacin; Caz, ceftazidime; Cf, cephalothin; Cip, ciprofloxacin; Ctx, cefotaxime; Cxm, cefuroxime; Cz, cefazolin; E, erythromycin; Fep, cefepime; Fox, cefoxitin; G, gentamicin; K, kanamycin; N, nalidixic acid; S, streptomycin; Sxt, trimethoprim/sulfamethoxazole; T, tetracycline.

Figure 4

Antibiotic resistance profiles of Salmonella isolates. The antibiotic resistance profiles of Salmonella isolates are illustrated as a heat-map. The color of each cell represents the % of isolates resistant to the indicated antibiotic, as shown in the color legend on the right. Multidrug resistance (MDR∗) was defined as resistance to at least 3 antibiotic classes. Abbreviations: A, ampicillin; Amc, amoxicillin/clavulanic acid; An, amikacin; Caz, ceftazidime; Cf, cephalothin; Cip, ciprofloxacin; Ctx, cefotaxime; Cxm, cefuroxime; Cz, cefazolin; E, erythromycin; Fep, cefepime; Fox, cefoxitin; G, gentamicin; K, kanamycin; N, nalidixic acid; S, streptomycin; Sxt, trimethoprim/sulfamethoxazole; T, tetracycline.