Abstract
With the increase in commercial pig farming, there is a simultaneous increase in the use of antibiotics for prophylaxis as well as therapeutics in China. In this study, we evaluated the prevalence and resistance diversity of salmonellae isolated from feces of asymptomatic, live and slaughtered pigs. We analyzed 1,732 pig fecal samples collected over 8 months, at Henan province of China. The salmonellae were isolated and identified by PCR. They were serotyped using commercial antisera and assayed for the MIC of 16 antibiotics by broth microdilution method. The average prevalence of Salmonella was 19.4% (95% CI: 17.6–21.4). Large farms (herd size ≥1,000) were found to have a higher prevalence as compared to the small- and medium-scale farms (p < 0.0001). The prevalence of salmonellae in samples collected from the farms [11.77% (95% CI: 10.1–13.6)] and from the slaughterhouse [45.23% (95% CI: 40.3–50.30)] was statistically different (p < 0.0001). Uncommon serovars of Salmonella such as Agama and common serovars such as Derby and Typhimurium were isolated. High resistance (>80%) was recorded toward ciprofloxacin (100%), tetracycline (99.4%), doxycycline (97%), sulfamethoxazole (85.8%), ampicillin (81.6%), and amoxicillin (80.4%). Multidrug resistance (MDR) to four, five, and seven classes of antibiotics was recorded to be approximately 25% in the most prevalent serovar like Derby. We conclude that the presence of alarmingly high resistance, toward the critical antibiotics such as fluoroquinolones and beta-lactams, in large swine farms in China, should draw public attention. These results highlight the need for continued antibiotic stewardship programs for judicious use of critical antibiotics in animal health as well as for producing safe pork.
Highlights
Fuelled by the rapid socio-economic growth and urbanization of China, the average intake of meat, especially pork, increased from 37.1 g/day in 1992 to 64.3 g/day per person in 2012 (He et al, 2016)
This distribution shows that our sampling frame covered a larger geographical area within Henan; we believe that these results are representative of the total population
A total of 337 samples (180 rectal samples collected at the slaughterhouse, FIGURE 1 | The distribution of the various minimum inhibitory concentration (MIC) levels of the Salmonella against 16 antibiotics
Summary
Fuelled by the rapid socio-economic growth and urbanization of China, the average intake of meat, especially pork, increased from 37.1 g/day in 1992 to 64.3 g/day per person in 2012 (He et al, 2016). The boost in pig production and consumption in China has indirectly increased the risk of foodborne zoonoses, including salmonellosis. Previous studies have shown that Salmonella is one of the leading foodborne pathogens on food commodities, meat in particular, and play a significant role for causing human diarrhea in China and elsewhere (Pan et al, 2018, 2019; Paudyal et al, 2018). Routine surveillance of potential hazards is essential to minimize the risks of disease epidemics as well as other potential threats such as pathogens and antibiotic resistance (AR). There are numerous studies about antibiotic-resistant salmonellae in pigs in China. The prevalence of AR reported in these studies varies greatly but generally is reported toward critical drugs, including quinolones and cefotaxime (Bai et al, 2016), tetracyclines (Jiu et al, 2017), quinolones, and cephalosporins (Jiang et al, 2014) or toward trimethoprim-sulfamethoxazole, ampicillin, and tetracycline (Su et al, 2018)
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