Prevalence and Antimicrobial Susceptibility of Foodborne Pathogens from Raw Livestock Meat in China, 2021

The rising prevalence of pathogenic bacteria in livestock meat poses a growing public health concern in China. The determination of antimicrobial resistance (AMR) is critical for the clinical management of foodborne infections stemming from livestock meat consumption. This study aimed to assess the prevalence of pathogenic bacteria in livestock meat (pork, beef, and mutton) sampled in China in 2021 and to identify the most common AMR patterns among the isolated pathogens. A total of 2515 raw livestock meat samples were collected across 15 provinces in China during 2021. Pathogen detection, including <i>Listeria monocytogenes</i>, <i>Salmonella</i>, and diarrheagenic <i>Escherichia coli</i> (DEC), followed China's national food safety standards. All <i>Salmonella</i> isolates underwent serotyping via slide agglutination. Antimicrobial susceptibility of <i>Salmonella</i> and DEC isolates was assessed using the broth dilution method. The detection rates for <i>L. monocytogenes</i>, <i>Salmonella</i>, and DEC in raw livestock meat were 9.06% (228/2, 515), 10.54% (265/2, 515), and 6.16% (155/2, 515), respectively. Pork showed the highest contamination rates for <i>Salmonella</i> and DEC, with prevalence rates of 17.60% (214/1, 216, χ2 = 124.62, <i>p</i> < 0.05) and 7.89% (96/1, 216, χ2 = 14.466, <i>p</i> < 0.05), respectively. <i>L. monocytogenes</i> contamination was notably higher in chilled (14.43%, 84/582) and frozen (12.39%, 55/444) meat than in fresh meat (χ2 = 43.510, <i>p</i> < 0.05). In contrast, <i>Salmonella</i> (12.09%, 180/1489, χ2 = 15.173, <i>p</i> < 0.05) and DEC (7.25%, 108/1489, χ2 = 12.275, <i>p</i> < 0.05) were more prevalent in fresh meat than in chilled or frozen samples. The predominant <i>Salmonella</i> serotypes identified were <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Typhimurium, followed by <i>Salmonella enterica</i> serovar Derby, <i>Salmonella enterica</i> serovar Rissen, <i>Salmonella enterica</i> serovar London, and <i>Salmonella enterica</i> serotype Enteritidis. Enteroaggregative <i>E. coli</i> was the most frequent pathotype among DEC (84.7%, 133/157), followed by enteropathogenic <i>E. coli</i> (8.3%, 13/157) and enterohemorrhagic <i>E. coli</i> (5.1%, 8/157). Among the 14 tested antimicrobial agents, <i>Salmonella</i> isolates demonstrated an overall resistance rate of 87.50%, while DEC exhibited a resistance rate of 84.70%. Ampicillin and tetracycline showed the highest resistance rates in both pathogens. Multi-drug resistance (MDR) was observed in 67.53% of <i>Salmonella</i> isolates (183 isolates) and 57.96% of DEC isolates (91 isolates). This study highlights the significant contamination of retail raw livestock meat in China by <i>L. monocytogenes</i>, <i>Salmonella</i>, and DEC. The high resistance of MDR in both pathogens poses serious public health risks. Chinese food safety and veterinary authorities should implement stricter measures to control pathogen contamination and regulate the use of antimicrobials in livestock to mitigate these risks.