Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
Appl Environ Microbiol. 2013 Sep;79(17):5167-78. doi: 10.1128/AEM.01419-13. Epub 2013 Jun 21.
The aim of this longitudinal study was to determine and compare the prevalences and genotypic profiles of antimicrobial-resistant (AR) Salmonella isolates from pigs reared in antimicrobial-free (ABF) and conventional production systems at farm, at slaughter, and in their environment. We collected 2,889 pig fecal and 2,122 environmental (feed, water, soil, lagoon, truck, and floor swabs) samples from 10 conventional and eight ABF longitudinal cohorts at different stages of production (farrowing, nursery, finishing) and slaughter (postevisceration, postchill, and mesenteric lymph nodes [MLN]). In addition, we collected 1,363 carcass swabs and 205 lairage and truck samples at slaughter. A total of 1,090 Salmonella isolates were recovered from the samples; these were isolated with a significantly higher prevalence in conventionally reared pigs (4.0%; n = 66) and their environment (11.7%; n = 156) than in ABF pigs (0.2%; n = 2) and their environment (0.6%; n = 5) (P < 0.001). Salmonella was isolated from all stages at slaughter, including the postchill step, in the two production systems. Salmonella prevalence was significantly higher in MLN extracted from conventional carcasses than those extracted from ABF carcasses (P < 0.001). We identified a total of 24 different serotypes, with Salmonella enterica serovar Typhimurium, Salmonella enterica serovar Anatum, Salmonella enterica serovar Infantis, and Salmonella enterica serovar Derby being predominant. The highest frequencies of antimicrobial resistance (AR) were exhibited to tetracycline (71%), sulfisoxazole (42%), and streptomycin (17%). Multidrug resistance (resistance to ≥ 3 antimicrobials; MDR) was detected in 27% (n = 254) of the Salmonella isolates from the conventional system. Our study reports a low prevalence of Salmonella in both production systems in pigs on farms, while a higher prevalence was detected among the carcasses at slaughter. The dynamics of Salmonella prevalence in pigs and carcasses were reciprocated in the farm and slaughter environment, clearly indicating an exchange of this pathogen between the pigs and their surroundings. Furthermore, the phenotypic and genotypic fingerprint profile results underscore the potential role played by environmental factors in dissemination of AR Salmonella to pigs.
本纵向研究旨在确定和比较在无抗菌药物（ABF）和常规生产系统中饲养的猪的抗菌药物耐药（AR）沙门氏菌分离株的流行率和基因型谱，分别在农场、屠宰场及其环境中进行。我们从 10 个常规和 8 个 ABF 纵向群组的不同生产阶段（产仔、保育、育肥）和屠宰（内脏后、冷却后和肠系膜淋巴结 [MLN]）采集了 2889 份猪粪便和 2122 份环境（饲料、水、土壤、泻湖、卡车和地板拭子）样本。此外，我们还在屠宰时采集了 1363 份胴体拭子和 205 份待宰和卡车样本。从样本中总共回收了 1090 株沙门氏菌分离株；常规饲养猪（4.0%；n=66）及其环境（11.7%；n=156）中的分离株明显高于 ABF 猪（0.2%；n=2）及其环境（0.6%；n=5）（P<0.001）。沙门氏菌在两个生产系统的屠宰各个阶段均有分离，包括冷却后步骤。从常规胴体提取的 MLN 中分离出的沙门氏菌的流行率明显高于从 ABF 胴体提取的 MLN（P<0.001）。我们共鉴定了 24 种不同血清型，其中肠炎沙门氏菌血清型 Typhimurium、肠炎沙门氏菌血清型 Anatum、肠炎沙门氏菌血清型 Infantis 和肠炎沙门氏菌血清型 Derby 占优势。对四环素（71%）、磺胺二甲嘧啶（42%）和链霉素（17%）的耐药率最高。常规系统分离的沙门氏菌中有 27%（n=254）表现出多药耐药（对≥3 种抗菌药物耐药；MDR）。本研究报告了农场中猪的两种生产系统中沙门氏菌的低流行率，而屠宰场的胴体中检测到较高的流行率。猪和胴体中沙门氏菌流行率的动态在农场和屠宰环境中相互呼应，清楚地表明该病原体在猪及其周围环境之间的传播。此外，表型和基因型指纹图谱结果强调了环境因素在 AR 沙门氏菌传播给猪中的潜在作用。
