Nelson Amy, Manandhar Sulochana, Ruzante Juliana, Gywali Arrogya, Dhakal Bimala, Dulal Santosh, Chaulagai Rupendra, Dixit Sameer M
RTI International, Research Triangle Park, NC USA.
Center for Molecular Dynamics Nepal (CMDN), Kathmandu, Nepal.
One Health Outlook. 2020 Oct 1;2:18. doi: 10.1186/s42522-020-00025-4. eCollection 2020.
Antimicrobial resistance (AMR) among bacterial pathogens is a fast-growing public health concern. AMR in non-typhoidal serovars (NTS) among food animals is of special concern as this may transmit resistant pathogens to humans during handling or consumption of animal products. In Nepal, the possibility of AMR serovars among food animals is an important area of research, particularly in light of the rapidly growing poultry industry, lack of surveillance and proper biosecurity measures; and paucity of relevant data. This study was conducted with the aim to estimate the burden of NTS and associated antimicrobial resistance in the environments of commercial poultry farms and the poultry carcasses in slaughter house. This study also intends to find some basic knowledge of the poultry farmers and their practice relating to the use of antimicrobials, vaccination and biosecurity measures.
Taking one health approach, a cross-sectional study was carried out in Chitwan district of Nepal between May and October 2017. Various environmental samples viz. farm litter, feed, water, poultry faeces, vehicle swabs, farm swabs from 12 broiler poultry farms and various sections of poultry carcasses from 21 slaughter houses were aseptically collected. These were microbiologically assessed for the presence of NTS serovars and their phenotypic and genotypic indicators of antimicrobial resistance. The poultry farmers were also briefly interviewed regarding their basic biosecurity related knowledge and practices before collecting the environmental samples.
Overall, of total environmental samples collected, 50% (31/62) tested positive for NTS serovars with environmental swabs (70%, 8/12) being the most culture positive sample types. Similarly, of 159 tissue samples collected from 24 carcasses, 79% (126/159) were culture positive for NTS serovars. Nearly 97% (153/157) of isolates showed antimicrobial resistance to tetracycline, while 11% (17/157) to ciprofloxacin and 5% (8/157) of isolates were resistant against azithromycin. All 157 isolates were sensitive to meropenem. In terms of AMR genes, tetA (83%, 131/157), QrnS (40%,64/157), mefA (8%, 13/157) and VIM-1 (0.6%, 1/157) were detected in the isolates that corresponded to the AMR to tetracycline, ciprofloxacin, azithromycin and meropenem respectively. In farmers interview, only 42% (5/12) of farmers mentioned of using basic biosecurity measures such as applying lime powder around the farm; 84% (10/12) of farmers reported vaccinating their birds with some vaccine and 75% (9/12) of farmers used various antimicrobials prophylactically such as neomycin (33%, 4/12), colistin (33%, 4/12), furaltadone (33%, 4/12), doxycycline (25%, 3/12), sulfatrimethoprim (25%, 3/12) and tylosin (16%, 2/12).
This study revealed gross contamination of farm environment and subsequent poultry meat samples with NTS serovars that were resistant to several clinically important antimicrobials. Further, inadequacy of even basic biosecurity measures and frequent prophylactic use of antimicrobials in the commercial poultry farms was observed. This reinforces an urgent need to raise awareness and implement proper biosecurity approaches from farms to slaughter houses in order to reduce the burden of NTS contamination of surrounding environment and poultry products. Further, high prevalence AMR among NTS isolates also underscores the need to strengthen the policies to prevent the rampant use of clinically used human antimicrobials in poultry sector.
细菌病原体中的抗菌药物耐药性（AMR）是一个快速增长的公共卫生问题。食用动物中非伤寒血清型（NTS）的AMR尤其令人担忧，因为这可能在处理或食用动物产品期间将耐药病原体传播给人类。在尼泊尔，食用动物中AMR血清型的可能性是一个重要的研究领域，特别是鉴于家禽业的迅速发展、缺乏监测和适当的生物安全措施，以及相关数据的匮乏。本研究旨在估计商业家禽养殖场环境和屠宰场家禽尸体中NTS及其相关抗菌药物耐药性的负担。本研究还旨在了解家禽养殖户关于抗菌药物使用、疫苗接种和生物安全措施的一些基本知识及其做法。
采用“同一健康”方法，于2017年5月至10月在尼泊尔奇旺地区开展了一项横断面研究。无菌采集了各种环境样本，即12个肉鸡养殖场的农场垫料、饲料、水、家禽粪便、车辆拭子、农场拭子，以及21个屠宰场不同部位的家禽尸体。对这些样本进行微生物学评估，以检测NTS血清型的存在及其抗菌药物耐药性的表型和基因型指标。在采集环境样本之前，还对家禽养殖户进行了简短访谈，了解他们与基本生物安全相关的知识和做法。
总体而言，在所采集的全部环境样本中，50%（31/62）的NTS血清型检测呈阳性，其中环境拭子（70%，8/12）是培养阳性率最高的样本类型。同样，从24具尸体采集的159份组织样本中，79%（126/159）的NTS血清型培养呈阳性。近97%（153/157）的分离株对四环素显示出抗菌药物耐药性，而对环丙沙星耐药的分离株占11%（17/157），对阿奇霉素耐药的分离株占5%（8/157）。所有157株分离株对美罗培南敏感。在AMR基因方面，在分别对四环素、环丙沙星、阿奇霉素和美罗培南耐药的分离株中检测到tetA（83%，131/157）、QrnS（40%，64/157）、mefA（8%，13/157）和VIM-1（0.6% , 1/157）。在养殖户访谈中，只有42%（5/12）的养殖户提到采取了基本生物安全措施，如在农场周围撒石灰粉；84%（10/12）的养殖户报告给家禽接种了某种疫苗，75%（9/12）的养殖户预防性使用了各种抗菌药物，如新霉素（33%，4/12）、黏菌素（33%，4/12）、呋喃他酮（33%，4/12）、强力霉素（25%，3/12）、磺胺甲恶唑（25%，3/12）和泰乐菌素（16%，2/12）。
本研究揭示了农场环境以及随后的家禽肉样本被对几种临床重要抗菌药物耐药的NTS血清型严重污染。此外，观察到商业家禽养殖场甚至基本生物安全措施不足，且频繁预防性使用抗菌药物。这强化了迫切需要提高认识，并从农场到屠宰场实施适当的生物安全措施，以减轻周围环境和家禽产品中NTS污染的负担。此外，NTS分离株中AMR的高流行率也凸显了加强政策以防止在家禽行业滥用临床使用的人类抗菌药物的必要性。
