Abdelfattah Essam M, Ekong Pius S, Okello Emmanuel, Chamchoy Tapakorn, Karle Betsy M, Black Randi A, Sheedy David, ElAshmawy Wagdy R, Williams Deniece R, Califano Daniela, Tovar Luis Fernando Durán, Ongom Jonathan, Lehenbauer Terry W, Byrne Barbara A, Aly Sharif S
Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California, Davis, Tulare, CA, USA.
Department of Animal Hygiene, and Veterinary Management, Faculty of Veterinary Medicine, Benha University, Moshtohor, Qalyubia, Egypt.
PeerJ. 2021 Apr 20;9:e11108. doi: 10.7717/peerj.11108. eCollection 2021.
This study describes the occurrence of antimicrobial resistance (AMR) in commensal and spp. (ES) isolated from fecal samples of dairy cows and assesses the variation of AMR profiles across regions and seasons following the implementation of the Food and Agricultural Code (FAC) Sections 14400-14408 (formerly known as Senate Bill, SB 27) in California (CA).
The study was conducted on ten dairies distributed across CA's three milk sheds: Northern California (NCA), Northern San Joaquin Valley (NSJV), and the Greater Southern California (GSCA). On each study dairy, individual fecal samples were collected from two cohorts of lactating dairy cows during the fall/winter 2018 and spring/summer 2019 seasons. Each cohort comprised of 12 cows per dairy. The fecal samples were collected at enrollment before calving (close-up stage) and then monthly thereafter for four consecutive time points up to 120 days in milk. A total of 2,171 and 2,158 ES isolates were tested for antimicrobial susceptibility using the broth microdilution method against a select panel of antimicrobials.
The isolates showed high resistance to florfenicol (83.31% ± 0.80) and sulphadimethoxine (32.45%), while resistance to ampicillin (1.10% ± 0.21), ceftiofur (1.93% ± 0.29), danofloxacin (4.01% ± 0.42), enrofloxacin (3.31% ± 0.38), gentamicin (0.32% ± 0.12) and neomycin (1.61% ± 0.27) had low resistance proportions. The ES isolates were highly resistant to tildipirosin (50.18% ± 1.10), tilmicosin (48% ± 1.10), tiamulin (42%) and florfenicol (46% ± 1.10), but were minimally resistant to ampicillin (0.23%) and penicillin (0.20%). Multidrug resistance (MDR) (resistance to at least 1 drug in ≥3 antimicrobial classes) was observed in 14.14% of isolates and 39% of ES isolates. isolates recovered during winter showed higher MDR prevalence compared to summer isolates (20.33% vs. 8.04%). A higher prevalence of MDR was observed in NSJV (17.29%) and GSCA (15.34%) compared with NCA (10.10%).
Our findings showed high rates of AMR to several drugs that are not labeled for use in lactating dairy cattle 20 months of age or older. Conversely, very low resistance was observed for drugs labeled for use in adult dairy cows, such as cephalosporins and penicillin. Overall, our findings identified important differences in AMR by antimicrobial class, region and season.
本研究描述了从奶牛粪便样本中分离出的共生菌和特定葡萄球菌属（ES）中抗菌药物耐药性（AMR）的发生情况，并评估了在加利福尼亚州（CA）实施《食品与农业法典》（FAC）第14400 - 14408节（原称为参议院法案，SB 27）后，不同地区和季节AMR谱的变化。
该研究在分布于加利福尼亚州三个奶区的十个奶牛场进行：北加利福尼亚（NCA）、北圣华金谷（NSJV）和大南加利福尼亚（GSCA）。在每个研究奶牛场，于2018年秋冬和2019年春夏季节，从两组泌乳奶牛中采集个体粪便样本。每个奶牛场每组由12头奶牛组成。粪便样本在产犊前（围产期）入组时采集，此后每月采集一次，共连续采集四个时间点，直至产奶120天。使用肉汤微量稀释法，针对一组选定的抗菌药物，对总共2171株特定葡萄球菌属和2158株ES分离株进行了抗菌药物敏感性测试。
特定葡萄球菌属分离株对氟苯尼考（83.31% ± 0.80）和磺胺二甲氧嘧啶（32.45%）显示出高耐药性，而对氨苄西林（1.10% ± 0.21）、头孢噻呋（1.93% ± 0.29）、达氟沙星（4.01% ± 0.42）、恩诺沙星（3.31% ± 0.38）、庆大霉素（0.32% ± 0.12）和新霉素（1.61% ± 0.27）的耐药比例较低。ES分离株对替地罗新（50.18% ± 1.10）、替米考星（48% ± 1.10）、泰妙菌素（42%）和氟苯尼考（46% ± 1.10）高度耐药，但对氨苄西林（0.23%）和青霉素（0.20%）耐药性最低。在14.14%的特定葡萄球菌属分离株和39%的ES分离株中观察到多重耐药性（MDR，对至少3类抗菌药物中的至少1种耐药）。与夏季分离株相比，冬季分离出的特定葡萄球菌属分离株显示出更高的MDR流行率（20.33%对8.04%）。与北加利福尼亚（NCA，10.10%）相比，北圣华金谷（NSJV，17.29%）和大南加利福尼亚（GSCA，15.34%）的MDR流行率更高。
我们的研究结果表明，对几种未标明用于20月龄及以上泌乳奶牛的药物存在高AMR率。相反，对于标明用于成年奶牛的药物，如头孢菌素和青霉素，观察到的耐药性非常低。总体而言，我们的研究结果确定了按抗菌药物类别、地区和季节划分的AMR存在重要差异。
