Department of Pathobiology, Science and Research Branch, Islamic Azad University, Tehran, Iran.
Arch Razi Inst. 2023 Aug 31;78(4):1247-1255. doi: 10.32592/ARI.2023.78.4.1247. eCollection 2023 Aug.
(MG) is a contagious avian pathogen that causes financial losses to the poultry industry. Isolation of the pathogen is difficult and time-consuming, and therefore, far from a routine method. Serological testing methods to detect antibodies resistant to MG are widely used in routine diagnosis. Tylosin is a class of macrolide antibiotics tremendously administered in veterinary medicine for the treatment of mycoplasmosis and prophylaxis. This study aimed to detect MG by immunoassay testing, culture, and polymerase chain reaction (PCR) in commercial poultry farms and to investigate the tylosin susceptibility of the isolates. To verify the presence of antibodies resistant to MG, 750 blood samples were randomly collected from 38 broiler farms from 2019 to 2022 in Mazandaran and Golestan provinces, Iran, and rapid slide agglutination (RSA) assay was performed. Positive results were analyzed by the enzyme-linked immunosorbent assay (ELISA) for further investigation. Here, 920 swab samples were collected from 38 non-vaccinated commercial farms for culture, and PCR tests were performed for the isolated strains. The activities of tylosin were tested against these isolates using the broth microdilution method. The lowest antibiotic concentration that resulted in a color change was considered the minimum inhibitory concentration (MIC) value. Twenty-four (63.1%) farms were positive in the RSA test, and 21 (55.2%) farms were positive in the ELISA test. Nine (23.68%) of the farms grew on culture media, and 8 (21.05%) were detected as Gallisepticum species by PCR. The geometric mean of MIC for tylosin was 5.75 µg/ml, MIC50 was 4 µg/ml, and MIC90 was 8 µg/ml. The results indicated that commercial farms were infected with MG. Considering the ability of MG to spread and the probable use of the RSA test as a rapid and cheap method, it can be argued that ELISA and RSA serological tests can be used to find MG in poultry flocks, and the positive result should be confirmed by standard microbiological tests or PCR. It was also found that the isolated parts of MG changed their sensitivity to tylosin, indicating the need for routine testing to optimize treatment dose and efficiency.
（MG）是一种具有传染性的禽类病原体，给家禽养殖业造成了经济损失。该病原体的分离既困难又耗时，因此远非常规方法。检测对 MG 具有抗性的抗体的血清学检测方法广泛应用于常规诊断。泰乐菌素是一类在兽医临床上大量用于治疗支原体病和预防的大环内酯类抗生素。本研究旨在通过免疫检测、培养和聚合酶链反应（PCR）检测商业家禽养殖场中的 MG，并研究分离株对泰乐菌素的敏感性。为了验证对 MG 具有抗性的抗体的存在，从 2019 年至 2022 年，在伊朗马赞达兰省和戈勒斯坦省的 38 个肉鸡养殖场中，随机采集了 750 份血液样本进行快速 slide agglutination（RSA）检测。阳性结果通过酶联免疫吸附试验（ELISA）进一步分析。在这里，从 38 个未接种疫苗的商业农场中采集了 920 个拭子样本进行培养，并对分离株进行了 PCR 检测。使用肉汤微量稀释法对这些分离株进行了泰乐菌素活性测试。导致颜色变化的最低抗生素浓度被认为是最小抑菌浓度（MIC）值。24 个（63.1%）农场的 RSA 检测呈阳性，21 个（55.2%）农场的 ELISA 检测呈阳性。9 个（23.68%）农场在培养基上生长，8 个（21.05%）农场通过 PCR 检测为禽败血支原体。泰乐菌素的几何平均 MIC 为 5.75 µg/ml，MIC50 为 4 µg/ml，MIC90 为 8 µg/ml。结果表明，商业农场受到 MG 的感染。考虑到 MG 的传播能力以及 RSA 试验作为一种快速且廉价的方法的可能性，可以认为 ELISA 和 RSA 血清学检测可用于在禽群中发现 MG，阳性结果应通过标准微生物学检测或 PCR 来确认。还发现，MG 的分离部分对泰乐菌素的敏感性发生了变化，这表明需要进行常规检测以优化治疗剂量和效率。
