Department of Clinical Sciences, Box 7054, 750 07 Uppsala, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Department of Clinical Sciences, Box 7054, 750 07 Uppsala, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, Uppsala, Sweden; National Veterinary Institute, SE-750 07 Uppsala, Sweden.
Vet Microbiol. 2018 Sep;223:107-112. doi: 10.1016/j.vetmic.2018.07.016. Epub 2018 Jul 27.
The aim of the study was to use culture, qPCR and seM sequencing to map Streptococcus equi subspec. equi (S.equi) isolates in long term carrier animals. A strangles outbreak affecting 41 Icelandic horses was followed to determine strangles free status using nasal and/or guttural pouch lavages collected serially on eleven separate occasions over 13 months. Ten persistent carriers, of which eight had repeated culture positive samples for S. equi, were selected for the study. Of 115 samples collected, 61 were S. equi positive on qPCR; from which 32 were also culture positive. Amplification of parts of the gene encoding the M-protein seM was performed on isolated colony material (n = 32) or, where only PCR product was obtained, directly on the DNA sample (n = 29) with a nested amplification approach. The seM sequence could be determined for six of the 29 samples that were solely qPCR positive. The outbreak was due to a S. equi strain of seM type 72. Three months after initial sampling isolates from two horses had seM gene sequences with one amino acid change. After six months S. equi with truncated seM genes were found in two horses; one variant in a single horse once, and in the other horse a variant that persisted and that was later identified in two additional horses. Non- mucoid S. equi colonies were found in two horses. Importantly, after acute strangles outbreaks many horses not only remain persistently qPCR positive for S. equi but are also intermittently culture positive.
本研究旨在使用培养、qPCR 和 seM 测序技术，对长期携带动物中的马链球菌兽疫亚种（Streptococcus equi subspec. equi，S.equi）分离株进行定位。对 41 匹冰岛马发生的马腺疫暴发进行了跟踪调查，通过对 11 头马在 13 个月内的 11 次鼻拭子和/或咽囊冲洗采样，确定马腺疫的无疫状态。从 10 头持续性携带者中（其中 8 头重复培养出 S. equi 阳性样本），选择了 10 头进行研究。在采集的 115 份样本中，61 份 qPCR 检测为 S. equi 阳性；其中 32 份培养结果也为阳性。对分离的菌落材料（n=32）或仅获得 PCR 产物的样本（n=29），采用巢式扩增方法，对部分编码 M 蛋白 seM 的基因进行扩增。对 29 份仅 qPCR 阳性的样本中的 6 份进行了 seM 序列测定。此次暴发是由 seM 型 72 的 S. equi 菌株引起的。在初次采样后 3 个月，2 匹马的分离株 seM 基因序列发生了 1 个氨基酸变化。6 个月后，2 匹马中发现了截短 seM 基因的 S. equi；1 匹马中的 1 个变体仅出现过 1 次，另 1 匹马中的变体持续存在，并在另外 2 匹马中发现。2 匹马中还发现了非黏液型 S. equi 菌落。重要的是，急性马腺疫暴发后，许多马不仅持续 qPCR 检测 S. equi 阳性，而且间歇性培养也呈阳性。
