Faculty of Veterinary Medicine and Animal Husbandry, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Acta Vet Scand. 2012 Feb 8;54(1):11. doi: 10.1186/1751-0147-54-11.
Methicillin-resistant Staphylococcus aureus (MRSA) in animals is a rare finding in Sweden. In horses, MRSA was first detected in a screening survey in 2007. In 2008, six clinical cases occurred in an equine hospital, indicating an outbreak.
All MRSA isolates detected, 11 spa-type t011 and one t064 (n = 12), in infected horses (n = 10) and screening of horses (n = 2) in Sweden from December 2007 to March 2010 were retrospectively analysed with pulsed-field gel electrophoresis (PFGE) using Cfr9I and ApaI restriction enzymes, to study relationship between the isolates. Medical records of infected horses and outbreak investigation notes were scrutinised to monitor the clinical outcome and other aspects of the outbreak.
Eight of the 10 infected horses were linked to one equine hospital and two to another hospital in the same region. The six horses infected with MRSA in 2008 underwent surgery during the period 22 May-7 July in one of the hospitals. Four more infections linked to the two hospitals were notified between 2009 and March 2010.Nine of the 11 spa-type t011 isolates had identical Cfr9I and ApaI PFGE pattern. All six infected horses from 2008 presented with this MRSA. Two t011 isolates differed in one and two bands, respectively, in PFGE.Nine horses suffered from surgical site infections (SSI). No antimicrobials were used following the MRSA diagnosis and the infections cleared. The time from surgery to MRSA diagnosis differed greatly between the horses (range 15-52 days).
Association in time and space of six horses infected with an identical MRSA strain of spa-type t011 confirmed an outbreak. Two isolates found in 2009 and 2010 in the outbreak hospital were closely related to the outbreak strain, indicating one circulating strain. Both spa-type t011 and t064 have been reported in horses in Europe prior to these findings. The observation that the infections cleared although antimicrobials were not used is encouraging for future prudent use of antimicrobials. The time from surgery to bacteriological diagnosis was not acceptable in most cases, as contagious spread was a risk. Sampling when symptoms of infection are noticed and accurate analysis are thus important.
耐甲氧西林金黄色葡萄球菌（MRSA）在动物中较为罕见。在瑞典，2007 年首次在筛查中发现了马中的 MRSA。2008 年，一家马医院发生了 6 例临床病例，表明发生了暴发。
从 2007 年 12 月至 2010 年 3 月，对瑞典 10 匹受感染马（n = 10）和 2 匹筛查马（n = 2）中检测到的所有 11 株 spa 型 t011 和 1 株 t064（n = 12）的耐甲氧西林金黄色葡萄球菌分离株，采用 Cfr9I 和 ApaI 限制性内切酶进行脉冲场凝胶电泳（PFGE）进行回顾性分析，以研究分离株之间的关系。对受感染马的病历和暴发调查记录进行了仔细检查，以监测临床结果和暴发的其他方面。
10 匹受感染的马中有 8 匹与一家马医院有关，2 匹与同一地区的另一家医院有关。2008 年感染耐甲氧西林金黄色葡萄球菌的 6 匹马在一家医院于 5 月 22 日至 7 月 7 日期间接受了手术。2009 年至 2010 年 3 月期间，又有另外 4 例与两家医院有关的感染病例。11 株 spa 型 t011 中有 9 株分离株的 Cfr9I 和 ApaI PFGE 图谱完全相同。2008 年所有 6 匹受感染的马均携带这种耐甲氧西林金黄色葡萄球菌。在 PFGE 中，有 2 株 t011 分离株的带型分别存在 1 个和 2 个差异。9 匹马患有手术部位感染（SSI）。在诊断出耐甲氧西林金黄色葡萄球菌后，未使用任何抗生素，感染得到清除。马之间从手术到耐甲氧西林金黄色葡萄球菌诊断的时间差异很大（范围为 15-52 天）。
6 匹感染同种 spa 型 t011 耐甲氧西林金黄色葡萄球菌的马在时间和空间上的关联证实了暴发的存在。2009 年和 2010 年在暴发医院发现的两株分离株与暴发株密切相关，表明存在一种流行株。spa 型 t011 和 t064 在此之前在欧洲的马中已有报道。尽管未使用抗生素，但感染得到清除的观察结果令人鼓舞，这为未来合理使用抗生素提供了参考。在大多数情况下，从手术到细菌学诊断的时间是不可接受的，因为存在传染性传播的风险。因此，在出现感染症状时进行采样和准确分析非常重要。
