Elstrøm Petter, Grøntvedt Carl Andreas, Gabrielsen Christina, Stegger Marc, Angen Øystein, Åmdal Solfrid, Enger Hege, Urdahl Anne Margrete, Jore Solveig, Steinbakk Martin, Sunde Marianne
The Norwegian Institute of Public Health, Oslo, Norway.
The Norwegian Veterinary Institute, Oslo, Norway.
Front Microbiol. 2019 Feb 8;10:139. doi: 10.3389/fmicb.2019.00139. eCollection 2019.
Farm animals have been identified as an emerging reservoir for transmission of livestock-associated methicillin-resistant (LA-MRSA) to humans. The low incidence of MRSA in humans and farm animals in Norway has led to the implementation of a national strategy of surveillance and control of LA-MRSA aiming to prevent livestock becoming a domestic source of MRSA to humans. In 2015, MRSA clonal complex 1 -type t177 was identified in nine Norwegian pig herds in two neighboring counties. An outbreak investigation was undertaken, and measures of control through eradication were imposed. We performed a register-based cohort study including pig herds and MRSA-positive persons in Norway between 2008 and 2016 to investigate the livestock-association of MRSA CC1, the transmission of the outbreak strain to humans before and after control measures, and the effect of control measures imposed. Data from the Norwegian Surveillance System of Communicable Diseases were merged with data collected through outbreak investigations for LA-MRSA, the National Registry and the Norwegian Register for Health Personnel. Whole-genome sequencing was performed on isolates from livestock and humans identified through contact tracing, in addition to t177 and t127 isolates diagnosed in persons in the same counties. It is likely that a farm worker introduced MRSA CC1 to a sow farm, and further transmission to eight fattening pig farms through trade of live pigs confirmed the potential for livestock association of this MRSA type. The outbreak strain formed a distinct phylogenetic cluster which in addition to the pig farms included one sheep herd and five exposed persons. None of the investigated isolates from possible cases without direct contact to the MRSA positive farms were phylogenetically related to the outbreak strain. Moreover, isolates of t177 or t127 from healthcare and community-acquired cases were not closely related to the outbreak cluster. Eradication measures imposed were effective in eliminating MRSA t177 from the positive pig holdings, and the outbreak strain was not detected in the national pig population or in persons from these counties after control measures.
农场动物已被确认为与家畜相关的耐甲氧西林金黄色葡萄球菌（LA-MRSA）向人类传播的一个新出现的储存宿主。挪威人类和农场动物中耐甲氧西林金黄色葡萄球菌的低发病率促使实施一项全国性的LA-MRSA监测和控制战略，旨在防止家畜成为耐甲氧西林金黄色葡萄球菌在国内传播给人类的源头。2015年，在挪威两个相邻县的9个猪群中发现了耐甲氧西林金黄色葡萄球菌克隆复合体1型t177。开展了一次疫情调查，并实施了根除控制措施。我们进行了一项基于登记的队列研究，纳入了2008年至2016年期间挪威的猪群和耐甲氧西林金黄色葡萄球菌阳性个体，以调查耐甲氧西林金黄色葡萄球菌CC1与家畜的关联、控制措施前后疫情菌株向人类的传播以及所实施控制措施的效果。挪威传染病监测系统的数据与通过LA-MRSA疫情调查、国家登记处和挪威卫生人员登记处收集的数据进行了合并。除了对在同一县被诊断出的t177和t127分离株进行全基因组测序外，还对通过接触追踪从家畜和人类中鉴定出的分离株进行了全基因组测序。很可能是一名农场工人将耐甲氧西林金黄色葡萄球菌CC1引入了一个母猪场，通过活猪交易进一步传播到8个育肥猪场，这证实了这种耐甲氧西林金黄色葡萄球菌类型与家畜关联的可能性。疫情菌株形成了一个独特的系统发育簇，除了猪场之外，还包括一个羊群和5名暴露个体。从可能病例中调查的与耐甲氧西林金黄色葡萄球菌阳性农场无直接接触的分离株，在系统发育上均与疫情菌株无关。此外，来自医疗保健和社区获得性病例的t177或t127分离株与疫情簇没有密切关系。实施的根除措施有效地从阳性猪舍中清除了耐甲氧西林金黄色葡萄球菌t177，在控制措施实施后，在全国猪群或这些县的人群中均未检测到疫情菌株。
