A Comparison of Passive and Active Dust Sampling Methods for Measuring Airborne MRSA in Pig Farms

Study Abstract: Authors: Anne Rittscher, Abel A. Vlasblom, Birgitta Duim, Peter Scherpenisse, Isabella van Schothorst, Inge M. Wouters, Liese Van Gompel, Lidwien A.M. Smit Methicillin resistant strains of <em>Staphylococcus aureus </em>(MRSA) are resistant to most b-lactam antibiotics. Pigs are an important reservoir of livestock associated MRSA (LA-MRSA), which is genetically distinct from both hospital and community acquired MRSA. Occupational exposure to pigs on farms can lead to LA-MRSA carriage by workers. There is a growing body of research on MRSA found in the farm environment, the airborne route of transmission, and its implication on human health. This study aims to compare two sampling methods used to measure airborne MRSA in the farm environment; passive dust sampling with electrostatic dust fall collectors (EDCs), and active inhalable dust sampling using stationary air pumps with Teflon filters. Paired dust samples using passive and active sampling, totaling 87 samples, were taken from seven Dutch pig farms, in multiple compartments housing pigs of varying ages. Total nucleic acids of both types of dust samples were extracted and targets indicating MRSA (<em>femA, nuc, mecA</em>) and total bacterial count (16S rRNA) were quantified using quantitative Real Time PCRs. MRSA could be measured in all stationary pump samples and in 94% of the EDCs, additionally MRSA was present on every farm sampled. There was a strong positive relationship between the paired MRSA levels found in EDCs and those measured on filters (Normalized by 16S rRNA; Pearson’s correlation coefficient r=0.94, Not Normalized; Pearson’s correlation coefficient r=0.84). This study suggests that EDCs can be used as an affordable and easily standardized method for quantifying airborne MRSA levels in the pig farm setting.研究摘要：作者：安妮·里特舍（Anne Rittscher）、阿贝尔·A.弗拉斯布卢姆（Abel A. Vlasblom）、比吉塔·杜伊姆（Birgitta Duim）、彼得·谢彭伊斯（Peter Scherpenisse）、伊莎贝拉·范·肖托斯特（Isabella van Schothorst）、因格·M.武特斯（Inge M. Wouters）、莉泽·范·贡佩尔（Liese Van Gompel）、利德温·A.M.斯米特（Lidwien A.M. Smit） 耐甲氧西林金黄色葡萄球菌（*Staphylococcus aureus*，MRSA）对绝大多数β-内酰胺类抗生素具有耐药性。猪是家畜相关耐甲氧西林金黄色葡萄球菌（livestock associated MRSA, LA-MRSA）的重要储存宿主，该菌株在遗传学上有别于医院获得性MRSA与社区获得性MRSA。猪场工作人员因职业性接触猪只，可能会携带LA-MRSA。当前针对农场环境中检出的MRSA、其空气传播路径及对人类健康的影响的相关研究正日益增多。 本研究旨在对比两种用于检测农场环境空气传播MRSA的采样方法：一是采用静电沉降集尘器（electrostatic dust fall collectors, EDCs）的被动集尘采样，二是搭配特氟龙（Teflon）滤膜的固定式空气泵主动吸入式粉尘采样。 本研究从7家荷兰猪场的多个饲养不同日龄猪只的栏舍中，采集了配对的被动与主动采样粉尘样本，合计87份。对两类粉尘样本均提取总核酸，并通过实时定量聚合酶链反应（quantitative Real Time PCR, qPCR）定量检测MRSA相关靶标（*femA*、*nuc*、*mecA*）及总细菌计数靶标（16S rRNA）。 所有固定式空气泵采集的样本中均可检出MRSA，94%的EDCs样本亦检出MRSA；此外，所有采样猪场均检出MRSA。EDCs与滤膜样本中测得的配对MRSA水平（经16S rRNA归一化处理后，皮尔逊相关系数r=0.94；未归一化处理时，皮尔逊相关系数r=0.84）呈现极强的正相关关系。 本研究结果证实，EDCs可作为一种成本低廉且易于标准化的检测方法，用于量化猪场环境中的空气传播MRSA水平。