Evidence for Human Adaptation and Foodborne Transmission of Livestock-Associated Methicillin-Resistant Staphylococcus aureus
Investigation published in Clinical Infectious Diseases : an official publication of the Infectious Diseases Society of America
November 15th, 2016
We investigated the evolution and epidemiology of a novel livestock-associated methicillin-resistant Staphylococcus aureus strain, which colonizes and infects urban-dwelling Danes even without a Danish animal reservoir. Genetic evidence suggests both poultry and human adaptation, with poultry meat implicated as a probable source.
Food-producing animals constitute an expanding reservoir of so-called livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) strains worldwide, of which clonal complex (CC) 398 predominates in Europe [1]. Whole-genome phylogenetic analysis showed that CC398 consists of 2 epidemiologically and evolutionarily distinct groups: a human-adapted progenitor subpopulation and a livestock-adapted subpopulation derived thereof [2]. The analysis also showed that the human-to-livestock host jump was accompanied by the loss of the ΦSa3 phage encoding proteins that protect S. aureus from the human innate immune response [2]. LA-MRSA CC398 is a frequent and increasing cause of infections among persons working in the livestock industry, and infection rates are also increasing among the general public [3, 4]. These patients usually live in rural areas where livestock is raised, suggesting that LA-MRSA CC398 in the general public is mainly due to spillover from nearby animal farms [3, 4].
LA-MRSA CC9/CC398 displaying spa type t899 represents a unique genotype that consists of a CC398 chromosomal backbone and a smaller CC9 region, which contains the staphylococcal protein A (spa) gene [2]. By analyzing national surveillance data, we observed that LA-MRSA CC9/CC398 has caused sporadic illness in persons living in urban areas of Denmark despite an apparent lack of a Danish livestock reservoir for this genotype (Supplementary Appendix 1 and Supplementary Table 1), raising questions about possible sources and modes of transmission. In the present study, we investigated the epidemiology of all LA-MRSA CC9/CC398 cases in Denmark and used whole-genome phylogenetic analysis to compare the Danish isolates with a European collection of S. aureus CC9/CC398 isolates from humans, animals, and retail foods
Larsen J., Stegger M., Andersen PS., Petersen A., Larsen AR., Westh H., Agerso Y., Fetsch A., Kraushaar B., Kasbohrer A., Febler AT., Schwarz S., Cuny C., Witte W., Butaye P., Denis O., Haenni M., Madec JY., Jouy E., Laurent F., Battisti A., Franco A., Alba P., Mammina P., Pantosti A., Monaco M., Wagenaar J., de Boer E., van Duijkeren E., Heck M., Dominguez L., Torres C., Zarazaga M., Price LB. and Skov LR.
 | Statens Serum Institut (SSI). |
 | University of Copenhagen (UCPH). |
 | Hvidovre Hospital. |
 | Technical University of Denmark (DTU). |
 | Translational Genomics Research Institute (TGEN). |
 | George Washington University. |
 | Federal Institute for Risk Assessment (BfR). |
 | Friedrich Loeffler Institut-Bundesforschungsinstitut fuer Tiergesundheit (FLI). |
 | Robert Koch Institute (RKI). |
 | University of Ghent (UGENT). |
 | Université Libre de Bruxelles (ULB). |
 | School of Veterinary Medicine. Ross University. |
 | Université Claude Bernard Lyon. |
 | Hospices Civils de Lyon. |
 | Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana (IZSLT). |
 | Istituto Superiore di Sanità. |
 | University of Palermo. |
 | Utrecht University (UU). |
 | Netherlands Food and Consumer Product Safety Authority. |
 | Central Veterinary Institute. Wageningen University (UR). |
 | National Institute for Public Health and the Environment (RIVM). Ministry of Health, Welfare and Sport. Government of the Netherlands. |
 | Servicio de Zoonosis de Transmisión Alimentaria y Resistencia a Antimicrobianos (ZTA). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM). |
 | Universidad de La Rioja (UR). |
