Epidemiological Characteristics And Transmission Dynamics Of Staphylococcus Aureus Along A Pork Production Chain And In The Surrounding Urban And Rural Communities

The global epidemic of human-pathogenic livestock-associated methicillin-resistant Staphylococcus aureus(LA-MRSA)among pigs has become a recognised public health concern,as its increasingly occurrence in community residents without livestock exposure.Since more than half of the world's swine stock resides in China,these animals might represent the largest LA-MRSA reservoir in the world.However,the occurrence and epidemiology of LA-MRSA has not been extensively studied compared to European countries,especially the LA-MRSA situation in the Chinese pig production and its occurrence in the surrounding environment and communities.To improve the knowledge about epidemiological characteristics and transmission dynamics of Staphylococcus aureus along a pork production chain and in the surrounding urban and rural communities,various samples from commercial farms,a slaughterhouse,a pork market along a typical Chinese pork production chain,and surrounding communities in Shandong,China,were collected.The occurrence of MRSA in various sectors,including 899 pig and pig related samples,845 human nasal samples and 239 environmental samples were surveyed using selective cultures.A high occurrence of MRSA was detected in samples from commercial pig farms(49.0%,146/298),farm workers(64.3%,9/14)and various environmental samples(15.5%,33/213),while a lower occurrence was noted in samples from the slaughterhouse(pigs,8.2%,7/85;carcasses,1.0%,1/98;operation workers,0%;environment samples,3.8%,1/26),the pork market(pork,14.3%,2/14;sellers,0%,0/3)and individuals in the urban(6.8%,4/59)and rural(pigs,1.7%,7/404;humans,1.7%,13/753)communities.spa typing indicates a high diversity of MSSA isolates(47 spa types;t899,93%)compared to MRSA isolates(4 spa types;t034,35%;t899,13%).MRSA isolates were typical resistance to cefoxitin,erythromycin,clindamycin and gentamicin.Resistance to florfenicol,tiamulin,tetracycline,were strongly associated with the porcine MRSA isolates.MRSA isolates from rural communities exhibited a high occurrence of tigecycline resistance(human isolates,46.2%,6/13;pig isolates,85.7%,6/7),as well as borderline susceptibility to linezolid(human isolates,84.6%,11/13;pig isolates,85.7%,6/7).A further study of presence and molecular characteristics of oxazolidinone resistance in rural communities reveals a wide distribution of oxazolidinone resistance genes optrA and cfr in household animals in rural areas of China,antimicrobial resistance phenotype,genotype and genetic environments analysis reveals the co-selection of optrA and cfr from phenicols and macrolides antibiotics could be a reason of the wide distribution.To further explore the transmission dynamics and genomic characteristics of isolates from pig to pork,and potential "spill-over" to the environment and surrounding communities,a total of 92 MRSA and 36 MSSA isolates were selected and whole genome sequenced and followed by bioinformatic analysis.There was a significant difference in population structures,antibiotic susceptibility profiles,and resistance and virulence gene occurrence between human-and pig-derived isolates.The phylogenetic analysis confirmed dissemination of LA-MRSA between various sectors along and around the pork production chain,while did not reveal any evidence of "spill-over" of MRSA and MSSA from the pork production chain to the surrounding communities.