Core Genome MLST for Source Attribution of .

species are among the leading foodborne bacterial agents of human diarrheal illness. The majority of campylobacteriosis has been attributed to (85% or more), followed by (5-10%). The distribution of and varies by host organism, indicating that the contribution to human infection may differ between isolation sources. To address the relative contribution of each source to infections in humans, core genome multilocus sequence type with a 200-allele difference scheme (cgMLST) was used to determine cgMLST type for 3,432 isolated from food animals ( = 2,613), retail poultry meats ( = 389), human clinical settings ( = 285), and environmental sources ( = 145). Source attribution was determined by analyzing the core genome with a minimal multilocus distance methodology (MMD). Using MMD, a higher proportion of the clinical population was attributed to poultry (49.6%) and environmental (20.9%) sources than from cattle (9.8%) and swine (3.2%). Within the population of clinical isolates, 70% of the isolates that were attributed to non-cecal retail poultry, dairy cattle, beef cattle and environmental waters came from two cgMLST groups from each source. The most common antibiotic resistance genes among all were (65.6%), (54.2%), (23.5%), and (20.1%). Of the antibiotic resistance determinants, only one gene was isolated from a single source: was only isolated from retail poultry. Within cgMLST groups, 17/17 cgMLST-435 and 89/92 cgMLST-707 isolates encoded for and 16/16 cgMLST-319 harbored genes. Distribution of alleles showed 49/50 cgMLST-5 isolates contained while was present in 37/38 cgMLST-650 isolates. The cgMLST-514 group revealed both (6) and resistance genes in 23/23 and 22/23 isolates, respectively. Also, cgMLST-266 and cgMLST-84 had GyrAT86I mutation with 16/16 (100%) and 14/15 (93.3%), respectively. These findings illustrate how cgMLST and MMD methods can be used to evaluate the relative contribution of known sources of to the human burden of campylobacteriosis and how cgMLST typing can be used as an indicator of antimicrobial resistance in .