Spatial analysis and molecular typing of Corynebacterium pseudotuberculosis in Korean native goats show a cohesive...

Caseous lymphadenitis (CLA), caused by Corynebacterium pseudotuberculosis, is endemic in Korean native goats, but relationships among antimicrobial resistance (AMR), spatial distribution, and population structure remain unclear. We profiled AMR and multidrug resistance (MDR) in 286 pld-positive isolates from CLA lesions of 1177 goats in the Jeolla provinces, South Korea, integrating spatial analysis with five-locus multilocus sequence typing (MLST) and phylogenetics. Susceptibility to 12 antimicrobials was determined by disk diffusion, and MDR was defined as resistance to ≥ 3 antimicrobial classes. Farm-level spatial analyses included 54 farms with valid MDR estimates. Resistance was dominated by aminoglycosides, with streptomycin and gentamicin resistance of 99.7% and 88.1%, respectively. MDR occurred in 96 of 286 isolates (33.6%) and comprised 35 resistance-class patterns; the eight most frequent accounted for 61.5% of MDR isolates. Local indicators of spatial association (LISA) identified three significant farm-level patterns: one high-low outlier, one low-high outlier, and one low-low cluster, whereas no significant local patterns were detected at the gun/si level. Global Moran's I was non-significant at both scales. The CLA-MDR association was non-significant at the farm level but positive at the gun/si level by Pearson correlation. Neither AMR-profile dissimilarity nor differences in MDR prevalence showed significant isolation by distance using Haversine or road-network distances. MLST of 49 representative isolates indicated a cohesive, locally diversified lineage, with MDR distributed across related isolates rather than confined to a dominant typed lineage. These findings support herd-level antimicrobial stewardship and integrated phenotypic, spatial, and molecular surveillance for CLA control.