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Objective.Studies conducted in Europe have observed resistance to trace metals such as zinc chloride and copper sulfate in livestock-associated Staphylococcus aureus. This study was conducted to determine the prevalence of zinc and cadmium resistance in S. aureusisolated in the United States.Design.Cross-sectional study of convenience sample of S. aureusisolates.Participants.Three hundred forty-nine S. aureusisolates, including methicillin-resistant S. aureus(MRSA) and methicillin-susceptible S. aureus(MSSA) obtained from human, swine, and retail meat were included in the sample set.Methods.Polymerase chain reaction was used to test for the presence of genes for zinc and cadmium resistance (czrC), methicillin resistance (mecA), and staphylococcal complement inhibitor (scn). Antibiotic susceptibility of isolates was tested using the broth microdilution method. Data were analyzed using the multivariable logistic regression method.Results.Twenty-nine percent (102/349) of S. aureusisolates were czrCpositive. MRSA isolates were more likely to be czrCpositive compared to MSSA (MRSA czrCpositive: 12/61, 19.6%; MSSA czrCpositive: 12/183, 6.6%). After adjustment for oxacillin and clindamycin susceptibility in analysis, multidrug-resistant S. aureuswas observed to have low odds of being czrCpositive (P= .03). The odds of being czrCpositive were observed to be significantly high in tetracycline-resistant S. aureusisolated from noninfection samples (P = .009) and swine (P< .0001).Conclusions.Resistance to zinc and cadmium was observed to be associated with MRSA, a finding consistently observed in European studies. Prolonged exposure to zinc in livestock feeds and fertilizers could propagate resistance to the metal ion, thereby hindering use of zinc-based topical agents in treating S. aureusinfections.

The nonrandom three-dimensional organization of chromatin plays an important role in the regulation of gene expression. However, it remains unclear whether this organization is conserved and whether it is involved in regulating gene expression during speciation after whole-genome duplication (WGD) in plants. In this study, high-resolution interaction maps were generated using high-throughput chromatin conformation capture (Hi-C) techniques for two poplar species, Populus euphraticaand Populus albavar. pyramidalis, which diverged ~14 Mya after a common WGD. We examined the similarities and differences in the hierarchical chromatin organization between the two species, including A/B compartment regions and topologically associating domains (TADs), as well as in their DNA methylation and gene expression patterns. We found that chromatin status was strongly associated with epigenetic modifications and gene transcriptional activity, yet the conservation of hierarchical chromatin organization across the two species was low. The divergence of gene expression between WGD-derived paralogs was associated with the strength of chromatin interactions, and colocalized paralogs exhibited strong similarities in epigenetic modifications and expression levels. Thus, the spatial localization of duplicated genes is highly correlated with biased expression during the diploidization process. This study provides new insights into the evolution of chromatin organization and transcriptional regulation during the speciation process of poplars after WGD.