title: Nasal carriage of mecA-positive methicillin-resistant Staphylococcus aureus in pigs exhibits dose-response to zinc supplementation.
abstract: Zinc (Zn) is often supplemented at elevated concentrations in swine diets, particularly in piglets, to prevent enteric infections and promote growth. Previous studies from Denmark have suggested a genetic linkage and a phenotypic association between Zn resistance, encoded by czrC, and methicillin-resistance conferred by mecA in Staphylococcus aureus. Such an association has not been reported in the U.S. swine population. We conducted an analysis of the effects of Zn, supplemented as zinc oxide (ZnO), on the nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) in nursery (n=40) and finisher pigs (n=40) enrolled in a nutritional study. Nasal swabs, collected from nursery and finisher pigs, were inoculated onto MRSA CHROMagar and presumptive MRSA colonies were tested for the presence of mecA and czrC genes by polymerase chain reaction. Zinc susceptibility was determined by the agar dilution method. The prevalence of mecA-positive MRSA was 10% (4/40) and 20% (8/40) among nursery and finisher pigs, respectively. Of the 12 mecA-positive S. aureus isolates, 7 had the czrC gene (58.3%) compared to none among the 68 mecA-negative isolates. The presence of both mecA (p=0.002) and czrC (p=0.006) genes were positively associated with higher levels of Zn supplementation. The median minimum inhibitory concentrations of Zn for czrC-positive and czrC-negative isolates were 12 and 2 mM, respectively (p<0.0001). The link between czrC and mecA genes suggests the importance of elevated Zn supplementation in the co-selection and propagation of methicillin resistance among S. aureus in pigs.
authors.affiliation: 1 Department of Diagnostic Medicine and Pathobiology, Kansas State University , Manhattan, Kansas.
authors.forename: Raghavendra G
authors.initials: RG
authors.lastname: Amachawadi
authors.forename: Harvey M
authors.initials: HM
authors.lastname: Scott
authors.forename: Sureemas
authors.initials: S
authors.lastname: Nitikanchana
authors.forename: Javier
authors.initials: J
authors.lastname: Vinasco
authors.forename: Mike D
authors.initials: MD
authors.lastname: Tokach
authors.forename: Steve S
authors.initials: SS
authors.lastname: Dritz
authors.forename: Jim L
authors.initials: JL
authors.lastname: Nelssen
authors.forename: Robert D
authors.initials: RD
authors.lastname: Goodband
authors.forename: Tiruvoor G
authors.initials: TG
authors.lastname: Nagaraja
mesh_terms: D000367:Age Factors; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use; D019072:Antibiotic Prophylaxis / Q000009:adverse effects / Q000662:veterinary; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019587:Dietary Supplements / Q000009:adverse effects*; D004751:Enteritis / Q000209:etiology / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary; D007615:Kansas; D016106:Methicillin Resistance; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D009297:Nasal Mucosa / Q000382:microbiology*; D046915:Penicillin-Binding Proteins; D013203:Staphylococcal Infections / Q000209:etiology / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D013552:Swine; D013553:Swine Diseases / Q000209:etiology* / Q000382:microbiology / Q000517:prevention & control; D015034:Zinc Oxide / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D019287:Zinc Sulfate / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus; D019287:Zinc Sulfate; D015034:Zinc Oxide