Molecular characterization of Staphylococcus aureus isolated from humans related to a livestock farm in Spain, with detection of MRSA-CC130 carrying mecC gene: A zoonotic case?

OBJECTIVES To conduct a study of Staphylococcus aureus carriage in members of a livestock-farmer's family with different degrees of animal contact, and to characterize the recovered isolates. METHODS Nasal samples from 11 members of the family were taken in three sampling periods (every six months) (n=31), and 9 skin samples from superficial lesions were also obtained in 5 of them. Samples were analyzed for S. aureus susceptible (MSSA) and resistant to methicillin (MRSA). S. aureus isolates were tested for antibiotic-resistance phenotype and genotype and for the detection of virulence and IEC-system genes. Molecular typing of isolates was also performed (spa- and multilocus-sequence typing). RESULTS Eighteen S. aureus isolates were recovered (1 MRSA and 17 MSSA) in the 40 samples analyzed. S. aureus was detected in nasal and skin samples of 7/11 and 4/5 of tested humans, respectively. The MRSA strain was detected in the skin lesion of a farmer with high animal contact, and carried the mecC gene, and was typed as ST130-CC130-t843. The 17 MSSA isolates were ascribed to 9 different spa-types and sequence types included in the clonal complexes CC22, CC30, CC45, CC121, and in the livestock-associated lineages CC9 and CC133. Six strains harbored eta or tsst-1 genes. Three of 18 strains lacked the immune-evasion-cluster (IEC) genes (MRSA-ST130, MSSA-ST1333, and MSSA-ST133), and the remaining isolates were ascribed to IEC type-A or -B. CONCLUSIONS Animal-associated S. aureus lineages were detected in samples of the farmer's family, highlighting the detection of MSSA-CC133 and mecC-MRSA-ST130.