Detection of MRSA ST3061-t843-mecC and ST398-t011-mecA in white stork nestlings exposed to human residues

[Objectives]: The objective of this study was to analyse the prevalence of tracheal carriage of Staphylococcus aureus/MRSA in storks and to study the resistance and virulence genes in the obtained isolates. [Methods]: Tracheal samples from 92 stork nestlings of two landfill-associated and two natural-habitat colonies were inoculated in specific media for S. aureus and MRSA recovery. Antimicrobial susceptibility was tested, and the presence of resistance, virulence and immune evasion cluster (IEC) genes was analysed by PCR. S. aureus isolates were characterized by spa and agr typing. Staphylococcal cassette chromosome (SCC) mec type was determined for mecC-positive isolates, and MLST was performed for 17 selected S. aureus isolates. [Results]: S. aureus isolateswere identified in 32/92 samples (34.8%), and 38 isolateswere recovered. The prevalence of S. aureus was higher in nestlings from landfills (24/43, 55.8%) than in those fromnatural habitats (8/49, 16.3%). Three birds from landfill-associated colonies carried MRSA, two with mecA-positive strains [clonal complex (CC) 5-spa-t002 and CC398-spa-t011] and one with a mecC-positive strain [sequence type (ST) 3061-CC130-spat843- agr-III-SCCmecXI). None of the MRSA isolates presented IEC genes. Thirty-five MSSA isolates, which showed 18 different spa types (ascribed to CC5, CC7, CC22, CC30, CC45, CC59, CC133 and CC398), were obtained. The agr types detected were I (63%), II (29%) and III (8%). Resistance and virulence genes identified in MSSA were blaZ (n=25), erm(T) (n=9), erm(A) (n=1), tet(M) (n=2), fexA (n=3), str (n=2), tst (n=2), eta (n=1) and cna (n=15). The IEC types B, C, D and G were found in MSSA isolates, and two new STs were identified (ST3060 and ST3061). [Conclusions]: White storks are frequently tracheal carriers of S. aureus, including ST398 isolates. MRSA isolates of lineages CC398-mecA and CC130-mecC were detected in storks from landfill-associated colonies exposed to human residues.This work was supported by project SAF2012-35474 from the Ministerio de Economía y Competitividad (MINECO) of Spain and Fondo Europeo de Desarrollo Regional (FEDER) and by the project RTA2011-00111-C03-02 from the National Institute for Research in Agricultural and Alimentary Technology (INIA) and by EU FP7 EMIDA ERA-NET grant APHAEA on wildlife disease surveillance in Europe. P. G. has a predoctoral fellowship from the Universidad de La Rioja (Spain), and C. L. has a contract associated with project SAF2012-35474.Peer Reviewe