First report on MRSA CC398 recovered from wild boars in the north of Portugal

More than 47% of the Portuguese hospital S. aureus isolates are methicillin-resistant (MRSA): one of the highest rates in Europe [1]. Anyhow, MRSA are becoming increasingly prevalent in community-acquired infections and, in recent years, new genetic lineages of MRSA were associated to livestock animals (LA-MRSA) [2, 3]. Nevertheless, less information do exists about the prevalence of MRSA in wild animals but, since 2013, these animals are pointed as natural hosts of MRSA strains [4]. The aim of the present study was to evaluate the antimicrobial resistance in Staphylococcus aureus recovered from wild boars, to analyze their genetic lineages, and to investigate the susceptibility to oxacillin. Samples from mouth and nose of 45 wild boars (Sus scrofa) were collected during hunt activity from November 2012 to January 2013 in the North of Portugal. S. aureus isolates were recovered from 30 of these samples (33%); one isolate/sample was further studied. The susceptibility of the isolates was tested by disk-diffusion test against 14 antimicrobial agents and minimal inhibitory concentration was used to test oxacillin according to EUCAST 2014 guidelines. The genetic lineages of S. aureus were characterized by agr-typing, spa-typing and MLST. From the 30 isolates, 18 S. aureus were susceptible to all antibiotics tested and 7 presented resistance to one or more of the following antibiotics: penicillin (n=3), oxacillin (n=4), cefoxitin (n=1), clindamycin (n=2), gentamicin (n=1), fusidic acid (n=1), ciprofloxacin (n=2), tetracycline (n=1) and linezolid (n=1). One MRSA CC398 (spa-type t899) isolate was detected (oxacillin MIC=32mg/L and mecApositive), which presented resistance to penicillin, tetracycline, and ciprofloxacin and contained the genes of immune evasion cluster (IEC) system (type B). The 29 methicillin-susceptible isolates were typed as ST1 (t1533), ST133 (t3583), ST1643 (t10712), ST2328 (t3750) and the new STs (3220, 3222, 3223, 3224) associated to new spa-types t14311 and t14312. The agr types I, II, III and IV were identified. It is a matter of concern when MRSA and some specific lineages of S. aureus are taken as commensal habitants of the skin and nose of wild animals and are characterized with resistance to various antimicrobial agents in clinical use.