Abstract
The aim of this study was to investigate the presence of methicillin-resistant Staphylococcus (MRS) strains in non-managed wild ungulates present in a typical Mediterranean forest in Spain. For this purpose, nasal swabs were obtained from 139 animals: 90 wild boar (Sus scrofa), 42 red deer (Cervus elaphus) and 7 fallow deer (Dama dama), which were subsequently pre-enriched in BHI+ NaCl (6.5%) (24 h/37 °C), and then seeded in Columbia blood agar (24 h/37 °C)). The presence of the mecA gene was investigated by PCR, first from the confluent and then from individual colonies. A total of 10 mecA+ colonies were obtained of which only seven showed phenotypic resistance to oxacillin/cefoxitin (methicillin resistance). All MRS strains belonged to the Staphylococcus sciuri group. Methicillin-resistant Staphylococcus aureus (MRSA) was not detected. In addition, a significant number of MRS strains showed resistance to other antimicrobials, mainly β-lactam (7/7), gentamicin (7/7), fusidic acid (6/7) and quinupristin-dalfopristin (6/7), showing an irregular correlation with their coding genes. The genetic profiles grouped the seven strains obtained according to the bacterial species but not in relation to the animal source or the geographical place of origin. The presence of SCCmec type III, common to animals and humans, has been detected in three of the strains obtained. In conclusion, the study reveals that the wild ungulates investigated play a role as potential reservoirs of multi-resistant strains of MRS. Such strains, due to their characteristics, can be easily transferred to other wild or domestic animal species and ultimately to humans through their products.
Highlights
Antimicrobial resistance is widespread in animal reservoirs
Due to its severe clinical and therapeutic implications, most studies referring to this resistance have focused on coagulase-positive Staphylococcus (CoPS), especially MRSA isolated from humans and domestic species
From the 139 nasal swabs processed, methicillinresistant Staphylococcus (MRS) were obtained in seven of them (5.03%; 95%, CI: 1.4–8.7): five in wild boar and two in red deer, with prevalences of 5.55% (95%, CI: 0.8–10.3) and 4.76% (95%, CI: 0.1–11.2), respectively
Summary
Antimicrobial resistance is widespread in animal reservoirs. This resistance has been observed mainly in domestic animals, due to the selective pressure exerted by the frequent and non-specific use of antimicrobials for preventive or curative purposes, and, mainly in pigs and poultry, as growth promoters as well. A paradigmatic example of this phenomena is what happened with methicillin resistance (MR) in the genus Staphylococcus This resistance, first noted in 1961 in Staphylococcus aureus (MRSA) isolated from humans in the UK [4], spread rapidly to other countries and environments, eventually colonizing domestic and wild animals. The presence of this resistance is related to the acquisition of the mecA gene as part of a mobile genetic element called Staphylococcal Cassette Chromosome mec (SCCmec) [5]. The importance that these species may have as a long-term reservoir of these and other resistance genes is underestimated
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