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Resistome profiling of the genus Macrococcus, a potential reservoir of antibiotic resistance determinants for the genus Staphylococcus

Shahneela Mazhar

Members of the Macrococcus genus are disseminated in natureas animal commensals that are evolutionarily closely related to the species Staphylococcus. Recent reports have identified a plasmid-encoded methicillin resistance determinant, mecB, in Staphylococcus aureus o macrococcal origin, obtained from an elderly cardiology patient. Other reports have identified a novel mecD gene in Macrococcus caseolyticus strains isolated from bovine and canine sources. The mecD gene confers resistance to all classes of β-lactams including anti-MRSA cephalosporins. Thus, there is an increasing body of evidence emerging recognizing macrococci as reservoirs of antibiotic resistance determinants. However, due to the lack of availability of genomic data for species of the Macrococcus genus information on the genome-wide distribution of antibiotic resistance determinants across Macrococcus species is limited. In this study, we used a whole genome sequencing approach to characterize and identify antibiotic resistance genes present in a collection of the type strains of six Macrococcus species; Macrococcus bovicus ATCC 51825T, Macrococcus carouselicus ATCC 51828T, Macrococcus equipercicus ATCC 51831T, Macrococcus brunensis CCM4811T, Macrococcus hajekii CCM4809 Macrococcus lamae CCM4815T as well as in a collection of 14 strains from the Teagasc DPC culture collection belonging to Macrococcus caseolyticus, Macrococcus canis,Macrococcus bohemicus, and Macrococcus goetzii isolated from bovine tongue and milk samples. In silico analysis of the resistome using resistance gene identifier (RGI) identified the methicillin resistance mecD gene in M. bohemicus strain DPC7215. This gene displayed 100% sequence identity to that of M. caseolyticus strain IMD0819. Further analysis withIslanviewer4 revealed that this mecD gene complex is harbored on a genomic island within the chromosome. Interestingly, the complete sequence of a plasmid found in S. aureus pS0385-2,(GenBank: AM990994.1)carrying streptomycin resistance, was also found to be integrated in the M. bohemicus DPC7152 genome. All other sequenced genomes illustrated partial identity to various other resistance determinants including tetracycline, aminoglycosides and glycopeptides. Conclusion & Significance.