Characterization of mannitol-fermenting methicillin-resistant staphylococci isolated from pigs in Nigeria

<p>This study was conducted to determine the species distribution, antimicrobial resistance pheno- and genotypes and virulence traits of mannitol-positive methicillin-resistant staphylococci (MRS) isolated from pigs in Nsukka agricultural zone, Nigeria. Twenty mannitol-positive methicillin-resistant coagulase-negative staphylococcal (MRCoNS) strains harboring the <italic>mecA</italic> gene were detected among the 64 <italic>Staphylococcus</italic> isolates from 291 pigs. A total of 4 species were identified among the MRCoNS isolates, namely, <italic>Staphylococcus sciuri</italic> (10 strains), <italic>Staphylococcus lentus</italic> (6 strains), <italic>Staphylococcus cohnii</italic> (3 strains) and <italic>Staphylococcus haemolyticus</italic> (one strain). All MRCoNS isolates were multidrug-resistant. In addition to β-lactams, the strains were resistant to fusidic acid (85%), tetracycline (75%), streptomycin (65%), ciprofloxacin (65%), and trimethoprim/sulphamethoxazole (60%). In addition to the <italic>mecA</italic> and <italic>blaZ</italic> genes, other antimicrobial resistance genes detected were <italic>tet</italic>(K), <italic>tet</italic>(M), <italic>tet</italic>(L), <italic>erm</italic>(B), <italic>erm</italic>(C), <italic>aacA-aphD</italic>, <italic>aphA3</italic>, <italic>str</italic>, <italic>dfrK</italic>, <italic>dfr</italic>G, <italic>cat</italic>_pC221, and <italic>cat</italic>_pC223. Thirteen isolates were found to be ciprofloxacin-resistant, and all harbored a Ser84Leu mutation within the QRDR of the GyrA protein, with 3 isolates showing 2 extra substitutions, Ser98Ile and Arg100Lys (one strain) and Glu88Asp and Asp96Thr (2 strains). A phylogenetic tree of the QRDR nucleotide sequences in the <italic>gyrA</italic> gene revealed a high nucleotide diversity, with several major clusters not associated with the bacterial species. Our study highlights the possibility of transfer of <italic>mecA</italic> and other antimicrobial resistance genes from MRCoNS to pathogenic bacteria, which is a serious public health and veterinary concern.