Characterization of mannitol-fermenting methicillin-resistantstaphylococci isolated from pigs in Nigeria

摘要

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 mecA gene were detected among the 64 Staphylococcus isolates from 291 pigs. A total of 4 species were identified among the MRCoNS isolates, namely, Staphylococcus sciuri (10 strains), Staphylococcus lentus (6 strains), Staphylococcus cohnii (3 strains) and Staphylococcus haemolyticus (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 mecA and blaZ genes, other antimicrobial resistance genes detected were tet(K), tet(M), tet(L), erm(B), erm(C), aacA-aphD, aphA3, str, dfrK,dfrG, catpC221, and catpC223. Thirteen isolates were found to be ciprofloxacin-resistant, and allharbored a Ser84Leu mutation within the QRDR of the GyrA protein, with 3 isolatesshowing 2 extra substitutions, Ser98Ile and Arg100Lys (one strain) and Glu88Asp andAsp96Thr (2 strains). A phylogenetic tree of the QRDR nucleotide sequences in thegyrA gene revealed a high nucleotide diversity, with severalmajor clusters not associated with the bacterial species. Our study highlights thepossibility of transfer of mecA and other antimicrobial resistancegenes from MRCoNS to pathogenic bacteria, which is a serious public health andveterinary concern.