The borderline oxacillin-resistant Staphylococcus aureus (BORSA) strains have a low-level resistance to penicillinase-resistant penicillins. The aim of this study was to study the prevalence and the antimicrobial susceptibility of BORSA strains in Bamako. A retrospective study was conducted at the University Teaching Hospital of the Point G in Bamako. The S. aureus strains were isolated on Columbia agar supplemented with 5% sheep blood, nalidixic acid and colistin. Antimicrobial susceptibility testing was performed using the disc diffusion method on Mueller-Hinton agar. β-lactamase production was determined by nitrocephin disc. Among 735 nonrepetitive strains of S. aureus, 41 (5.6%) were BORSA and 335 (45.6%) methicillin-resistant S. aureus (MRSA). The prevalence of BORSA strains was 25 (4.9%) and 16 (7.2%) in hospital and out-patients areas, respectively. Of the 41 BORSA strains, five were not β-lactamase producers. Cefoxitin (100%), cephalothin (97.6%), gentamycin (90.2%), amikacin (90.2%), netilmicin (87.8%), pristinamycin (87.8%), tobramycin (82.9%), fusidic acid (83%), lincomycin (78%), amoxicillin combined with clavulanic acid (73.2%), sulfonamides (73.2%), kanamycin (73.2%) fosfomycin (73%) and chloramphenicol (70.7%) were the most active against the BORSA strains. The prevalence of BORSA strains was not high in this study, and the strains were susceptible to a great range of antibiotics.
Key words: Antimicrobial susceptibility, borderline oxacillin-resistant Staphylococcus aureus, prevalence, Bamako (Mali).
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