Prevalence and antibiotic susceptibility pattern of methicillin resistant Staphylococcus aureus in burns and pressure ulcer patients

Abstract

Methicillin resistant Staphylococcus aureus (MRSA) is a multidrug resistant bacterium that threatens the continued effectiveness of antibiotics worldwide. The objective of this study was to investigate the prevalence of MRSA and its antibiotic susceptibility pattern in patients with burns and bedsore. This was a cross- sectional study that was carried out at National Orthopaedic Hospital, Enugu, Nigeria. A structured questionnaire was used to obtain information on demographic and source of wounds. Pus from the wound was collected with swab sticks or 2ml syringe and analyzed bacteriologically, using mannitol salt agar sheep red cell blood agar. Isolates of Staphyloccus aureus were subjected to oxacillin and cefoxitin disc-diffusion assay and confirmed by chromogenic Brilliance MRSA 2 Agar; for identification of MRSA and MSSA. The MRSA and MSSA strains were tested for antimicrobial susceptibility patterns and multiple antibiotic index calculated. Of 104 wound swabs analyzed, 52 (50%) were Staphylococcus aureus isolates, while 21 (20.2%) were MRSA and 31 (29.8%) were MSSA. No significant differences were observed in the prevalence of MRSA among gender, duration of wounds, wound dressing interval and source of wound. There was an association between age, prolonged hospital admission MRSA infection. Methicillin-resistant Staphylococcus aureus isolates showed high resistance to ampicillin 90.5% followed by erytromycin 81% and ciprofloxacillin 71.4%.All the MRSA isolates were susceptible to vancomycin. All isolates of MRSA were resistant to β-lactams, aminoglycosides and quinolones group of antibiotic used. Minimum Inhibitory Concentration of vancomycin showed that the break point was between 0.5-2kg/ml and that of ampicillin was ranges from 4 kg/ml-128 kg/ml. MAR Index was >0.2 which indicates the resistance emanates from hospital. The high prevalence of MRSA and antibiotics resistance may increase the disease burden amongst these patients. It is necessary to establish an antimicrobial susceptibility surveillance system and to improve current infection control programs in the hospitals and community settings, to prevent the spread of MRSA.

Keywords: MRSA, Brillience ChromAgar, ampicillin, vancomycin, multiple antibioticindex