EJMS

Abstract

Staphylococcus aureus (S. aureus) is a prominent human pathogen that causes a wide variety of infections. Vancomycin has been the drug of choice for 30 years for the treatment of methicillin-resistant Staphylococcus aureus (MRSA). Emergence of decreased vancomycin susceptibility in MRSA strains presents a significant clinical problem with few therapeutic options. In this study, 135(34.6%) strains of Staphylococcus spp. were isolated from 390 clinical samples collected from patients attending Assiut University Hospitals. The strains were isolated from 21 (15.5%) burns, 31 (23%) wounds, 49 (36.3%) sputum and 34 (25.2%) urine specimens. All strains were identified microscopically, cultured on mannitol salt agar and blood agar, and then tested by catalase, coagulase and DNAse tests. The strains identified by traditional microbiological method were further identified by API Staph strips to confirm identification of the isolated strains. Out of the 135 Staphylococcus spp, 94 (69.63%) were coagulase-positive (COPS) and 41 (30.37%) were coagulase-negative (CONS). While the result of API Staph strips were 97 (71.85%) S. aureus, 32 (23.7%) S. epidermidis and 6 (4.45%) S.haemolyticus. All strains were screened for determination of vancomycin-resistant staphylococci by antibiotic sensitivity disc diffusion method and vancomycin agar screen plate. According to disc diffusion, vancomycin-resistant COPS were 23 (24.5%), while vancomycin resistant CONS were 2 (4.8%). The screening by vancomycin agar screen plate revealed that vancomycin-resistant COPS were 39 (41.4%) while vancomycin resistant CONS were 6 (14.6%). MICs of vancomycin was determined by broth microdilution method, BioTimer assay method (BTA), and Hicomb MIC E-test, where vancomycin-resistant COPS isolates by broth microdilution method, BTA method and Hicomb MIC E-test were 39 (41.4%), 43 (45.7%) and 44 (46.7 %) respectively, While vancomycin-resistant CONS isolates were 7 (17%), 9 (22 %) and 9 (22%) respectively. Genotypic detection of vanA and vanB genes by PCR was parallel with phenotypic results.