Thesis (Ph.D.) - Cairo University - Faculty of Medicine - Department of Microbiology and Immunology

The prevalence of methicillin resistant Staphyloccoccus. aureus (MRSA) strains has presented a new challenge in antimicrobial medication. Linezolid is a new drug with potent activity on Gram positive pathogens such as MRSA. The aim of the study was to investigate the in vitro activity of linezolid alone and in combination with imipenem, vancomycin or rifampicin to determine the most active therapy against MRSA strains linezolid may be combined with other antimicrobial agents in order to provide broad-spectrum coverage, prevent the emergence of resistant mutants, and obtain a synergy between both antimicrobial agents. Twenty clinical MRSA strains were isolated from patients admitted to inpatient departments and outpatient clinics of theodor bilharz research Institute. Standard strain MRSA ATCC 43300 was included as a control. The MICs of MRSA strains to linezolid, vancomycin, imipenem and rifampicin were evaluated using E test. Time kill curve experiments were used to assess the in vitro activity of linezolid (at 8x MIC) alone and in combination with imipenem (at 32x MIC), vancomycin or rifampicin (at 8x MIC). Scanning and transmission electron microscopy were performed to compare bacterial morphological alterations owing to the different combinations

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