Zmira Samra1, Orit Ofer, Haim Shmuely. 1. National Staphylococcus Center, Department of Microbiology, (Beilinson Campus), Petah Tiqva, Israel. zsamra@clalit.org.il
Abstract
BACKGROUND: Methicillin-resistant Staphylococcus aureus is a major nosocomial pathogen worldwide. Vancomycin is the traditional drug of choice, but decreasing susceptibility to vancomycin and other glycopeptides has been reported since 1996. OBJECTIVES: To test the in vitro activity of linezolid (oxazolidinone) and other antimicrobial agents against MRSA isolates recovered from hospitalized patients. METHODS: We tested 150 MRSA isolates recovered from hospitalized patients. The minimal inhibitory concentration of vancomycin, teicoplanin, pristinamycin (quinupristin-dalforistin) and linezolid was determined by the Etest method. Susceptibility to other antibiotics was tested by the disk diffusion method. RESULTS: All isolates were sensitive to vancomycin, teicoplanin, pristinamycin, and linezolid. The MIC90 was 2.0 microg/ml for vancomycin and teicoplanin (range 0.5-2.0 microg/ml and 0.125-2.0 microg/ml, respectively), and 0.5 microg/ml for pristinamycin and linezolid (range 0.125-0.75 microg/ml and 0.125-0.5 microg/ml, respectively). Of the other antibiotics, fusidic acid showed the best in vitro activity, with 96.7% susceptibility, associated with trimethoprim/sulfamethoxazole (85.8%) and minocycline (84%). Penicillin was associated with the lowest susceptibility (1.3%), associated with ofloxacin (3%) and erythromycin (14%). An increase in the minimal inhibitory concentration value of vancomycin was associated with a significant decrease in resistance to TMP-SMZ (P < 0.01) and an apparent increase in resistance to other antibiotics. CONCLUSION: The excellent in vitro activity of linezolid and its reported in vivo effectiveness renders it an important therapeutic alternative to vancomycin in the treatment of MRSA infection.
BACKGROUND: Methicillin-resistant Staphylococcus aureus is a major nosocomial pathogen worldwide. Vancomycin is the traditional drug of choice, but decreasing susceptibility to vancomycin and other glycopeptides has been reported since 1996. OBJECTIVES: To test the in vitro activity of linezolid (oxazolidinone) and other antimicrobial agents against MRSA isolates recovered from hospitalized patients. METHODS: We tested 150 MRSA isolates recovered from hospitalized patients. The minimal inhibitory concentration of vancomycin, teicoplanin, pristinamycin (quinupristin-dalforistin) and linezolid was determined by the Etest method. Susceptibility to other antibiotics was tested by the disk diffusion method. RESULTS: All isolates were sensitive to vancomycin, teicoplanin, pristinamycin, and linezolid. The MIC90 was 2.0 microg/ml for vancomycin and teicoplanin (range 0.5-2.0 microg/ml and 0.125-2.0 microg/ml, respectively), and 0.5 microg/ml for pristinamycin and linezolid (range 0.125-0.75 microg/ml and 0.125-0.5 microg/ml, respectively). Of the other antibiotics, fusidic acid showed the best in vitro activity, with 96.7% susceptibility, associated with trimethoprim/sulfamethoxazole (85.8%) and minocycline (84%). Penicillin was associated with the lowest susceptibility (1.3%), associated with ofloxacin (3%) and erythromycin (14%). An increase in the minimal inhibitory concentration value of vancomycin was associated with a significant decrease in resistance to TMP-SMZ (P < 0.01) and an apparent increase in resistance to other antibiotics. CONCLUSION: The excellent in vitro activity of linezolid and its reported in vivo effectiveness renders it an important therapeutic alternative to vancomycin in the treatment of MRSA infection.
Authors: Daina Zeng; Dmitri Debabov; Theresa L Hartsell; Raul J Cano; Stacy Adams; Jessica A Schuyler; Ronald McMillan; John L Pace Journal: Cold Spring Harb Perspect Med Date: 2016-12-01 Impact factor: 6.915