Susceptibility of clinically isolated strains of methicillinresistant Staphylococcus aureus to vancomycin in Tehran

Background and Aim : Several drug-resistant bacteria have emerged in recent decades, whichhave challenged many antibiotics' effectiveness, particularly in hospital infections, and manyhealthcare settings have incurred a lot of costs as a result. The impressive ability of Staphylococcusaureus to acquire resistance to numerous other antibiotic classes, including methicillin-resistantS.aureus (MRSA) strains, has major ramifications for current and future treatment options againstthis pathogen. As long as the early ۱۹۶۰s, vancomycin has been considered to be the administrateddrug to treat MRSA infections in hospitalized patients, although the Centers for Disease Control(CDC) reported Vancomycin intermediate-resistant (VISA) in the United States in ۲۰۰۲ afterbeing identified in Japan for the first time in ۱۹۹۷. In terms of significance, this study wasconcerned to evaluate the level of MIC and MBC of vancomycin on MRSA isolated from theclinic.Methods : S.aureus clinical samples were collected from ۱۰۰ hospitalized patients at differentparts of the Imam Khomeini and the Sina hospitals. Following biochemical tests for confirmationof Staphylococcus aureus, ۶۰ strains of MRSA were identified and isolated by antibioticsusceptibility tests, and MICs and MBCs were determined by broth microdilution and agar diskdiffusion. By broth microdilution method, we identified two strains of Vancomycin IntermediateS.aureus and the other sensitive strains to Vancomycin. Death kinetics of selected resistant strainswere evaluated.Results : Among selected strains, Vancomycin is more effective against the MRSA S۱ strainwhich is considered most sensitive than against the MRSA S۹۵ and the MRSA S۱۵۲ strains. TheMRSA S۹۵ and MRSA S۱۵۲ strains have almost similar death kinetics, but MRSA S۱ has arelatively faster death rate due to its sensitivity to vancomycin.Conclusion : Even though no vancomycin Resistant S.aureus strains were not found in the presentstudy, the frequency of VISA strains poses a drastic threat, not only to Iran's future health but alsoto those around the world due to facing more resistant strains.

کلیدواژه ها:

Staphylococcus aureus ، Vancomycin ، MRSA ، Vancomycin intermediate-resistant(VISA)