Study of susceptibility to vancomycin from clinical isolates of Staphylococcus aureus

Abstract

Vancomycin has been considered for over 40 years as the primary treatment option for Methicillin-Resistant Staphylococcus aureus (MRSA) strains. However, excessive, indiscriminate, or inappropriate use has led to the appearance of MRSA strains with intermediate resistance (VISA) and total resistance to vancomycin (VRSA) 1. In Central America, particularly in Honduras, no VRSA strains have been reported. However, it is vitally important to implement an epidemiological surveillance program where this isolation can be traced since its appearance has been considered a severe public health problem in the last two decades 2. By 2002, the first two VRSA strains were isolated, specifically in Michigan and Pennsylvania. Since then, a total of 52 VRSA isolates have been reported worldwide. The only country in Latin America that has reported VRSA strains is Brazil3. In this sense, we have carried out an assay to determine the MIC of the 96 clinical isolates of S.aureus obtained from patients who attended two of the essential hospital centers in Tegucigalpa, Honduras: the Hospital Escuela (HE) and the Honduran Institute of Social Security (IHSS). The samples were the same with which we studied resistance to methicillin, and it is a follow-up to the study that was previously published in this journal4. The MIC of S. aureus to vancomycin was determined using the E-test® strips (Solna, Sweden) under the same conditions reported in the previous study4 and based on what is recommended by the CLSI5 (figure 1). The cohort points to determine the susceptibility and resistance of S.aures to vancomycin can be seen in Table 1.