Antibiotic Tolerance in Methicillin-Sensitive Staphylococcus aureus Strains

Abstract

The aim of this study was to detect the antibiotic tolerance in Staphylococcus aureus strains against ?-lactam antibiotics. MIC and MBC levels of penicillin, ampicillin, cefazolin, cefoxitin and ceftriaxone against Staphylococcus aureus strains isolated from various clinical specimens have been investigated. If the MIC/MBC ratio is equivalent to 1/32 or higher, the strains have been accepted as being tolerant to the tested antibiotic. In in vitro conditions 2 out of 5 penicillin sensitive strains, 3 out of 7 ampicillin sensitive strains, 9 (27.3%) out of 33 (82.5%) cefazolin sensitive strains, 11 (31.4%) out of 35 (87.5%) cefoxitin sensitive strains, 6 (15.8%) out of 38 (95%) imipenem sensitive strains, have exhibited antibiotic tolerance and the development of common tolerance has been detected against cephalosporines in 6 of the 40 Staphylococcus aureus strains. As a result, the exhibition of lowest level of bacterial tolerance in methicillin sensitive Staphylococcus aureus strains have been detected against imipenem.