Chemical and physical factors influencing methicillin resistance of Staphylococcus aureus and Staphylococcus epidermidis

Abstract

Seven physical or chemical factors have been demonstrated to increase or decrease the proportion of cells expressing methicillin resistance in populations of methicillin resistant Staphylococcus aureus and Staphylococcus epidermidis . These factors are: (1) temperature, (2) visible light, (3) osmolality, (4) pH, (5) chelating agents, (6) trace metals, and (7) the presence of β-lactam antibiotics in the medium. All of these factors were first noted in S. aureus , but it now appears that they also influence the expression of methicillin resistance in S. epidermidis . Although many of the studies of these factors to date have been directed to techniques for detecting resistance, it is quite possible that many (or possibly all) of these factors are important clues to the mechanism of this resistance and its operation in human infections.