An enzymic and physical chemical study of antibiotic sensitive and resistant Staphylococci

Abstract

Microelectrophoretic and enzyme assay techniques were used to investigate the surface properties of cells of strains of Staphylococcus aureus which were sensitive or resistant to methicillin.

An alkaline phosphatase enzyme system was found in cells with natural resistance to methicillin; cells sensitive to the antibiotic or which had been repeatedly grown in the presence of the antibiotic showed no phosphatase activity. This heat labile enzyme system had an optimum activity at pH 10.00--10.20 and 37°C and was firmly attached to the cell. The alkaline phosphatase was not inhibited by inorganic phosphate, although excess phosphate in the growth medium repressed its formation.

The production of the enzyme was sensitive to the Temperature of growth of the cells; cells grown at 27° and 37 °C exhibited a high phosphatase activity whereas cells grown at 42°C showed little or no activity.

There was a correlation between the production of the enzyme system, the amount of surface teichoic acid associated with the cells and methicillin resistance. It was concluded that this alkaline phosphatase enzyme system was the temperature dependent enzyme suggested previously to account for the temperature response of resistant cells of Staph. aureus to methicillin.