Correlation of teichoic acid D-alanyl esterification with the expression of methicillin resistance in Staphylococcus aureus.

Methicillin-susceptible and -resistant isolates of Staphylococcus aureus, including a teichoic acid-deficient mutant, were examined under varying physiological conditions for their degree of teichoic acid and lipoteichoic acid D-alanyl esterification. Methicillin-resistant strains grown in the presence of methicillin and NaCl possessed significantly decreased amounts of D-alanyl ester when compared with methicillin-susceptible isolates. These strains also exhibited reduced autolysis. An autoradiographic procedure was used to detect mutants, isolated by Tn917 and nitrosoguanidine mutagenesis of methicillin-susceptible strains, which were defective in D-alanyl ester formation. The quantitative uptake of D-[14C]alanine in these mutants was determined and the effect of methicillin on the growth and viability of each mutant was compared with the wild-type strain. S. aureus mutant strains, defective in the uptake and incorporation of D-alanine, were shown to exhibit slightly reduced autolysis and an enhanced expression of methicillin resistance.