Methicillin-Resistant Staphylococci: Genetics of the Minority Population

Publisher Website
Google Scholar
Abstract
A methicillin-resistant strain of Staphylococcus aureus (no. 5982) contained cocci with differing intrinsic resistances to methicillin. Most of the population was slightly more resistant that a typical methicillin-sensitive staphylococcal isolate, but a few were mutants with ability to grow at markedly increased concentrations of methicillin (500 ug./ml. or more). Penicillinase production was not essential for methicillin resistance since a penicillinase-negative variant of strain 5982 was able to produce penicillinase-negative strains with high degrees of methicillin resistance. Methicillin-sensitive strains also gave rise to mutants with increased intrinsic resistance to methicillin, but, in the mutants from methicillin-resistant strains, the increase in resistance was much greater. The mutants were characteristically slower growing than the wild type. Many were small colony variants which reverted to the parent type when passed in liquid media. With 5% NaCl-methicillin plates strain 5982 exhibited a phenotypic increase in resistance. On such plates a few L-type colonies were produced at high concentrations of methicillin.

This publication has 3 references indexed in Scilit: