[Frequency of methicillin resistance varies with conditions, in a population of staphylococci from a hospital environment].

The incidence of methicillin-resistant Strains is increasing in these last years. This increase is particularly evident in Strains isolated from hospital environments. In this work we evaluated the methicillin-resistance of 58 Staphylococcus Strains, isolated from a surgical intensive care ward, in various experimental conditions, which changing in: culture medium, inoculum, incubation period and antibiotic concentration. Besides this we took in consideration various factors which can influence the frequency of methicillin-resistance and can also lead to errors in the evaluation itself. From our study we can conclude that the factors are: survey "in vitro" of the resistance or of the sensitivity, exclusion or inclusion of staphylococci different from Staphylococcus aureus, double count of the same Strains isolated in different times.