Age-related susceptibility of mice to staphylococcal infection.

The virulence of six strains of staphylococci in experimental subcutaneous infection in mice of three age groups (3, 10 and 21 days) was studied. The results showed an age-related susceptibility to infection, in that the newborn mice were more susceptible than older mice to death and lesion formation. Resistance, i.e., ability to survive challenge of 10(7) c.f.u., developed at about 5 days. The strains used varied in toxin and enzyme pattern and there were marked differences in response to challenge as measured by mortality and lesion development. The Staphylococcus epidermidis strain was least virulent, while some strains of S. aureus produced lesions at low doses (10(4) c.f.u.). Two distinct types of lesion were observed, abscesses and necrotic lesions. Development of necrotic lesions appeared to be correlated with the ability to produce toxin in vitro.