Fate of Staphylococcus aureus in Bruised Tissue

Abstract

This investigation was initiated to determine the fate and behavior of a virulent marker strain of Staphylococcus aureus (MS) injected intramuscularly into both control and traumatized tissues. Control tissues appeared to possess a clearing mechanism highly active against this organism, whereas bruised tissues stimulated and supported its growth. This stimulation may be due to the presence of extrastromal hemoglobin in the bruised areas. By use of the disc-sensitivity procedure, extrastromal hemoglobin was found to enhance the growth of S. aureus (MS) and this stimulation was linearly dependent on concentration in the range of 0.002 to 0.008 μmole per disc. Physical and physiological factors affecting the fate of staphylococci in poultry tissues were studied. The results showed that the number of viable cells of S. aureus (MS) in the initial inoculum exerted little effect on the survival activity patterns of this organism in the traumatized tissues. Control tissues, however, only became infected when a suspension containing 1.34 × 10 9 cells of the marker strain was injected. Regardless of the concentration of cells of this test culture inoculated into bruised areas, the staphylococci did not increase in number above a log of 8.5 organisms per gram of tissue. The extent of both tissue damage and accumulation of blood and fluid seemed to play an important role in the fate of staphylococci in experimentally induced infection. A correlation was noted between the severity of the bruise and the rate of growth and multiplication of virulent staphylococci in the tissue. The rate of growth showed a 100-fold increase in 1 day in the severe bruise, in 2 days in the medium bruise, and in 3 days in the superficial bruise. Time-course studies revealed that virulent S. aureus (MS) was able to persist in bruised tissue for long periods of time (18 days) even in the absence of noticeable infection. Therefore, it is believed that bruised tissue is a source of contamination to other birds and a health hazard to man.