Host response to coagulase-negative staphylococci in abscesses induced within mice

A model whereby a known number of coagulase-negative staphylococci were packed into capillary tubes and implanted into the peritoneal cavity of mice proved to be a satisfactory method for generating abscesses that could be easily removed free of extraneous host tissue, and that permitted measurement of the survival of the organisms and accumulation of lipid in the lesion. Strains of S. epidermidis, S. schleiferi and S. lugdunensis, differing in their ability to produce fatty acid modifying enzyme (FAME) and lipase, were packed into either glass or plastic capillary tubes and used to generate abscesses. Abscesses produced by S. aureus served as comparators. Lipids accumulated within the abscesses caused by S. aureus in the same manner as previously described for the organism inoculated without tubes. Lipids also accumulated within abscesses produced by all the coagulase-negative staphylococci, but the rate of accumulation was slower and the lipid droplets were smaller than seen with S. aureus. The mobilisation of lipid did not differ in response to cocci in plastic or glass tubes. Strains of S. epidermidis and S. schleiferi producing FAME and lipase were better able to survive within abscesses than strains unable to produce these enzymes. However, FAME and lipase production did not appear to be the sole determinants of survival within abscesses. Regardless of whether they produced FAME and lipase, the two S. epidermidis strains were significantly better able to survive within plastic tubes than in glass tubes. No such difference was seen with S. aureus between plastic and glass tubes.