Production of slime by staphylococcal isolates from blood cultures

The aim was to examine the ability of staphylococci isolated from blood cultures to produce slime and to compare the slime production of strains considered clinically significant and of strains considered mere contaminants. The ability to produce slime was examined in 359 staphylococcal isolates from blood cultures by the congo red agar method. The clinical significance of an isolate was estimated according to the frequency of its occurrence in a series of blood cultures. Only strains isolated at least twice from the series of two or more blood cultures were considered significant. The slime production was detected in 18 of 32 strains (56.2%) of Staphylococcus aureus, in 61 of 231 strains (26.4%) of S. epidermidis and in 14 of 101 strains (14.6%) of the remaining seven species. Out of 80 strains considered significant, 33 strains (41.2%) produced slime, out of 132 strains considered contaminants, 24 strains (18.2%) were slime producers. The significance of the remaining isolates was non-evaluable. We conclude that the staphylococcal isolates from blood cultures considered clinically significant produced slime more often than the isolates considered mere contaminants.