Slime-producing properties of coagulase-negative staphylococci isolated from blood cultures

OBJECTIVE: To evaluate five methods for the determination of slime-producing properties in coagulase-negative staphylococci (CNS). METHODS: One hundred and sixty-two strains of CNS considered as 'contaminants' and 162 strains associated with 'bacteremia' were tested with the tube test with tryptic soy broth, the tube test with brain---heart infusion broth supplemented with 5% sucrose, the Congo red agar method, and the microtiter-plate test with trypan blue and crystal violet, both with tryptic soy broth. RESULTS: Of the 324 strains tested, 188 were negative and 58 were positive with all methods. The remaining 78 strains were positive with one or more methods. CONCLUSIONS: There was a significant difference (p<0.001) in slime production between 162 strains of CNS pertaining to 'bacteremia' and 162 strains considered as 'contaminants', with 84 (51.8%) and 52 (32.8%) positive, respectively. The slime-producing strains were significantly more resistant (p<0.001) to cloxacillin, tobramycin, gentamicin, trimethoprim, erythromycin and ciprofloxacin.