A 140-kilodalton extracellular protein is essential for the accumulation of Staphylococcus epidermidis strains on surfaces

Impact of bacterial biofilm formation on in vitro and in vivo activities of antibiotics

The impact of bacterial adherence on antibiotic activity was analyzed with two isogenic strains of Staphylococcus epidermidis that differ in the features of their in vitro biofilm formation. The eradication of bacteria adhering to glass beads by amikacin, levofloxacin, rifampin, or teicoplanin was studied in an animal model and in a pharmacokinetically matched in vitro model. The features of S. epidermidis RP62A that allowed it to grow on surfaces in multiple layers promoted phenotypic resistance to antibiotic treatment, whereas strain M7 failed to accumulate, despite initial adherence on surfaces and growth in suspension similar to those for RP62A. Biofilms of S. epidermidis M7 were better eradicated than those of strain RP62A in vitro (46 versus 31%; P < 0.05) as well as in the animal model (39 versus 9%; P < 0.01).

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.