Biofilm formation by persistent and non-persistent isolates of Staphylococcus epidermidis from a neonatal intensive care unit.

Correlation of biofilm formation and presence of the icaADBC genes was studied in 161 clinical isolates of S. epidermidis from persistent and non-persistent neonatal infections. Biofilm formation was compared in trypticase soy broth with or without added glucose (0.5-9.23%), and total parenteral nutrition (TPN) containing 9.23% glucose. Detection of icaADBC genes was carried out using polymerase chain reaction and ica-specific primers. Quantitative biofilm formation for all isolates was highest in the presence of 1% glucose, followed by trypticase soy broth and TPN. There was no significant difference between the amount of biofilm formed by persistent and non-persistent isolates under different test conditions. In contrast, 70% of the persistent isolates produced biofilm in TPN compared to the 56.3% of the non-persistent group. Neither the persistent bacterial phenotype nor presence of the icaADBC operon was correlated with biofilm formation.