Peer Review #1 of "Biofilm released cells can easily be obtained in a fed-batch system using ica+ but not with ica- isolates (v0.1)"

Abstract

Staphylococcus epidermidis is one of the major opportunistic bacterial pathogens in healthcare facilities, mainly due to its strong ability to form biofilms in the surface of indwelling medical devices. To study biofilms under in vitro conditions, both fed-batch and flow systems are widely used, with the first being the most frequent due to their low cost and ease of use. Aim. To assess if a fed-batch system previously developed to obtain biofilm released cells (Brc) from strong biofilm producing S. epidermidis isolates could also be used to obtain and characterize Brc from isolates with lower abilities to form biofilms. Methodology. The applicability of a fed-batch system to obtain Brc from biofilms of 3 ica + and 3 ica isolates was assessed by quantifying the biofilm and Brc biomass by optical density (OD) and colonyforming units (CFU) measurements. The effect of media replacement procedures of fed-batch systems on the amount of biofilm was determined by quantifying the biofilm and biofilm bulk fluid, by CFU, after consecutive washing steps. Results. The fed-batch model was appropriate to obtain Brc from ica + isolates, that presented a greater ability to form biofilms and release cells. However, the same was not true for ica-isolates, mainly because the washing procedure would physically remove a significant number of cells from the biofilm. Conclusions. This study demonstrates that a fed-batch system is only feasible to be used to obtain Brc from S. epidermidis when studying strong and cohesive biofilm-forming isolates.