Figure 2 : SEM imaging of bacteria attachment using different concentration of inoculum. A) inoculum size: OD600=0.04; attachment time: 2h. B) inoculum size: OD600=0.04; attachment time: 24h. C) inoculum size: OD600=0.4; attachment time: 2h.
Device performance repeatability for biofilm culture
The device performance was further confirmed by testing its repeatability on the formation of 48h-old biofilms over a determined number of experiments. Three rounds of experiments were performed (biological triplicates), and each round contains six technical replicates. A total of eighteen replicates for each biofilm model (ALI and LLI) were obtained. The inoculum solutions were standardized at OD600 = 0.42 ± 0.03 (mean ± SD), which corresponds to Log (CFU/mL) = 8.58 ± 0.14 (mean ± SD). After 48h of growth, the number of attached cells (biofilm) and the number of detached cells washed off from the membrane after rinsing was obtained by viable colony counts. Results expressed as Log (CFU/mL) and statistical analysis are presented in Table 1 for the ALI and LLI systems. The standard deviation (SD) for detached, attached, and total biofilm cultured on ALI was 0.99, 0.87 and 0.97 log CFU/mL, respectively, and was 0.98, 0.95 and 0.91 for LLI, respectively. To our knowledge, no comparable data is available since other microdevices are unable of collecting CFU numbers due to the constrain related to the nature of other devices that cannot be disassembled without damaging the cells.
Table 1. Summary statistics of the number of sessile cells recovered from membranes after biofilm formation on ALI and LLI model surfaces.