Development of an in vitro biofilm model for the study of the impact of fluoroquinolones on sewer biofilm microbiota

Sewer biofilms are likely to constitute hot spots for selecting and accumulating antibiotic-resistant bacteria and antibiotic resistance genes. The objective of this study was to optimize culture conditions to obtain a stable and reproducible in vitro biofilm, mimicking the biofilm collected in sewers, in order to study the impact of fluoroquinolones on sewer biofilm microbiota. Biofilms were produced on coupons in CDC Biofilm Reactors®, continuously fed with nutrient and inoculum. Different culture conditions were tested: (i) initial inoculum: diluted wastewater with or without sewer biofilm, (ii) coupon material: concrete vs polycarbonate, and (iii) time of culture: 7 days (d7) vs 14 days (d14). Biofilms were collected on d7 and d14. Once the growth conditions have been determined, the impact of fluoroquinolones on sewer biofilm microbiota, alone or in combination, was evaluated.