Prudent use of antibiotics in livestock is widely considered to be important to prevent antibiotic resistance. This study aimed to evaluate the interactions between biofilms and veterinary antibiotics in therapeutic concentrations administrated via drinking water through a standardized experimental setup. In this context, two biofilms formed by pseudomonads (Pseudomonas (P.) aeruginosa or P. fluorescens) and a susceptible Escherichia (E.) coli strain were developed in a nutrient-poor medium on the inner surface of polyvinyl chloride pipe pieces. Subsequently, developing biofilms were exposed to sulfadiazine/trimethoprim (SDZ/TMP) or tylosin A (TYL A) in dosages recommended for application in drinking water for 5 or 7 days, respectively. Various interactions were detected between biofilms and antibiotics. Microbiological examinations revealed that only TYL A reduced the number of bacteria on the surface of the pipes. Additionally, susceptible E. coli survived both antibiotic treatments without observable changes in the minimum inhibitory concentration to 13 relevant antibiotics. Furthermore, as demonstrated by HPLC-UV, the dynamics of SDZ/TMP and TYL A in liquid media differed between the biofilms of both pseudomonads over the exposure period. We conclude that this approach represents an innovative step toward the effective evaluation of safe veterinary antibiotic use.
Keywords: flock treatment; poultry production; sessile bacteria; sulfadiazine; trimethoprim; tylosin A.