Mature Pseudomonas aeruginosa biofilms prevail compared to young biofilms in the presence of ceftazidime

Abstract

Phenotypic tolerances to antibiotics of mature and young Pseudomonas aeruginosa PAO1 biofilms and released planktonic bacteria were compared for four antibiotics. Resistance levels were similar for gentamicin and ciprofloxacin but differed for ceftazidime and meropenem. β-Lactamase mapping showed that, after 5 h of ceftazidime exposure, mature biofilms produced more β-lactamase than young biofilms, facilitating the growth of released planktonic bacteria. This shows the importance of early treatment and choice of antibiotics for P. aeruginosa biofilm infections.

Fig 1

Antibiotic susceptibilities of a young (4-h) biofilm (a) and a mature (24-h) biofilm (b), showing the log-transformed MBEC of the biofilm and the MIC and MBC values of the bacteria released from the biofilm following 24 h exposure to antibiotics.

Fig 2

β-Lactamase activity from young (4-h) and mature (24-h) biofilms and levels of their released planktonic bacteria and the supernatant per indicated protein concentration after 5 h (a) and 24 h (b) of antibiotic exposure. All values represent the averages of the results of three replicate experiments, with error bars indicating standard errors. * indicates a significant difference between the results of 5-h and 24-h antibiotic exposure, and ** indicates a significant difference between the results determined for young and mature biofilms (P < 0.05).