Antibiotic Pulse Experiments in a 3-Species Mixed Culture

Pseudomonas aeruginosa, Burkholderia cepacia and Staphylococcus aureus are opportunistic infectants, which occur as mixed cultures in the lungs of cystic fibrosis (CF) patients. Knowledge on possible interactions and growth characteristics of this microbial community in the lung obviously cannot be obtained in situ. It would be very desirable to be able to predict the mixed culture’s reaction, e.g. on antibiotic treatment, for optimal therapy of patients. We established mixed culture cultivations in a chemostat bioreactor, which are used as a model system related to the microbial community in CF lungs [1]. Our experimental setup ensures defined and controllable conditions for such cultures. With comprehensive quantitative analytical methods we study bacterial growth characteristics and metabolic activity. For quantification of species specific cell number a T-RFLP method was developed and optimized [1]. In combination with mathematical modelling we focus on identifying microbial interactions and analyze the dynamics of the system, e.g. by disturbing the quasi steady state in chemostat experiments. Here, we show results of antibiotic pulse experiments in batch culture. We use mathematical models to describe the results of the single culture experiments and compare it with results from mixed culture experiments. [1]Schmidt, J.K. et al.: (2007) BiotechBioeng 96(4):738-75