Antibiotic Pulse Experiments of a 3-species Mixed Culture : Experimental Results and Mathematical Modelling

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 the 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 a mixed culture in a chemostat bioreactor and use it as a model system related to the microbial community in CF lungs [1]. Our experimental setup ensures defined and controllable conditions for the mixed culture. With comprehensive quantitative analytical methods we study bacterial growth characteristics and metabolic activity. For quantification the 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