Synergistic interactions in mixed-species biofilms of pathogenic bacteria from the respiratory tract.

INTRODUCTION Mixed-species biofilms are involved in a wide variety of infections. We studied the synergistic interactions during dual-species biofilm formation among isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia. METHODS Isolates were cultured as single-species and all possible combinations of dual-species biofilms. RESULTS The 61 A. baumannii biofilms increased by 26-fold when cultured with S. maltophilia isolates; 62 A. baumannii biofilms increased by 20-fold when cultured with S. maltophilia isolates; and 31 P. aeruginosa biofilms increased by 102-fold when cultured with S. maltophilia 106. CONCLUSIONS Synergy was observed between two isolates, including those that inherently lacked biofilm formation ability.