Abstract: ObjectiveTo inspect the capability of biofilm formation by pseudomonas aeruginosa isolated from lower respiratory tract infections,and examine the relationship between biofilm of pseudomonas aeruginosa and recurrent infection.MethodsAfter 28 strains of pseudomonas aeruginosa were isolated from sputum samples by routine method.The capability of biofilm formation was examined by micro-cell plate.The biofilm model was established on small silica gel slice in vitro, and the morphology changes of biofilm were observed by light microscope after 1% azaleine staining.Meanwhile,the number of living bacteria in biofilm was calculated by plate culture method.ResultsIn 28 strains of pseudomonas aeruginosa,22 strains produced biofilm,and the positive rate of biofilm was 78157% (22/28).The course of biofilm development in vitro was that,on first day,the bacteria attached the surface of silica gel slice and partly formed small cluster;on second day,the small cluster expanded;on third day and sixth day,the mature membrane-like structure appeared;on tenth day,with membrane-like structure partly destruction,small cluster appeared again.The number of living bacteria in biofilm changed as follows,slowly decreased during first day to second day,then sharply falled during second day to third day,retained a stabilization level during second day to third day,and slowly increased again during sixth day to tenth day.ConclusionIn vitro,the biofilm development of pseudomonas aeruginosa contains four stages,attachment phase during first day,transition phase during second day,maturity phase during third day to sixth day,and destruction phase during sixth day to tenth day.In the process of biofilm development,the number of living bacteria in biofilm changes with four stages,and can be used to evaluate the phase of biofilm.The biofilm formation of pseudomonas aeruginosa is an important factor of recurrent infection.