Abstract: Abstract Objective: To investigate the current situations and resistance of Stenotrophomonas Maltophiliaclinical strains collected from Tianjin Area, we investigated the in vitro effects of antibiotics on the SMA biofilms. Methods: The distribution and drug resistant situations of clinical strains of SML isolated were analyzed. Subseqently, The model of SMA biofilms in vitro was developed, challenged by antibiotics and calculated biofilm inhibitory concentrations, and to observe the change of biofilms by scanning electron microscopy. Rusults: The resistance rates of SMA were as following: 13.73％；25.49％；37.25％；45.10％;88.25％；60.78％；49.02％；43.14％；45.10％；94.12％；90.20％；82.35％; Of 42 strains which could be formed bacterial biofilms; The drug experiments and scanning electron microscopeand biofilms formation that, after each antibiotic resistance and resistance strains were increased substantially. Conclusion: SMA may be one of the most important pathogenic bacteria in Tianjin Area, with features of high drug resistance rate and multidrug resistance. The susceptibility testings demonstrate, levofloxacin and cefoperazone/sulbactam have high level antimicrobial activity. Comparing to planktonic bacterial growth, SMA growing as biofilms proves to be highly resistant to most antimicrobials.

Key words: Stenotrophomonas Maltophiliaclinical, biofilm, minimal inhibitory concentration, biofilm inhibitory concentration, antibiotics