Identification Of Stenotrophomonas Maltophilia With Biofilms And In Vitro Effects Of Antibiotic Agents On Biofilms

Objective:To investigate the current situations and resistance of Stenotrophomonas maltophilia(SMA)clinical strains collected from Tianjin Area,and to evaluate the efficacy of silver staining for detection of the SMA bacterial biofilm(BBF).Finally,we investigated the in vitro effects of eight antibiotic agents on the SMA biofilms when used alone and combinated.Methods:The model of SMA biofilms in vitro was established in the Mueller-Hinton broth—silica film system,and was identified by scanning electron microscopy and silver staining.The distribution and drug resistant situations of clinical strains of SMA isolated were analyzed,strains of SMA resistant to all the 12 antibiotics were analyzed through broth macrodilution according to the guideline of Clinical and Laboratory Standards Institute(CLSI).Subseqently,the model of SMA biofilms in vitro was developed in the Mueller-Hinton broth——Microtiter inoculator, challenged by 8 antibiotic agents(levofloxacin,ciprofloxacin,ceftazifime, piperacillin,cefoperazone/sulbactam,erythromycin,sulfamethoxazole,gentamycin) and calculated biofilm inhibitory concentrations(BIC).Finally,the experiments of combination effects of erythromycin with the levofloxacin,cefoperazone/sulbactam and piperacillin,respectively,on the formed biofilms of SMA were designed and worked out,and to observe the change of biofilms by scanning electron microscopy.Rusults:The model of SMA biofilms established in vitro might be identified by scanning electron microscopy and silver staining.The resistance rates of SMA were as following:levofloxacin 12.70%,ofloxacin 25.70%,ciprofloxacin 37.50%, cefoperazone/sulbactam 43.90%,piperacillin 44.60%,cefepime 45.10%, cefoperazone 49.00%,ciprofloxacin 37.50%,gentamycin 81.80%,ceftriaxone 87.90%,amikacin 90.60%,cefotaxime 95%.Among 51 clinical strains,47 strains(92.16%)were resistant two or more antibiotics.Of 42 strains which could be formed bacterial biofilms,the BIC₅₀of levofloxacin,ciprofloxacin,ciprofloxacin, cefoperazone/sulbactam,piperacillin,erythromycin and sulfamethoxazole, gentamyxin are 4μg/ml,8μg/ml,128μg/ml,128μg/ml,256μg/ml,128μg/ml, 304μg/ml,256μg/ml,respectively.The effects using levofloxacin alone or with erythromycin could inhibit growth of SMA biofilms,by destroying their structure.Conclusion:SMA may be one of the most important pathogenic bacteria in Tianjin Area,with features of high drug resistance rate and multidrug resistance. Comparing to planktonic bacterial growth,SMA growing as biofilms proves to be highly resistant to most antimicrobial agents.The susceptibility testings demonstrate, levofloxacin,cefoperazone/sulbactam and piperacillin have high level antimicrobial activity.The silver staining could be simple method for identifying SMA biofilms. Combination of levofloxacin with erythromycin might be destroy the structure of SMA biofilms and promote therapeutic effect.