The Researches Of Antibiotic Resistance Changing Tendency In Acinetobacter Baumannii And The Effects Of Bacterial Quorum Sensing System During Acinetobacter Baumannii Biofilm Formation Process

Objection:Infection caused by drug-resistant bacteria is still the big challenge in the clinical treatment.Acinetobacter baumannii(A.baumannii)is one of the most commonly encountered opportunistic pathogens in clinical samples because of its ability for wide spectrum of antimicrobial resistance.This research aims to realize the epidemiological characteristics and drug resistance of A.baumannii,then preliminary discuss the related regulatory mechanism of its quorum sensing system on bacterial biofilm formation and antibiotic resistanceMethods:①A retrospective study of spectrum of pathogens was conducted in a comprehensive hospital,its burn wards and CHINET between 2007 and 2013 Antimicrobial susceptibility surveillance of A.baumannii isolates from 2007 to 2013 in the hospital and burn wards were collected and analyzed.②To further understand biofilm formation characteristics of clinical strains on A.baumannii in vitro and discuss effects of different signal molecules on biofilm formation,then confirm the relationships between QS and biofilm formation.③Construct a gene knockout model of signal molecular receptor-abaR for exploring the relationships between abaR and bacterial behaviors,such as biofilm formation and antibiotic resistanceResults:①Escherichia coli,Staphylococcus aureus,Acinetobacter baumannii,Pseudomonas aeruginosa and Klebsiella pneumoniae were the top five pathogens isolated from the hospital.In the burn wards,the top five microorganisms included Staphylococcus aureus,Acinetobacter baumannii,Pseudomonas aeruginosa,Staphylococcus epidermidis and Escherichia coli.Compared to the data from the hospital and CHINET,A.baumannii showed higher resistance to Ceftazidime,Amikacin,Ciprofloxacin,Imipenem and Cefoperazone-sulbactam in burn wards(with P value<0.05).②Whatever sensitive strains or extensive drug resistant strains,they have the strongest biofilm formation while they grow for 24 h.?Compared with control group,10μM C7-HSL has a obvious inhibitory effect on clinical strains S87 and S96 biofilm formation at 24h(P<0.01),while 100μM C7-HSL has the same effect at 12h(P<0.01).The biofilm formation change trend is consistent among OH-dDHL and control group in clinical strains S87 and S96,but the biofilm formation has no obvious difference(P>0.05).④One step inactivation of abaR gene in A.baumannii using PCR methods continuesConclusion:As one of the most important gram-negative pathogens,A.baumannii is highly resistant to common antibiotics,especially in the burn wards.Both extensive drug resistant strains and sensitive strains have the strongest biofilm formation while they grow for 24 h.As a LuxR antagonist,C7-HSL has a negative effect on biofilm formation for A.baumannii clinical strains,which is associated with the signal molecular receptor abaR.