Study On The Pathogenicity,Drug Resistance And Epidemiological Of Acinetobacter Baumannii Isolated From Patients With Clinical Infection

Objective To study the biofilm forming ability of Acinetobacter baumannii(Ab)isolated from patients with clinical infections in Tianjin Medical University General Hospital,especially for the biofilm formation of multidrug-resistant Acinetobacter baumannii(MDR-AB).To study the relationship among biofilm formation,related antibiotic resistance,and biofilm-associated genes,to realize the epidemiology of MDR-AB,to uncover the characteristics of biofilm-producing strains and the antibiotic resistance,to clarify the mechanism of related genes affecting biofilm formation and drug resistance,so as to provide clinical diagnosis,treatment basis and infection control plan for MDR-AB.Methods A total of 65 Ab strains isolated from patients with clinical infections during 2013 to 2015 were collected from Tianjin Medical University General Hospital.The types,specific sources,drug sensitivity testing results of the strains were analyzed.The biofilm forming ability was detected by crystal violet staining method,and the related genes--CsuC,CsuD,CsuE,abaI,Bap,bfmS,OmpA and IntI1are tested by PCR.Then the biofilm forming ability,drug resistance,and the presence of the related genes were statistically analyzed.PFGE and MLST were used for the epidemiological study of MDR-AB in our hospital.Results Among the 65 Ab strains isolated from patients with clinical infection,there were 9,3,16 and 37 strains of negative,weak positive,moderate positive and strong positive respectively.The positive rate of biofilm formation was 86%,among which the positive rate of biofilm was 95.3%in MDR-AB group and 68.1%in non-MDR-AB group.The difference of the positive rate of the biofilms formation of the two groups was statistically significant(X~2=6.871,P=0.009,P<0.05).The positive rate of Ab biofilm detected from catheter samples and from ICU samples was100%,and both of them were strongly positive.The antibiotic resistance of biofilm-positive Ab was significantly higher than that of the biofilm-negative Ab.Among them,the increase in drug resistance rates of FEP,IMP,TZP,and CIP were of significant differences between groups(P<0.05).With the increase of biofilm forming ability,the drug resistance rates of ATM,FEP,IMP,TZP,CIP,LVX,and SXT decreased.The resistance rate of LVX and SXT decreased significantly with statistical significance(P<0.05).In addition to IntI1 in Ab,the detection rates of CsuC,CsuD,CsuE,AbaI,Bap,bfmS,and OmpA were high(>50%).The detection rates of AbaI,Bap and bfmS in the MDR-AB group were higher than those in the non-MDR-AB group(P<0.05).The detection rate of other 7 genes,except for Intl,in the biofilm-positive group was higher than that in the biofilm-negative group,and the detection rate of Bap was of statistically significant difference(P<0.05).The antibiotic resistance rates of the positive group biofilm-associated gene was higher than that of the negative group,and the resistance rates of the AbaI,Bap,bfmS,and IntI1-positive groups to FEP,IMP,TZP,and CIP were increased significantly,when compared with those of the negative group(P<0.05).The drug resistance rates of AbaI,Bap and bfmS positive groups to TOB and GEN were significantly higher than those of the negative group(P<0.05).The drug resistance to SXT was significantly higher in the bap,bfms,and intI1-positive groups than in the negative group(P<0.05),and the drug resistance to LVX in the bap positive group was significantly higher than that in the negative group(P<0.05).The main clones of the MDR-AB in our hospital were A clone group,followed by C clones.The main sequence type of the epidemic is ST195,and the remainder is ST208,ST381,ST368,and one new ST types(ST1779).Conclusion The positive rate of biofilm in Ab isolated from clinical infection patients in our hispital is high,and the drug resistance rate of biofilm-positive strains is higher than that of biofilm-negative strains.However,as the biofilm forming ability increases,the resistance rate of some antibiotics will decline.All of CsuC,CsuD,CsuE,AbaI,Bap,bfmS,and OmpA have high detection rates in Ab,and the presence of these genes is responsible for the high rate of drug resistance and presents an important factor in multi-drug resistance,pan-drug resistance and biofilm formation.The main clones of MDR-AB was A and C clones(PFGE),ST195 and ST208.One new ST types(ST1779)was found,and which all ST were related to CC208.So,the prevalence of MDR-AB is closely related to CC208.