| Objective（1）The drug resistance and biofilm formation rate of Acinetobacter baumannii（AB）in the microorganism samples clinically examined in our hospital from July 2019 to December2019 were statistically analyzed;An AB biofilm（BF）model was established,and the biofilm formation process was observed by scanning electron microscopy（SEM）.（2）The destruction process of Acinetobacter baumannii biofilm by erythromycin was observed by scanning electron microscopy.（3）the detection of erythromycin destruction of acinetobacter baumannii quorum-sensing system after the biofilm gene（abaI,abaR）m RNA expression of erythromycin Ab biological membrane and the relationship between the quorum sensing system,and further explore the mechanism of erythromycin Ab biological membrane,so as to provide experimental basis for clinical application,to better guide the rational use of clinical antibiotics,also is advantageous to the development of new clinical medicine.Methods（1）Microbial specimens were collected for clinical examination in our hospital from July 2019 to December 2019.AB strain was identified by VITEK2-COMPACT automatic microbial identification system and drug sensitivity test was performed.AB biofilm was identified by Alexin blue-Congo red staining.AB strain that could form BF was selected to establish in vitro biofilm model,and the morphology of AB biofilm was observed at 24h,48h,72h and 5d respectively.（2）AB biofilm-positive strains were selected and divided into experimental group（with erythromycin）and control group（without erythromycin）.The morphology of AB biofilm was observed at 24h,48h,72h and 5d,respectively.（3）AB biofilm-positive strains were selected and divided into experimental group（with erythromycin）and control group（without erythromycin）.The m RNA expression of quorum sensing system gene（abaI、abaR）were detected by fluorescence quantitative PCR at 24h,48h,72h and 5d,respectively.The relative m RNA expression data were analyzed by 2–??CTmethod,and SPSS22was used for statistical analysis.Results（1）From July to December,2019,61 cases of AB were submitted for clinical examination in our hospital,of which 24 cases were multi-drug resistant AB strains,accounting for 39.34%of AB strains.Most of AB was from sputum culture and wound secretion,and most of the departments submitted for examination were respiratory department,geriatric department and burn department.Drug sensitivity experiment result:the imine south,cefotaxime resistant rate of 32.8%,to piperacillin/he azole temple,cefepime,cephalosporins he organism,amikacin resistant rate to 31.1%,the new Ming resistant rate of 27.9%,compound of cefoperazone/shu ba resistant rate of 8.2%,ceftriaxone,ampicillin resistant rate of 34.4%,for tobramycin resistant rate of 37.7%,to ciprofloxacin,ofloxacin,gentamicin,resistant rate of 36.1%,of minocycline resistant rate of 14.8%,the beauty from south resistant rate of 29.6%.AB is prone to form multi-drug resistant bacteria,and most commonly used clinical antibiotics are ineffective against multi-drug resistant bacteria.Under SEM,the number of bacteria increased and formed a small amount of extracellular matrix after 24h.At 48 hours,the bacteria became more and more numerous,aggregating and arranging in piles.Compared with 24h,the extracellular matrix continued to increase,and cross-linked hyphae could be seen among bacteria,and a small number of bacteria formed biofilm.After 72h,the bacteria and the matrix gathered in large numbers,and the hyphae between the bacteria were cross-linked and interbedded with each other,forming a biofilm obviously.On day 5,the bacteria were covered by a large amount of extracellular matrix,and the bacteria were wrapped and adhered to each other,forming an obvious biofilm.In the process of AB biofilm formation,three fields were randomly selected for bacterial count.It was found that the number of bacteria,the number of bacteria in the biofilm and the number of biofilm formation all increased gradually,with statistical difference（p<0.05）.（2）SEM observation after the addition of erythromycin showed that the number of bacteria in the control group continued to increase,and the bacteria were wrapped by biofilm,adhered to each other,and the bacterial gap became smaller and smaller until it disappeared;In the experimental group,the number of bacteria,the number of biofilm and the number of bacteria in the biofilm decreased after adding erythromycin for 24 hours,and the bacterial gap increased compared with the control group,and the bacterial morphology changed slightly.At48h,the bacteria in the experimental group had obvious changes compared with the control group.The bacterial gap increased,the cross-linking of the hyphae between the bacteria decreased,the bacterial morphology changed,and some of the bacteria changed from cylindrical to spherical.At 72h,the number of biofilms in the experimental group was significantly reduced,and there was almost no cross-linking among bacteria.The morphology of bacteria was mainly spherical.After 5 days,there was almost no biofilm,and only a few bacteria survived,and the bacterial morphology was spherical,without columnar bacteria.After erythromycin was added,bacteria count,biofilm count and bacteria count in the biofilm were performed again,and there were statistical differences between the experimental group and the control group at 24h,48h,72h and 5d（p<0.05）,indicating that erythromycin can destroy AB biofilm and inhibit bacterial growth to a certain extent.（3）Fluorescence quantitative PCR results showed that the expressions of ABAI and ABAR genes were gradually up-regulated with time,and the expressions of ABAI and ABAR genes were up-regulated by 5.2 and 2.6times at 5d compared with 24h,indicating that the role of quorum sensing system was more obvious with time,and the formation of biofilm was related to the quorum sensing system of AB.After erythromycin treatment,the m RNA expressions of ABAI and ABAR in the experimental group were down-regulated,while those in the control group were higher than those in the control group,and the down-regulated expression could occur after 24h,but the effect was not significant,and there was no statistical difference（p>0.05）;At 48h,72h and 5d,the expression level of the experimental group was significantly down-regulated（p<0.05）.The results of this study suggest that the formation of AB biofilm is related to the quorum sensing system,and erythromycin plays a certain role in destroying the quorum sensing system of AB.Conclusion（1）In recent years,the drug resistance rate of Acinetobacter baumannii is high,and multiple drug resistant strains are formed,and biofilm is easily formed.（2）Erythromycin can destroy the biofilm of Acinetobacter baumannii and inhibit the growth of Acinetobacter baumannii to some extent.（3）The m RNA expressions of ABAI and ABAR with the addition of Erythromycin were significantly decreased compared with those without the addition of Erythromycin.The effect of erythromycin on the destruction of Acinetobacter baumannii biofilm was deduced by the destruction of the quorum sensing system. |
PDF Full Text Request