Research Of Resistant Gene And Molecular Epidemiological Of Multi-drug Resistant Acinetobacter Baumannii

Acinetobacter baumannii, an opportunistis pathogen, is a kind of glucose-nonfermenting gram-negative bacilli, which can be widely found in water,soil,hospital, and the skin of body.It has become one of the most important pathogenic bacteriums of acquired character infected in hospital.Nosocomial infections caused by Acinetobacter baumannii include acquired pneumonia,especially ventilator-associated pneumonia,bloodstream,urinary tract infection,and soft tissue infections.Following the widely use of broad-spectrum antimicrobials and immunosuppressant,Multi-drug resistant Acinetobacter baumannii which resistant to commonly used antimicrobial agents such as beta lactams,aminoglycosides,fluoroquinolones increased quickly, causing nosocomial outbreak, which is difficult to deal with in clinical anti infection treatment.At the same time, there is a new challenge for nosocomial infection control. For this reason, this study aims through statistical analysis for the antibiotics resistant characteristics and clinical distribution of multi-drug resistant Acinetobacter baumannii, detection of related resistant gene of multi-drug resistant Acinetobacter baumanniiby PCR and the Homology analysis for multi-drug resistant Acinetobacter baumanni to guide the clinical rational use of antimicrobial agents,explore the main mechanism of multi-drug resistant Acinetobacter baumannii,and to provide a scientific proof for the prevention and treatment of infection.In this study,62 strains of multi-drug resistant Acinetobacter baumanniiwere isolated from the Affiliated Hospital of Sichuan Medical University through Sep 2013 to Sep 2014.Acinetobacter baumannii were identified by MicroScan WalkAway 96 Plus automated microbial identification/susceptibility test system.The minimum inhibitory concentration of 23 kinds of antimicrobial drugs in these strains were detected by the agar dilution method.PCR was used to detect resistance gene,namely TEM、SHV、VIM、IMP、OXA-23、OXA-24 of these strais.The positive gene amplification products were sent to Shanghai boshang to sequence.compare the results with GenBank database.Molecular typing and homology analysis for 62 strains multi-drug resistant Acinetobacter baumanni was analysed by pulsed field gel electrophoresis.The results showed that 62 strains of multi-drug resistant Acinetobacter baumannii were mainly isolated from sputum, among which,40 strains were isolated from sputum and 11 strains were isolated from secretion.The other strains isolated from blood,urine,cerebrospinal fluid and pleural effusion were 4,3,2 and 2.24 strains were isolated from the intensive care unit,10 strains were isolated from respiratory department,8 strains were isolated from department of neurosurgery,the remaining strains were isolated from other clinical departments.All the 62 collected isolates showed 100% resistance to penicillin,The resistance rate to cephalosporin drugs:ceftriaxone was 96.8%;the rest are 100%;the resistance rate to ampicillin/sulbactam rate was 80.6%;the resistance rate to carbapenem antibiotics such as imipenem,meropenem was 90.3%,88.7%;the resistance rate to aminoglycoside antibiotics such as Gentamicine,Amikacin,Tobramycine rate respectively was 93.5%,80.6%,53.2%;the resistance rate to quinolone drugs such as Ciprofloxacin,Levofloxacin,Gatifloxacine was 100%,85.5%,64.5%;the resistance rate to Colistin and Polymyxin B was 12.9%,11.3%;the resistance rate to Tetracycline,Minocycline,Tigecycline was 90.3%,17.7%,3.2%;the resistance rate to Sulfamethoxazole and Rifampicine was 69.4%and 92%.4 kinds of resistant genes were detected in which TEM positive were 52 strains(83.9%),VIM positive were 53 strains(85.5%),IMP positive were 41 strains(66.1%),OXA-23 positive were 58 strains(93.5%);the OXA-24 and SHV gene were not detected.The homology were 98% to 100% between 4 kinds of resistant gene and the corresponding gene sequences in GenBank which had been submitted.Homology results showed that 62 strains multidrug-resistant Acinetobacter baumannii were classified into 4 types on PFGE patterns,type A and B were the main clone.32 strains were type A which includes 4 subtypes,19 strains were type B which includes 2 subtypes,8 strains were type C and 3 strains were type D.In brief,multi-drug resistant Acinetobacter baumannii in our hospital were mainly isolated from Respiratory department,ICU,and Department of Neurosurgery.Infection cases were mainly in lower respiratory tract infection,which is related to all kinds of invasive operation.The resistance of multidrug-resistant Acinetobacter baumannii is very serious,levels of 62 strains multidrug-resistant Acinetobacter baumannii for 23 kinds of antimicrobial in this study were higher than the level of bacterial resistance monitoring network.The rate of OXA-23 gene in 62 strains multidrug-resistant Acinetobacter baumanniiwas was the highest,was 93.5%.And the rate of VIM,TEM,IMP gene is as high as 85.5%,83.9%,66.1%,indicating that multiple resistance genes carried in multidrug-resistant Acinetobacter baumannii was very common.62 strains of multidrug-resistant Acinetobacter baumannii in our hospital were divided into 4 type,type A was the main clone,accounting for 51.6%(32strains).These strains were mainly isolated from ICU,Respiratory department,Department of Neurosurgery,Department of Orthopedics and Department of Hematology.followed by B type,mainly in ICU,Respiratory department and Department of Pediatrics.Multidrug-resistant Acinetobacter baumannii with the same genetic basis were widely distributed and spread in different clinical departments of our hospital,Cloning spread of strains within the hospital has become a global problem,which is an important reason for drug-resistant strains increasing.Therefore,we should strengthen the nosocomial infection control efforts,formulate stricter system of nosocomial infection,use antibiotics carefully and reasonably,control multidrug-resistant Acinetobacter baumannii outbreaking of epidemic.