Study On The Characteristics And Genetic Polymorphisms Of MRSA Infection At A War Zone Hospital In Southeast Coastal Region Of Fujian Province

Objectives:These years multiple drug-resistant bacteria infection keeps increasing.Particularly, methicillin-resistant staphylococcus aureus (MRSA) infection has brou-ght severe challenge to the treatment on patients suffering severe burns or woun-dsand critically ill patients. Current lack of materials studying the characteristics ofMRSA infection in war zone hospitals at the southeast coast areas of Fujian Provincewill adversely affect the treatment and cure of patients suffering burns and wounds innormal times and wartime. This study tries to clarify the characteristics of multipledrug-resistant bacteria infection (especially MRSA infection) through microbiologicalexamination on hospitalized patients in a war zone hospital in the last3years, makeclear of the genotype characteristics of MRSA by means of molecular biologymethods and propose and study the preventive measures against cross infection andepidemic breakout of MRSA, increasing the remedy achievement ratio of local areaon patients seriously injured by wounds and burns, reducing disability rate andshortening the hospitalization time of patients.Methods：We made microbiological tests on specimens collected from part of hospitalizedpatients in our hospital between2011and2013and their accompanying personneland medical stuff and primary screening of MRSA strains were conducted by meansof Cefoxitin Disk Diffusion Method. Then we applied drug sensitivity tests toextracted strains to clarify their drug resistance. We used bacteria DNA extraction kitto extract the DNA of selected strains and detected the mecA gene of each bacterialstrain with polymerase chain reaction (PCR) technology, making final identificationon MRSA. Then we used synthetic primer and random amplification of polymorphicDNA (RAPD) technology to categorize the genotypes of strains and conducted clusteranalysis on the genetic map of each strain.Results：1. The total number of MRSA strains in the experiment was39,21from male (53.8%) and18from female (46.2%), aging between2~93. They were hospitalizedfor2~156days,36.3days on average. Of all specimens from which MRSA wasdetected, sputum was the biggest contributor with18specimens on record (42.86%),followed by wound discharge with10specimens on record (23.80%). Regarding thetreatment effect, the overwhelming majority of the patients were cured and releasedfrom the hospital; treatment failed for2patients who died of complications ofunderlying diseases;4patients received ineffectual treatment and chose to leave thehospital.7strains of drug-resistant staphylococcus aureus were extracted from thehands and nasal vestibules of family members of patients and medical stuff,3of themidentified as MRSA strains. General status of planted bacteria extracted from thehands nasal vestibule of accompanying family members and medical stuff is as follow:major planted bacteria include staphylococcus epidermidis (accounting for73.5%),streptococcus, diplococcus pneumonlae and staphylococcus aureus, etc.7strains ofstaphylococcus aureus were extracted,3of them being MRSA.2MRSA strains camefrom the nasal vestibule of a family member of a patient received in the NeurosurgeryDepartment and the other strain came from the hand of a nurse in the ICU Depart-ment.2. Cefoxitin paper method of positive staphylococcus aureus56strains, to mecAgene by PCR detection,42strains positive, was eventually identified as MRSAstrains;we used RAPD technology to differentiate the genotypes of MRSA.Homologous analysis categorized42clinical MRSA strains into12genotypes,7strains of Type I,2of Type II,4of Type III,4of Type IV,7of Type V, one each forType VI, Type VII and Type VIII,8of Type IX,2of Type X,3of Type XI and2ofType XII.3.The results of drug sensitivity tests show that all MRSA strains extracted in theexperiment can resist Oxacillin, Penicillin, Cefazolin, Piperacillin/Tazobactam, andtheir resistance rates against SXT, Erythrocin, Tetracycline, Clindamycin, Levoflo-xacin, Moxifloxacin and Rifampicin are respectively92.9%,92.9%,88.1%,88.1%,87.5%,76.5%,64.3%and61.9%. All extracted strains are sensitive to Linezolid,Teicoplanin and Vancomycin. Conclusions：1. In recent years major multiple drug-resistant bacteria seen in every clinicaldepartment of our hospital include MRSA, pseudomonas aeruginosa, klebsiellapneumoniae, acinetobacter baumannii and enterobacter cloacae, etc. MRSA has adetection rate of38.9%of multiple drug-resistant bacteria.2. Generally all detected MRSA strains could resist antibiotics of penicillins,cephalosporins, aminoglycosides, macrolides and quinolones. Strains that could resistvancomycin, linezolid and tigecycline have not been identified.3. Departments in our hospital vulnerable to MRSA infection are NeurosurgeryDepartment, Burn and Plastic Surgery Department, ICU Department and RespiratoryDepartment. Genotypes of strains are mainly of Type I, Type V and Type IX.Specifically, Neurosurgery Department was usually plagued with Type I MRSAstrains, Burn and Plastic Surgery Department mostly saw Type V, from ICUDepartment most extracted MRSA strains were of Type IV, while Type IX MRSAstrains were mainly seen in Respiratory Medicine Department. Strains of varioustypes have genetic distances of different sizes of similarity.4. Mutual spread and cross infection of MRSA is possible among patients, theiraccompanying personnel and medical stuff. Adopting such preventive measures asstrengthening hand hygiene, isolating sources of diseases in a timely manner,disinfection, periodical MRSAdetection on medical stuff and bacteriopexia-removing,etc, could effectively cut off the spread paths of MRSAand lower the infection rate.