Main Bacteria And Their Drug-resistant Trend That Caused Infection Of Burn Patients In Wuxi During 2012-2014 And Bacterial Homology Analysis In Burn-ward’s Environment

Part I. Main bacteria and their drug-resistant trend that caused infection of burn patients in Wuxi during 2012-2014OBJECTIVE:To provide suggestion for clinical diagnosis and treatment, main bacteria and their drug-resistant trend that caused infection of burn patients in Wuxi during 2012-2014 were retrospectively analyzed.METHODS:1. Data collectionWHONET 5.6 software was applied to analyze the bacteria species that caused infection of burn patients in Wuxi during 2012-2014. Specimen types included wound secretions, blood, catheters and urine in middle section.2. Identification of bacteria and their drug susceptibilityThe Automatic instrument(France BIOMERIEUX Vitek 2 Compact 30) was used for bacterial identification and drug susceptibility analysis. In bacterial drug susceptibility analysis, 20 kinds of Antibacterial agents were used(Attached table).Attached table. Antibacterial agents that used for bacterial drug susceptibility analysis3. Comparison of drug susceptibility between Methicillin resistant and sensitive Staphylococcous aureusMethicillin resistant Staphylococcous aureus(MRSA) and Methicillin sensitive Staphylococcous aureus(MSSA) were distinguished by their sensitivity to oxacillin according to American NCCLS(National Committee for Clinical and Laboratory Standards Institute) suggestion. Amoxicillin, penicillin G, cefuroxime sodium, gentamicin, vancomycin, rifampin, ciprofloxacin, levofloxacin, tetracycline, and erythromycin were used in drug susceptibility experiment.4. Statistical analysisAll data were expressed as mean ± standard deviations. All statistics were performed using the SPSS version 19.0 software. Statistical analysis were performed using Student’s t test and Chi-Square test with a significance level of P-value < 0.05 and a highly significance level of P-value < 0.01.RESULTS:1. Bacteria isolated from burn patientsThe total strains of bacteria that isolated from burn patients during 2012-2014 were 6826. However, only 4624 strains bacteria(690 strains in 2012, 948 strains in 2013 and 2986 strains in 2014) were left after excluding the repeated data. The strains isolated from wound secretions, blood, catheter and urine in middle section were 2366, 1861, 237 and 160, respectively.2. The identification and distribution of bacteria that caused infection of burn patientsAmong the total 4624 specimen, Gram-negative bacteria and Gram-positive bacteria accounted for 67.8% and 29.4% respectively. And fungi accounted for 2.8%. The top 5 pathogens in Gram-negative bacteria were Pseudomonas aeruginosa, Acinetobacter baumannii, Proteus, klebsiella pneumonia and Escherichia coli; and the top 5 in Gram-positive bacteria were Staphylococcus aureus, Epidermis staphylococcus aureus, Enterococcus aureus, Excrement enterococcus and Hemolytic staphylococci(attached figure). Among these, the most common infection were caused by Pseudomonas aeruginosa, Acinetobacter baumannii and Staphylococcus aureus.The proportions of Pseudomonas aeruginosa in 2012, 2013 and 2014 were 18.0%, 19.6% and 25.7% respectively, showing a rising trend(P < 0.05). But the proportions of Acinetobacter baumannii were 20.1%, 18.78% and 17.3% respectively in 2012-2014, showing a declining trend(P < 0.05), Staphylococcus epidermidis were in the similar performance. Attached figure. The distribution of bacteria in burn patients infected from 2012 to 20143. Drug susceptibility analysisThe top 3 bacteria that caused infection of burn patients were Pseudomonas aeruginosa, Acinetobacter baumannii and Staphylococcus aureus. All them had very serious drug resistance. For Pseudomonas aeruginosa, except to piperacillin/tazobactam, amikacin, ciprofloxacin, levofloxacin and polymyxin(drug resistance rate to polymyxin was 0), bacterial drug resistance rate was greater than 50.0% to other 15 antibacterial agents. For Acinetobacter baumannii, except to cefoperazone/sulbactam, amikacin, levofloxacin, polymyxin and minocycline(drug resistance rate to polymyxin was 0), bacterial drug resistance rate was greater than 50.0% to other 15 antibacterial agents. Pseudomonas aeruginosa and Acinetobacter baumannii that only sensitive to polymyxin accounted for 15.4% and 11.9%, respectively.The resistance rates of Staphylococcus aureus to 13 antibiotics were greater than 70.0%, except to trimoxazole, linezolid, moxifloxacin, tigecycline, vancomycin, nitrofurantoin and quinupristin/dalfopristin with drug resistance relatively low.The 5 antibacterial agents that most frequently used for patients infected with Pseudomonas aeruginosa and Acinetobacter baumannii were ftriaxone, piperacillin/tazobactam, levofloxacin, cefoperazone/sulbactam and Imipenem, except to ceftriaxone, the drug resistance rates of Pseudomonas aeruginosa to other 4 antibiotics were increasing(P < 0.05) from 2012 to 2014. And drug resistance of Acinetobacter baumannii increased except to cefoperazone/sulbactam and levofloxacin(P < 0.05). The 5 antibacterial agents most frequently used for Staphylococcus aureus were cefepime, oxacillin, levofloxacin, Cotrimoxazole and vancomycin. Staphylococcus aureus showed an increasing drug resistance to oxacillin(P < 0.05).4. Drug susceptibility between MRSA and MRSAThe sensitivity rate of MRSA to vancomycin and rifampicin was 100% and 83.56%, respectively, while to the other antibacterial agents, the sensitivity rates were less than 20.0%(among them, the sensitivity rates to penicillin G and amoxicillin were 0). The sensitivity rates of MSSA to penicillin G and amoxicillin were 0 and 15.09% respectively, while to the other antibacterial agents, the sensitivity rates were greater than 60.0%(among them, the sensitivity rate to vancomycin was 100%). All the differences had statistical significance(P < 0.05). Part ⅡHomology analysis of bacteria in burn ward’s envioronmentOBJECTIVE:The homology of bacteria isolated in burn ward’s envioronment was investigated to analyze the possible transmission routes of hospital’s cross-infection and to provide suggestions for developing effective sterilization measures and control the spread of microbesMETHODS:Bacteria in the pool, bed rail, bedside counter top, ECG buttons and infusion pump keys were collected for 5 days(from 28 th August to 5th September).1.Contact plates adoptingSamples including the leg wounds of patient(No. 450475) and the burn ward’s environment were collected according to the suggestion of Good Manufacturing Practice(GMP),and incubated at 37℃ for 48 h.2.Colony counting3.Identification of microbesBacteria were identified using automatic bacterial identification system(France BIOMERIEUX Vitek 2 Compact 30).4.Homology analysis of bacteriaThe homology of bacteria were analyzed using Enterobacterial Repetitive Intergenic Consensus-polymerase chain reaction(ERIC-PCR). Number ―1‖ was on behalf of the band existing, and number ―0‖ was behalf of the band absence according to PCR products on gel electrophoresis. The original data matrix was composed of each strain’s data. Squared Euclidean distance calculation in SPSS 19.0 software was used to execute cluster analysis for obtaining homologic relationship between the strains.5. Comparison the pathogens’ detection before and after disinfection treatmentAfter sampling on the last day(5th September) of this experiment, the pool, bed rail, bedside counter top, ECG buttons and infusion pump keys were disinfected with sodium hypochlorite disinfectants(available chlorine concentration was 500-1000mg/L). Then samples were collected and incubated at 37℃ for 48 hours then colony counting and strain identification were performed. Comparison of the detection before and after desinfection treatment was analyzed by SPSS 19.0 software.RESULTS:1. Colony count and identificationThe bacteria in 5 consecutive sampling days from the wound of patient were Acinetobacter baumannii and Staphylococcus aureus, and the colony counts for the two bacteria were up to 1.2 cfu/cm2(30 colonies/plate). There were no bacteria detected from pool, bed rail, bedside counter top, ECG buttons and infusion pump keys before the patient moved in, but from the 2nd to the 5th sampling day, Acinetobacter baumannii or Staphylococcus aureus were present and increased in burn ward’s envioronment.2. Homology analysis of bacteriaTotal 33 strains of bacteria were detected from the burn ward’s environmen, including 20 strains of Acinetobacter baumannii and 13 strains of Staphylococcus aureus.2.1 Homology analysis of Acinetobacter baumanniiBy ERIC-PCR analysis, 20 strains of Acinetobacter baumannii could be divided into four types, named as A, B, C, D respectively with A-type 6 strains, B-type 12 strains, C-type 1 strain, D-type 1 strain. Similarity coefficient between type A and type B was 0.995, and the homology of these 18 trains of Acinetobacter baumannii was between 99.5% and 100%.2.2 Homology analysis of Staphylococcus aureusBy ERIC-PCR analysis, 13 strains of Staphylococcus aureus could be divided into three types,named as a, b, c respectively with a-type 11 strains, b-type 1 strain, c-type 1 strain. The similarity coefficients between the three types were all high, from 0.65 to 0.85. That the homology of 13 strains was between 65% and 100%, among them homology of 11 strains was 100%.3. Comparison the pathogens’ detection before and after disinfection treatmentBefore disinfection treatment, the colony counts of Acinetobacter baumannii and Staphylococcus aureus were all greater than or equal to 0.20 cfu/cm2(5 colonies/plate) from pool, bed rail, bedside counter top, ECG buttons, infusion pump keys. And after disinfection treatment, the colony counts of Acinetobacter baumannii and Staphylococcus aureus were 0 cfu/cm2 from the same sites except for bed rail detection(P < 0.01).CONCLUSIONS:1. Among burn patients, the most common infection were caused by Pseudomonas aeruginosa, Acinetobacter baumannii and Staphylococcus aureus.2. The detection of Pseudomonas aeruginosa were increasing during 2012-2014, while Acinetobacter baumannii’s detection showed a declining trend. The drug resistance of the two prime bacteria were very serious, and a large number of extremely-drug resistant bacteria were emerging.3. The detection of MRSA were increasing from 2012 to 2014, and its resistance to antibacterial agents was serious. MSSA was more sensitive to antibacterial agents, while it was resistant to penicillin G and amoxicillin.4. The detection of Acinetobacter baumannii and Staphylococcus aureus in burn ward’s environment were increased along with the patient’s moving in who infected with the corresponding bacteria.5. The homology of 18 strains of Acinetobacter baumannii was more than 99.5%, and the homology of 11 strains of Staphylococcus aureus was 100%. The results demonstrated they shared the same source.6. After disinfection treatment, bacteria were significantly decreased in the burn ward’s environment, which indicated strict disinfection was essential to prevent the spread of microbes.