| BackgroundStaphylococcus aureus is an important pathogen which can cause all kinds of infections. The emergence and widespread of methicillin-resistant Staphylococcus aureus (MRSA) is a serious threat for public health in the world, which not only increases the difficulty of treatment and prevention, but also increases costs. The study of Staphylococcus aureus and MRSA is the focus all around the world. It is important for clinical diagnosis and treatment to explore the Epidemic Features and resistance characteristics of Staphylococcus aureus. So a lot of molecular biology methods such as PCR and sequencing technology have been applied in the study. Staphylococcus aureus is an important pathogen in the hospital and community infections locally, there is also a tendency in MRSA infections, but there is the lack of systematic research on popular features and resistant characteristics in Staphylococcus aureus locally. Because there are a lot of difficulty in the application of molecular typing in primary health care institutions, the characteristic of local strains of MRSA has not been clear in molecular epidemiology. In order to provide evidence for clinical diagnosis, treatment and prevention, many methods such as epidemiological investigation, Antibiogram and molecular biology techniques have been applied in the research. The objective of this study includes three aspacts, To determine the epidemic features and resistant characteristics of Staphylococcus aureus, To explore the application of molecular typing in the primary hospital, To find out the main features and molecular type of local popular MRSA.Part One The popular features and drug resistance ofStaphylococcus aureus isolated from 2007 to 2014 ObjectiveTo determine the popular features and resistance profiles of Staphylococcus aureus locally.MethodsThe susceptibility data and epidemiological data of the Staphylococcus aureus isolated from Jingzhou Central Hospital have been colleted from 2007 to 2014, all data in the retrospective study has been processed by software SPSS19.0 and WHONET5.6.Results1355 strains of Staphylococcus aureus have been collected.911 cases of low respiratory tract infections which accounted for 67.2%,337 cases of skin and wound-related infections which accounted for 24.9%,70 cases of bloodstream infection which accounted for 5.2%,37 cases of other infections accounted for 2.7%. Age and ward of patients infected by Staphylococcus aureus have statistically significant (P <0.05) on the type of infection.The proportion of MRSA is 28.8% in all strains. There is significant difference in age, sex and ward type between MRSA and MSSA, but no difference in type of infection and patient. The strains of MRSA isolated from ICU ward are more resistant than the strains of non-ICU ward, The strains of MRSA isolated from pediatric ward are more sensitive than the strains of non- pediatric ward. MRSA is multi-drug resistant bacteria, which is more resistant than MSSA in erythromycin, clindamycin, penicillin, gentamicin, chloramphenicol, tetracycline, ciprofloxacin, levofloxacin and rifampin, but more sensitive than MSSA in sulfamethoxazole/trimethoprim. The positive rate of inducible clindamycin resistance is 14.5%. There is significant difference in the positive rate of different ward, but no difference between the positive rate of MRSA and MSSA.ConclusionStaphylococcus aureus can cause a lot of infections. There are different infection types and characteristics in patients from different age and ward. The total proportion of MRSA is currently at a low level, but which is different in different wards, the trend of which has continually increased in recent years. The fact of inducible clindamycin resistance has been existed in MRSA and MSSA. The risk of clindamycin treatment failure of Staphylococcus aureus infection can been reduced by detected inducible clindamycin resistance.Part Two Epidemiology and antibiotic resistance of CA-MRSA and HA-MRSAObjectiveTo investigate epidemiology and resistance characteristic of CA-MRSA and HA-MRSA in Jingzhou, To discuss the application of cluster analysis of antibiogram in homologous correlation of MRS A.MethodsStaphylococcus aureus and clinical data were collected from outpatient and inpatient,159 strains of MRSA were confirmed by conventional PCR, The minimum inhibitory concentration of 16 classes of antimicrobial drugs were detected by Vitek2 Compact. The SCCmec type of all strains were detected by multiplex PCR, The strains of MRSA isolated from ICU were detected in homology by PFGE and cluster analysis of antibiogram.Results84.2% of MRSA are HA-MRSA in the local district. There were differences of ward distribution, age and type of infection of patients between CA-MRSA and HA-MRSA. HA-MRSA is multi-drug resistant bacteria, which is more resistant than CA-MRSA in moxifloxacin, rifampin, levofloxacin, ciprofloxacin and gentamicin, but more sensitive than CA-MRSA in erythromycin and clindamycin.SCCmec Ⅱ, Ⅲ and Ⅳ were found in 12,113 and 26 isolates in 159 MRSA isolates, Most of CA-MRSA and HA-MRSA isolates were SCCmec Ⅳ and Ⅲ respectively. Six different PFGE patters were found in 49 MRSA isolates of ICU,85.7% of the PFGE patters were A1,A2 and B in all isolates. Three groups of isolates had high correlation in cluster analysis of antibiogram, which belong to A1,A2 and B of PFGE patter respectively.mecA gene was detected by PCR in 80 strains of MRSA.ConclusionMost of the MRSA was HA-MRSA in the local district, There are differences of ward distribution, age and type of infection of patients between CA-MRSA and HA-MRSA. Cluster analysis of antibiogram can be used to track MRSA homology, which could compensate for the lack of PFGE typing.Part Three Molecular typing of MRSAObjectiveTo explore the application of molecular typing in the primary hospital, To find out the main features and molecular type of local popular MRSA.MethodsFirstly, the biochemical identification and susceptibility of all strains were detected in Vitek2 Compact. Secondly, mecA gene was confirmed by PCR. Thirdly, spa typing, SCCmec typing and pvl genetic test were applied in all strains. All data has been processed by software SPSS 19.0.Results16 types of spa have been detected in all MRSA, the main types are t030 and t437 which accounted for 50% and 28.8% respectively, t14314 is the new type which been reported by this article firstly in the world.5 types of SCCmec have been detected in 77 strains of MRSA, the main types are SCCmecⅢ and SCCmecⅣ which accounted for 45.0% and35.0% respectively. There were differences of ward distribution and age between MRSA t030 and MRSA t437. MRSA t030 is more resistant than MRSA t437 in rifampin, quinupristin/dalfopristin, tetracycline, levofloxacin, moxifloxacin, ciprofloxacin and gentamicin, but more sensitive than MRSA t437 in erythromycin. There were differences of ward distribution and age between the first group(SCCmec Ⅰ, Ⅱ and Ⅲ) and the second group(SCCmecⅣ and Ⅴ). The first group is more resistant than the second group in rifampin, tetracycline, levofloxacin, moxifloxacin, ciprofloxacin and gentamicin. The positive rate of pvl gene is 13.8% in all strains, which maily isolated from sputum and pus.ConclusionThe discriminatory power of spa typing is higher than SCCmec typing. The technicality and cost effectiveness of spa typing is less difficult and expensive than PFGE typing, So spa typing has more advantages in primary clinical microbiology laboratory. There are many genotypes in the local popular strains of MRSA, t030-Ⅲ and t437-Ⅳ are the main types. There are difference of patient, ward and resistance between the main types, which is in accordance with the characteristics of HA-MRSA and CA-MRSA respectively. The main genotype is t437-Ⅳ which isolated from low respiratory tract infection and skin and wound-related infection. |
PDF Full Text Request