Investigation On Staphylococcus Aureus Biofilm Genotype And Its Molecular Evolution

Staphylococcus aureus, gram positive bacteria, through a variety ways of contaminated food, is one of the common foodborne pathogenic bacteria. Staphylococcus aureus can produce large amounts polysaccharide and protein matrix around itself and formation biofilm then cause serious food safety problems. At present, the study of Staphylococcus aureus biofilm mostly concentrated in the phenotype and inert material modification and so on. Carrying on key regulatory genes of biofilm and the relationship between the genome background and biofilm gene is insufficient. So this paper from the mobile genetic elements of SCC mec, the Staphylococcus aureus genomic island type and bioinformatics analysis to find the trends of biofilm was affected in the evolution. Then, analyzed the core group of gene cloning so that to study the effect of biofilm genotype in the process of evolution.1.In this experiment, 262 strains of Staphylococcus as the research object, the initial adhesion gene of biofilm atl gene, ica operon regulation gene, the accumulation-associated protein gene, mature biofilm regulation gene agr was detected by PCR. The results showed the carrying rate is respectively 98.1 %, 81.7%, 87% and 84.4%. Based on biofilm associated gene interaction analysis, the genotype could be divided into 11 kinds, the main 4 kinds type atl+ ica+ aap+ agr+, atl+ ica+ aap+ agr-, atl+ ica+ aap- agr+, atl+ ica- aap+ agr+ type accounted for 62.6%, 9.9%, 6.5% and 12.2%.2. The Staphylococcus species specific factor 16 S r RNA, fem A and mec A were detected by multiple PC R method and the carrying rate 100%, 94.3% and 92.7%. The SCC mec carrying rate was reached 92.7% of Staphylococcus. The SCCmec genotype showed 17.6% type II, 56.8% and 6.2% for III and IIIA, 10.7% IV, 4.1% V and 2.1% VI, indicating that the current major epidemic was compound SCC mec in China. Type VI international reported less, but the experiment showed that 5 strains and(2.5%) cannot type.3. The correlation between Staphylococcus biofilm genotype and SCC mec were analyzed. The results showed, the biofilm ability with SCC mec was stronger than without SCC mec strains. In the evolution of SCC mec were shown to influence on biofilm associated genotypes. Biofilm mature regulatory factor agr gene, may be inhibition of type 2 ccr complexes in II SCCmec.4. Staphylococcus were classified by RAPD the results showed that AP1,AP7 and ERIC-2 primers amplified 7, 8 and 7 bands, the range is 400-5000 bp. Based on the above results Staphylococcus were divided into 33 genotypes. The representative 33 strains amplified and sequenced. 33 strains could be divided into 4 series: ST5(4/33), ST45(4/33), ST239(24/33) and ST546(1/33). ST5 belonged to the CC5 clone complex and did not carry the agr gene; ST45 and ST546 belonged to the CC45 clone complex, carrying aap gene is relatively low; ST239 belonged to the CC8 clone complex ica operon,carrying less than other biofilm regulator.5. Spa typing 33 representative strains, the results for 5 types: t037 accounted for 57.6%, t1081 21.2%, t030 12.1%, t002 6.1% and t1714 3%. Analysis relationship of genomic and biological background with biofilm genotype: 50% atl+ ica+ aap+ agr+ gene clone in ST239-III; ST5-II clone75% carrying atl+ ica+ aap+ agr- gene type. ST5 clones with type 2 ccr complexes, biofilm showed more thickening and very curing. The ST45-V and ST45-II clones biofilm genotypes carrying the atl+ ica+ aap+ agr+.