Drug resistance and biofilm formation mechanisms of Staphylococcus aureus causing catheter-related and bloodstream infection
OBJECTIVE To explore the relationship between the drug resistance,biofilm-forming ability and bio-film-associated genes in clinical isolates of Staphylococcus aureus causing catheter-related and bloodstream infec-tion.METHODS A total of 42 strains of S.aureus were isolated from clinical blood specimens and catheter speci-mens,including 13 catheter strains and 29 non-catheter strains.The biofilm forming ability was analyzed by crys-tal violet staining method,the polysaccharide encoding genes and virulence genes were detected by means of poly-merase chain reaction(PCR).RESULTS Among the 42 strains of S.aureus,there were 16 strains of methicillin-resistant S.aureus(MRSA)and 26 strains of methicillin-sensitive S.aureus(MSSA);the percentage of MSSA strains was higher in the catheter group.There were 5 strains of strong film-producing isolates,20 strains of weak film-producing isolates and 17 strains of no-film-producing isolates,and the biofilm-producing rate of the catheter group was higher than that of the non-catheter group.The expression rates of ica A,icaD,icaBC,agr and sarA were 69％,42.9％,4.8％,42.9％and 85.7％,respectively;the expression rates of the catheter group were high-er than those of the non-catheter group.The virulence genes tsst,sea,pvl and hlg were only expressed in the non-catheter group.The expression rates of virulence genes clfB,fnbA,fnbB,hla,hlb and hlg-2 as well as ad-hesin genes were higher in the catheter group than in the non-catheter group,while the expression rates of entero-toxin genes and toxic shock syndrome virulence genes were higher in the non-catheter group than in the catheter group.CONCLUSION There is similarity in the catheter and non-catheter,drug resistance and biofilm-producing a-bility among the strains of same genus.The implants inside the catheter is more likely to result in the diffusion of biofilm forming,and the related genes are highly expressed.The biofilms show strong forming ability in the cathe-ter-related strains,and the drug resistance rates of the biofilm-producing strains are high.The polysaccharide en-coding genes and adhesin genes may positively regulate the formation of the biofilms and are positively associated with the catheters.The enterotoxin genes and toxic shock syndrome virulence genes are the negative regulation factors.
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