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An extracellular Staphylococcus epidermidis polysaccharide: relation... » Isaúde
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BMC microbiology [electronic resource]
2012-05-17 09:30:40

An extracellular Staphylococcus epidermidis polysaccharide: relation to Polysaccharide Intercellular Adhesin and its implication in phagocytosis

Descrição: Background:The skin commensal and opportunistic pathogen Staphylococcus epidermidis is a leadingcause of hospital-acquired and biomaterial-associated infections. The polysaccharideintercellular adhesin (PIA), a homoglycan composed of beta-1,6-linked N-acetylglucosamineresidues, synthesized by enzymes encoded in icaADBC is a major functional factor in biofilmaccumulation, promoting virulence in experimental biomaterial-associated S. epidermidisinfection. Extracellular mucous layer extracts of S. epidermidis contain another majorpolysaccharide, referred to as 20-kDa polysaccharide (20-kDaPS), composed mainly out ofglucose, N-acetylglucosamine, and being partially sulfated. 20-kDaPS antiserum preventsadhesion of S. epidermidis on endothelial cells and development of experimental keratitis inrabbits. Here we provide experimental evidence that 20-kDaPS and PIA represent distinctmolecules and that 20-kDaPS is implicated in endocytosis of S. epidermidis bacterial cells byhuman monocyte-derived macrophages.Results:Analysis of 75 clinical coagulase-negative staphylococci from blood-cultures and centralvenous catheter tips indicated that 20-kDaPS is expressed exclusively in S. epidermidis butnot in other coagulase-negative staphylococcal species. Tn917-insertion in various locationsin icaADBC in mutants M10, M22, M23, and M24 of S. epidermidis 1457 are abolished forPIA synthesis, while 20-kDaPS expression appears unaltered as compared to wild-typestrains using specific anti-PIA and anti-20-kDaPS antisera. While periodate oxidation anddispersin B treatments abolish immuno-reactivity and intercellular adhesive properties ofPIA, no abrogative activity is exerted towards 20-kDaPS immunochemical reactivityfollowing these treatments. PIA polysaccharide I-containing fractions eluting from QSepharose were devoid of detectable 20-kDaPS using specific ELISA. Preincubation of non-20-kDaPS-producing clinical strain with increasing amounts of 20-kDaPS inhibitsendocytosis by human macrophages, whereas, preincubation of 20-kDaPS-producing strainATCC35983 with 20-kDaPS antiserum enhances bacterial endocytosis by humanmacrophages.Conclusions:In conclusion, icaADBC is not involved in 20-kDaPS synthesis, while the chemical andchromatographic properties of PIA and 20-kDaPS are distinct. 20-kDaPS exhibits antiphagocytic properties, whereas, 20-kDaPS antiserum may have a beneficial effect oncombating infection by 20-kDaPS-producing S. epidermidis.

Identificador: doi:10.1186/1471-2180-12-76
Volume: 0
Página: 7 a


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