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SaPIs (Staphylococcus aureus or superantigen pathogenicity islands) are a family of mobile genetic elements resident in the genome of some strains of Staphylococcus aureus.[1] Much like bacteriophages, SaPIs can be transferred to uninfected cells and integrate into the host chromosome. Unlike the bacterial viruses, however, integrated SaPIs are mobilized by host infection with "helper" bacteriophages (specific SaPIs may require specific helper bacteriophages for mobilization, though Staphylococcus phage 80alpha appears to mobilize all known SaPIs).[2]

One particular SaPI, SaPI1, is encapsidated in and exits the host cell in particles assembled from proteins encoded by its helper phage.[3]

Role in pathogenicity[edit]

SaPIs were found to carry the gene encoding toxic shock syndrome toxin.[1] Other SaPI subtypes have been found to provide host Staphylococcus strains with the ability to coagulate animal host blood plasma by coding for different alleles of a von Willebrand factor-binding protein. This virulence factor may help S. aureus adapt to distinct animal hosts such as horses or ruminants.[4]


  1. ^ a b Lindsay, JA; Ruzin, A; Ross, HF; Kurepina, N; Novick, RP (Jul 1998). "The gene for toxic shock toxin is carried by a family of mobile pathogenicity islands in Staphylococcus aureus.". Molecular Microbiology. 29 (2): 527–43. doi:10.1046/j.1365-2958.1998.00947.x. PMID 9720870. 
  2. ^ Christie, G.E.; Matthews, A.M.; King, D.G.; Lane, K.D.; Olivarez, N.P.; Tallent, S.M.; Gill, S.R.; Novick, R.P. (1 November 2010). "The complete genomes of Staphylococcus aureus bacteriophages 80 and 80α—Implications for the specificity of SaPI mobilization". Virology. 407 (2): 381–390. doi:10.1016/j.virol.2010.08.036. PMC 2952651Freely accessible. PMID 20869739. 
  3. ^ Tallent, S. M.; Langston, T. B.; Moran, R. G.; Christie, G. E. (10 August 2007). "Transducing Particles of Staphylococcus aureus Pathogenicity Island SaPI1 Are Comprised of Helper Phage-Encoded Proteins". Journal of Bacteriology. 189 (20): 7520–7524. doi:10.1128/JB.00738-07. 
  4. ^ Viana, D; Blanco, J; Tormo-Más, MA; Selva, L; Guinane, CM; Baselga, R; Corpa, JM; Lasa, I; Novick, RP; Fitzgerald, JR; Penadés, JR (Sep 2010). "Adaptation of Staphylococcus aureus to ruminant and equine hosts involves SaPI-carried variants of von Willebrand factor-binding protein.". Molecular Microbiology. 77 (6): 1583–94. doi:10.1111/j.1365-2958.2010.07312.x. PMID 20860091.