Prevalence of Staphylococcus aureus protein A spa mutants in the community and hospitals in OxfordshireReport as inadecuate




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BMC Microbiology

, 14:63

Clinical microbiology and vaccines

Abstract

BackgroundStaphylococcal protein A spa is an important virulence factor which enables Staphylococcus aureus to evade host immune responses. Genotypes known as -spa-types-, based on highly variable Xr region sequences of the spa-gene, are frequently used to classify strains. A weakness of current spa-typing primers is that rearrangements in the IgG-binding region of the gene cause 1-2% of strains to be designated as -non-typeable-.

ResultsWe developed an improved primer which enabled sequencing of all strains, containing any type of genetic rearrangement, in a large study among community carriers and hospital inpatients in Oxfordshire, UK 6110 isolates. We identified eight novel spa-gene variants, plus one previously described. Three of these rearrangements would be designated -non-typeable- using current spa-typing methods; they occurred in 1.8% 72-3905 asymptomatically carried and 0.6% 14-2205 inpatient S. aureus strains. Some individuals were simultaneously colonized by both formerly non-typeable and typeable strains; previously such patients would have been identified as carrying only currently typeable strains, underestimating mixed carriage prevalence and diversity. Formerly non-typeable strains were found in more spa-types associated with multilocus sequence type ST398 35%, common among livestock, compared to other groups with any non-typeable strains 1-4%, suggesting particular spa-types may have been under-represented in previous human studies.

ConclusionsThis improved method allows us to spa-type previously non-typeable strains with rearrangements in the spa-gene and to resolve cases of mixed colonization with deletions in one or more strains, thus accounting for hidden diversity of S. aureus in both community and hospital environments.

KeywordsStaphylococcus aureus Spa-typing Spa-gene Deletions Non-typeable isolates Community and hospital strains Electronic supplementary materialThe online version of this article doi:10.1186-1471-2180-14-63 contains supplementary material, which is available to authorized users.

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Author: Antonina A Votintseva - Rowena Fung - Ruth R Miller - Kyle Knox - Heather Godwin - David H Wyllie - Rory Bowden - Derric

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