Abstract
Background Staphylococcus aureus is commonly carried asymptomatically in the human anterior nares and occasionally enters the bloodstream to cause invasive disease. Much of the global diversity of S. aureus remains uncharacterised, and is not clear how disease propensity varies between strains, and between host populations.MethodologyWe compared 147 isolates recovered from five kindergartens in Chengdu, China, with 51 isolates contemporaneously recovered from cases of pediatric infection from the main hospital serving this community. The samples were characterised by MLST, the presence/absence of PVL, and antibiotic resistance profiling.Principal FindingsGenotype frequencies within individual kindergartens differ, but the sample recovered from cases of disease shows a general enrichment of certain MLST genotypes and PVL positive isolates. Genotypes under-represented in the disease sample tend to correspond to a single sequence cluster, and this cluster is more common in China than in other parts of the world.Conclusions/SignificanceVirulence propensity likely reflects a synergy between variation in the core genome (MLST) and accessory genome (PVL). By combining evidence form biogeography and virulence we demonstrate the existence of a “native” clade in West China which has lowered virulence, possibility due to acquired host immunity.
Highlights
Staphylococcus aureus is a significant human pathogen world-wide, in health-care settings
The danger posed to public health by a high frequency of Panton-Valentine Leukocidin (PVL) positive strains circulating in the community is currently unclear, as factors other than PVL may contribute to the virulence of CA-MRSA [17,18]
We present Mulitlocus Sequence Typing (MLST) data from five contemporaneous samples of carried S. aureus isolates from kindergartens in Chengdu, China, and a single sample from cases of pediatric disease from the main hospital serving the same community
Summary
Staphylococcus aureus is a significant human pathogen world-wide, in health-care settings. More severe CA-MRSA infection is often associated with specific toxins encoded by mobile elements [4]; the most notorious of these being the phage-encoded Panton-Valentine Leukocidin (PVL) toxin [12,13]. PVL is an exotoxin which kills leukocytes by creating pores in the cell membrane. It is encoded by two cotranscribed genes, lukF-PV, and lukS-PV, which are currently known to be carried on four different phage [14,15]. The danger posed to public health by a high frequency of PVL positive strains circulating in the community is currently unclear, as factors other than PVL may contribute to the virulence of CA-MRSA [17,18]. Much of the global diversity of S. aureus remains uncharacterised, and is not clear how disease propensity varies between strains, and between host populations
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