Abstract
Nasal carriage of Staphylococcus aureus has long been hypothesized to be a major vector for the transmission of virulent strains throughout the community. To address this hypothesis, we have analyzed the relatedness between a cohort of nasal carriage strains and clinical isolates to understand better the genetic conformity therein. To assess the relatedness between nasal carriage and clinical isolates of S. aureus, a genetic association study was conducted using multilocus sequence typing (MLST) and typing of the hypervariable regions of clumping factor and fibronectin binding protein genes. At all loci analyzed, genetic associations between both nasal carriage and clinical isolates were observed. Computational analyses of MLST data indicate that nasal carriage and clinical isolates belong to the same genetic clusters (clades), despite differences in sequence type assignments. Genetic analyses of the hypervariable regions from the clumping factor and fibronectin binding protein genes revealed that not only do clinically relevant strains belong to identical genetic lineages as the nasal carriage isolates within our cohort, but they also exhibit 100% sequence similarity within these regions. The findings of this report indicate that strains of S. aureus being carried asymptomatically throughout the community via nasal colonization are genetically related to those responsible for high levels of morbidity and mortality.
Highlights
Staphylococcus aureus is a prevalent human pathogen of increasing concern to public health worldwide
Multilocus sequence typing (MLST) of all 93 S. aureus strains analyzed in this study identified 34 different sequence types (STs)
The observation of nasal carriage and clinical isolates belonging to ST5 and ST8 is in agreement with previous reports in which both nasal carriage and clinical isolates belong to these same major clusters [9,15,27]
Summary
Staphylococcus aureus is a prevalent human pathogen of increasing concern to public health worldwide. This pathogen is one of the leading causes of hospital-acquired infection, and leads to significant levels of infection via community transmission. Though nasal carriage of S. aureus is hypothesized to be a major vector for transmission throughout hospitals and the community, neither the determinants of nasal colonization nor the role of carriage in the propagation of S. aureus infection throughout these settings are well established [2]. Multiple studies have shown that nasal carriage of S. aureus is a risk factor for pathogenic infection [3,4], but just recently was it observed that heightened risk is only evident in persistent nasal carriers whereas intermittent and non-carriers exhibit low levels of infection [1]. Aside from straightforward incidences in which endogenous strains establish pathogenic infections in their hosts, the overall extent to which nasal carriage strains are responsible for transmissible infection is not currently known
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