title: The clonality of Staphylococcus aureus nasal carriage.
abstract: Nasal carriage of Staphylococcus aureus is often a prelude to infection with the same strain. The prevailing assumption has been that colonized individuals carry a single strain. The present study investigated the frequency of simultaneous nasal carriage of multiple strains of S. aureus. Three bacterial colonies from plated samples from colonized subjects were initially compared by pulsed-field gel electrophoresis. Fourteen of 148 S. aureus-positive samples demonstrated at least a difference of a single band; 7 of these 14 samples contained different strains, and 3 of these 7 also belonged to different accessory gene regulator (agr) types. The remaining 7 samples contained clonally related isolates; 3 of these 7 contained pairs that differed by the presence or absence of the staphylococcal chromosomal cassette mec type IV. A mathematical model that we developed predicted that approximately 6.6% of S. aureus-colonized individuals carry >1 strain. The present study demonstrates that carriage of discordant S. aureus strains in individuals with nasal colonization occurs regularly and suggests that the nares are likely sites for horizontal genetic exchange among strains.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Columbia University, New York, New York 10032, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Cespedes
authors.forename: Battouli
authors.initials: B
authors.lastname: Said-Salim
authors.forename: Maureen
authors.initials: M
authors.lastname: Miller
authors.forename: Shaw-Hwa
authors.initials: SH
authors.lastname: Lo
authors.forename: Barry N
authors.initials: BN
authors.lastname: Kreiswirth
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Gordon
authors.forename: Peter
authors.initials: P
authors.lastname: Vavagiakis
authors.forename: Robert S
authors.initials: RS
authors.lastname: Klein
authors.forename: Franklin D
authors.initials: FD
authors.lastname: Lowy
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D015233:Models, Statistical; D009666:Nose / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification* / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents