Molecular distinctions exist between community-associated methicillin-resistant Staphylococcus aureus colonization and disease-associated isolates in children.

Thomsen I, McKenna BD, Saye EJ, Jimenez N, Edwards KM, Creech CB
Pediatr Infect Dis J. 2011 30 (5): 418-21

PMID: 21263373 · PMCID: PMC3077447 · DOI:10.1097/INF.0b013e31820d7fd5

OBJECTIVE - To define the molecular epidemiology of colonization and disease-associated isolates of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA).

DESIGN - Laboratory-based comparative study of clinical staphylococcal isolates.

METHODS - We analyzed 255 pediatric CA-MRSA isolates for molecular characteristics associated with colonization and disease. We used polymerase chain reaction to determine the presence of Panton-Valentine Leukocidin and the lantibiotic element, bsaB, and to characterize the staphylococcal cassette chromosome mec type and accessory gene regulator locus. Pulsed-field gel electrophoresis was used to determine genetic relatedness between strains.

RESULTS - A total of 150 isolates were obtained from patients with clinical disease (37 invasive infections, 113 noninvasive infections) and 105 from subjects with nasal colonization alone. Of 150 disease-associated isolates, 123 (82%) belonged to pulsed-field gel electrophoresis group USA300, whereas only 19 (18%) of 105 colonization isolates were of the USA300 lineage. Colonization isolates were less likely to possess staphylococcal cassette chromosome mec type IV, Panton-Valentine Leukocidin, or agr type 1 (P < 0.001).

CONCLUSIONS - Colonization strains of CA-MRSA in children differ significantly from those strains recovered from patients with staphylococcal infections. This suggests that only colonization with specific strain types, rather than methicillin-resistant Staphylococcus aureus colonization in general, increases the risk for CA-MRSA disease.

MeSH Terms (19)

Bacterial Proteins Bacterial Toxins Bacterial Typing Techniques Bacteriocins Carrier State Child Child, Preschool Community-Acquired Infections Electrophoresis, Gel, Pulsed-Field Exotoxins Humans Leukocidins Methicillin-Resistant Staphylococcus aureus Molecular Epidemiology Molecular Typing Penicillin-Binding Proteins Polymerase Chain Reaction Staphylococcal Infections Trans-Activators

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