Increase of the USA300 clone among community-acquired methicillin- susceptible Staphylococcus aureus causing invasive infections

Michelle L. McCaskill, Edward Mason, Sheldon Kaplan, Wendy Hammerman, Linda B. Lamberth, Kristina G. Hultén

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87 Scopus citations


BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) USA300 is a predominant cause of community-acquired (CA) infection in the United States. We compared clinical characteristics of children with USA300 versus non-USA300 CA-methicillin-susceptible S. aureus (CA-MSSA) invasive infections at Texas Children's Hospital (TCH). METHODS: Medical records were reviewed from children with invasive CA-MSSA infections at TCH between August 1, 2001 and September 30, 2006. Isolates were characterized by pulsed-field gel electrophoresis and polymerase chain reaction for Panton-Valentine leukocidin genes (pvl). RESULTS: Invasive CA-MSSA infections increased from 14 in year 1 to 36 in year 5 (5-year total = 122 patients). Among the CA-MSSA isolates available for typing in the 5-year period, USA300 MSSA strains increased from 14% (2 of 14) to 35% (11 of 31) (P = 0.03). USA300 MSSA strains were more likely than non-USA300 MSSA strains to be nonsusceptible to erythromycin [66% (19 of 29) versus 28% (25 of 88); P < 0.01]. Osteomyelitis cases increased from 43% (6 of 14) in year 1 to 67% (24 of 36) in year 5. The majority of pvl MSSA isolates were USA300 (71% (25 of 35); only 5% (4 of 82) of pvl MSSA isolates were USA300. Patients with osteomyelitis caused by pvl isolates had significantly higher mean values for erythrocyte sedimentation rate at admission (P = 0.005) and erythrocyte sedimentation rate maximum value (P = 0.002), maximum C-reactive protein (P = 0.04), and absolute neutrophil count at presentation (P = 0.04) compared with patients whose isolates were pvl. CONCLUSIONS: USA300 accounted for a growing proportion of CA-MSSA isolates among children and was associated with increased numbers of invasive CA-MSSA infections at TCH, especially osteomyelitis. Associations were found in CA-MSSA osteomyelitis between pvl and increased concentrations of systemic inflammatory markers in patients.

Original languageEnglish (US)
Pages (from-to)1122-1127
Number of pages6
JournalPediatric Infectious Disease Journal
Issue number12
StatePublished - Jan 1 2007


  • Community-acquired
  • Methicillin susceptible
  • Staphylococcus aureus
  • USA300

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Microbiology (medical)


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