Severe Staphylococcus aureus infections caused by clonally related community-acquired methicillin-susceptible and methicillin-resistant isolates

Clin Infect Dis. 2003 Oct 15;37(8):1050-8. doi: 10.1086/378277. Epub 2003 Sep 23.


We investigated the genetic relatedness of 5 community-acquired (CA) Staphylococcus aureus isolates obtained from 4 consecutive pediatric patients presenting with sepsis syndrome and severe pneumonia during a 3-week period in 2000. Two patients were infected with methicillin-susceptible S. aureus (MSSA), and 2 were infected with methicillin-resistant S. aureus (MRSA). The pulsed-field gel electrophoresis patterns for the 2 CA-MRSA isolates were identical to each other, as were the patterns for the 3 CA-MSSA isolates. A 2-band difference reflecting the presence of a staphylococcal cassette chromosome mec (SCCmec) element distinguished the CA-MRSA isolates from the CA-MSSA isolates. The small, mobile type IV SCCmec element was present in the CA-MRSA isolates. These data suggest that an insertion or, less likely, a deletion of the SCCmec type IV element occurred in a highly virulent S. aureus background. Staphylococcal toxin genes sea, seh, lukS-PV, and lukF-PV were detected in all isolates. Also, in all isolates, was a partial homolog of seo (seo'). The relationship among these patient isolates strengthens the assumption that CA-MRSA infections may be caused by isolates closely related to MSSA isolates.

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Community-Acquired Infections / microbiology*
  • Female
  • Humans
  • Infant
  • Male
  • Methicillin / pharmacology*
  • Methicillin Resistance / genetics*
  • Microbial Sensitivity Tests
  • Staphylococcal Infections / microbiology*
  • Staphylococcus aureus / drug effects*
  • Staphylococcus aureus / genetics


  • Methicillin