title: Severe Staphylococcus aureus infections caused by clonally related community-acquired methicillin-susceptible and methicillin-resistant isolates.
abstract: 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.
authors.affiliation: Section of Pediatric Infectious Diseases, University of Chicago, Department of Pediatrics, Chicago, Illinois 60637, USA.
authors.forename: Kanokporn
authors.initials: K
authors.lastname: Mongkolrattanothai
authors.forename: Susan
authors.initials: S
authors.lastname: Boyle
authors.forename: Madelyn D
authors.initials: MD
authors.lastname: Kahana
authors.forename: Robert S
authors.initials: RS
authors.lastname: Daum
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000382:microbiology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008712:Methicillin / Q000494:pharmacology*; D016106:Methicillin Resistance / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics
chemical_list: D008712:Methicillin