title: Capsular serotype of Staphylococcus aureus in the era of community-acquired MRSA.
abstract: Capsular polysaccharide (CP) plays an important role in the pathogenicity and immunogenicity of Staphylococcus aureus, yet the common serotypes of S. aureus isolated from US pediatric patients have not been reported. We investigated capsular serotype as well as methicillin susceptibility, presence of Panton-Valentine leukocidin (PVL), and clonal relatedness of pediatric S. aureus isolates. Clinical isolates were tested for methicillin susceptibility, presence of mecA, lukS-PV and lukF-PV, cap5 and cap8 genes by PCR, and for capsular or surface polysaccharide expression (CP5, CP8, or 336 polysaccharide) by agglutination. Genetic relatedness was determined by pulsed-field gel electrophoresis. All S. aureus isolates encoded cap5 or cap8. Sixty-nine percent of 2004-2005 isolates were methicillin-susceptible (MSSA) and most expressed a detectable capsule. The majority of MRSA isolates (82%) were unencapsulated, exposing an expressed cell wall techoic acid antigen 336. Pulsed-field type USA300 were MRSA, PVL-positive, unencapsulated strains that were associated with deep skin infections and recurrent disease. Over half (58%) of all isolates from invasive pediatric dermatologic infections were USA300. All pediatric isolates contained either capsule type 5 or capsule type 8 genes, and roughly half of the S. aureus clinical disease isolates from our population were diverse MSSA-encapsulated strains. The majority of the remaining pediatric clinical disease isolates were unencapsulated serotype 336 strains of the PVL(+) USA300 community-associated-MRSA clone.
authors.affiliation: Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, MD, USA. deena.sutter@amedd.army.mil
authors.forename: Deena E
authors.initials: DE
authors.lastname: Sutter
authors.forename: Amy M
authors.initials: AM
authors.lastname: Summers
authors.forename: Christine E
authors.initials: CE
authors.lastname: Keys
authors.forename: Kimberly L
authors.initials: KL
authors.lastname: Taylor
authors.forename: Carl E
authors.initials: CE
authors.lastname: Frasch
authors.forename: LoRanee E
authors.initials: LE
authors.lastname: Braun
authors.forename: Ali I
authors.initials: AI
authors.lastname: Fattom
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Bash
mesh_terms: D000293:Adolescent; D016667:Bacterial Capsules / Q000032:analysis / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D017714:Community-Acquired Infections / Q000382:microbiology*; D005098:Exotoxins / Q000235:genetics; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007956:Leukocidins / Q000235:genetics; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000737:chemistry / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D013203:Staphylococcal Infections / Q000382:microbiology*; D014481:United States
chemical_list: D001427:Bacterial Toxins; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin