TY - JOUR
T1 - Contribution of genetically restricted, methicillin- susceptible strains to the ongoing epidemic of community-acquired staphylococcus aureus infections
AU - Orscheln, Rachel C.
AU - Hunstad, David A.
AU - Fritz, Stephanie A.
AU - Loughman, Jennifer A.
AU - Mitchell, Kimberly
AU - Storch, Emily K.
AU - Gaudreault, Monique
AU - Sellenriek, Patricia L.
AU - Armstrong, Jon R.
AU - Mardis, Elaine R.
AU - Storch, Gregory A.
N1 - Funding Information:
Financial support. This work was supported by National Institutes of Health grants K08-DK067894 and UL1-RR024992 and by the Washington University Department of Pediatrics.
PY - 2009/8/15
Y1 - 2009/8/15
N2 - Background. Within the current worldwide epidemic of community-acquired Staphylococcus aureus infections, attention has focused on the role of methicillin-resistant strains. We characterize methicillin-susceptible strains that also contribute to this epidemic.Methods. We tracked cultures from abscess specimens submitted to the microbiology laboratory at St. Louis Children's Hospital and examined Panton-Valentine leukocidin (PVL) genes in methicillin-susceptible S. aureus (MSSA) isolates. We further characterized some isolates by multilocus sequence typing, pulsed-field gel electrophoresis, antibiotic susceptibility, accessory gene regulator (agr) allele, and presence of the arcA gene of the arginine catabolic mobile element.Results. From 1999 to 2007, we detected a 250-fold increase in cultures of abscesses yielding methicillin- resistant S. aureus (MRSA) and a 5-fold increase in abscess cultures yielding MSSA. MSSA isolates from abscesses and wounds were more likely to encode PVL than isolates from other sources. In contrast to PVL-negative isolates of MSSA, which were genetically diverse, PVL-positive isolates were predominantly multilocus sequence typing type 8 and agr type 1. More than half of PVL-positive MSSA isolates were resistant to erythromycin and susceptible to clindamycin with the absence of inducible resistance, a pattern uncommon in PVL-negative MSSA but frequent in the USA300 clone of MRSA. In addition, pulsed-field gel electrophoresis of PVL-positive MSSA strains revealed the USA300 pattern. Conclusions. In addition to methicillin-resistant strains, the current epidemic of S. aureus infections includes infections caused by methicillin-susceptible strains that are closely related genetically and share phenotypic characteristics other than susceptibility to methicillin. These findings suggest that factors other than methicillin resistance are driving the epidemic.
AB - Background. Within the current worldwide epidemic of community-acquired Staphylococcus aureus infections, attention has focused on the role of methicillin-resistant strains. We characterize methicillin-susceptible strains that also contribute to this epidemic.Methods. We tracked cultures from abscess specimens submitted to the microbiology laboratory at St. Louis Children's Hospital and examined Panton-Valentine leukocidin (PVL) genes in methicillin-susceptible S. aureus (MSSA) isolates. We further characterized some isolates by multilocus sequence typing, pulsed-field gel electrophoresis, antibiotic susceptibility, accessory gene regulator (agr) allele, and presence of the arcA gene of the arginine catabolic mobile element.Results. From 1999 to 2007, we detected a 250-fold increase in cultures of abscesses yielding methicillin- resistant S. aureus (MRSA) and a 5-fold increase in abscess cultures yielding MSSA. MSSA isolates from abscesses and wounds were more likely to encode PVL than isolates from other sources. In contrast to PVL-negative isolates of MSSA, which were genetically diverse, PVL-positive isolates were predominantly multilocus sequence typing type 8 and agr type 1. More than half of PVL-positive MSSA isolates were resistant to erythromycin and susceptible to clindamycin with the absence of inducible resistance, a pattern uncommon in PVL-negative MSSA but frequent in the USA300 clone of MRSA. In addition, pulsed-field gel electrophoresis of PVL-positive MSSA strains revealed the USA300 pattern. Conclusions. In addition to methicillin-resistant strains, the current epidemic of S. aureus infections includes infections caused by methicillin-susceptible strains that are closely related genetically and share phenotypic characteristics other than susceptibility to methicillin. These findings suggest that factors other than methicillin resistance are driving the epidemic.
UR - http://www.scopus.com/inward/record.url?scp=67651095590&partnerID=8YFLogxK
U2 - 10.1086/600881
DO - 10.1086/600881
M3 - Article
C2 - 19589082
AN - SCOPUS:67651095590
SN - 1058-4838
VL - 49
SP - 536
EP - 542
JO - Clinical Infectious Diseases
JF - Clinical Infectious Diseases
IS - 4
ER -