Complex molecular epidemiology of methicillin-resistant staphylococcus aureus isolates from children with cystic fibrosis in the era of epidemic community-associated methicillin-resistant S aureus.
BACKGROUND
Limited data exist about the molecular types of methicillin-resistant Staphylococcus aureus (MRSA) strains found in children with cystic fibrosis (CF). We sought to characterize MRSA strains from these patients and compare them with MRSA strains from non-CF pediatric patients.


METHODS
All MRSA isolates were collected prospectively at Children's Medical Center in Dallas, TX, and the University of Chicago Comer Children's Hospital in 2004 to 2005. All CF MRSA isolates underwent susceptibility testing, multilocus sequence typing, Panton-Valentine leukocidin gene detection (pvl+), and staphylococcal chromosome cassette mec (SCCmec) typing.


RESULTS
A total of 22 of 34 MRSA isolates (64.7%) from patients with CF belonged to clonal complex (CC) 5 and contained SCCmec II, so-called health-care associated MRSA (HA-MRSA) strains. Nine of 34 MRSA strains (26.5%) were CC 8, and contained SCCmec IV, so-called community-associated MRSA (CA-MRSA) strains. The CA-MRSA strains tended to be isolated from newly colonized CF patients. In contrast, CC8 isolates predominated among the non-CF patients (294 of 331 patients; 88.8%). MRSA isolates from children with CF were more likely to be resistant to clindamycin (65% vs 19%, respectively) and ciprofloxacin (62% vs 17%, respectively) compared with strains from non-CF patients (p < 0.001). There was no difference in the rate of pvl+ isolate recovery from children with CF undergoing a surveillance culture (7 of 23 children) compared with those with pulmonary exacerbation (3 of 11 children; p = 1.0).


CONCLUSIONS
Both CA-MRSA (CC8) isolates and HA-MRSA (CC5) isolates populate the respiratory tracts of children with CF. HA-MRSA isolates predominated, but CA-MRSA strains predominated among CF patients with newly acquired MRSA strains and among the non-CF patients. The presence of CA-MRSA strains in children with CF was not associated with exacerbation or necrotizing pneumonia.
Glikman
Daniel
D
Sections of Infectious Diseases, Department of Pediatrics, University of Chicago, Chicago, IL.
Siegel
Jane D
JD
Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX.
David
Michael Z
MZ
Sections of Infectious Diseases, Department of Pediatrics, University of Chicago, Chicago, IL.
Okoro
Ngozi M
NM
Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX.
Boyle-Vavra
Susan
S
Sections of Infectious Diseases, Department of Pediatrics, University of Chicago, Chicago, IL.
Dowell
Maria L
ML
Pulmonary Medicine, Department of Pediatrics, University of Chicago, Chicago, IL.
Daum
Robert S
RS
Sections of Infectious Diseases, Department of Pediatrics, University of Chicago, Chicago, IL. Electronic address: rdaum@peds.bsd.uchicago.edu.
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000382:microbiology; D003550:Cystic Fibrosis / Q000382:microbiology*; D006801:Humans; D016106:Methicillin Resistance; D017720:Molecular Epidemiology; D011446:Prospective Studies; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification*