Multicenter Observational Study on Factors and Outcomes Associated with Various Methicillin-Resistant Staphylococcus aureus Types in Children with Cystic Fibrosis.
BACKGROUND
Methicillin-resistant Staphylococcus aureus (MRSA) prevalence continues to increase in patients with cystic fibrosis (CF) in the United States, reaching 26.5% in 2012. Approximately 30% of strains are SCCmec (staphylococcal cassette chromosome mec) IV type, frequently USA300, which in the general population have different genotypic and phenotypic features than SCCmec II type.


OBJECTIVE
We hypothesized that risk factors for acquisition and outcomes in patients with CF differed for "health care-associated" (SCCmec II) versus "community-associated" (SCCmec IV) MRSA strains.


METHODS
To determine the role of SCCmec type and Panton-Valentine leukocidin (PVL), MRSA isolates from patients not more than 18 years old at seven CF centers were typed and the association of potential risk factors and subsequent clinical course was assessed, using data provided by the CF Patient Registry.


RESULTS
Participants with chronic MRSA (295) had typeable isolates and clinical data; 205 (69.5%) had SCCmec II PVL(-), 39 (13.2%) had SCCmec IV PVL(-), and 51 (17.3%) had SCCmec IV PVL(+) strains. SCCmec IV, compared with SCCmec II, increased during the study period, 1996-2010 (P = 0.03). SCCmec II was associated with Pseudomonas aeruginosa-positive cultures and three or more clinic visits in the 6 months preceding the first positive MRSA culture (adjusted odds ratio, 2.05; 95% confidence interval, 1.13-3.74; P = 0.019). Lung function and anthropometrics remained unchanged in the 6 months after initial MRSA detection compared with the 6 months prior. Although CF care increased for participants in both groups in the 6 months after MRSA detection, inhaled antibiotics were prescribed more frequently in those with SCCmec II strains and increased hospitalizations occurred in those with SCCmec IV PVL(-) strains compared with those with PVL(+) strains (adjusted difference, 34.10%; 95% confidence interval, 7.58-60.61; P = 0.012). Participants in both groups had an increase in CF care in the 2 years after MRSA detection compared with the 2 years prior.


CONCLUSIONS
Increased exposure to CF clinics and P. aeruginosa may constitute risk factors for acquisition of SCCmec II MRSA strains. Clinical interventions increased 6 months and 2 years after initial MRSA detection regardless of SCCmec type.
1 Department of Pediatrics, Division of Pediatric Pulmonology, and.
Marianne S
MS
Muhlebach
2 Seattle Children's Research Institute, and.|3 Division of Pediatric Pulmonology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington.
Sonya L
SL
Heltshe
4 Departments of Medicine and of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Elena B
EB
Popowitch
4 Departments of Medicine and of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Melissa B
MB
Miller
2 Seattle Children's Research Institute, and.
Valeria
V
Thompson
2 Seattle Children's Research Institute, and.
Margaret
M
Kloster
5 Department of Pediatrics and Department of Genetics, Washington University in St. Louis, St. Louis, Missouri.
Thomas
T
Ferkol
6 Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama.
Wynton C
WC
Hoover
7 Emory University School of Medicine, Atlanta, Georgia.
Michael S
MS
Schechter
8 Department of Pediatrics, Columbia University Medical Center, and Department of Infection Prevention and Control, New York-Presbyterian Hospital, New York, New York.
Lisa
L
Saiman
D000293:Adolescent; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001427:Bacterial Toxins / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D060085:Coinfection; D003550:Cystic Fibrosis / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology; D004269:DNA, Bacterial / Q000032:analysis; D005098:Exotoxins / Q000032:analysis; D005260:Female; D060005:Genotyping Techniques; D006801:Humans; D007956:Leukocidins / Q000032:analysis; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification; D011552:Pseudomonas Infections / Q000150:complications / Q000175:diagnosis; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification*; D012042:Registries; D012129:Respiratory Function Tests; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology; D014481:United States / Q000453:epidemiology; D037521:Virulence Factors / Q000032:analysis
D000900:Anti-Bacterial Agents; D001427:Bacterial Toxins; D004269:DNA, Bacterial; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin; D037521:Virulence Factors
Panton–Valentine leukocidin; SCCmec type; clinic visits; methicillin-resistant Staphylococcus aureus; risk factor