Respiratory colonization with methicillin-resistant Staphylococcus aureus predicts worse health outcomes in Cystic Fibrosis patients. The objective of this study was to determine if CF patients colonized with MRSA containing different Staphylococcal cassette chromosome mec types showed variation in clinical outcomes.
Isolates from clinical respiratory cultures identified as MRSA were collected on pediatric CF patients from April 2014 to February 2015 and analyzed using whole genome sequencing technology. MRSA colonization date was determined using a standard definition and a case-control study was developed using a pre- and post- MRSA acquisition design. Patients were grouped based on SCCmec type; SCCmec II or SCCmec IV. Ten patients from the SCCmec IV group were matched by age and gender with ten patients with SCCmec II isolates. Number of hospitalizations, pulmonary exacerbations, Body Mass Index percentile, FEV1%, clinic visits, and prescribed oral antibiotics were compared. MRSA isolates were analyzed for the presence of virulence and antibiotic resistance genes along with phenotypic antimicrobial susceptibility patterns.
Patients in the SCCmec II group showed a statistically significant decrease in FEV1% (Figure 1) and BMIp. They averaged twice as many sick visits along with a significantly increased amount of prescribed anti-Staphylococcal antibiotics (Figure 2). SCCmec II MRSA isolates were resistant to more anti-Staphylococcal antibiotics (Figure 3) and contained more virulence and antibiotic resistance genes. There was no statistically significant difference in the number of hospitalizations or pulmonary exacerbation episodes.
SCCmec II MRSA strains do effect health outcomes in CF patients in the first year post-acquisition compared to CF patients with SCCmec IV MRSA. SCCmec II strains have the potential to be more virulent and drug resistant which may contribute to increased pathogenicity. It is relevant to identify MRSA strain type in CF patients in order to understand the potential clinical impact.
J. Mortensen, None
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