Prevalence and Clinical Significance of <i>Staphylococcus aureus</i> Small-Colony Variants in Cystic Fibrosis Lung Disease

<jats:title>ABSTRACT</jats:title> <jats:p> Small-colony variants (SCVs) of <jats:italic>Staphylococcus aureus</jats:italic> can be isolated from the chronically infected airways of patients suffering from cystic fibrosis (CF). These slow-growing morphological variants have been associated with persistent and antibiotic-resistant infections, such as osteomyelitis and device-related infections, but no information is available to date regarding the clinical significance of this special phenotype in CF lung disease. We therefore investigated the prevalence of <jats:italic>S. aureus</jats:italic> SCVs in CF lung disease in a 12-month prospective study and correlated the microbiological culture results with the patients' clinical data. A total of 252 patients were screened for the presence of SCVs. The prevalence rate was determined to be 17% (95% confidence interval, 10 to 25%) among <jats:italic>S. aureus</jats:italic> carriers. <jats:italic>S. aureus</jats:italic> isolates with the SCV phenotype showed significantly higher antibiotic resistance rates than those with the normal phenotype. Patients positive for SCVs were significantly older ( <jats:italic>P</jats:italic> = 0.0099), more commonly cocolonized with <jats:italic>Pseudomonas aeruginosa</jats:italic> ( <jats:italic>P</jats:italic> = 0.0454), and showed signs of more advanced disease, such as lower forced expiratory volume in 1 s ( <jats:italic>P</jats:italic> = 0.0148) than patients harboring <jats:italic>S. aureus</jats:italic> with a solely normal phenotype. The logistic regression model determined lower weight ( <jats:italic>P</jats:italic> = 0.016), advanced age ( <jats:italic>P</jats:italic> = 0.000), and prior use of trimethoprim-sulfamethoxazole ( <jats:italic>P</jats:italic> = 0.002) as independent risk factors for <jats:italic>S. aureus</jats:italic> SCV positivity. The clinical status of CF patients is known to be affected by multiple parameters. Nonetheless, the independent risk factors determined here point to the impact of <jats:italic>S. aureus</jats:italic> SCVs on chronic and persistent infections in advanced CF lung disease. </jats:p>