Mucoid Staphylococcus aureus: A Clinical Trial of Its Prevalence and Association with Lung Function in People with Cystic Fibrosis.

Abstract

Rationale: The mucoid phenotype of Staphylococcus aureus is caused by adaptation. Excessive biofilm formation associated with a protective effect for mucoid S. aureus was observed in isolates from respiratory samples of people with cystic fibrosis (pwCF). Objectives: There is little knowledge about the prevalence of mucoid S. aureus in pwCF and a potential association with CF lung disease. Methods: A prospective multicenter study was conducted (cross-sectional and longitudinal). Specimens and case report forms were sent to the central study laboratory for characterization of S. aureus and analysis of clinical parameters. Measurements and Main Results: In the cross-sectional study, in 41 (9.1%) of 451 S. aureus-positive pwCF from 13 CF centers, mucoid S. aureus was cultured. In the longitudinal study, the distribution of CFTR genotypes and the number of pwCF with highly effective modulator therapy and coinfection with Pseudomonas aeruginosa were equivalent in the mucoid group (35 pwCF) versus the control group (only nonmucoid S. aureus; 36 pwCF). Although lung function did not differ between groups as a whole, a subgroup analysis revealed significantly worse lung function for female pwCF with mucoid S. aureus as well as for pwCF if P. aeruginosa coinfection was excluded. Conclusions: In the era of highly effective modulator therapy, worse lung function was associated with female and P. aeruginosa-negative pwCF with mucoid S. aureus compared with pwCF with only nonmucoid S. aureus. Therefore, appropriate culture conditions should be established to detect mucoid S. aureus. Further investigations are needed to elucidate the relationship between mucoid S. aureus and CF lung disease. Clinical trial registered with www.clinicaltrials.gov (NCT04171583).