Nasal Staphylococcus aureus carriage is not a risk factor for lower-airway infection in young cystic fibrosis patients

Abstract

Staphylococcus aureus is one of the first pathogens which often persistently infect the airways of cystic fibrosis (CF) patients. Nasal S. aureus carriage is a risk factor for S. aureus infections in non-CF patients. Topical treatment strategies successfully eradicate nasal S. aureus carriage, thereby decreasing S. aureus infection. A prospective longitudinal multicenter study was conducted to assess whether nasal carriage represents a risk factor for S. aureus colonization of the oropharynx in young CF patients. Cross-sectional analysis revealed a significantly higher prevalence of S. aureus-positive nasal (28/80 [35%] versus 20/109 [18%]; P < 0.01) and oropharyngeal (35/80 [44%] versus 20/109 [18%]; P < 0.001) cultures in children with CF compared to a control group. The first site of S. aureus detection was the nose in 6 patients and the oropharynx in 14 patients, respectively. Longitudinal analysis demonstrated a significantly higher S. aureus prevalence (61/62 [98%] versus 47/62 [76%]; P < 0.001) and persistence (46/62 [74%] versus 31/62 [50%]; P < 0.01) in the oropharynx than in the nose. In CF patients, the oropharynx, and not the nose, was the predominant site of S. aureus infection and persistence. Hence, it is unlikely that CF patients will benefit from topical treatment strategies to eradicate nasal carriage.

FIG. 1.

Prevalence of S. aureus nasal and oropharyngeal carriage in children with CF and control children. There was a statistically significantly higher prevalence of S. aureus in children with CF than in healthy controls without respiratory disease in the nose (28/80 versus 20/109) and in the oropharynx (35/80 versus 20/109).

FIG. 2.

Cumulative frequency of S. aureus-positive cultures in the nose and/or oropharynx. During the longitudinal part of this study, S. aureus was cultured from the oropharynx and the nose in 47 children, only from the oropharynx in 14 children, and only from the nose in 1 child, while 1 child was never colonized by S. aureus.

FIG. 3.

Sequence of S. aureus-positive cultures on the clonal level. (A) PFGE analysis of S. aureus isolates from a CF patient from whom S. aureus was cultured first from the nose (N) and later from the oropharynx (O). (B) PFGE patterns of sequential isolates of a patient from whom S. aureus was cultured first from the oropharynx and later from the oropharynx and the nose at the same time. (C) PFGE patterns of isolates from a patient from whom two different S. aureus clones were cultured from the oropharynx and from the nose at the same time.