The microbiome of the middle meatus in healthy adults

Abstract

Rhinitis and rhinosinusitis are multifactorial disease processes in which bacteria may play a role either in infection or stimulation of the inflammatory process. Rhinosinusitis has been historically studied with culture-based techniques, which have implicated several common pathogens in disease states. More recently, the NIH Human Microbiome Project has examined the microbiome at a number of accessible body sites, and demonstrated differences among healthy and diseased patients. Recent DNA-based sinus studies have suggested that healthy sinuses are not sterile, as was previously believed, but the normal sinonasal microbiome has yet to be thoroughly examined. Middle meatus swab specimens were collected from 28 consecutive patients presenting with no signs or symptoms of rhinosinusitis. Bacterial colonization was assessed in these specimens using quantitative PCR and 16S rRNA pyrosequencing. All subjects were positive for bacterial colonization of the middle meatus. Staphylococcus aureus, Staphylococcus epidermidis and Propionibacterium acnes were the most prevalent and abundant microorganisms detected. Rich and diverse bacterial assemblages are present in the sinonasal cavity in the normal state, including opportunistic pathogens typically found in the nasopharynx. This work helps establish a baseline for understanding how the sinonasal microbiome may impact diseases of the upper airways.

Figure 1. Phylum- and species-level diversity.

(A) Phylum-level classification for each subject demonstrates community diversity, but also variability between subjects. Only phyla with median relative abundances greater than 0.5% are shown. (B) Species-level analysis with a minimum 0.5% abundance demonstrates diversity and variability between subjects.

Figure 2. Correlation between relative abundances of Corynebacteria and Lactobacilli.

16S rRNA sequence abundances of Lactobacillus spp. and (A) Corynebacterium tuberculostearicum and (B) Corynebacterium spp. X- and Y-axes represent the percent abundances of the specified OTUs, normalized to total sequence counts. Each circle represents a study participant.

Figure 3. Age-associated differences in the healthy microbiome.

Differences in the phylum-level (panel A) and species-level (panel B) percent relative abundances of 16S rRNA sequences between subjects categorized by age (over or under 50 years of age) are shown. Only taxa with percent relative abundances greater than 0.5% are included; the abundant species are normalized to 100% in order to better depict between-group differences. Multivariate analyses of microbiome datasets revealed significant differences at both the phylum-level (*: p = 0.03) and species-level (**: p = 0.004).

Figure 4. Effects of smoking on the healthy microbiome.

Differences in the species-level (panel A) percent relative abundances of 16S rRNA sequences between subjects categorized by history of smoking are shown. Only taxa with percent relative abundances greater than 0.5% are included; the abundant species are normalized to 100% in order to better depict between-group differences. Although multivariate analyses of microbiome datasets did not reveal a significant association between smoking and microbiome composition (p = 0.15), select taxa differed significantly in percent relative abundance between smoking categories (panel B).