Attempts
to recover organisms from non-inflamed tonsils were carried out for over seven
decades. Some studies failed to find any microorganisms and others recovered
them only in a portion of the cases. Only three studies identified bacteria in
all sinus sample.
Brook evaluated the microbiology of maxillary sinuses of 12
adults and found an average of 4 isolates/sinus of aerobic and anaerobic bacteria. The
predominant anaerobes were Prevotella
Fusobacterium
,and Peptostreptococcus spp., and
Propionibactreium acnes. The most
common aerobic bacteria were beta-hemolytic Streptococcoci, Staphylococcus aureus, Streptococcus pneumoniae, and Haemophillus parainfluenzae.
Ramakrishnanet al. collected middle meatus specimens from 28 individuals with no sinusitis.
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. S. aureus, S. epidermidis and P. acnes were
the most prevalent and abundant microorganisms detected. The authors found rich
and diverse bacterial assemblages in all of the individuals, including
opportunistic pathogens typically found in the nasopharynx.
Aurora et al. compared the microbiome and immune response from 30 patients with
chronic rhino-sinusitis (CRS) and 12 healthy controls. The microbiome was
analyzed by deep sequencing of the bacterial 16S and fungal 18S ribosomal RNA
genes. Although quantitative increase in most bacterial and fungal species was
observed in patients with CRS relative to controls, the microbiomes of patients
with CRS were qualitatively similar to the controls. The predominate aerobic
organisms were Cyanobacterium ,
Curtobacterium, and Pseudomonas spp., and staphylococcus
aureus. The commonest anaerobes were Propionbacterium,
and Prevottela spp.
Patients
with CRS had increased levels of the following cytokines: IL-4, IL-5, IL-8, and
IL-13, along with increased levels of eosinophils and basophils in the lavage.
Furthermore, peripheral blood leukocytes obtained from some patients with CRS
responded to control lavage samples (ie, to commensals) to produce IL-5. In
contrast, the same lavage sample evoked no IL-5 production in leukocytes from
healthy controls. These results may explain why systemic steroid treatment
provides relief for some patients with CRS.
Colonization
of non-inflamed “normal “ sinus is possible because there is direct
communication between the sinuses nasal cavity through the ostia which could
enable organisms that reside in the nasopharynx to spread into the sinus. The
presence of bacteria in the sinus can explain why following closure of the
ostium, these organisms may become involved in the emerging inflammatory
process.
The
study by Aurora et al. that the host response or lack of response to the normal
sinus flora may be key to the development of sinus inflammation. Modulation the
sinus flora by topical antimicrobial and/or probiotic organisms that may
interfere with the growth of pathogens may be used to prevent and treat sinus inflammation. Future studies that would explore these
modalities are warranted.
CT of normal sinuses
