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FIGURE 3.
Similarity of bacterial communities between time points and sampling sites. The Morisita-Horn similarity index was used to quantify differences in
microbiota in order to compare the 6-week ethmoid sample to the anterior nares, ethmoid, and nasopharynx at the time of surgery, the ethmoid at 2 weeks
postoperatively, and between the ethmoid at 2 weeks postoperatively and the ethmoid at the time of surgery. The 6-week ethmoid sample was most similar
to the anterior nares and ethmoid samples at the time of surgery, suggesting these may be potential sources for repopulation of bacteria postoperatively. *A
value of 1 indicates identical bacterial community, and 0 is complete dissimilarity. AN
=
anterior nasal cavity, AN
=
anterior nares; NP
=
nasopharynx.
exhibit altered immune responses and are more suscepti-
ble to other bacterial infections.
36,38
A study investigating
the effects of antibiotics and steroids on the sinonasal mi-
crobiome in acute exacerbations of CRS changes in the
sinonasal microbiome similarly found a decrease in diver-
sity at the completion of courses of antibiotics and steroids.
Though this suggests that antibiotics may contribute to a
decrease in diversity, resolution of the acute exacerbation
may also have contributed to the changes seen, as there
was no baseline steady-state sample collected.
33
There is
evidence in humans to support that a more diverse micro-
biome is associated with improved health outcomes and
less disease burden.
35,39,40
We noted a trend toward a less
complex bacterial community after surgery and antibiotics,
which became more diverse again at the 6-week time point
(
p
=
0.09). More significant temporal differences in mi-
crobial diversity may have been more evident in a larger
cohort. These results suggest that treatment interventions
(surgery and antibiotics) can increase bacterial diversity;
whether these changes will contribute to improved clin-
ical outcomes is currently under investigation. Our data
illustrate an initial perturbation in the microbiome due to
therapeutic intervention, from which many subjects may
recover their preoperative bacterial community and some
may continue to shift toward a new and different commu-
nity makeup, a model that has been previously proposed
for microbiome effects on disease states.
37
In humans, re-
silience is variable by subsite and subject, but the nasal
cavity appears to be 1 of the most stable,
41
as supported by
our findings.
Possible sources for the bacteria that recolonize the si-
nuses after sinus surgery include reservoirs within paranasal
biofilms, colonized intramucosal sites refractory to antibi-
otic therapy, within the nasopharynx, or even de novo bac-
teria from extranasal sources.
8–11
We found that 6-week
postoperative microbiota most closely represented the an-
terior nares and ethmoid samples from the time of surgery,
and were least similar to the nasopharynx, suggesting that
the former sites may be critical reservoirs for sinus micro-
biota.
New research suggests that in multiple mucosal surfaces
individuals do in fact have signature bacterial species and
even strains.
42
We have previously showed that the ante-
rior nares microbiome is stable over time in the absence of
mitigating factors such as antibiotics
43
and also that a more
diverse sinus microbial ecology is associated with healthy
sinuses.
44
In this study, our preoperative and postoperative
ethmoid samples were largely similar (mean M-H 0.59),
indicating that this “fingerprint” may persist in the sinuses,
but can be subject to milder changes. Although it is possi-
ble that we may have seen more resiliency in our samples,
or more recovery of baseline microbiota, if we had sam-
pled the ethmoids at a later time point, it was thought that
6 weeks was enough time to reach a new postoperative
steady state because microbiota in the gut have been noted
to return to baseline within 2 to 4 weeks after cessation
of antibiotics.
7,9,11,29,36,45
It is also possible that microbial
disruptions caused by surgical and medical interventions
leave a patient susceptible to recolonization by opportunis-
tic pathogens. Further study will hopefully elucidate the
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