2016 Section 5 Green Book

Bacterial repopulation after surgery & antibiotics

FIGURE 2. Bacterial loads in sinus specimens. Bars show the mean qPCR 16S gene copy number of the ethmoid sample at the time of surgery, 2 weeks, and 6 weeks postoperatively. Bacterial load showed a trend toward increase in total bacteria at 2 weeks compared to the time of surgery ( p = 0.09), and significantly more total bacteria at 2 weeks compared to 6 weeks ( p = 0.03). Error bars indicate standard error of the mean. qPCR = quantitative polymerase chain reaction.

disease. Microbial cultivation studies have shown that pathogen recolonization is a hallmark of poor outcomes after ESS. The source of these bacteria has been debated and little is known about how the sinus microbiome is es- tablished or transformed in the postoperative period after surgery, rinses, and antibiotics. Surprisingly, we found that the bacterial burden of the ethmoid swab was higher in the early postoperative period than at 6 weeks and the time of surgery. This may be a result of broad disruption of mu- cociliary and immune function from surgical intervention, despite meticulous mucosal preservation FESS technique and irrigation at the end of surgery. Our findings strongly indicate that antibiotic therapy after surgery is not elimi- nating local flora during the wound healing process. Addi- tionally, the bacterial makeup at measured time points was quite different. Bacterial communities colonizing the eth- moid at 6 weeks postoperatively were most similar to ante- rior nasal cavity and pretreatment sinus microbial profiles, suggesting these sites may be likely sources for bacterial repopulation, or alternatively, that all sites may naturally return to their baseline states. The microbiome is a diverse, complex community of mi- crobiota that exists in a delicate symbiotic relationship

within a human microenvironment. 29–31 Initial investiga- tions into this complex human-microbial relationship in the sinuses have shown that treatment interventions such as intranasal corticosteroid use may alter the sinonasal micro- biota and that medical management of acute exacerbations of CRS may decrease diversity, 32,33 but more research is needed to understand the effects of these and other thera- pies. We expected to find that the paranasal sinuses would have relatively low bacterial loads after sinus surgery, ir- rigation, and postoperative antibiotics; however, our data showed that bacterial load actually increased. Although the sinuses are not sterile in either healthy or diseased states, the effects of such therapeutic interventions on the sinus microbiome and the implications for patient outcomes re- main largely unknown. 34,35 Studies from the gut micro- biome suggest that antibiotic administration results in a decrease in the diversity of the gut microbiota, which can sometimes be prolonged. 36,37 For instance, a murine model found that following an antibiotic-induced disturbance, the microbial composition would often return to baseline within a number of weeks, although some communities exhibit persistently depleted diversity despite returning to pretreatment microbial densities. 36 Antibiotic-treated mice

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