Reproducible perioperative changes in the skin microbiome were observed in patients following colorectal surgery, according to data published in Clinical Infectious Diseases. However, a low incidence of surgical site infections (SSIs) in the cohort prevented analysis of associations between dysbiosis and infection, investigators noted.
To investigate whether dysbiosis contributes to SSIs, investigators analyzed bacterial 16S rRNA gene sequences isolated from clinical samples and used a culture-independent strategy to monitor perioperative changes in microbial diversity of fecal samples and the skin.
A total of 882 samples from 61 patients passed quality filtering after sequencing and amplification. Alpha diversity was higher in rectal swabs, fecal samples, and colonic luminal contents compared to skin swabs. Chest and abdominal skin swabs were similar in alpha diversity at all time points except during hospital stay, where abdominal swab alpha diversity was significantly lower on postoperative days 1 and 2.
Alpha diversity on chest swabs decreased before surgery, possibly due to self-administered chlorhexidine bath on the night before surgery, although levels quickly returned to preoperative levels despite the use of perioperative antibiotics. Alpha diversity near the abdominal incision decreased on the day of surgery and remained significantly lower during hospitalization until day 3, returning to normal by the postoperative visit.
The abundance of Enterobacteriaceae increased the first 2 days after surgery with a coinciding decrease in Corynebacteriaceae. Similarly, the abundance of Propionibacterium decreased considerably after surgery. Taxonomic analysis of subcutaneous swabs revealed an increased abundance of colonic anaerobes Lachnospiraceae and Bacteroidaceae in the extraction incision at closure but not at opening.
A single patient developed a wound infection. Enterococcus faecalis was grown on a swab of wound drainage on postoperative day 11, although Enterococcus was not identified on any swabs preoperatively, perioperatively, or postoperatively. This appearance of Enterococcus on the wound corresponded with a decrease in the skin commensals Corynebacterium, Staphylococcus, and Propionibacterium.
According to investigators, the low incidence of SSI in the cohort prevented testing the hypothesis that pathogens responsible for SSIs would be present on postoperative swabs prior to onset of infection. Investigators noted a key finding of the study to be, “transient postoperative loss of the skin commensals Corynebacterium and Propionibacterium and a transient colonization by potential pathogens as well as anaerobes from the gut.”
Future work that allow for the identification of patterns associated with infection could provide actionable opportunities for improved perioperative care, investigators concluded. Furthermore, they believe this study raises questions about the unfocused approach of eliminating the perioperative skin microbiome to prevent SSIs.
Holder-Murray J, Yeh A, Rogers MB, et al. Time-dependent displacement of commensal skin microbes by pathogens at the site of colorectal surgery. Clin Infect Dis. Published online October 24, 2020. doi: 10.1093/cid/ciaa1615.