Surgical site infections (SSIs) are a major cause of morbidity and mortality in the postoperative period. A prospective study was done at a single district general hospital in the United Kingdom to investigate the effect of a departmental oral antibiotic bowel preparation protocol on the occurrence of SSIs following surgery. Oral antibiotic bowel preparation (OABP) with neomycin and metronidazole and mechanical bowel preparation (MBP) were combined in this protocol and was compared with MBP alone. The study was performed between May 2016 and April 2018. 

A cost-effectiveness analysis was also done. Patients who did not undergo elective surgery or were found to have intraperitoneal contamination were excluded from the study. The primary outcome was the overall incidence of SSI within a month of the surgery, while the secondary outcomes were anastomotic leak, duration of hospitalization and mortality rate. 

The study included 311 patients, who were randomized to two groups: preintervention control group receiving MBP alone (n=156) and the second group, who were given a combination of MBP and OABP group (n=155). Tight hemicolectomy, anterior resection with or without ileostomy were the most commonly performed surgical procedures.

The overall incidence of SSIs was found to significantly decrease in the MBP+OABP group vs MBP only group; 4.5% (7/155) vs 16.0% (25/156), respectively (p = 0.001). The superficial SSI showed a decrease from10.3% to 2.6%; organ space infections also declined, from 7.1% to 3.2%. No patient in developed deep SSI in either of the groups. Expectedly, the patients receiving both MBP and OABP also had shorter duration of hospitalization, 8.2 days vs 10.2 days, respectively (p = 0.012). The secondary outcomes were also reduced in the combined group compared to MBP group, although this was non-signficant.

The combination of MBP+OABP was also found to be cost-effective as well. An estimated cost saving of £239.13 per patient and £37,065 for the institution over a one-year period was found.

These findings establish the efficacy and cost-effectiveness of combination of MBP and OABP in reducing the rates of SSIs in patients undergoing elective resectional colorectal surgery for benign and malignant lesions. The observed benefits are for both the patient as well as the institution. OABP in elective colorectal surgery is a routine practice in the US. This prospective study provides evidence for inclusion of OABP along with MBP in UK guidelines for elective colorectal surgery.

Vadhwana B, et al. Ann R Coll Surg Engl. 2020 Feb;102(2):133-140.