Combo reduced the rate of infections by over 50%

Compared with other bowel preparation antibiotic treatment options in patients undergoing elective colorectal surgery, the addition of oral antibiotics to intravenous (IV) antibiotics reduces the incidence of incisional surgical site infections (SSIs) by over 50%, according to results from a network meta-analysis conducted by researchers from New Zealand.

Their results were published in JAMA Surgery.

“The best way to prepare the bowel among patients undergoing elective colorectal surgery continues to be controversial,” wrote John C. Woodfield, PhD, of Otago Medical School, Dunedin, New Zealand, and colleagues, adding that approaches to bowel prep in these patients varies greatly throughout the world.

To clarify differences and elucidate which practices were most effective, Woodfield and colleagues conducted this network meta-analysis by searching MEDLINE, Embase, Cochrane, and Scopus databases for all randomized studies of adults undergoing elective colorectal surgery with aerobic and anaerobic antibiotic cover that reported incisional SSI or anastomotic leaks. They identified 35 randomized controlled trials including 8,377 patients.

Woodfield and colleagues reviewed the different bowel preparation interventions, including the use of IV antibiotics, oral antibiotics, mechanical bowel preparation (MBP), enemas, and combinations of these treatments, which were as follows:

  • 33% of patients received IV antibiotics.
  • 3% received IV antibiotics with enema.
  • 7% received IV antibiotics with oral antibiotics, with or without enema.
  • 32% received MBP with IV antibiotics.
  • 11% received MBP with IV antibiotics with oral antibiotics with good IV antibiotic cover.
  • 4% received MBP with IV antibiotics with oral antibiotics and good overall antibiotic cover.
  • 3% received MBP with oral antibiotics.
  • 6% received oral antibiotics.

Compared with all other treatment options, patients treated with IV antibiotics with oral antibiotics with/without enema and patients who received MBP with adequate IV antibiotics with OA were less likely to have incision SSI.

“The best ranking of treatments to reduce SSI was achieved with IV + [oral antibiotics ± enema] (86% chance of being the best treatment option) followed by MBP + IVA + [oral antibiotics] (85% chance of being the second best treatment option),” the study authors wrote.

In order of ranking, these options were followed by IV alone, IV plus enema, MBP plus IV, MBP plus IVB plus oral antibiotics, oral antibiotics alone, and MBP plus oral antibiotics. MBP plus IV and IV plus enema were significantly better than MBP plus oral antibiotics, and there was no significant difference between IV plus oral antibiotics with or without enema (628 patients [7%]) and MBP plus IV plus oral antibiotics (925 patients [11%]), they reported.

Adding oral antibiotics to IV antibiotics with and without MBP was also associated with a greater than 50% reduction in incisional SSI.

Researchers found minimal differences between all treatments in the incidence of anastomotic leak and in infections, mortality, ileus, and adverse effects of preparation. However, patients treated with either IV antibiotics, oral antibiotics, and enema or with MBP, IVA, and oral antibiotics had lower rates of anastomotic leak (7% and 11%, respectively) compared with patients treated with other options.

Olle Ljungqvist, MD, PhD, of Örebro University, Örebro, Sweden, and Dileep N. Lobo, MS, DM, of Nottingham University Hospitals Trust and University of Nottingham, Queen’s Medical Centre, Nottingham, U.K., authors of an accompanying editorial, noted that the analysis by Woodfield et al “showed, on the surface, that adding [oral antibiotics] to intravenous antibiotics reduced surgical site infection by more than 50%. This implies that [oral antibiotics] is the essential component to reduce surgical site infection after colorectal surgery, not MBP,” they wrote.

But the role of the gut microbiome and microbial diversity—especially as effected by antibiotics, MBP, and even cultural, ethnic, and social disparities—on postoperative outcomes remains unanswered, added Ljungqvist and Lobo.

“Host–gut flora interactions are important for the immune system, and microbial diversity is a key component to keeping this interaction optimal. Yet the combination of oral and intravenous antibiotics that both reduce microbial diversity seems to be the most effective way to minimize postoperative infections. How these seemingly contradictory findings can be reconciled remains to be elucidated,” they wrote.

Study limitations include the complexity inherent with the inclusion of too many bowel preparation options, differences in definitions and methods in individual randomized controlled trials, and the limited number of studies and patients included.

  1. Bowel preparation that includes the addition of oral antibiotics to intravenous antibiotics may reduce incisional surgical site infection among patients undergoing elective colorectal surgery.

  2. This combination reduced the incidence of incisional surgical site infection by more than 50% but had no effects on the incidence of anastomotic leak or other clinical outcomes.

Liz Meszaros, Deputy Managing Editor, BreakingMED™

This study was funded by the University of Otago.

Woodfield reported no conflicts of interest.

Ljungqvist and Lobo reported no conflicts of interest.

Cat ID: 23

Topic ID: 78,23,730,16,23,192,925,159