The Effectiveness of Current Sterility Techniques in Natural Orifice Transluminal Endoscopic Surgery (NOTES)

Abstract

Background: NOTES represents a potentially less invasive alternative to conventional laparoscopy. However, breach of the gut wall raises the specter of intra-peritoneal infection. Various anti-microbial techniques have been employed in animal survival studies—including sterile saline rinse, intravenous and topical antibiotics, and Betadine—despite a paucity of data regarding their general effectiveness. Aim: To assess the effectiveness of existing sterilization techniques for NOTES by quantifying and speciating colony-forming units (CFU's) before and after treatment in ex vivo porcine organs. Method: Stomachs and distal colons were harvested en bloc from six fasted adult female white pigs following euthanasia. Four of these animals received 1g of Cefazolin intravenously prior to sacrifice. After the organs were filleted open in sterile fashion, they were further sub-divided into 2.0 cm × 2.0 cm full-thickness square samples. Each tissue sample was then assigned to one of five treatment arms: (1) sterile 0.9% saline lavage, (2) Betadine lavage, (3) lavage with a Cefazolin/Metronidazole suspension, (4) 4% Chlorhexidine lavage, or (5) no treatment. Following 10 minutes of contact time with the treatment solution, the mucosal surface of each tissue sample was swabbed with a sterile cotton applicator and inoculated in 5 ml of normal saline for 1 hour, followed by serial dilutions. 100 mL aliquots of each dilution were plated onto Sheep's blood agar plates and incubated in aerobic conditions at 24 degrees Celsius. Colony-forming units (CFU's) were quantified after seven days, and representative samples were sent to a commercial veterinary laboratory for speciation. Results: Initial bacterial density was estimated to be 1.0 × 106 CFU's/cm2 for stomach and 1.2 × 106 CFU's/cm2 for colon. The predominant organisms were Escherichia coli in stomach and both Escherichia coli and Enterococcus sp in colon. Sterile normal saline lavage caused a 1-log reduction to 2.3 × 105 CFU's/cm2. Antibiotic lavage caused a 2-log reduction to 6 × 104 CFU's/cm2. Betadine lavage a 5-log reduction to 4.1 × 101 CFU's/cm2. Finally, Chlorhexidine lavage also caused a 5-log reduction to 6.0 × 101 CFU's/cm2. The use of intravenous antibiotics alone diminished bacterial load to 10 CFU's/cm2. The combined use of intravenous antibiotics and Betadine or Chlorhexidine decreased counts to zero. Data was analyzed using ANOVA 2-way analysis method and found to be statistically significant (P = 0.001). Conclusions: The use of intravenous antibiotics in addition to topical Betadine or Chlorhexidine effectively eradicated bacteria in both gastric and colonic mucosa in this porcine model.