Tinidazole in the prevention of wound infection after elective colorectal surgery

Antimicrobial prophylaxis for colorectal surgery

BACKGROUND

Research shows that administration of prophylactic antibiotics before colorectal surgery prevents postoperative surgical wound infection. The best antibiotic choice, timing of administration and route of administration remain undetermined.

OBJECTIVES

To establish the effectiveness of antimicrobial prophylaxis for the prevention of surgical wound infection in patients undergoing colorectal surgery. Specifically to determine:1. whether antimicrobial prophylaxis reduces the risk of surgical wound infection;2. the target spectrum of bacteria (aerobic or anaerobic bacteria, or both);3. the best timing and duration of antibiotic administration;4. the most effective route of antibiotic administration (intravenous, oral or both);5. whether any antibiotic is clearly more effective than the currently recommended gold standard specified in published guidelines;6. whether antibiotics should be given before or after surgery.

SEARCH METHODS

For the original review published in 2009 we searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE (Ovid) and EMBASE (Ovid). For the update of this review we rewrote the search strategies and extended the search to cover from 1954 for MEDLINE and 1974 for EMBASE up to 7 January 2013. We searched CENTRAL on the same date (Issue 12, 2012).

SELECTION CRITERIA

Randomised controlled trials of prophylactic antibiotic use in elective and emergency colorectal surgery, with surgical wound infection as an outcome.

DATA COLLECTION AND ANALYSIS

Data were abstracted and reviewed by one review author and checked by another only for the single, dichotomous outcome of surgical wound infection. Quality of evidence was assessed using GRADE methods.

MAIN RESULTS

This updated review includes 260 trials and 68 different antibiotics, including 24 cephalosporins and 43,451 participants. Many studies had multiple variables that separated the two study groups; these could not be compared to other studies that tested one antibiotic and had a single variable separating the two groups. We did not consider the risk of bias arising from attrition and lack of blinding of outcome assessors to affect the results for surgical wound infection.Meta-analyses demonstrated a statistically significant difference in postoperative surgical wound infection when prophylactic antibiotics were compared to placebo/no treatment (risk ratio (RR) 0.34, 95% confidence interval (CI) 0.28 to 0.41, high quality evidence). This translates to a reduction in risk from 39% to 13% with prophylactic antibiotics. The slightly higher risk of wound infection with short-term compared with long-term duration antibiotic did not reach statistical significance (RR 1.10, 95% CI 0.93 to 1.30). Similarly risk of would infection was slightly higher with single-dose antibiotics when compared with multiple dose antibiotics, but the results are compatible with benefit and harm (RR 1.30, 95% CI 0.81 to 2.10). Additional aerobic coverage and additional anaerobic coverage both showed statistically significant improvements in surgical wound infection rates (RR 0.44, 95% CI 0.29 to 0.68 and RR 0.47, 95% CI 0.31 to 0.71, respectively), as did combined oral and intravenous antibiotic prophylaxis when compared to intravenous alone (RR 0.56, 95% CI 0.43 to 0.74), or oral alone (RR 0.56, 95% CI 0.40 to 0.76). Comparison of an antibiotic with anaerobic specificity to one with aerobic specificity showed no significant advantage for either one (RR 0.84, 95% CI 0.30 to 2.36). Two small studies compared giving antibiotics before or after surgery and no significant difference in this timing was found (RR 0.67, 95% CI 0.21 to 2.15). Established gold-standard regimens recommended in major guidelines were no less effective than any other antibiotic choice.

AUTHORS' CONCLUSIONS

This review has found high quality evidence that antibiotics covering aerobic and anaerobic bacteria delivered orally or intravenously (or both) prior to elective colorectal surgery reduce the risk of surgical wound infection. Our review shows that antibiotics delivered within this framework can reduce the risk of postoperative surgical wound infection by as much as 75%. It is not known whether oral antibiotics would still have these effects when the colon is not empty. This aspect of antibiotic dosing has not been tested. Further research is required to establish the optimal timing and duration of dosing, and the frequency of longer-term adverse effects such as Clostridium difficile pseudomembranous colitis.

Pharmacokinetics and tissue penetration of a single 1,000-milligram, intravenous dose of metronidazole for antibiotic prophylaxis of colorectal surgery

The levels of metronidazole in serum and tissue penetration of metronidazole were studied after prophylactic administration in 11 patients undergoing elective colorectal surgery. A single dose of 1,000 mg given intravenously was administered before surgery. Adequate drug levels in serum (greater than or equal to MIC for 90% of strains tested [MIC90] for Bacteroides fragilis) were found in all patients throughout the procedure. Mean peak (15-min) and last-determined (24-h) metronidazole levels in serum were 28.8 +/- 8 and 4.2 +/- 1.7 mg/liter, respectively. The beta-phase elimination half-life was 9.5 +/- 2.3 h, and the clearance and apparent volume of distribution were 57 +/- 13 ml/min and 0.7 +/- 0.1 liter/kg, respectively. In the colonic wall at surgical anastomosis, tissue metronidazole levels greater than or equal to MIC90 for B. fragilis were found in 91% of patients. In the abdominal wall fat and epiploic fat, tissue metronidazole levels greater than or equal to MIC90 for B. fragilis were found in 40 to 60% of patients at surgical incision and closure. No anaerobic infection occurred during the study.

Pharmacokinetics and tissue penetration of a single dose of ornidazole (1,000 milligrams intravenously) for antibiotic prophylaxis in colorectal surgery

Levels in serum and tissue penetration of ornidazole were studied after a single intravenous injection of 1,000 mg given to 14 patients for prophylaxis of surgical infection. They were scheduled for elective colorectal surgery. Adequate levels in blood (greater than or equal to MIC for 90% of Bacteroides fragilis strains tested) were found in all patients throughout the procedure and up to hour 24. Mean-maximal (15 min) and last-determined (24 h) ornidazole levels in serum were 24 +/- 5.2 and 6.3 +/- 1.4 mg/liter, respectively. beta-Phase elimination half-life was 14.1 +/- 2.7 h, and clearance and apparent volume of distribution were 47 +/- 12 ml/min and 0.9 +/- 0.13 liters/kg, respectively. In all patient, adequate levels in tissue were found in the abdominal wall and the epiploic fat at time of incision and in the colonic wall at time of anastomosis. At time of closure, all but one patient had adequate levels in tissue in the abdominal wall and the epiploic fat. No anaerobic nor aerobic infection occurred in the study patients.

Intraincisional antibiotic in addition to systemic antibiotic treatment fails to reduce wound infection rates in contaminated abdominal surgery. A controlled clinical trial

One hundred ninety patients with peritonitis at the time of abdominal surgery were allocated at random to systemic antibiotic treatment alone or systemic antibiotic treatment combined with topical application of antibiotics in the wound at the time of wound closure. The overall wound infection rate was 17 percent without significant difference between the two treatment groups (P greater than 0.80).

Wound infection rates after intraincisional plus systemic antibiotic prophylaxis in an animal model

The effect of intraincisional application of antibiotics in addition to systemic antibiotic prophylaxis was evaluated in a randomized blind study using a guinea pig model of surgical wound infection. Wounds were contaminated with 10(7) Escherichia coli plus 10(8) Bacteroides fragilis. Wound infection was defined as accumulation of pus draining spontaneously or after opening the wound. Systemic antibiotic prophylaxis with gentamicin plus clindamycin significantly reduced the wound sepsis rate from 83% in the control group to 20% in the treated group (p less than 0.001). Intraincisional application of antibiotics in addition to systemic prophylaxis did not further reduce the rate of wound sepsis (p greater than 0.8).

Wound infection rates following preoperative versus intraoperative commencement of antibiotic prophylaxis

The effect of antibiotic prophylaxis initiated one hour prior to contamination or at the time of contamination was evaluated in a randomized blind study using a guinea pig model of surgical wound infection. Would infection, defined as accumulation of pus draining spontaneously or after opening of the wound, developed in 135 guinea pigs after intraincisional contamination before wound closure with 10(7) Escherichia coli plus 10(8) Bacteroides fragilis. Antibiotic prophylaxis with gentamicin plus clindamycin significantly reduced the wound sepsis rate from 82% in the control group of 61 animals to 19% in the two treated groups of 68 and 67 animals (p less than 0.001). However, the timing of antibiotic prophylaxis did not influence wound sepsis rates, rectal temperature during the postoperative period, or bacterial recovery from wound infections.

Intraincisional antibiotics in laparotomy wounds

Concentrations of ampicillin after intraincisional instillation in laparotomy wounds were measured in ten patients undergoing appendectomy. Ampicillin, 1 gm, was instilled under the fascia and 1 gm in the subcutaneous space during wound closure. Wound secretion was collected every two hours during the first 24 postoperative hours by cannulation of a fine perforated drain placed in the subcutaneous space. Ampicillin was determined by a disk diffusion method. During the first eight hours the median concentration of ampicillin in wound secretion exceeded 1000 microgram/ml; 14 hours and 20 hours after wound closure the median concentrations were 73 and 14 microgram/ml, respectively. The effect of ampicillin in high concentrations on "resistant" strains of Bacteroides fragilis was demonstrated in an in vitro experiment. It is concluded that in colorectal surgery the effect on wound sepsis of intraincisional antibiotics as an addition to systemic antibiotic prophylaxis should be evaluated in a clinical trial.

Experimental animal model of surgical wound infection applicable to antibiotic prophylaxis

Wound infection, defined as accumulation of pus draining spontaneously or after opening of the wound, developed in 19 out of 22 guinea pigs (86%) after intraincisional contamination with 10(7) Escherichia coli plus 10(8) Bacteroides fragilis before wound closure. Antibiotic prophylaxis with gentamicin plus clindamycin significantly reduced the wound sepsis rate from 86% to 29% (p less than 0,001). Pus for bacteriological studies was available in all cases of wound infection but one, and culture always revealed both Escherichia coli and Bacteroides fragilis. The animal model presented employs widely accepted criteria for wound infection, and avoids culture of tissue homogenates.

Pharmacokinetics of tinidazole in chronic renal failure and in patients on haemodialysis

The pharmacokinetics of tinidazole after infusion (800 mg in 15 min) were studied in 12 patients with chronic renal failure (RI) and in five patients undergoing regular dialysis treatment (RD). Tinidazole elimination plasma half-life was 15.09 +/- 0.68 h (mean +/- s.e. mean) (RI) and 12.9 +/- 1.0 h after dialysis (RD), but there was a significant decrease in half-life during dialysis (4.25 +/- 0.43 h) P less than 0.001). The apparent volume of distribution (0.64 +/- 0.03 l/kg) was equal to extra and intracellular water volume and tinidazole was little bound to plasma protein (8%). There was a slight sex difference in apparent volume of distribution between male patients (0.70 +/- 0.09 l/kg) and female patients (0.59 +/- 0.10 l/kg) (P = 0.07), but as body clearance decreases in the same order, there was no modification of plasma half-life. In renal failure, pharmacokinetics of tinidazole were not disturbed because no correlation between half-life, body clearance and creatinine clearance occurred; urine elimination was about 7% of administered dose. Plasma clearance during dialysis was 49.9 +/- 3.2 ml/min and about 43% of the available drug was eliminated during the 6 h dialysis procedure. These results suggest that an additional half-dose infusion should be given after the end of dialysis in patients undergoing regular dialysis treatment.

Effects of prophylactic antibiotics on wound infection after elective colon and rectal surgery: 1960 to 1980

Wound infection continues to be a common complication of elective colon and rectal surgery. During the period from 1960 to 1980, 42 prospective, controlled prophylactic antibiotic trials were undertaken which addressed this problem. In this report we have analyzed these trials and compared them to all noncontrolled, prospective wound infection surveys and a representative sample of the retrospective surveys of the same period. From this analysis several conclusions have become apparent: (1) wound infection remains a common complication for which prophylactic antibiotics are generally effective, (2) the most effective agents are those with activity against anaerobic bacteria, (3) orally administered nonabsorbable antibiotics have little effect on reducing wound infection following these procedures, and (4) the optimal antibiotic regimen is yet to be found. The data do suggest, however, the more preferred regimens currently available as well as those worthy of further investigation.

Tinidazole--microbiology, pharmacology and efficacy in anaerobic infections

Tinidazole is a 5-nitroimidazole with selective activity against anaerobic bacteria and protozoa. It is bactericidal at low concentrations and its spectrum covers most anaerobic bacteria and some capnophilic microorganisms. Anaerobic bacteria known to be resistant to tinidazole include anaerobic streptococci, actinomyces and propionibacteria. Tinidazole is one of the most active antibacterial agents against Bacteroides fragilis which is one of the most resistant species of anaerobic bacteria. Only a few strains have been reported to be resistant. Tinidazole has been shown to be efficacious in protozoal infections such as trichomonal vaginitis, amoebiasis and giardiasis. Clinical studies have also shown that tinidazole is efficacious in the treatment of anaerobic infections including respiratory tract infections, intra-abdominal sepsis and obstetrical and gynecological infections. Since tinidazole has no activity against aerobic bacteria, it must be combined with other antibacterial agents in the treatment of mixed infections involving aerobic and anaerobic bacteria. Tinidazole has also been used successfully alone or in combination with other antimicrobial agents for prophylaxis in patients undergoing elective colonic and abdominal surgery, emergency appendectomy and gynecological surgery.

Criteria audit of surgery for carcinoma of the large intestine in Melbourne teaching hospitals

A criteria audit of patients undergoing surgery for carcinoma of the large intestine in three Melbourne teaching hospitals revealed a considerable variation in the degree of compliance with individual criteria, and a high complication rate with approximately two-thirds of the patients suffering one or more complications. The uniform system of data gathering used provides a baseline for future studies.