Infection after colorectal surgery: a randomized trial of prophylaxis with piperacillin versus sulbactam/piperacillin. West of Scotland Surgical Infection Study Group

Mismatch of populations between randomised controlled trials of perioperative interventions in major abdominal surgery and current clinical practice

BACKGROUND

Demographics of patients undergoing major abdominal surgery are changing. External validity of relevant RCTs may be limited by participants not resembling patients encountered in clinical practice. We aimed to characterise differences in age, weight, BMI, and ASA grade between participants in perioperative trials in major abdominal surgery and patients in a reference real-world clinical practice sample. The secondary aim was to investigate whether time since trial publication was associated with increasing mismatch between these groups.

METHODS

MEDLINE and Embase were searched for multicentre RCTs from inception to September 2022. Studies of perioperative interventions in adults were included. Studies that limited enrolment based on age, weight, BMI, or ASA status were excluded. We compared trial cohort age, weight, BMI, and ASA distribution to those of patients undergoing major abdominal surgery at our tertiary referral hospital during September 2021 to September 2022. We used a local, single-institution reference sample to reflect the reality of clinical practice (i.e. patients treated by a clinician in their own hospital, rather than averaged nationally). Mismatch was defined using comparison of summary characteristics and ad hoc criteria based on differences relevant to predicted mortality risk after surgery.

RESULTS

One-hundred and six trials (44,499 participants) were compared to a reference cohort of 2792 clinical practice patients. Trials were published a median (IQR [range]) 13.4 (5-20 [0-35]) years ago. A total of 94.3% of trials were mismatched on at least one characteristic (age, weight, BMI, ASA). Recruitment of ASA 3 + participants in trials increased over time, and recruitment of ASA 1 participants decreased over time (Spearman's Rho 0.58 and - 0.44, respectively).

CONCLUSIONS

Patients encountered in our current local clinical practice are significantly different from those in our defined set of perioperative RCTs. Older trials recruit more low-risk than high-risk participants-trials may thus 'expire' over time. These trials may not be generalisable to current patients undergoing major abdominal surgery, and meta-analyses or guidelines incorporating these trials may therefore be similarly non-applicable. Comparison to local, rather than national cohorts, is important for meaningful on-the-ground evidence-based decision-making.

A pilot study: intraoperative 16S rRNA sequencing versus culture in predicting colorectal incisional surgical site infection

BACKGROUND

Surgical Site Infection (SSI) of the abdominal incision is a dreaded complication following colorectal surgery. Identifying the intraoperative surgical site microbes may provide clarity in the pathogenesis of SSIs. Genomic sequencing has revolutionized the ability to identify microbes from clinical samples. Utilization of 16S rRNA amplicon sequencing to characterize the intraoperative surgical site may provide the critical information required to predict and prevent infection in colorectal surgery.

METHODS

This is a pilot, prospective observational study of 50 patients undergoing elective colorectal resection. At completion of surgery, prior to skin closure, swabs were taken from the subcutaneous tissue of the abdominal incision to investigate the microbial profile. Dual swabs were taken to compare standard culture technique and 16S rRNA sequencing to establish if a microbial profile was associated with postoperative SSI.

RESULTS

8/50 patients developed an SSI, which was more likely in those undergoing open surgery (5/15 33.3% versus 3/35, 8.6%; P = 0.029). 16S rRNA amplicon sequencing was more sensitive in microbial detection compared to traditional culture. Both culture and 16S rRNA demonstrated contamination of the surgical site, predominantly with anaerobes. Culture was not statistically predictive of infection. 16S rRNA amplicon sequencing was not statistically predictive of infection, however, it demonstrated patients with an SSI had an increased biodiversity (not significant) and a greater relative abundance (not significant) of pathogens such as Bacteroidacaea and Enterobacteriaceae within the intraoperative site.

CONCLUSIONS

16S rRNA amplicon sequencing has demonstrated a potential difference in the intraoperative microbial profile of those that develop an infection. These findings require validation through powered experiments to determine the overall clinical significance.

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.

Epidemiology of methicillin-resistant Staphylococcus aureus carriage and MRSA surgical site infections in patients undergoing colorectal surgery: a cohort study in two centers

BACKGROUND

Surgical site infections (SSIs) after colorectal surgery usually are caused by commensal intestinal bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) may be responsible for additional SSI-related morbidity. The aim of this retrospective cohort study was to describe the epidemiology of SSIs caused by MRSA after colorectal surgery in two tertiary-care centers, one in Geneva, Switzerland (G), and the other in Chicago, Illinois (C).

METHODS

Adult patients undergoing colorectal resections during periods of universal screening for MRSA on admission were identified retrospectively. Demographic characteristics, surgery-related factors, and occurrence of MRSA SSI were compared in patients with and without MRSA carriage before surgery.

RESULTS

There were 1,069 patients (G=194, C=875) with a median age of 67 years fulfilling the inclusion criteria. Of these, 45 patients (4.2%) had a positive MRSA screening result within 30 days before surgery (G=18, C=27; p<0.001). Ten patients (0.9%; G=6, C=4) developed MRSA SSI, detected a median of 17.5 days after surgery, but only two of them were MRSA-positive before surgery. Nine of the 45 MRSA carriers identified by screening received pre-operative prophylaxis with vancomycin (G 6/18, C 3/27), and 17 of these patients (37.8%; G 7/18, C 10/27) were started on MRSA decolonization therapy before surgery. Pre-operative administration of either decolonization or vancomycin was not protective against MRSA SSI (p=0.49).

CONCLUSION

Methicillin-resistant S. aureus seems to be an infrequent cause of SSI after colorectal resections, even in MRSA carriers. Systematic universal screening for MRSA carriage prior to colorectal surgery may not be beneficial for the individual patient. Post-operative factors seem to be important in MRSA infections, as the majority of MRSA SSIs occurred in patients negative for MRSA carriage.

Antimicrobial prophylaxis for colorectal surgery

BACKGROUND

Research shows that administration of prophylactic antibiotics before colorectal surgery prevents postoperative surgical wound infection (SWI). 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 SWI in patients undergoing colorectal surgery: specifically to determine, 1 Whether it reduces risk of SWI. 2 The target spectrum/a of bacteria (aerobic and/or anaerobic). 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.

SEARCH STRATEGY

CENTRAL, MEDLINE, and EMBASE, were searched from January, 1980 to December, 2007.

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

Data were abstracted and reviewed by three authors for only the single, dichotomous outcome of SWI.

MAIN RESULTS

The review included 182 trials (30,880 participants), and 50 different antibiotics, including 17 cephalosporins. Many studies had multiple variables that separated the two study groups and could not be compared to other studies that tested one antibiotic and had a single variable separating the two groups. Meta-analyses demonstrated a statistically significant difference in postoperative SWI when prophylactic antibiotics were compared to placebo/no treatment (relative risk (RR) 0.30, 95% confidence intervals (CI) 0.22 to 0.41). No statistically significant differences were shown when comparing short- and long-term duration of prophylaxis (RR 1.06, 95% CI 0.89 to 1.27); or single dose versus multiple dose antibiotics (RR 1.17, 95% CI 0.67 to 2.05). Additional aerobic coverage and additional anaerobic coverage both showed statistically significant improvements in SWI rates (RR 0.41, 95% CI 0.23 to 0.71 and RR 0.55, 95% CI 0.35 to 0.85, respectively); as did combined oral and intravenous antibiotic prophylaxis when compared to intravenous alone (RR 0.55, 95% CI 0.41 to 0.74), or oral alone (RR 0.34, 95% CI 0.13 to 0.87). Established gold standard regimens were no less effective than any other antibiotic choice.

AUTHORS' CONCLUSIONS

Antibiotics covering aerobic and aerobic bacteria should be delivered orally and intravenously prior to colorectal surgery. Antibiotics delivered within this framework will reduce the risk of postoperative SWI by at least 75%. Further research is required to establish the optimal timing and duration of dosing, and frequency of longer-term adverse effects such as Clostridium difficile pseudomembranous colitis.

Surgical antibiotic prophylaxis: effect in postoperative infections

OBJECTIVE

to assess the risk of surgical wound infection and hospital acquired infections among patients with and without adequate antibiotic prophylaxis. Also, to provide models to predict the contributing factors of hospital infection and surgical wound infection.

DESIGN

survey study. Prospective cohort study over 14 months, with data collected by a nurse and a epidemiologist through visits to the surgical areas, a review of the medical record and consultation with the medical doctor and nurses attending the patients.

SETTING

Two hundred and fifty bed, general hospital serving Puertollano (Ciudad Real), population--50,000.

RESULTS

between February 1998 and April 1999, 754 patients underwent surgery, 263 (34.88%) received appropriate perioperative prophylaxis while 491 (65.12%) received inadequate prophylaxis. For those who received adequate antibiotic prophylaxis, the percentage of nosocomial infection was 10.65% compared with the group who received inadequate prophylaxis in which the percentage of nosocomial infection was 33.40%. The relative risk of nosocomial infection was, therefore, 4.21 times higher in the latter group (confidence intervals 95%: 2.71-6.51). A patient in the inadequate prophylaxis group had a 14.87% chance of wound infection while a patient in the adequate prophylaxis group had a 4.56% chance of wound infection. The relative risk of wound infection was 3.65 times higher in the group that received inadequate prophylaxis (confidence intervals 95%: 1.95-6.86). The final regression logistic model to assess nosocomial infection incorporated seven prognostic factors: age, length of venous periferic route, vesicle catheter, duration of operation, obesity, metabolic or neoplasm diseases and adequate or inadequate prophylaxis. When we incorporated these variables in the multi-factorial analysis we found that the relative risk of developing nosocomial infection was 2.33 times higher in the group which received inadequate prophylaxis. When we applied the second logistic multiple regression model (wound infection), we discovered that the probability of developing surgical wound infection was 2.32 times higher in the group which received inadequate prophylaxis as opposed to the group, which received adequate prophylaxis. The goodness of fit (Hosmer-Lemeshow test) showed a correct significance in all models.

CONCLUSIONS

a multi-factorial analysis was applied to identify the high-risk patients and the risk factors for postoperative infections. Through the application of these multiple regression logistic models, we conclude that the correct antibiotic prophylaxis is effective and will subsequently reduce postoperative infection rates, especially in high-risk patients. Therefore, the choice of antimicrobial agent should be made on the basis of the criteria of hospital committee.

Antimicrobial prophylaxis in colorectal surgery: a systematic review of randomized controlled trials

BACKGROUND

A systematic review was carried out to assess the relative efficacy of antimicrobial prophylaxis for the prevention of postoperative wound infection in patients undergoing colorectal surgery.

METHODS

MEDLINE, EMBASE, the Cochrane Trials Register and the references cited in retrieved studies were searched to identify relevant trials published between 1984 and 1995.

RESULTS

Some 147 relevant trials were identified. The quality of trials has improved over the past 12 years. The results confirm that the use of antimicrobial prophylaxis is effective for the prevention of surgical wound infection after colorectal surgery. There was no significant difference in the rate of surgical wound infections between many different regimens. However, certain regimens appear to be inadequate (e.g. metronidazole alone, doxycycline alone, piperacillin alone, oral neomycin plus erythromycin on the day before operation). A single dose administered immediately before the operation (or short-term use) is as effective as long-term postoperative antimicrobial prophylaxis (odds ratio 1.17 (95 per cent confidence interval (c.i.) 0.90-1.53)). There is no convincing evidence to suggest that the new-generation cephalosporins are more effective than first-generation cephalosporins (odds ratio 1.07 (95 per cent c.i. 0.54-2.12)).

CONCLUSION

Antibiotics selected for prophylaxis in colorectal surgery should be active against both aerobic and anaerobic bacteria. Administration should be timed to make sure that the tissue concentration of antibiotics around the wound area is sufficiently high when bacterial contamination occurs. Guidelines should be developed locally in order to achieve a more cost-effective use of antimicrobial prophylaxis in colorectal surgery.