The Surgical Infection Society Guidelines on the Management of Intra-Abdominal Infection

Introduction

Intra-abdominal infections (IAIs) are a significant, often life-threatening condition affecting millions of patients annually, with treatment responsibility typically distributed across various healthcare providers, including surgeons, infectious disease specialists, and critical care physicians. The Surgical Infection Society (SIS), founded in 1981, has played a key role in developing clinical guidelines for IAI management. These guidelines have evolved over time, with updates in 1992, 2002, 2010, and the most recent in 2017. Given the dynamic nature of patient demographics, the rise of drug-resistant microorganisms, and advancements in antimicrobial agents, regular updates to these guidelines are essential. The 2022 update aims to address the complex landscape of IAI treatment, focusing solely on adults, utilizing higher-quality evidence from randomized controlled trials and systematic reviews, and continuing the work of previous guidelines.

This latest update differs from previous versions by adopting a broader, more inclusive approach, including a wide literature search and incorporating both new and existing recommendations based on the latest evidence. The strength of each recommendation is determined using the GRADE system, which rates the quality of evidence and the strength of the recommendation. The guidelines emphasize the importance of risk stratification, especially for patients with multi-drug-resistant (MDR) organisms or those with specific clinical risks, such as sepsis or septic shock. The document also highlights the significance of source control procedures and their timing in conjunction with pharmacologic therapies. Ultimately, these guidelines are designed to support evidence-based treatment decisions for adult IAI patients, while recognizing the need for clinical judgment in individual cases, especially given the increasing challenge of antimicrobial resistance.

Methods

In 2022, a writing group was formed to update the SIS guidelines, consisting of members from the SIS Therapeutics and Guidelines Committee, expert content writers, and a professional librarian. A systematic review was conducted using databases like PubMed/Medline, the Cochrane Library, Embase, and Web of Science, covering studies from January 2016 to September 2022. The search focused on randomized controlled trials (RCTs), systematic reviews, and meta-analyses related to surgical site infections and intra-abdominal infections in adults. Literature reviews, case reports, and non-English studies were excluded.

After screening 5,070 studies, 3,701 unique articles were identified. The screening process involved 15 reviewers, and 295 studies underwent full-text review, resulting in 75 studies that were included for data extraction and quality review. The review adhered to the PRISMA guidelines, and a follow-up search was conducted in February 2024 to incorporate the latest literature. The final dataset was used to inform the updated guidelines for IAI management.

Figure 1. PRISMA flow diagram.

Evaluation of the evidence was performed using the GRADE system. The strength of each recommendation was graded strong (1) or weak (2). Strong recommendations begin with the phrase “We recommend…,” whereas weak recommendations begin with “We suggest… .” Quality of the evidence was graded high (A), moderate (B), or weak (C). For new recommendations not contained in previous guidelines, GRADE was applied only to evidence in the current literature search. For updates to recommendations from previous IAI guideline versions, GRADE was applied to evidence from the current literature search as well as prior evidence. Final guideline recommendations were developed by an iterative process to achieve consensus. All writing group members voted to accept or reject each recommendation.

Results

Antimicrobial agent therapy

Aminoglycosides

• We recommend against aminoglycoside-based combination regimens for empiric therapy of higher risk patients (Grade 1-A).

This updated recommendation is based on a systematic review of 69 trials, involving 7,863 patients with sepsis. The review compared β-lactam monotherapy (penicillins, cephalosporins, carbapenems) combined with a β-lactamase inhibitor (BLIC) versus β-lactam-aminoglycoside combination therapy for sepsis-associated infections, including UTIs, pneumonia, IAI, skin infections, and infections of unknown origin. The primary outcome was all-cause mortality, with secondary endpoints including treatment failure, superinfections, and adverse events (AEs).

The review found no significant difference in all-cause mortality between the study arms when the same β-lactam was used in both treatments. However, when comparing different regimens, β-lactam monotherapy showed a trend for lower mortality and a substantial advantage in terms of clinical failure. Subgroup analyses revealed no major differences, but β-lactam monotherapy was associated with significantly lower nephrotoxicity compared to combination therapy. All findings were based on low- to very low-quality evidence.

Beta-lactamase inhibitor combinations

Cefoperazone-sulbactam

• We recommend cefoperazone-sulbactam for empiric therapy of lower risk patients (Grade 1-B).

This updated recommendation is based on a systematic review and meta-analysis of 12 studies involving 1,674 patients with IAIs, post-operative IAIs, and biliary tract infections. The comparison was made between cefoperazone/sulbactam and several other treatments, including clindamycin plus gentamicin, ceftriaxone, ceftazidime, or amikacin plus metronidazole, and ciprofloxacin or levofloxacin plus metronidazole.

Cefoperazone-sulbactam showed significantly higher clinical efficacy, including a higher clinical cure rate, a lower clinical failure rate, and a higher microbiologic eradication rate compared to the comparators. However, there was no significant difference in the mortality rate between cefoperazone-sulbactam and the other treatments.

Cefoperazone-sulbactam

• We recommend imipenem-cilastatin-relebactam for empiric therapy (Grade 1-A).
• We suggest reserving imipenem-cilastatin-relebactam for higher risk patients due to its broader spectrum antimicrobial agent activity (Grade 2-C).

The new recommendations are based on two double-blind, multi-center RCTs and a systematic review and meta-analysis involving 398 patients with IAI treated with imipenem-cilastatin-relebactam compared to other agents. The first RCT involved two dose regimens of imipenem-cilastatin-relebactam versus imipenem-cilastatin in 351 patients. Both regimens showed equivalent clinical response rates, and there was no difference in safety profiles. However, few non-susceptible organisms were identified, which may limit the utility of relebactam.

The second RCT compared imipenem-cilastatin-relebactam with imipenem-cilastatin plus colistin in 47 patients with healthcare-associated pneumonia, IAI, or complicated UTIs. The clinical response rates were similar, but the imipenem-cilastatin-relebactam group had fewer serious adverse events and less nephrotoxicity. The systematic review and meta-analysis, including these studies, found imipenem-cilastatin-relebactam to have similar efficacy and safety to comparators for treating IAI and other severe bacterial infections.

Ceftazidime-avibactam

• We recommend ceftazidime-avibactam plus metronidazole for empiric therapy (Grade 1-A).
• We suggest reserving ceftazidime-avibactam for higher risk patients because of its broader spectrum antimicrobial agent activity (Grade 2-C).
• We recommend ceftazidime-avibactam plus metronidazole for empiric therapy of patients at risk for infection with ESBL-producing Enterobacterales (Grade 1-B).

The updated recommendations are based on three systematic reviews, one meta-analysis, one phase 3 RCT, and a subgroup analysis, totaling over 1,300 patients with IAI treated with ceftolozane-tazobactam plus metronidazole versus other therapies. These studies report that ceftolozane-tazobactam plus metronidazole is non-inferior to meropenem, with no significant differences in treatment-related AEs, serious AEs, tolerability, or mortality. The subgroup analysis showed equivalent efficacy for ceftolozane-tazobactam plus metronidazole when P. aeruginosa infection was involved. However, the systematic review on ceftolozane-tazobactam for severe ESBL-producing Enterobacterales infections may be biased due to the inclusion of a single small retrospective study.

Glycylcyclines

Eravacycline

• We recommend eravacycline for empiric therapy (Grade 1-A).
• We suggest reserving eravacycline for higher risk patients due to its broader spectrum antimicrobial agent activity (Grade 2-C).

The updated recommendations are based on two double-blind RCTs, four meta-analyses, and two systematic reviews, involving a total of 1,080 patients with intra-abdominal infections (IAI) treated with eravacycline compared to ertapenem or meropenem. The first RCT included 541 patients and compared eravacycline with ertapenem. The primary endpoint was clinical response at the test-of-cure (TOC) visit, and the results showed no significant differences in clinical cure rates between the treatment groups. Treatment failure was mainly due to unplanned surgical procedures or the initiation of rescue antimicrobial therapy. The second RCT, involving 400 patients, compared eravacycline to meropenem and also found no difference in clinical cure rates between the two treatments. Both studies found that while there were more treatment-emergent adverse events (AEs) in the eravacycline group, the number of severe or life-threatening AEs was similar between groups.

Additionally, systematic reviews and meta-analyses, which included these RCTs and a third phase 2 study, confirmed similar clinical efficacy between eravacycline and the comparator agents. The phase 2 study, which involved 139 patients, compared two dose regimens of eravacycline with ertapenem and found no significant differences in clinical success between the groups. Overall, the evidence from these studies suggests that eravacycline is as effective as ertapenem or meropenem for the treatment of IAI, with no major differences in safety profiles.

Tigecycline

• We recommend against tigecycline for empiric therapy of low- and high-risk patients (Grade 1-B).
• We suggest reserving tigecycline for patients with resistant infections or as part of a combination regimen when no therapeutic alternative exists (Grade 2-B).

These updated recommendations are based on an open-label, single-center RCT, one systematic review and meta-analysis of four retrospective studies, and one systematic review and network meta-analysis, totaling 14,479 patients with IAI treated with tigecycline versus meropenem, standard- versus high-dose tigecycline with or without concomitant antimicrobial agent administration, or tigecycline versus multiple other regimens, including cefepime plus metronidazole, ceftolozane-tazobactam, carbapenems, fluoroquinolones, and BLIC monotherapies or combination therapy with metronidazole.49–51 Whereas the RCT and systematic review and meta-analysis report tigecycline as non-inferior to meropenem or no difference between high- and standard-dosing, respectively, these studies have small sample sizes or are observational with high risk of bias. The systematic review and network meta-analysis reports significantly higher risk of all-cause mortality with tigecycline versus cefepime plus metronidazole, and significantly higher risk of serious AEs with tigecycline versus imipenem-cilastatin.

Carbapenems

Biapenem

• We suggest biapenem for empiric therapy (Grade 2-B).
• We suggest reserving biapenem for higher risk patients because of its broader spectrum antimicrobial agent activity (Grade 2-C).

These new recommendations are based on one meta-analysis of eight RCTs totaling 1,685 patients, but only one multi-center study of 118 patients with IAI, treated with biapenem versus imipenem-cilastatin. There was no difference in clinical success (complete resolution or substantial improvement in symptoms) or mean microbiologic success (eradication or presumed eradication of pathogens between biapenem and imipenem-cilastatin.) There was no difference in drug-related AEs or numbers of withdrawn patients due to AEs between biapenem and imipenem-cilastatin. Compared with imipenem-cilastatin, biapenem had significantly higher numbers of laboratory AEs possibly or probably related to treatment.

Doripenem

• We recommend doripenem for empiric therapy (Grade 1-A).
• We suggest reserving doripenem for higher risk patients because of its broader spectrum antimicrobial agent activity (Grade 2-C).

These updated recommendations are based on one systematic review and meta-analysis of eight RCTs totaling 3,499 patients, but only one phase 3, double-blind, multi-center non-inferiority RCT of 476 patients with IAIs, treated with doripenem versus meropenem.54,55 The primary outcome was clinical success rate, and secondary outcomes were microbiologic eradication rate and risk of AEs. Compared with meropenem, doripenem had similar clinical success and microbiologic eradication rates and treatment-emergent AEs.

Fluoroquinolones

• We recommend ciprofloxacin plus metronidazole for empiric therapy of lower risk patients (Grade 1-A).
• We suggest moxifloxacin for empiric therapy of lower risk patients (Grade 2-A).

These updated recommendations are based on a meta-analysis of seven multi-center RCTs involving 4,125 patients treated with fluoroquinolone-based (ciprofloxacin, moxifloxacin) versus β-lactam-based (piperacillin/tazobactam, ceftriaxone plus metronidazole, ertapenem, imipenem-cilastatin) regimens for intra-abdominal infections (IAI). The primary outcomes—treatment success at the test-of-cure (TOC) visit and all-cause mortality—showed no significant difference between the two regimens. Secondary outcomes, including treatment success in different patient populations and treatment-related adverse events (AEs), also revealed no major differences between the groups.

Subgroup analysis indicated that moxifloxacin was significantly less effective than β-lactam-based regimens, particularly in patients with complicated appendicitis. Despite this, no overall differences were observed between fluoroquinolone- and β-lactam-based treatments, suggesting similar efficacy for both regimens in managing IAI.

Glycopeptides

Vancomycin

• We recommend against vancomycin for empiric therapy of low- and high-risk patients (Grade 1-B).

This new recommendation is based on a post hoc analysis of a multi-center open-label RCT involving 518 patients with IAI treated with short- versus long-course antibiotics after source control. Patients were grouped based on whether they received vancomycin or not, with the primary endpoint being a composite of surgical site infections (SSI), recurrent IAI, and death at 30 days. The analysis found no significant difference in the composite outcome between patients who received vancomycin and those who did not, despite higher APACHE-II scores and longer hospital stays in the vancomycin group.

Although vancomycin treatment did not independently predict the composite outcome, patients who received vancomycin had higher rates of hospital-acquired infections. Additionally, there were more patients in the vancomycin group who received piperacillin-tazobactam, while those not receiving vancomycin were more likely to receive ertapenem.

Metronidazole

• We recommend metronidazole as the preferred anti-anaerobic agent in combination regimens for empiric therapy of low- and high-risk patients (Grade 1-A).

Metronidazole is the preferred anti-anaerobic agent for combination regimens in low- and high-risk patients (Grade 1-A). A systematic review of eight studies (including over 1,100 patients) compared metronidazole combinations (e.g., with cefepime, cefotaxime, ceftazidime/avibactam) to carbapenems (imipenem-cilastatin, meropenem) for intra-abdominal infections. Outcomes showed no differences in clinical success, microbiologic eradication, drug-related adverse events, or all-cause mortality between groups. However, after excluding high-bias studies, metronidazole combinations demonstrated significantly better clinical success than carbapenem monotherapy.

Polymyxins

• We suggest polymyxin B for empiric therapy of higher risk patients with MDR infection, including P. aeruginosa, Acinetobacter baumannii complex, Klebsiella pneumoniae, Escherichia coli, and Enterobacter spp. (Grade 2-B).

Polymyxin B is suggested for empiric therapy in high-risk patients with MDR infections, including P. aeruginosa, Acinetobacter baumannii complex, Klebsiella pneumoniae, E. coli, and Enterobacter spp. (Grade 2-B). Based on a meta-analysis of 27 studies (2,900+ patients), including those with IAIs, polymyxin B (mono- or combination therapy) shows similar mortality rates to colistin but potentially less severe nephrotoxicity.

Anti-fungal therapy

• We suggest against empiric anti-fungal therapy in lower risk patients (Grade 2-B).

Empiric anti-fungal therapy is not recommended for lower-risk patients with intra-abdominal infections (Grade 2-B). A meta-analysis of six RCTs (1,067 patients) found no differences in short-term mortality or secondary outcomes (e.g., adverse events, ICU stay, or quality of life) between untargeted anti-fungal treatments (e.g., fluconazole, micafungin) and placebo/no treatment. Most studies had a high risk of bias due to unclear allocation or financial influence.

Anidulafungin

• We recommend anidulafungin for empiric therapy of higher risk patients with infections from Candida spp. (Grade 1-B).

This updated recommendation is based on one pooled analysis of five prospective studies (one comparative, four open-label), totaling 79 adult surgical patients with microbiologically confirmed Candida IAI, treated with IV anidulafungin, with possible switching to an oral azole after 5–10 days of IV therapy. The primary outcome was the global response rate (GRR) at the conclusion of IV treatment, and secondary endpoints were GRR at the end of therapy, all-cause mortality at days 14 and 28, and safety. The most common pathogens were C. albicans and C. glabrata. The GRR of anidulafungin was similar to a previous trial comparing the drug with fluconazole for invasive candidiasis. Anidulafungin was well-tolerated with only mild-to-moderate AEs.

Anti-enterococcal therapy

• We recommend against empiric therapy targeting Enterococcus spp. in lower risk patients with CA-IAI (Grade 1-B).
• We suggest empiric therapy targeting Enterococcus spp. in higher risk patients (Grade 2-B).

Updated recommendations are based on a post hoc analysis of an RCT and a meta-analysis of 23 RCTs and 13 observational studies. The post hoc analysis (50 patients with Enterococcus spp. isolation) found no significant difference in SSI, recurrent IAI, or mortality between short- and long-term antibiotic courses. The meta-analysis showed no improvement in treatment success, mortality, or AEs with empiric anti-enterococcal therapy compared to controls. While most patients were low-risk with CA-IAI, high-risk CA-IAI and HA-IAI may benefit from such coverage.

Specific Disease States

Hepatopancreatobiliary malignant disease

• We recommend targeted, perioperative antibiotic agent prophylaxis based on a positive preoperative bile culture in patients undergoing surgical procedures for hepatopancreatobiliary malignant disease (Grade 1-A).

This recommendation is based on studies evaluating targeted versus standard prophylactic antibiotic regimens in hepatopancreatobiliary surgeries. Targeted prophylaxis (e.g., piperacillin-tazobactam, third-/fourth-generation cephalosporins) significantly reduced incisional and organ-space SSIs compared to standard regimens. An RCT of 778 patients undergoing pancreaticoduodenectomy found piperacillin-tazobactam more effective than cefoxitin in reducing 30-day SSIs, pancreatic fistula, sepsis, and mortality, regardless of preoperative biliary stents. Despite frequent Enterococcus isolation, regimens lacking anti-enterococcal activity were effective.

• We suggest antibiotic agent prophylaxis for at least 24 hours in patients undergoing pancreatoduodenectomy with positive bile cultures following preoperative biliary drainage to prevent organ-space SSI (Grade 2-C).

This recommendation is based on a meta-analysis of eight studies (1,170 patients) comparing perioperative (24-hour) and prolonged (>24-hour) antibiotic prophylaxis after pancreaticoduodenectomy, with or without preoperative biliary drainage. While prolonged prophylaxis (2–10 days) did not reduce organ/space SSIs overall compared to perioperative prophylaxis, it significantly decreased organ/space SSIs in patients with preoperative biliary drainage. No differences were observed in superficial SSI rates, and the optimal duration of antibiotics remains uncertain.

Acute appendicitis

Non-operative management of uncomplicated appendicitis

• We recommend oral moxifloxacin for empiric therapy of lower risk patients undergoing non-operative management of acute uncomplicated appendicitis (Grade 1-B).

This new recommendation is based on an open-label, multi-center, non-inferiority RCT of 599 patients with acute uncomplicated appendicitis managed non-operatively and administered either oral moxifloxacin for seven days or IV ertapenem for two days followed by oral levofloxacin and metronidazole for five days.70 The primary outcome was treatment success (≥65%,) defined as hospital discharge without a surgical procedure and no recurrent appendicitis during a one-year follow-up, and if oral antibiotic agents alone were non-inferior to IV plus oral antibiotic agents. The study groups showed similar treatment success (70.2% vs. 73.8%,), and thus, oral moxifloxacin demonstrated non-inferiority versus IV plus oral antibiotic agents.

Complicated appendicitis

• We recommend substitution of oral for IV antibiotic agents to complete a short course (24 h) of therapy in lower risk patients with acute complicated appendicitis undergoing adequate source control by laparoscopic appendectomy (Grade 1-B).

This recommendation is based on an RCT of 104 patients with complicated appendicitis (primarily gangrenous) treated with 24 hours of oral versus IV antibiotics post-laparoscopic appendectomy. Both groups received amoxicillin-clavulanic acid, with no significant differences in 30-day complications, Comprehensive Complication Index, or hospital stay. As most patients had gangrenous appendicitis, the findings may not apply to those with more severe cases, like diffuse peritonitis.

• We suggest a carbapenem for empiric therapy of patients undergoing non-operative management of acute appendicitis (Grade 2-B).

This recommendation is based on a meta-analysis of 21 studies (4,551 patients) comparing antibiotic therapy or prophylaxis plus appendectomy for acute appendicitis. Surgery had higher one-year treatment success than cephalosporins or BLICs but not carbapenems. Carbapenems also had fewer treatment-related adverse events compared to surgery.

• We suggest limiting post-operative antibiotic agents to 24-48 hours for low- and high-risk patients with adequate source control for complicated appendicitis undergoing appendectomy (Grade 2-B).

This recommendation is based on two RCTs. The first, a multi-center study of 1,066 patients with complicated appendicitis, compared two- versus five-day IV antibiotic courses after appendectomy. There was no difference in infection rates or complications, but the two-day group had fewer adverse effects and more frequent readmissions. Patients undergoing open surgery in the two-day group were at higher risk of infection. The second, a single-center study of 80 patients, compared 24-hour versus extended antibiotic courses. The 24-hour group had fewer complications (17.9% vs. 29.3%) and shorter hospital stays.

Chronic appendicitis

• We suggest against antibiotic agent prophylaxis in lower risk patients undergoing elective laparoscopic appendectomy for chronic appendicitis (Grade 2-B).

This recommendation is based on a double-blind, single-center RCT with 106 patients undergoing laparoscopic appendectomy for chronic appendicitis. Patients received preoperative IV antibiotics (cefuroxime or clindamycin) or saline. The primary outcome, SSI, and secondary outcomes (post-operative complications, time to return of gastrointestinal function, and resolution of pain) showed no significant differences between the two groups. The study involved mostly young, healthy patients, so these findings may not apply to higher-risk individuals.

Abdominal trauma

• We suggest ertapenem for antibiotic agent prophylaxis in low- and high-risk patients undergoing laparotomy for traumatic injury (Grade 2-B).

This recommendation is based on a single-center study of 302 trauma patients undergoing exploratory laparotomy. The pre-protocol group received antibiotics based on surgeon preference, while the post-protocol group received ertapenem before incision. The primary outcome, trauma-related infections within 30 days, was significantly reduced with ertapenem compared to pre-protocol treatment. Secondary outcomes, including incisional SSI and IAI, also showed improvements. Ertapenem usage increased from 2% to 54%, while cephalosporin use decreased from 84% to 35%.

Duration of antibiotic agent therapy

• We recommend limiting antimicrobial agent therapy to four days for low- and high-risk patients with source control achieved via a percutaneous drainage procedure (Grade 1-B).

This new recommendation is based on one post hoc analysis of an open-label, multi-center RCT of 129 patients with IAIs who underwent percutaneous drainage versus surgical procedure for source control.58,77 There was no difference in outcome (recurrent IAI, Clostridioides difficile infection, hospital days) between shorter and longer durations of antimicrobial agent therapy.

• We recommend limiting antimicrobial agent therapy to four days after achieving source control in high-risk patients with sepsis (Grade 1-B).

This new recommendation is based on one post hoc analysis of an open-label, multi-center RCT of 112 patients with IAI who met systemic inflammatory response syndrome criteria for sepsis (temperature <36°C or >38°C and white blood cell count <4,000 cells/mm3 or >12,000 cells/mm3) treated with short- versus long-course antibiotic agents after adequate source control. The analysis showed no difference in incidence of SSI, recurrent IAI, extra-abdominal infection, C. difficile infection, number of hospital days, or mortality between groups.

• We recommend limiting antimicrobial agent therapy to four days after achieving source control in higher risk patients at increased risk of complications from diabetes mellitus, obesity, or higher illness severity (Grade 1-B).

This recommendation is based on a post hoc analysis of 152 obese patients, 64 diabetic patients, and 83 critically ill patients with IAI, comparing short- versus long-course antibiotic therapy. The analysis showed no difference in outcomes like SSI, recurrent IAIs, or mortality. A separate RCT and systematic review of 489 critically ill patients also indicated that shorter antibiotic courses (8 vs. 15 days or 5 vs. 10 days) had similar outcomes, with shorter courses providing more antibiotic-free days. We suggest limiting antibiotic therapy to eight days after source control in critically ill patients (Grade 2-B).

De-escalation of antibiotic agent therapy

• We suggest de-escalation of antibiotic agent therapy in ICU patients with HA-IAI (Grade 2-B).
• We suggest maintaining anaerobic coverage with de-escalation of antibiotic agent therapy (Grade 2-C).

These updated recommendations are based on a study of 206 ICU patients with HA-IAI, analyzing the de-escalation process of empiric antibiotic therapy. Empiric therapy included piperacillin-tazobactam or imipenem-cilastatin with amikacin and vancomycin, and de-escalation occurred in 53% of patients. No clinical difference was found at day seven between de-escalation and non-de-escalation groups. Key factors for de-escalation included adequate empiric therapy and use of vancomycin, carbapenems, and aminoglycosides, while the presence of non-fermenting gram-negative bacilli and MDR strains hindered de-escalation. No emergence of MDR organisms occurred after de-escalation in reoperation patients.

Timing of source control procedures

• We recommend undertaking source control within 12 hours in lower risk patients (Grade 1-B).
• We recommend undertaking source control within six hours in higher risk patients with associated septic shock (Grade 1-B).

These updated recommendations are based on two reports. The first is a systematic review and meta-analysis of 3,373 IAI patients, showing that early surgical intervention (within 12 hours) significantly reduced mortality, hospital length of stay, and procedure-related complications. Early exploration within six hours notably improved survival, especially for patients with septic shock. The second report, from a cohort study of 4,792 ICU patients with sepsis, found that delays in surgical source control increased mortality, with better outcomes for those treated within six hours, particularly in cases of CA-IAI.

Antimicrobial agent stewardship

• We recommend initiating antimicrobial agent therapy within an hour in higher risk patients with sepsis (Grade-1B).

This updated recommendation is based on a cohort study of 4,792 ICU patients with sepsis, showing that delays in antimicrobial therapy beyond six hours significantly increased mortality and the risk of septic shock. Patients receiving antimicrobial therapy within the first hour were more likely to have CA-IAI compared to those with delayed treatment.

• We recommend implementation of empiric antimicrobial agent therapy protocols to improve antimicrobial agent stewardship (Grade 1-B).

This new recommendation is based on two prospective cohort studies. The first, a single-center trial of 310 patients with CA- or HA-IAI, found that protocol compliance with empiric antimicrobial therapy was 52.3%. Non-compliance was linked to higher mortality and complications. The second study, a multi-center trial with 4,439 surgical patients, evaluated a stewardship program to reduce antibiotic treatment duration. The program led to a significant decrease in prolonged antibiotic use from 15.0% to 11.4%, with 91.5% of recommendations being accepted.

Discussion

For over 30 years, the SIS has provided updated, evidence-based guidelines for the prevention and treatment of IAI. This update includes new recommendations based on a comprehensive literature review and aims to enhance clinical decision-making. Notable updates include shorter antibiotic durations following percutaneous source control, earlier source control procedures, and new anti-infective agents like eravacycline and imipenem-cilastatin-relebactam. The guideline emphasizes antimicrobial stewardship, recommending early antibiotic initiation in sepsis, de-escalation in ICU patients, and considering oral antibiotics for complicated appendicitis. It also highlights non-operative management for uncomplicated appendicitis, specifically oral moxifloxacin. Despite these advancements, there are still unanswered questions regarding treatment failure prediction and dosing optimization for high-risk patients. The SIS encourages continued research, including exploring AI and machine learning, to address these clinical challenges.

Source: Huston, Jared M., et al. “The Surgical Infection Society guidelines on the management of intra-abdominal infection: 2024 update.” Surgical infections 25.6 (2024): 419-435