Complicated intra-abdominal infections (IAI) remain significant causes of morbidity and mortality. The classical types of intra-abdominal infections are abscesses and diffuse peritonitis (eg, from an anastomotic leak). Recently, the Infectious Diseases Society of America, in collaboration with the Surgical Infection Society, published updated guidelines (previously published in 2003) for the management of these common infections.1,2
The following are selected recommendations from this new set of guidelines:
* In adult patients not undergoing immediate laparotomy, computed tomography (CT) is the imaging modality of choice to determine the presence of an intra-abdominal infection and its source (A-II; the grading system reflects the strength of recommendation, with A being he highest level of evidence and with I being the highest; see the guidelines for further explanation).
* An appropriate source control procedure to drain infected foci, control ongoing peritoneal contamination by diversion or resection, and restore anatomic and physiological function to the extent feasible is recommended for nearly all patients with intra-abdominal infection (B-II). Patients with diffuse peritonitis should undergo an emergency surgical procedure as soon as possible, even if ongoing measures to restore physiologic stability need to be continued during the procedure (B-II).
* Where feasible, percutaneous drainage of abscesses and other well-localized fluid collections is preferable to surgical drainage (B-II).
* For hemodynamically stable patients without evidence of acute organ failure, an urgent approach should be taken. Intervention may be delayed for as long as 24 hours if appropriate antimicrobial therapy is given and careful clinical monitoring is provided (B-II).
* Highly selected patients with minimal physiological derangement and a well-circumscribed focus of infection, such as a periappendiceal or pericolonic phlegmon, may be treated with antimicrobial therapy without a source control procedure provided that very close clinical follow-up is possible (B-II). Nonoperative management of selected patients with acute, nonperforated appendicitis can be considered if there is a marked improvement in the patient's condition before operation (B-II). Nonoperative management may also be considered part of a specific approach for male patients provided that the patient is admitted to the hospital for 48 hours and shows sustained improvement in clinical symptoms and signs within 24 hours while receiving antimicrobial therapy (A-II).
Comment: These recommendations follow the long-acknowledged principle to surgically drain a focus of infection. Source control is defined as "any single procedure or series of procedures that eliminate infectious foci, control factors that promote ongoing infection, and correct or control anatomic derangements to restore normal physiologic function."1
Regarding appendicitis, the guidelines stress the importance of using protocols for patient care management: "Locally adapted guidelines should be implemented to improve process of care variables and relevant clinical outcomes."1 For selected patients with acute appendicitis, the guidelines suggest that antimicrobial therapy alone without surgical intervention is adequate. Support for a less emergent approach comes from other clinical trials analyzing time to perforation, which indicate this to be an unusual early event.3,4
* Blood cultures do not provide additional clinically relevant information for patients with community-acquired intra-abdominal infection and are therefore not routinely recommended for such patients (B-III).
* If a patient appears clinically toxic or is immunocompromised, knowledge of bacteremia may be helpful in determining duration of antimicrobial therapy (B-III).
* For community-acquired infections, there is no proven value in obtaining a routine Gram stain of the infected material (C-III).
* For health care-associated infections, Gram stains may help define the presence of yeast (C-III).
* Routine aerobic and anaerobic cultures from lower-risk patients with community-acquired infection are considered optional in the individual patient but may be of value in detecting epidemiological changes in the resistance patterns of pathogens associated with community-acquired intra-abdominal infection and in guiding follow-up oral therapy (B-II).
Comment: For those of us with an infectious disease and/or microbiology background, the recommendations to not routinely obtain cultures may seem counter to our goal of pathogen-directed therapy; and I still prefer to have culture results to follow even in nonsevere cases. However, as the authors of the guidelines indicate, there are few data indicating that Gram stain and culture data provide information likely to alter outcome in patients with a community-acquired infection. However, the guidelines do recommend the importance of appropriate cultures for severe infections and for health care-related infections where resistance may be more prevalent. In addition, the guidelines do recommend pathogen-directed therapy if resistant bacteria are identified at the time of surgical intervention and there are persistent signs of infection.
Antimicrobial therapy: community-acquired
* Antimicrobial therapy should be initiated once a patient receives a diagnosis of an intra-abdominal infection or once such an infection is considered likely. For patients with septic shock, antibiotics should be given as soon as possible (A-III).
* Antibiotics used for empiric treatment of community-acquired intra-abdominal infection should be active against enteric gram-negative aerobic and facultative bacilli and enteric gram-positive streptococci (A-I).
* Coverage for obligate anaerobic bacilli should be provided for distal small bowel, appendiceal, and colon-derived infection and for more proximal gastrointestinal perforations in the presence of obstruction or paralytic ileus (A-I).
* Recommended antimicrobials are listed in Table 1.
* Ampicillin-sulbactam is not recommended for use because of high rates of resistance to this agent among community-acquired Escherichia coli (B-II).
* Cefotetan and clindamycin are not recommended for use because of increasing prevalence of resistance to these agents among the Bacteroides fragilis group (B-II).
* Coverage of Enterococcus is not necessary in patients with community-acquired intra-abdominal infection (A-I).
* Empiric antifungal therapy for Candida is not recommended for adult and pediatric patients with community-acquired intra-abdominal infection (B-II).
* Quinolone-resistant E. coli have become common in some communities, and quinolones should not be used unless hospital surveys indicate 190% susceptibility of E. coli to quinolones (A-II).
* Aztreonam plus metronidazole is an alternative, but addition of an agent effective against gram-positive cocci is recommended (B-III).
* In adults, routine use of an aminoglycoside or another second agent effective against gram-negative facultative and aerobic bacilli is not recommended in the absence of evidence that the patient is likely to harbor resistant organisms that require such therapy (A-I).
* Use of agents effective against methicillin-resistant Staphylococcus aureus (MRSA) or yeast is not recommended in the absence of evidence of infection because of such organisms (B-III).
* In high-risk patients, antimicrobial regimens should be adjusted according to culture and susceptibility reports to ensure activity against the predominant pathogens isolated.
Comment: These recommendations reflect the principle to initiate empirical therapy effective against the most likely relevant pathogens, and acknowledge the increasing resistance of E. coli to ampicillin/sulbactam and of B. fragilis to clindamycin and cefotetan. Compared with the prior guidelines, this version lists additional agents, which include tigecycline, moxifloxacin and doripenem, all recently approved for use in complicated IAI.
The rational to use broader-spectrum antimicrobials for severe disease is in part based on the concern that the consequences of treatment failure may be more significant than they are in patients with infection of mild-to-moderate severity. In addition, although routine coverage of Enterococcus is not recommended for mild IAIs, the guidelines do suggest that empiric therapy includes coverage if the infection is severe (B-II) or if documented on the basis of culture results.
Antimicrobial therapy: health care-associated infection in adults
* Empiric antibiotic therapy for health care-associated intra-abdominal infection should be driven by local microbiologic results (A-II).
* To achieve empiric coverage of likely pathogens, multidrug regimens that include agents with expanded spectra of activity against gram-negative aerobic and facultative bacilli may be needed. These agents include meropenem, imipenem/cilastatin, doripenem, piperacillin-tazobactam, or ceftazidime or cefepime in combination with metronidazole. Aminoglycosides or colistin may be required (B-III).
* Broad-spectrum antimicrobial therapy should be tailored when culture and susceptibility reports become available, to reduce the number and spectra of administered agents (BIII).
* Empiric antimicrobial coverage directed against MRSA should be provided to patients with health care-associated intra-abdominal infection who are known to be colonized with the organism or who are at risk of having an infection due to this organism because of prior treatment failure and significant antibiotic exposure (B-II).
* Vancomycin is recommended for the treatment of suspected or proven intra-abdominal infection due to MRSA (A-III).
Duration of antimicrobials
* Antimicrobial therapy for established infection should be limited to 4 to 7 days, unless it is difficult to achieve adequate source control. Longer durations of therapy have not been associated with improved outcome (B-III).
* Bowel injuries attributable to penetrating, blunt, or iatrogenic trauma that are repaired within 12 hours and any other intraoperative contamination of the operative field by enteric contents should be treated with antibiotics for 24 hours (A-I).
* Acute appendicitis without evidence of perforation, abscess, or local peritonitis requires only prophylactic administration of narrow-spectrum regimens active against aerobic and facultative and obligate anaerobes; treatment should be discontinued within 24 hours (A-I).
Comment: Similar to most other recent guidelines for other infections, there is a general trend to recommend less duration of antimicrobials. Recent data suggest that if appropriate antimicrobials and surgical intervention are used, optimal outcomes are achieved with shorter course therapy. Shorter course therapy can be associated with decreased cost, adverse events, and potentially antimicrobial resistance.