Procalcitonin Guided Antibiotic Therapy

The overuse of antibiotics is an enormous problem facing the healthcare system both in the United States and across the world. The investigators plan to test the hypothesis that using procalcitonin levels (blood test) to guide the length of antibiotic therapy in patients with complicated intra-abdominal infections leads to shorter antibiotic treatment courses.

A 2019 Centers for Disease Control (CDC) report describes the rate of antibiotic resistance as alarmingly high and says clinicians must make efforts to lower the development of resistance through more discerning antibiotic use. Complicated intra-abdominal infections (CIAIs), defined as an infection that extends beyond the hollow viscus of origin and into the peritoneal space, are a common problem with a 9.2% mortality rate worldwide, a morbidity of 5-50% and a 21.5% risk of extra-abdominal infections. The basic principles for treatment of CIAIs include source control and appropriate antibiotic coverage; however, source control cannot always be achieved in CIAIs, i.e. diverticular or appendiceal abscesses. The STOP-IT trial concluded that shorter courses of antibiotics for CIAIs with source control are equivalent to the traditional longer courses with regard to recurrent infections and mortality, even in the setting of sepsis, but the optimal duration of antibiotic treatment is unknown for patients with CIAIs without source control. Due to lack of guidelines, these patients are routinely treated with long antibiotic courses. Given the association of prolonged antibiotic courses and increased rates of post-treatment infectious complications and antimicrobial resistance, the Infectious Disease Society of America and the Surgical Infection Society acknowledge that there is an urgent need to study the appropriate duration of antimicrobial therapy for CIAIs. The biomarker procalcitonin is expressed by human epithelial cells in response to bacterial infections, distinguishes true bacterial infection from Systemic Inflammatory Response Syndrome (SIRS) and has been used in studies to identify CIAIs.

Procalcitonin-guided antibiotic management has been shown to decrease the number of antibiotic days in respiratory infections and reduce mortality among medical and surgical Intensive Care Unit (ICU) populations (including those with CIAIs). However, there is little data evaluating its role in guiding antibiotic therapy specifically for CIAIs.

Eligibility Criteria:
Inclusion Criteria:

* ≥ 18 years old
* Ability to give consent in English or Spanish
* Imaging proven intra-abdominal infection (CT, US, and/or MRI)

Exclusion Criteria:

* Unable to give informed consent
* Patients enrolled in another trial
* Those having surgery for source control
* Patients with anastomotic leak
* Unable or unwilling to return or be contacted for clinical follow-up visits
* Currently incarcerated in a detention facility or in police custody
* Conditions with altered immune response or at risk for bacterial seeding
* Immunodeficiency (e.g., absolute neutrophil count \<500/mm3, chronic immunosuppressive drugs, active chemotherapy or plans for chemotherapy in the following 30 days, or known AIDS \[CD4 count \<200 or AIDS-defining illness within the last year\] assessed by patient history)
* Uncompensated liver failure
* Taking medication to treat active inflammatory bowel disease
* Malignancy, not in remission (ongoing chemotherapy patients excluded)
* Pregnant or expectation of becoming pregnant in the 30 days following baseline/screening
* Expected concurrent hemodialysis, peritoneal dialysis, or treatments using indwelling venous catheters
* Recent (within 90 days) placement of surgical implant (e.g., pacemaker, joint prosthesis, mechanical valve)
* Indwelling Left Ventricular Assist Device
* Patients with another infection (e.g., pneumonia, urinary tract infection) that requires treatment with another antibiotic