The Epidemiology of Intra-Abdominal Flora in Critically Ill Patients with Secondary and Tertiary Abdominal Sepsis

Background: Different micro-organisms can be cultured from abdominal fluid obtained from patients with intra-abdominal infection resulting from a perforated digestive tract. We evaluated a cohort of patients with abdominal sepsis admitted to the intensive care with the aim of obtaining more insight into the type of microorganisms involved and the efficacy of treatment. Materials and Methods: A 5-year prospective observational cohort study was performed in patients admitted to the intensive care unit with abdominal sepsis syndrome, defined as a perforation of the digestive tract and inflammatory response with organ failure. Abdominal fluid was obtained for microbial culture during the surgical procedures and from abdominal drains. The initial treatment protocol was cefotaxim, ciprofloxacin, metronidazole, and amphotericin 8, tailored according to microbiological results. Selective decontamination of the digestive tract was administered to prevent secondary endogenous infections. Results: Abdominal fluid was taken for microbial culture from 221 of the 239 patients admitted with abdominal sepsis. Aerobic Gram-negative bacteria (AGNB) were found in 52.9% of the cultures of abdominal fluid taken at the time of operation, of which 45% were Escherichia coli; in 36% of patients more than one AGNB was found. The incidence of AGNB was highest in colorectal perforations (68.6%) and perforated appendicitis (77.8%) and lowest in gastroduodenal perforations (20.5%). Gram-positive bacteria were found in 42.5% of the abdominal fluid cultures and most frequently in colorectal perforations (50.0%). Candida was found in 19.9% of patients, with 59.1% of these cultures being Candida albicans. The incidence of Candida was 41.0% in gastroduodenal perforations and 11.8% in colorectal perforation. Anaerobic bacteria were cultured in 77.8% of patients with perforated appendicitis. Over time, the prevalence of AGNB in abdominal fluid decreased from 117 patients (52.9%) in the first culture to one patient (6.7%) in week 4 (efficacy 87%). The prevalence of Gram-positive bacteria increased from 42.5% to 86.7% in a 4-week period. Conclusion: The composition of the intra-abdominal flora found in critically ill patients with abdominal sepsis varies depending on the location of the perforation. The efficacy of combined surgical and antibiotic treatment was 87% in 4 weeks for AGNB.