Bacterial species-specific hospital mortality rate for intra-abdominal infections

Intra-abdominal infections (IAIs) are a major cause of morbidity and death. We hypothesized that the involvement of specific organisms would predict death independently.

All patients with IAIs treated at an academic tertiary-care facility over eight years (June 1999-June 2007) were included. The data collected were demographics, co-morbidities, source of infection, intra-abdominal culture results, type of infection (community-acquired vs. nosocomial), type of intervention (operative vs. percutaneous drainage), and outcome. The Charlson Comorbidity Index and multiple organ dysfunction score (MODS) were used in the analysis.

A total of 389 patients were admitted for 452 infection episodes (IEs) during the study period. None of the 129 patients with appendiceal-related infections died, and these patients were excluded from further analysis. Thus, 323 non-appendiceal IEs were evaluated. The overall mortality rate was 8.7%. The mean age of the patients was 54 y, and 50% of them were male. Intra-abdominal cultures were obtained from 303 IEs (93.8%). The most common cause of IAI was post-operative infection (44%). There were 49 distinct species isolated. The most common were Enterococcus (105), Escherichia coli (75), Streptococcus (62), Staphylococcus (51), and Bacteroides (46). Bivariable analysis revealed multiple risk factors associated with death. Logistic regression demonstrated that independent risk factors for death were age ≥65 years (odds ratio [OR] 3.92), cardiac event (OR=8.17), catheter-related blood stream infection (OR=6.16), and growth of Clostridium (OR=13.03). The growth of Streptococcus was predictive of survival. The C statistic was 0.89.

In addition to age and intrinsic patient factors, the presence of specific bacterial organisms independently predicts death in patients with non-appendiceal IAI.