Surgical Infections

Reported wound infection rates for infrainguinal bypass operations range from 17% to 44%, but there is limited appreciation of which characteristics of patients or operations are reliable markers of increased wound infection risk. The purpose of the present study was to analyze all wound infections observed after infrainguinal bypass operations during 20 years of practice in a large teaching institution. Independent risk factors for wound infection development were identified. During the 20-year period ending 31 December, 1997, 978 male patients underwent infrainguinal bypass operations at the Minneapolis Department of Veterans Affairs Medical Center. Wound infections complicated the recovery of 129 of these patients during a 30-day postoperative surveillance interval. Multivariate logistic regression analysis was used to test the association between wound infection occurrence and putative risk factors that were either features of patients or characteristics of the operations. The following variables were examined: obesity, prosthetic graft placement, diabetes mellitus, steroid use, anticoagulation use, length of preoperative hospital stay, development of incisional hematoma, duration of operation, and the preoperative presence of a non-healing wound in the extremity being revascularized. The overall wound infection rate was 13.2% (129/978). In a final logistic regression model, obesity was a significant and independent predictor of wound infection (Relative Risk 2.6, 95% confidence interval, 1.35-4.90), as was development of a post-operative incisional hematoma (Relative Risk 6.44, 95% confidence interval, 2.95-14.08). No other explanatory variable was significantly associated with wound infection development.

The mechanisms underlying the process of bacterial translocation are poorly defined. Possible routes for transmucosal passage of bacteria include transcellular and paracellular channels. Bacterial engulfment is a prerequisite for transcellular transport. To determine whether transcellular transport is required for transmucosal bacterial passage, we examined the effect of various inhibitors of endocytosis, such as colchicine, cytochalasin B, and sodium fluoride on transmucosal passage of bacteria across an ileal mucosal membrane mounted in the Ussing chamber. Colchicine and sodium fluoride increased the rate of decline of the potential difference across the membranes. However, neither colchicine, cytochalasin B, nor sodium fluoride affected the incidence of transmucosal bacterial passage. Sodium fluoride, which depletes intracellular ATP, significantly decreased the number of bacteria that passed per membrane. Our data suggest that transcellular transport may not be required for spontaneous transmucosal passage of bacteria, and furthermore bacterial passage may be, at least in part, an energy-dependent process.

Background: Heavy fungal colonization is a known risk factor for fungal infection, yet the value of fungal surveillance cultures is uncertain. Methods: To evaluate the utility of fungal surveillance cultures in predicting fungal infections, we evaluated surveillance fungal cultures over a three month period in a prospective, cohort study conducted at a university medical center with a large tertiary referral population. We enrolled 172 patients in the Oncology Center and the medical and surgical intensive care units at Johns Hopkins Hospital. Results: Surveillance cultures from five sites were obtained twice weekly and evaluated for prediction of subsequent fungal infection. Infections were prospectively defined and evaluated by a panel of clinicians. Test characteristics were assessed. Of 159 eligible patients, 14 (9%) developed invasive fungal infections. Having two or more surveillance sites positive in a single day had an odds ratio of 8.2 (1.1–358.0) (p = 0.03), a negative predictive value of 0.98, sensitivity of 0.92, and a likelihood ratio of 1.6 for a fungal infection. In a multiple logistic regression model and Kaplan-Meier analysis, fungal burden was strongly and independently associated with infection (p < 0.05). Conclusions: Surveillance cultures are helpful in determining fungal colonization but do not have a high positive predictive value for fungal infection in a broad population of intensive care unit patients. However, fungal infection is more likely in heavily colonized patients, and surveillance cultures show that fungal infection is extremely unlikely in patients without fungal colonization.