The infected diabetic foot: Bacteraemia and endocarditis complicating moderate and severe foot infections

Abstract

To identify the incidence of blood stream infections (BSIs) and endocarditis in patients with diabetic foot infections (DFIs), risk factors and clinical outcomes. A post hoc analysis of 280 patients using pooled patient level data from three RTCs. Blood cultures were drawn at time of admission for DFI. Deep intraoperative cultures were obtained from infected foot wounds. Data from the 12-month follow-up were used to determine clinical outcomes. 77.1% (N = 216) had blood cultures of which 15.7% (n = 34) had BSI. One patient (3.3%) had endocarditis. Risk factors for BSI included Charcot Neuroarthropathy history (20.6% vs. 7.1%, p = 0.03), low systolic blood pressure (128.3 ± 21.0 vs. 140.8 ± 22.2 p = 0.003), low diastolic blood pressure (71.6 ± 9.4 vs. 79.3 ± 11.5 p <0.001), leucocytosis >12 000 (55.9% vs. 29.1%, p = 0.002) and elevated C-reactive protein (CRP) (26.8 ± 31.2 vs. 12.0 ± 19.6, p <0.001). During the index hospitalization, BSI patients had longer median hospitalizations (14.0, 11.3-18.0 vs. 12.0, 9.0-16.0, p = 0.04). At 12-months, BSI patients were more likely to be admitted to the hospital (all cause hospital admissions 35.3% vs. 18.6%, p = 0.03). There was no difference in re-infection (20.6% vs. 32.9%, p = 0.21), foot-specific hospitalizations (17.6% vs. 22.5%, p = 0.65), wounds healing (64.7% vs. 67.5%, p = 0.88), time to heal (221.0, 74.0-365 vs. 109.5, 46.8-365, p = 0.16) or antibiotic duration (46.0, 39.3-76.5 vs. 45.0, 22.3-67.0, p = 0.09). The most common BSI pathogens were Staphylococcus aureus (79.4%) and Streptococcus spp. (50.0%) species. BSI is common in DFIs. Patients have longer hospitalizations and were more likely to be hospitalized after their initial discharge.

Keywords: amputation; bacteraemia; diabetic foot; endocarditis; osteomyelitis.

FIGURE 1

Outcome comparison in patients with bacteraemia or without bacteraemia. This bar chart compares the clinical outcomes in patients with bacteraemia to those without bacteraemia during the 12‐month follow‐up period after the index surgery. There was a significant difference in all cause readmissions. * is statistically significant.

FIGURE 2

Frequencies of systemic inflammatory response syndrome (SIRS) criteria in patients with bacteraemia and without bacteraemia and diabetic foot infections. Bar chart shows the frequency of systemic inflammatory response syndrome (SIRS) criteria at the time of admission in patients with and without bacteraemia. SIRS requires that 2 of 4 criteria are met to define sepsis. 47.1% of patients with bacteraemia met one of the criteria for SIRS, and 20.6% did not meet any of the criteria.

FIGURE 3

Frequencies of pathogens in blood cultures and intraoperative wound cultures. Bar chart shows the frequencies of pathogens found in blood cultures and intraoperative wound cultures. Polymicrobial infections were more likely in the intraoperative cultures compared with blood cultures.

FIGURE 4

Kaplan–Meier survival plot comparing the time to re‐infection in patients with and without bacteraemia. The Kaplan–Meier curve of time until re‐infection between patients with positive versus negative blood cultures. There was no significant difference between the two groups, p = 0.258. The total time assessed was 365 days. The red line indicates the proportion of patients with bacteraemia (positive blood culture) and freedom from re‐infection and the blue line represents the proportion of patients without bacteraemia (negative blood cultures) and freedom from re‐infection.

FIGURE 5

Kaplan–Meier survival plot comparing the time to heal in patients with and without bacteraemia. The Kaplan–Meier curve of time until healing between patients with positive blood cultures versus patients with negative blood cultures. No significant association was determined, p = 0.064. The total time assessed was 365 days. The red line indicates the proportion of patients with bacteraemia (positive blood culture) and proportion that healed and the blue line represents the proportion of patients without bacteraemia (negative blood cultures) and healed.