Antimicrobial resistance in bloodstream infection does not affect outcome in intensive care unit patients with acute renal failure treated with renal replacement therapy

Background

Bloodstream infections (BSI) have a worse outcome when the microorganisms involved are antimicrobial resistant (AM-R), compared with BSI with antimicrobial susceptible (AM-S) microorganisms. We evaluated whether this is also true in ICU patients with acute renal failure who are treated with renal replacement therapy (ARF-RRT), a particular severely ill cohort of ICU patients.

Methods

All ARF-RRT patients with BSI admitted in our 54-bed tertiary care ICU during the period 1995–2002 were included in the study. Enteroccci were defined AM-R when resistant to vancomycin, staphylococci when resistant to methicillin, Gram-negative bacteria when resistant to ceftazidim, Pseudomonas when resistant to ceftazidim, quinolones, piperacilin, or imipenem, and Candida when resistant to fluconazole. Catheter-related BSI and BSI of unknown origin were defined as primary BSI. Data are presented as number (percentage) or median (interquartile range).

Results

During the 8-year study period, 79 out of 1032 ARF-RRT patients (7.7%) developed BSI, incurring 88 different microorganisms. AM-R was present in 50 patients (63%). Gram-positive bacteria were more frequent in patients with AM-R BSI (72% vs 24%, P < 0.001), whereas Gram-negative bacteria (24% vs 53%, P = 0.006) or Candida (2% vs 18%, P = 0.008) were less frequent. A higher proportion of patients with AM-R BSI had primary BSI (58% vs 17%, P < 0.001). Patients with AM-R BSI and AM-S BSI had the same age (57 [42–67] years vs 62 [53–69] years, P = 0.150), and APACHE II score on admission (26 [17–32] vs 28 [18–37], P = 0.338). Time to BSI after start of RRT was longer in the AM-R group (11 [6–21] days vs 5 [1–19] days, P = 0.026). Patients with AM-R BSI had a higher need for vasopressor therapy (80% vs 52%, P = 0.008). Length of hospital stay was not different (42 [26–73] days vs 31 [16–75] days, P = 0.528) as was inhospital mortality (64% vs 72%, P = 0.443). Cox regression analysis identified, after adjustment for various covariates, older age (hazard ratio = 1.03 per year, 95% confidence interval: 1.01–1.05, P = 0.02), and primary BSI (hazard ratio = 0.42, 95% confidence interval: 0.21–0.85, P = 0.02) as associated with hospital mortality. There was no significant association between AM-R BSI and hospital mortality.

Conclusions

In a subset of ICU patients with ARF-RRT, antimicrobial resistance of microorganisms that caused BSI did not affect mortality. After adjustment for various covariates, older age was associated with higher mortality. In addition, primary BSI was associated with lower inhospital mortality.