Background: Antibiotics alter the composition of enteric bacteria and also alter the immune response to enteric pathogens. Patients in the intensive care unit (ICU) frequently receive antibiotics and are at high baseline risk for bacteremia. To better understand the relationship between antibiotics and bacteremia, we performed an ICU-based retrospective cohort study focused on bacteremia due to enteric or non-enteric organisms.
Methods: Adults were included in the study if they were admitted to one of 14 discrete ICUs in three different hospitals from 2008 to 2014and did not develop bacteremia within the first 3 days of ICU admission. The primary exposure was antibiotics, which were classified as present only if antibiotics preceded bacteremia by a minimum of 72 hours. Antibiotic exposure was further classified as broad narrow spectrum. The primary outcome was bacteremia, defined as bacterial growth in one or more blood cultures and was further classified as arising from an enteric versus a non-enteric organism. We followed subjects from the third day after ICU admission for 30 days or until death, discharge, or the development of bacteremia. Multivariable Cox proportional-hazards modeling was used to test for an association between antibiotics and bacteremia after controlling for other factors.
Results: We analyzed 25,568 adult ICU patients including 789 patients (3.1%) with ICU-onset bacteremia. Exposure to both broad (aHR 2.2, 95% CI 1.5-2.9) and to narrow spectrum (aHR 1.5 95% CI 1.2-1.8) antibiotics was associated with increased risk for ICU-onset bacteremia. The strength of the antibiotics-bacteremia relationship increased when we examined only patients who developed bacteremia with an enteric organism (aHR 2.8, 95% CI 1.7-4.0 and aHR 1.7, 95% CI 1.3-2.0 respectively).
Conclusion: Exposure to antibiotics was associated with increased risk for ICU-onset bacteremia and the antibiotic-bacteremia relationship was driven primarily by bacteremia due to enteric organisms. Antibiotic stewardship may help to prevent bacteremia from enteric organisms in the ICU.
E. Larson, None
J. Abrams, None
D. Freedberg, None
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