Gastrointestinal colonization with multidrug-resistant Gram-negative bacteria during extracorporeal membrane oxygenation: effect on the risk of subsequent infections and impact on patient outcome

Background: In ICU patients, digestive tract colonization by multidrug-resistant (MDR) Gram-negative (G-) bacteria is a significant risk factor for the development of infections. In patients undergoing extracorporeal membrane oxygenation (ECMO), colonization by MDR bacteria and risk of subsequent nosocomial infections (NIs) have not been studied yet. The aim of this study is to evaluate the incidence, etiology, risk factors, impact on outcome of gastrointestinal colonization by MDR G- bacteria, and risk of subsequent infections in patients undergoing ECMO.

Methods: This is a retrospective analysis of prospectively collected data: 105 consecutive patients, treated with ECMO, were admitted to the ICU of an Italian tertiary referral center (San Gerardo Hospital, Monza, Italy) from January 2010 to November 2015. Rectal swabs for MDR G- bacteria were cultured at admission and twice a week. Only colonization and NIs by MDR G- bacteria were analyzed.

Results: Ninety-one included patients [48.5 (37-56) years old, 63% male, simplified acute physiology score II 37 (32-47)] underwent peripheral ECMO (87% veno-venous) for medical indications (79% ARDS). Nineteen (21%) patients were colonized by MDR G- bacteria. Male gender (OR 4.03, p = 0.029) and duration of mechanical ventilation (MV) before ECMO > 3 days (OR 3.57, p = 0.014) were associated with increased risk of colonization. Colonized patients had increased odds of infections by the colonizing germs (84% vs. 29%, p < 0.001, OR 12.9), longer ICU length of stay (LOS) (43 vs. 24 days, p = 0.002), MV (50 vs. 22 days, p < 0.001) and ECMO (28 vs. 12 days, p < 0.001), but did not have higher risk of death (survival rate 58% vs. 67%, p = 0.480, OR 0.68). Infected patients had almost halved ICU survival (46% vs. 78%, p < 0.001, OR 4.11).

Conclusions: In patients undergoing ECMO for respiratory and/or circulatory failure, colonization by MDR G- bacteria is frequent and associated with more the tenfold odds for subsequent infection. Those infections are associated with an increased risk of death.