Study results published in the Journal of Infection revealed that invasive procedures, previous antibiotics, and corticosteroids may predispose patients to develop Enterobacter bacteremia. The study also found an increased mortality rate among high-risk patients and patients with severe infections; however, antibiotic resistance had no effect on outcomes.

Investigators performed an observational multicenter case-control study on risk factors and a prospective cohort for outcomes in patients with consecutive cases of Enterobacter bacteremia. Participants were recruited from 5 hospitals across Spain over a period of 3 years; matched controls in the study were patients with negative blood cultures and same sex, age, and hospitalization area.

A total of 570 controls and 285 cases were included: E cloacae was isolated in 68.8% of cases and E aerogenes in 31.2%. Factors independently associated with Enterobacter bacteremia were invasive procedures such as hemodialysis, nasogastric tube placement, mechanical ventilation, surgical drainage tube, and previous treatment with antibiotics or corticosteroids.

Attributable mortality of Enterobacter bacteremia was 7.8% (95% CI, 2.7-13.4), which was dissimilar to a McCabe index: nonfatal = 3.2%, ultimately fatal = 12.9%, and rapidly fatal = 0.12%.  Among participants with severe sepsis or septic shock, Enterobacter bacteremia remained an independent risk factor for mortality (odds ratio [OR], 5.75; 95% CI, 2.57–12.87; P <.001), with an attributable mortality of 40.3% (95% CI, 25.7-53.3). Conversely, 2 factors that were shown to be unrelated to outcome among participants with bacteremia were empiric therapy and antibiotic resistance.


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The investigators reported that the potential for bias existed in factors associated with mortality. In addition, they noted that data on clinical severity at the moment of obtaining blood cultures in control patients was not obtained; thus, multivariable analysis including these variables was not possible. Researchers also noted that the suitability of the chosen controls is open for discussion but the chosen method has been successfully used for other blood stream infections. Further, all methods will have both strengths and weaknesses that need to be addressed.

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Overall, according to the investigators this represents, “the largest prospective cohort of Enterobacter spp. bacteremia made in Europe, as well as the first matched multicenter case-control study.” They further concluded that the factors related to healthcare identified in the study, such as invasive devices, previous antibiotic therapy, and intensive care unit stay are the main factors for acquisition of Enterobacter bacteremia. And this entity increases mortality in fragile patients and patients with severe infections while antibiotic resistance does not affect outcome.

Reference

Álvarez-Marín R, Navarro-Amuedo D, Gasch-Blasi O, et al. A prospective, multicenter case control study of risk factors for acquisition and mortality in Enterobacter species bacteremia [published online October 1 2019]. J Infect. doi:10.1016/j.jinf.2019.09.017