Risk factors for relapse or persistence of bacteraemia caused by Enterobacter spp.: a case-control study

Patrick N A Harris; Anna M Peri; Anita M Pelecanos; Carly M Hughes; David L Paterson; John K Ferguson

doi:10.1186/s13756-017-0177-0

Risk factors for relapse or persistence of bacteraemia caused by Enterobacter spp.: a case-control study

Antimicrob Resist Infect Control. 2017 Jan 21:6:14. doi: 10.1186/s13756-017-0177-0. eCollection 2017.

Authors

Patrick N A Harris¹, Anna M Peri², Anita M Pelecanos³, Carly M Hughes⁴, David L Paterson⁵, John K Ferguson^{6

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Affiliations

¹ University of Queensland, UQ Centre for Clinical Research, Royal Brisbane and Women's Hospital, Building 71/918 Royal Brisbane & Women's Hospital Campus, 4029 Herston, QLD Australia.
² Department of Biomedical and Clinical Sciences Luigi Sacco, University of Milan, Milan, Italy.
³ QIMR Berghofer Medical Research Institute, Herston, QLD Australia.
⁴ Pathology North - Hunter, John Hunter Hospital, Newcastle, NSW Australia.
⁵ UQ Centre for Clinical Research, Royal Brisbane and Women's Hospital, QLD, Australia & Wesley Medical Research, University of Queensland, Toowong, QLD Australia.
⁶ School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, NSW Australia.
⁷ School of Rural Medicine, University of New England, Armidale, NSW Australia.

Abstract

Background: Enterobacter spp. possess chromosomal AmpC beta-lactamases that may be expressed at high levels. Previous studies have demonstrated a risk of relapsed bacteraemia following therapy with third generation cephalosporins (3GCs). What additional factors predict microbiological failure in Enterobacter bacteraemia is unclear. We aimed to determine factors associated with microbiological failure in Enterobacter bacteraemia.

Methods: We retrospectively identified cases of bacteraemia caused by Enterobacter spp. occurring in four hospitals. Using a case-control design, we determined clinical risk factors for persistence or relapse defined as repeated positive blood cultures collected between 72 hours and up to 28 days post initial positive blood culture.

Results: During the study period a total of 922 bacteraemia events caused by Enterobacter spp. in adults were identified. The overall risk of relapsed or persisting bacteraemia at 28 days was low (31 of 922, 3.4%), with only 2 patients experiencing emergent resistance to 3GCs. A total of 159 patients were included in the case-control study. Using multivariate logistic regression, independent predictors for relapse were a line-associated source of infection (OR 3.87; 95% CI 1.56-9.60, p = 0.004) and the presence of immunosuppression (OR 2.70; 95% CI 1.14-6.44, p = 0.02). On univariate analysis definitive therapy with a broad-spectrum beta-lactam-beta-lactamase inhibitor (BLBLI, e.g. piperacillin-tazobactam) was not associated with relapse (OR 1.83; 95% CI 0.64-5.21, p = 0.26) although the proportion of patients receiving a BLBLI as definitive therapy was relatively small (21/159, 13.2%).

Conclusions: The risk of relapsed or persistent Enterobacter bacteraemia appears to be low in Australia. A line-associated source of infection and immunocompromise were significant independent predictors for relapse. Larger, preferably randomized, studies are needed to address whether BLBLIs represent an effective carbapenem-sparing option for Enterobacter bacteraemia.

Keywords: AmpC; Bacteraemia; Beta-lactamase; Enterobacter aerogenes; Enterobacter cloacae; Outcomes; Relapse; Treatment.