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A Multicenter Case-Case Control Study for Risk Factors and Outcomes of Extensively Drug-Resistant Acinetobacter baumannii Bacteremia

  • Tat Ming Ng (a1), Christine B. Teng (a1) (a2), David C. Lye (a3) (a4) and Anucha Apisarnthanarak (a5)



Extensively drug resistant (XDR) Acinetobacter baumannii infections are increasing. Knowledge of risk factors can help to prevent these infections.


We designed a 1: 1: 1 case-case-control study to identify risk factors for XDR A. baumannii bacteremia in Singapore and Thailand. Case group 1 was defined as having infection due to XDR A. baumannii, and case group 2 was defined as having infection due to non-XDR A. baumannii. The control group comprised patients with blood cultures obtained to determine possible infection.


There were 93 patients in each group. Pitt bacteremia score (adjusted odds ratio [aOR], 2.570 [95% confidence interval (CI), 1.528–4.322]), central venous catheters (CVCs; aOR, 12.644 [95% CI, 2.143–74.620]), use of carbapenems (aOR, 54.391 [95% CI, 3.869–764.674]), and piperacillin-tazobactam (aOR, 55.035 [95% CI, 4.803–630.613]) were independently associated with XDR A. baumannii bacteremia. In case group 2, Pitt bacteremia score (aOR, 1.667 [95% CI, 1.265–2.196]) and third-generation cephalosporins (aOR, 2.965 [95% CI, 1.224–7.182]) were independently associated with non-XDR A. baumannii bacteremia. Concurrent infections (aOR, 3.527 [95% CI, 1.479–8.411]), cancer (aOR, 3.172 [95% CI, 1.135–8.865]), and respiratory source (aOR, 2.690 [95% CI, 1.160–6.239]) were associated with an increased risk of 30-day mortality. Survivors received more active empirical therapy (16.7% vs 9.6%; P = .157), had fewer cases of XDR bacteremia (45.8% vs 52.6%; P = .452), and received higher median definitive polymyxin B doses (840,000 units vs 700,000 units; P = .339)


Use of CVC and broad spectrum antibiotics were unique risk factors of XDR A. baumannii bacteremia. Effective antimicrobial stewardship together with use of a CVC bundle may reduce the incidence of these infections. Risk factors of acquisition and mortality may help identify patients for early initiation of polymyxin B therapy.


Corresponding author

Department of Pharmacy, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore, 308433 (


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A Multicenter Case-Case Control Study for Risk Factors and Outcomes of Extensively Drug-Resistant Acinetobacter baumannii Bacteremia

  • Tat Ming Ng (a1), Christine B. Teng (a1) (a2), David C. Lye (a3) (a4) and Anucha Apisarnthanarak (a5)


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