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Acinetobacter baumannii (Ab) bacteraemia in patients with haematological malignancies is fatal but rarely reported. We explored the clinical characteristics, drug resistances and prognostic factors in these patients. This multicentre, retrospective study was conducted at the department of haematology wards of 18 tertiary hospitals in China from January 2014 to June 2015. The total clinical isolates from every source were collected from patients with haematological malignancy. Haematological malignancy patients diagnosed with Ab bacteraemia were analysed. During the study period, 40 patients with Ab bacteraemia were identified, accounting for 2.9% (40/1358) of bacteraemia cases, of which 25 (62.5%) had acute leukaemia (AL) and 27 (67.5%) had neutropaenia. Compared with non-neutropaenic patients, neutropaenic patients showed higher Acute Physiology and Chronic Health Evaluation (APACHE) scores and 30-day mortality rates (p < 0.05). The in vitro antibiotic susceptibility of Ab to colistin was highest, at 100%, followed by that of tigecycline (91.30%) and amikacin (75.86%). Compared with the patients who had carbapenem-susceptible Ab infections, patients infected with carbapenem-resistant Ab (CRAB) had significantly longer hospital stays and were more likely to have had exposure to carbapenem before bacteraemia (p < 0.05). The 30-day mortality rate was 32.5%. CRAB, neutropaenia, higher APACHE score, Pitt bacteraemia score and inappropriate initial antimicrobial therapy were significantly associated with 30-day mortality. Multivariable analysis showed that APACHE score and CRAB were independent predictors of 30-day mortality. Haematologic patients with AL and febrile neutropaenia were at high risk of Ab bacteraemia. More attention should be paid to CRAB, which is an independent risk factor for mortality in haematological malignancy patients with Ab bacteraemia.

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Given that tigecycline-based combination therapy is recognized as a valuable option for the treatment of tigecycline-resistant Acinetobacter baumannii, we conducted this systematic review and meta-analysis to assess the overall evidence of its effectiveness. The synergy rate was defined as the primary outcome that was calculated separately for time-kill, Etest, and checkerboard microdilution methods. The secondary outcomes were bactericidal activity and the efficacy of combination treatment on the development of resistance. In total, 37 published papers and 16 conference proceedings were included. Nine classes consisting of 22 antibiotic types in combination with tigecycline against 1,159 A. baumannii strains were reported in the analysis. For the time-kill studies, combination therapy showed a synergy rate of 37.9% (95% confidence interval [CI], 30.7-46.5); the highest synergy rate was 67.4% (95% CI, 27.3-91.9) for tigecycline in combination with colistin. Moreover, combination with amikacin or colistin could efficiently inhibit the development of tigecycline resistance. Compared with checkerboard microdilution and Etest methods, time-kill studies always showed higher synergy rates. Altogether, these results suggest that the in vitro tigecycline-based combinations resulted in moderate synergy rates and that several combinations could suppress the resistance of A. baumannii to tigecycline, which should be further confirmed in animal models and clinical trials.