Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/53420
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Type: Journal article
Title: Colistin hetero-resistance in multidrug-resistant Acinetobacter baumannii clinical isolates from the Western Pacific region in the SENTRY antimicrobial surveillance programme
Author: Yau, W.
Owen, R.
Poudyal, A.
Bell, J.
Turnidge, J.
Yu, H.
Nation, R.
Li, J.
Citation: Journal of Infection, 2009; 58(2):138-144
Publisher: W B Saunders Co Ltd
Issue Date: 2009
ISSN: 0163-4453
1532-2742
Statement of
Responsibility: 
Wing Yau, Roxanne J. Owen, Anima Poudyal, Jan M. Bell, c, John D. Turnidge, c, Heidi H. Yu, Roger L. Nation and Jian Li
Abstract: Background Multidrug-resistant Acinetobacter baumannii has presented a global medical problem. Emergence of colistin resistance, including hetero-resistance, has been increasingly reported. This study examined the susceptibility to colistin of multidrug-resistant A. baumannii from the Western Pacific region. Methods A total of 30 isolates were studied from 10 clinical centres in various countries. MICs were measured against 21 antibiotics by broth microdilution. Colistin population analysis profiles (PAPs) (0, 0.5, 1, 2, 3, 4, 5, 6, 8 and 10 mg/L) were determined. Time–kill kinetics of colistin against 3 isolates (2 colistin-susceptible (one of which was colistin hetero-resistant) and 1 colistin-resistant) were studied over a wide range of concentrations and development of resistance was monitored by measurement of colistin PAPs after 24-h exposure. Results All the isolates were highly multiresistant. Colistin MICs were 0.5–2 mg/L except one isolate which had an MIC of 128 mg/L. Seven isolates were colistin hetero-resistant with subpopulations growing at >2 mg/L. For the 2 colistin-susceptible isolates examined, >3log killing was observed within 3 h even at 0.5× MIC. Interestingly, >3log killing was also observed with the colistin-resistant isolate within 1 h even at 0.5 mg/L. Regrowth occurred at 24 h for both colistin-susceptible and -resistant isolates. Emergence of resistance to colistin after 24-h exposure was confirmed by PAP. Conclusion Colistin was very active against A. baumannii based upon MICs and initial killing in time–kill studies. Hetero-resistance in this group of A. baumannii isolates was less common than in previous studies. Nevertheless, care is required with colistin monotherapy for A. baumannii infections.
Keywords: Colistin
Acinetobacter baumannii
Hetero-resistance
Killing kinetics
Description: Copyright © 2009 The British Infection Society Published by Elsevier Ltd.
DOI: 10.1016/j.jinf.2008.11.002
Appears in Collections:Aurora harvest 5
Molecular and Biomedical Science publications

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