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J Med Microbiol. 2015 Oct;64(10):1162-9. doi: 10.1099/jmm.0.000137. Epub 2015 Jul 17.

In vitro activity of colistin in antimicrobial combination against carbapenem-resistant Acinetobacter baumannii isolated from patients with ventilator-associated pneumonia in Vietnam.

Author information

1
1​Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam 2​Division of Infectious Diseases, Department of Medicine, University of California San Francisco, CA, USA.
2
1​Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam 3​School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland, Australia.
3
1​Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.
4
1​Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam 4​Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University, UK.
5
1​Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam 5​Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
6
5​Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
7
1​Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam 4​Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University, UK 6​Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, UK.
8
1​Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam 5​Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam 7​Pham Ngoc Thach University of Medicine, Ho Chi Minh City, Vietnam.
9
4​Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University, UK 8​London School of Hygiene and Tropical Medicine, London, UK 1​Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.

Abstract

Acinetobacter baumannii has become one of the major infection threats in intensive care units (ICUs) globally. Since 2008, A. baumannii has been the leading cause of ventilator-associated pneumonia (VAP) in our ICU at an infectious disease hospital in southern Vietnam. The emergence of this pathogen in our setting is consistent with the persistence of a specific clone exhibiting resistance to carbapenems. Antimicrobial combinations may be a strategy to treat infections caused by these carbapenem-resistant A. baumannii. Therefore, we assessed potential antimicrobial combinations against local carbapenem-resistant A. baumannii by measuring in vitro interactions of colistin with four antimicrobials that are locally certified for treating VAP. We first performed antimicrobial susceptibility testing and multilocus variable number tandem repeat analysis (MLVA) genotyping on 74 A. baumannii isolated from quantitative tracheal aspirates from patients with VAP over an 18-month period. These 74 isolates could be subdivided into 21 main clusters by MLVA and >80 % were resistant to carbapenems. We selected 56 representative isolates for in vitro combination synergy testing. Synergy was observed in four (7 %), seven (13 %), 20 (36 %) and 38 (68 %) isolates with combinations of colistin with ceftazidime, ceftriaxone, imipenem and meropenem, respectively. Notably, more carbapenem-resistant A. baumannii isolates (36/43; 84 %) exhibited synergistic activity with a combination of colistin and meropenem than carbapenem-susceptible A. baumannii isolates (2/13; 15 %) (P = 0.023; Fisher's exact test). Our findings suggest that combinations of colistin and meropenem should be considered when treating carbapenem-resistant A. baumannii infections in Vietnam, and we advocate clinical trials investigating combination therapy for VAP.

PMID:
26297024
PMCID:
PMC4755130
DOI:
10.1099/jmm.0.000137
[Indexed for MEDLINE]
Free PMC Article

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