Abstract
Acinetobacter baumannii causes severe, fulminant, community-acquired pneumonia (CAP) in tropical and subtropical regions. We compared the population structure, virulence and antimicrobial resistance determinants of northern Australian community-onset A. baumannii strains with local and global strains. We performed whole-genome sequencing on 55 clinical and five throat colonization A. baumannii isolates collected in northern Australia between 1994 and 2016. Clinical isolates included CAP (n=41), healthcare-associated pneumonia (n=7) and nosocomial bloodstream (n=7) isolates. We also included 93 publicly available international A. baumannii genome sequences in the analyses. Patients with A. baumannii CAP were almost all critically unwell; 82 % required intensive care unit admission and 18 % died during their inpatient stay. Whole-genome phylogenetic analysis demonstrated that community-onset strains were not phylogenetically distinct from nosocomial strains. Some non-multidrug-resistant local strains were closely related to multidrug-resistant strains from geographically distant locations. Pasteur sequence type (ST)10 was the dominant ST and accounted for 31/60 (52 %) northern Australian strains; the remainder belonged to a diverse range of STs. The most recent common ancestor for ST10 was estimated to have occurred in 1738 (95 % highest posterior density, 1626–1826), with evidence of multiple introduction events between Australia and Southeast Asia between then and the present day. Virulence genes associated with biofilm formation and the type 6 secretion system (T6SS) were absent in many strains, and were not associated with in-hospital mortality. All strains were susceptible to gentamicin and meropenem; none carried an AbaR resistance island. Our results suggest that international dissemination of A. baumannii is occurring in the community on a contemporary timescale. Genes associated with biofilm formation and the T6SS may not be required for survival in community niches. The relative contributions of host and bacterial factors to the clinical severity of community-onset A. baumannii infection require further investigation.
Highlights
IntroductionAcinetobacter baumannii is a ubiquitous Gram-negative bacterium which is a frequent cause of multidrug-resistantReceived 10 November 2018; Accepted 31 January 2019; Published 26 February 2019 Author affiliations: 1Global and Tropical Health Division, Menzies School of Health Research, Darwin 0810, Australia; 2Department of Infectious Diseases, Royal Darwin Hospital, Darwin 0810, Australia; 3School of Biomedical Sciences, Queensland University of Technology, Brisbane 4001, Australia; 4School of Life and Environmental Sciences, The University of Sydney, Sydney 2006, Australia; 5Department of Infectious Diseases, John Hunter Hospital and the University of Newcastle, Newcastle 2305, Australia; 6Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Sippy Downs 4072, Australia.Raw sequence data from this study are available in the Short Read Archive in Bioproject PRJNA478282 (https://www.ncbi.nlm.nih.gov/bioproject/?term=PRJNA478282).Data statement: All supporting data, code and protocols have been provided within the article or through supplementary data files
We found that northern Australian community-onset isolates were diverse, were not phylogenetically distinct from international isolates and in some cases were closely related to multidrug-resistant nosocomial strains from geographically distant locations [44]
We found no evidence of a difference in the presence of putative virulence genes in community-onset isolates
Summary
Acinetobacter baumannii is a ubiquitous Gram-negative bacterium which is a frequent cause of multidrug-resistantReceived 10 November 2018; Accepted 31 January 2019; Published 26 February 2019 Author affiliations: 1Global and Tropical Health Division, Menzies School of Health Research, Darwin 0810, Australia; 2Department of Infectious Diseases, Royal Darwin Hospital, Darwin 0810, Australia; 3School of Biomedical Sciences, Queensland University of Technology, Brisbane 4001, Australia; 4School of Life and Environmental Sciences, The University of Sydney, Sydney 2006, Australia; 5Department of Infectious Diseases, John Hunter Hospital and the University of Newcastle, Newcastle 2305, Australia; 6Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Sippy Downs 4072, Australia.Raw sequence data from this study are available in the Short Read Archive in Bioproject PRJNA478282 (https://www.ncbi.nlm.nih.gov/bioproject/?term=PRJNA478282).Data statement: All supporting data, code and protocols have been provided within the article or through supplementary data files. Acinetobacter baumannii is a ubiquitous Gram-negative bacterium which is a frequent cause of multidrug-resistant. Received 10 November 2018; Accepted 31 January 2019; Published 26 February 2019 Author affiliations: 1Global and Tropical Health Division, Menzies School of Health Research, Darwin 0810, Australia; 2Department of Infectious Diseases, Royal Darwin Hospital, Darwin 0810, Australia; 3School of Biomedical Sciences, Queensland University of Technology, Brisbane 4001, Australia; 4School of Life and Environmental Sciences, The University of Sydney, Sydney 2006, Australia; 5Department of Infectious Diseases, John Hunter Hospital and the University of Newcastle, Newcastle 2305, Australia; 6Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Sippy Downs 4072, Australia. Raw sequence data from this study are available in the Short Read Archive in Bioproject PRJNA478282 Data statement: All supporting data, code and protocols have been provided within the article or through supplementary data files. Three supplementary tables and four supplementary figures are available with the online version of this article
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
