Abstract
Using a combination of short- and long-read DNA sequencing, we have investigated the location of antibiotic resistance genes and characterized mobile genetic elements (MGEs) in three clinical multi-drug resistant Acinetobacter baumannii. The isolates, collected in Bolivia, clustered separately with three different international clonal lineages. We found a diverse array of transposons, plasmids and resistance islands related to different insertion sequence (IS) elements, which were located in both the chromosome and in plasmids, which conferred resistance to multiple antimicrobials, including carbapenems. Carbapenem resistance might be caused by a Tn2008 carrying the blaOXA–23 gene. Some plasmids were shared between the isolates. Larger plasmids were less conserved than smaller ones and they shared some homologous regions, while others were more diverse, suggesting that these big plasmids are more plastic than the smaller ones. The genetic basis of antimicrobial resistance in Bolivia has not been deeply studied until now, and the mobilome of these A. baumannii isolates, combined with their multi-drug resistant phenotype, mirror the transfer and prevalence of MGEs contributing to the spread of antibiotic resistance worldwide and require special attention. These findings could be useful to understand the antimicrobial resistance genetics of A. baumannii in Bolivia and the difficulty in tackling these infections.
Highlights
Acinetobacter baumannii is a non-fermenting Gram-negative bacilli and it is the second most common species after Pseudomonas aeruginosa in this group causing bacterial infections (Gonzalez-Villoria and Valverde-Garduno, 2016)
In A. baumannii, the blaOXA−23−like gene is associated with ISAba1, which contributes to its overexpression as well as its mobilization (Nigro and Hall, 2016)
Tn2008 has previously been described in Bolivian A. baumannii isolates and this mirrors the spread of this structure among different international clone (IC) leading to a carbapenem-resistant phenotype (Nigro and Hall, 2016; Sennati et al, 2016; Chen et al, 2017; Ewers et al, 2017; Cerezales et al, 2018)
Summary
Acinetobacter baumannii is a non-fermenting Gram-negative bacilli and it is the second most common species after Pseudomonas aeruginosa in this group causing bacterial infections (Gonzalez-Villoria and Valverde-Garduno, 2016). Acinetobacter baumannii is known to have a great genome plasticity, which is the capacity to acquire and disseminate genes, especially those related to antimicrobial resistance which are commonly associated with insertion sequence (IS) elements in transposons and plasmids; this dynamism in the genome of A. baumannii contributed to the rapid evolution of drug resistance (Adams et al, 2010) as has been demonstrated for ISAba mobilizing antimicrobial resistance genes (Mugnier et al, 2009). These processes are achieved thanks to mobile genetic elements (MGEs) harboring resistance genes. Antimicrobial resistance genes are often integrated into resistance cassettes related to translocation elements, causing cumulative resistance to multiple drugs (Roca et al, 2012)
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