Deletion of Tn
            <i>AbaR23</i>
            Results in both Expected and Unexpected Antibiogram Changes in a Multidrug-Resistant Acinetobacter baumannii Strain

Kochar, Mandira; Crosatti, Marialuisa; Harrison, Ewan M.; Rieck, Barbara; Chan, Jacqueline; Constantinidou, Chrystala; Pallen, Mark J.; Ou, Hong‐Yu; Rajakumar, Kumar

doi:10.1128/aac.05334-11

Cited by 21 publications

(24 citation statements)

References 36 publications

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“…Circles, intact attC sites ("59-bp elements"); red, interrupted gene fragments; dark red, putative pseudogenes. Additional gene abbreviations follow a previous convention (59).…”

Section: Resultsmentioning

confidence: 99%

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Resources for Genetic and Genomic Analysis of Emerging Pathogen Acinetobacter baumannii

et al. 2015

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Acinetobacter baumannii is a Gram-negative bacterial pathogen notorious for causing serious nosocomial infections that resist antibiotic therapy. Research to identify factors responsible for the pathogen's success has been limited by the resources available for genome-scale experimental studies. This report describes the development of several such resources for A. baumannii strain AB5075, a recently characterized wound isolate that is multidrug resistant and displays robust virulence in animal models. We report the completion and annotation of the genome sequence, the construction of a comprehensive ordered transposon mutant library, the extension of high-coverage transposon mutant pool sequencing (Tn-seq) to the strain, and the identification of the genes essential for growth on nutrient-rich agar. These resources should facilitate large-scale genetic analysis of virulence, resistance, and other clinically relevant traits that make A. baumannii a formidable public health threat. IMPORTANCEAcinetobacter baumannii is one of six bacterial pathogens primarily responsible for antibiotic-resistant infections that have become the scourge of health care facilities worldwide. Eliminating such infections requires a deeper understanding of the factors that enable the pathogen to persist in hospital environments, establish infections, and resist antibiotics. We present a set of resources that should accelerate genome-scale genetic characterization of these traits for a reference isolate of A. baumannii that is highly virulent and representative of current outbreak strains.A cinetobacter baumannii is a Gram-negative opportunistic pathogen that causes infections with serious morbidity and mortality and is one of a group of six pathogens responsible for most multidrug-resistant (MDR) nosocomial infections (the ESKAPE pathogens, i.e., Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) (1, 2). The pathogen is infamous for its ability to persist in hospital settings, a feature that reflects its capacity for long-term survival on abiotic surfaces through resistance to desiccation and disinfectants (3).Genomic and molecular epidemiological studies of A. baumannii isolates have helped define the pathogen's global population structure, its antibiotic resistance gene repertoire, the size and content of its pangenome, and phylogenetic relationships among outbreak strains (3-6). Three primary clonal lineages (GC1 to GC3) appear responsible for the majority of hospital outbreaks globally (7). Although these lineages display restricted genetic diversity among core genes (7), the species' genome is actually quite dynamic. Strains display striking variability in accessory gene content (5, 8), including antibiotic resistance genes (9), even among related isolates of a single outbreak (10). This genomic variability presumably reflects the actions of transmissible plasmids, insertion elements, phage, integrons, natural transformation, and reco...

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“…Circles, intact attC sites ("59-bp elements"); red, interrupted gene fragments; dark red, putative pseudogenes. Additional gene abbreviations follow a previous convention (59).…”

Section: Resultsmentioning

confidence: 99%

“…This smaller library is made up of two to three unique, sequence-verified mutants for most genes and is called the TnAbaR1-like island inserted in the comM gene. The TnAbaR modules are labeled according to a previous convention (59). Compared to most known comM islands, RI-1 is small and contains one rather than two copies of the Tn6018 module.…”

Section: Resultsmentioning

confidence: 99%

Resources for Genetic and Genomic Analysis of Emerging Pathogen Acinetobacter baumannii

et al. 2015

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“…Cultivation of A. baumannii was carried out in a defined medium supplemented with either succinate or carnitine (or both) as the sole carbon source. Targeted deletion of cntA/cntB was carried out by marker exchange mutagenesis, as described previously (56). The mutants (ΔcntA; ΔcntB) were complemented with plasmid pKR706 by cloning the native carnitine oxygenase gene cluster into the …”

Section: Methodsmentioning

confidence: 99%

Carnitine metabolism to trimethylamine by an unusual Rieske-type oxygenase from human microbiota

Zhu¹,

Jameson²,

Crosatti

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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290

317

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Dietary intake of L-carnitine can promote cardiovascular diseases in humans through microbial production of trimethylamine (TMA) and its subsequent oxidation to trimethylamine N-oxide by hepatic flavin-containing monooxygenases. Although our microbiota are responsible for TMA formation from carnitine, the underpinning molecular and biochemical mechanisms remain unclear. In this study, using bioinformatics approaches, we first identified a two-component Rieske-type oxygenase/reductase (CntAB) and associated gene cluster proposed to be involved in carnitine metabolism in representative genomes of the human microbiota. CntA belongs to a group of previously uncharacterized Rieske-type proteins and has an unusual "bridging" glutamate but not the aspartate residue, which is believed to facilitate intersubunit electron transfer between the Rieske center and the catalytic mononuclear iron center. Using Acinetobacter baumannii as the model, we then demonstrate that cntAB is essential in carnitine degradation to TMA. Heterologous overexpression of cntAB enables Escherichia coli to produce TMA, confirming that these genes are sufficient in TMA formation. Site-directed mutagenesis experiments have confirmed that this unusual "bridging glutamate" residue in CntA is essential in catalysis and neither mutant (E205D, E205A) is able to produce TMA. Taken together, the data in our study reveal the molecular and biochemical mechanisms underpinning carnitine metabolism to TMA in human microbiota and assign the role of this novel group of Rieske-type proteins in microbial carnitine metabolism. methylated amine metabolism | comparative genomics | gut microbiota

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“…AbaR1 is integrated into the ATPase gene (now called comM) and contains a large cluster of antimicrobial and heavy metal resistance genes. Some studies have revealed diverse related AbaR resistance islands in the same region of comM in A. baumannii isolates (4)(5)(6)(7)(8). Although most AbaR resistance islands have been reported in A. baumannii isolates, recently, AbaR4 was reported in A. nosocomialis isolates from South Korea and Thailand (9).…”

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confidence: 99%

AbaR-Type Genomic Islands in Non-baumannii Acinetobacter Species Isolates from South Korea

Kim¹,

Ko²

2015

Antimicrob Agents Chemother

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To investigate the presence and structure of AbaR-type genomic islands (GIs) in non-Acinetobacter baumannii isolates, a total of 155 non-baumannii Acinetobacter isolates from a South Korean hospital were analyzed. GIs were found in three Acinetobacter nosocomialis and two Acinetobacter seifertii isolates. Their structures were similar to those in A. baumannii isolates from Asian countries, including South Korea. The existence of AbaR-type GIs in non-baumannii Acinetobacter isolates is believed to be due to interspecies transfer of GI.

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Deletion of Tn AbaR23 Results in both Expected and Unexpected Antibiogram Changes in a Multidrug-Resistant Acinetobacter baumannii Strain

Abstract: ABSTRACTSince the 2006 discovery of theAcinetobacter baumanniistrain AYE AbaR1 resistance island, similar elements have been reported in numerous members of this species. As AbaR1 is distantly related to Tn7, we have renamed it TnAbaR1. TnAbaRtransposons are known to … Show more

Cited by 21 publications

References 36 publications

Resources for Genetic and Genomic Analysis of Emerging Pathogen Acinetobacter baumannii

Resources for Genetic and Genomic Analysis of Emerging Pathogen Acinetobacter baumannii

Carnitine metabolism to trimethylamine by an unusual Rieske-type oxygenase from human microbiota

AbaR-Type Genomic Islands in Non-baumannii Acinetobacter Species Isolates from South Korea

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