Academic Journal
Mobilization of the AbGRI4 resistance island in Acinetobacter baumannii: IS26 action and homologous recombination both contribute.
| Title: | Mobilization of the AbGRI4 resistance island in Acinetobacter baumannii: IS26 action and homologous recombination both contribute. |
|---|---|
| Authors: | Harmer CJ; School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia.; Sydney Infectious Diseases Institute, The University of Sydney, Sydney, New South Wales, Australia., Kenyon JJ; School of Pharmacy and Medical Sciences, Health Group, Griffith University, Gold Coast Campus, Southport, Queensland, Australia., Hall RM; School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia.; Sydney Infectious Diseases Institute, The University of Sydney, Sydney, New South Wales, Australia. |
| Source: | Microbiology spectrum [Microbiol Spectr] 2026 Jun 02; Vol. 14 (6), pp. e0038926. Date of Electronic Publication: 2026 Apr 17. |
| Publication Type: | Journal Article |
| Language: | English |
| Journal Info: | Publisher: ASM Press Country of Publication: United States NLM ID: 101634614 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 2165-0497 (Electronic) Linking ISSN: 21650497 NLM ISO Abbreviation: Microbiol Spectr Subsets: MEDLINE |
| Imprint Name(s): | Original Publication: Washington, DC : ASM Press, 2013- |
| MeSH Terms: | Acinetobacter baumannii*/genetics , Acinetobacter baumannii*/drug effects , Acinetobacter baumannii*/isolation & purification , Anti-Bacterial Agents*/pharmacology , Drug Resistance, Multiple, Bacterial*/genetics , Genomic Islands* , Homologous Recombination*, Carbapenems/pharmacology ; Integrons/genetics ; Acinetobacter Infections/microbiology ; Plasmids/genetics ; Aminoglycosides/pharmacology ; Bacterial Proteins/genetics ; Bacterial Proteins/metabolism ; Humans ; Microbial Sensitivity Tests ; DNA Transposable Elements |
| Abstract: | Carbapenem-resistant Acinetobacter baumannii isolate HUMC1 (USA, 2009), which is hypervirulent and extensively antibiotic resistant, has been used in many experimental studies. The complete sequence of the chromosome and two plasmids was determined, and the causes of the resistance phenotype were investigated. HUMC1 (ST2:ST1839:KL22:OCL3) is an unusual global clone 2 (GC2) isolate that lacks an AbGRI1 type resistance island interrupting the comM gene. However, a version of AbGRI2, which is present together with AbGRI1 in the oldest known GC2 isolate, and versions of AbGRI3 and the less common AbGRI4 were found in the chromosome. The oxa23 carbapenem resistance gene is carried by two copies of Tn2006. The remaining resistance gene complement is distributed among the three AbGRI, which each carry a sul1 type class 1 integron remnant bounded by IS26 with a gene cassette conferring resistance to useful aminoglycosides; aacC1 (gentamicin) in AbGRI2, aacA4 (gentamicin and tobramycin) in AbGRI3, and aadB (gentamicin and tobramycin) in AbGRI4. The armA gene (amikacin, gentamicin, tobramycin) was also in AbGRI3. The likely source of AbGRI4 was traced to an ST406 lineage. It was imported into HUMC1 or its ancestor, surrounded by a 23 Kbp ST406 segment that is not normally present in GC2 and incorporated into the chromosome by recombination in homologous flanking regions. The segment carrying AbGRI4 has also been acquired by the ST499 and ST229 lineages. The HUMC1 features highlight the importance of class 1 integrons, insertion sequences IS26 and ISAba1, and homologous recombination in the evolution of resistance in this species. Importance: HUMC1 is a carbapenem-resistant Acinetobacter baumannii isolate belonging to the dominant globally disseminated GC2 clonal complex that is often used in experimental studies as a highly virulent and extensively antibiotic-resistant representative of the species. However, its resistance gene complement had not been examined. The complete genome reported here revealed that HUMC1 carries multiple genes conferring resistance to aminoglycoside antibiotics within chromosomally located resistance islands, including AbGRI4, which is not widespread in GC2 isolates. AbGRI4 appears to have been acquired from an ST406 type co-circulating with GC2 in the USA. The ST499 clonal group, also co-circulating in the USA, has also acquired AbGRI4 from the same source. HUMC1 is also unusual because it lacks an AbGRI1 resistance island found in the comM gene in most current GC2 isolates and in the earliest currently available GC2 isolates from Europe. Hence, it may represent a form that is a precursor of those isolates. |
| Competing Interests: | The authors declare no conflict of interest. |
| Grant Information: | GNT1194978 National Health and Medical Research Council; FT230100400 Australian Research Council |
| Contributed Indexing: | Keywords: AbGRI4; Acinetobacter baumannii; aminoglycoside resistance; carbapenem resistance; global clone 2 |
| Substance Nomenclature: | 0 (Anti-Bacterial Agents) 0 (Carbapenems) 0 (Aminoglycosides) 0 (Bacterial Proteins) 0 (DNA Transposable Elements) |
| Entry Date(s): | Date Created: 20260417 Date Completed: 20260606 Latest Revision: 20260726 |
| Update Code: | 20260726 |
| PubMed Central ID: | PMC13228073 |
| DOI: | 10.1128/spectrum.00389-26 |
| PMID: | 41995356 |
| Database: | MEDLINE |
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| Header | DbId: cmedm DbLabel: MEDLINE An: 41995356 AccessLevel: 3 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Mobilization of the AbGRI4 resistance island in Acinetobacter baumannii: IS26 action and homologous recombination both contribute. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AU" term="%22Harmer+CJ%22">Harmer CJ</searchLink>; School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia.; Sydney Infectious Diseases Institute, The University of Sydney, Sydney, New South Wales, Australia.<br /><searchLink fieldCode="AU" term="%22Kenyon+JJ%22">Kenyon JJ</searchLink>; School of Pharmacy and Medical Sciences, Health Group, Griffith University, Gold Coast Campus, Southport, Queensland, Australia.<br /><searchLink fieldCode="AU" term="%22Hall+RM%22">Hall RM</searchLink>; School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia.; Sydney Infectious Diseases Institute, The University of Sydney, Sydney, New South Wales, Australia. – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22101634614%22">Microbiology spectrum</searchLink> [Microbiol Spectr] 2026 Jun 02; Vol. 14 (6), pp. e0038926. <i>Date of Electronic Publication: </i>2026 Apr 17. – Name: TypePub Label: Publication Type Group: TypPub Data: Journal Article – Name: Language Label: Language Group: Lang Data: English – Name: TitleSource Label: Journal Info Group: Src Data: <i>Publisher: </i><searchLink fieldCode="PB" term="%22ASM+Press%22">ASM Press </searchLink><i>Country of Publication: </i>United States <i>NLM ID: </i>101634614 <i>Publication Model: </i>Print-Electronic <i>Cited Medium: </i>Internet <i>ISSN: </i>2165-0497 (Electronic) <i>Linking ISSN: </i><searchLink fieldCode="IS" term="%2221650497%22">21650497 </searchLink><i>NLM ISO Abbreviation: </i>Microbiol Spectr <i>Subsets: </i>MEDLINE – Name: PublisherInfo Label: Imprint Name(s) Group: PubInfo Data: <i>Original Publication</i>: Washington, DC : ASM Press, 2013- – Name: SubjectMESH Label: MeSH Terms Group: Su Data: <searchLink fieldCode="MM" term="%22Acinetobacter+baumannii%22">Acinetobacter baumannii*</searchLink>/<searchLink fieldCode="MM" term="%22Acinetobacter+baumannii+genetics%22">genetics</searchLink> <br /><searchLink fieldCode="MM" term="%22Acinetobacter+baumannii%22">Acinetobacter baumannii*</searchLink>/<searchLink fieldCode="MM" term="%22Acinetobacter+baumannii+drug+effects%22">drug effects</searchLink> <br /><searchLink fieldCode="MM" term="%22Acinetobacter+baumannii%22">Acinetobacter baumannii*</searchLink>/<searchLink fieldCode="MM" term="%22Acinetobacter+baumannii+isolation+%26+purification%22">isolation & purification</searchLink> <br /><searchLink fieldCode="MM" term="%22Anti-Bacterial+Agents%22">Anti-Bacterial Agents*</searchLink>/<searchLink fieldCode="MM" term="%22Anti-Bacterial+Agents+pharmacology%22">pharmacology</searchLink> <br /><searchLink fieldCode="MM" term="%22Drug+Resistance%2C+Multiple%2C+Bacterial%22">Drug Resistance, Multiple, Bacterial*</searchLink>/<searchLink fieldCode="MM" term="%22Drug+Resistance%2C+Multiple%2C+Bacterial+genetics%22">genetics</searchLink> <br /><searchLink fieldCode="MM" term="%22Genomic+Islands%22">Genomic Islands*</searchLink> <br /><searchLink fieldCode="MM" term="%22Homologous+Recombination%22">Homologous Recombination*</searchLink><br /><searchLink fieldCode="MH" term="%22Carbapenems%22">Carbapenems</searchLink>/<searchLink fieldCode="MH" term="%22Carbapenems+pharmacology%22">pharmacology</searchLink> ; <searchLink fieldCode="MH" term="%22Integrons%22">Integrons</searchLink>/<searchLink fieldCode="MH" term="%22Integrons+genetics%22">genetics</searchLink> ; <searchLink fieldCode="MH" term="%22Acinetobacter+Infections%22">Acinetobacter Infections</searchLink>/<searchLink fieldCode="MH" term="%22Acinetobacter+Infections+microbiology%22">microbiology</searchLink> ; <searchLink fieldCode="MH" term="%22Plasmids%22">Plasmids</searchLink>/<searchLink fieldCode="MH" term="%22Plasmids+genetics%22">genetics</searchLink> ; <searchLink fieldCode="MH" term="%22Aminoglycosides%22">Aminoglycosides</searchLink>/<searchLink fieldCode="MH" term="%22Aminoglycosides+pharmacology%22">pharmacology</searchLink> ; <searchLink fieldCode="MH" term="%22Bacterial+Proteins%22">Bacterial Proteins</searchLink>/<searchLink fieldCode="MH" term="%22Bacterial+Proteins+genetics%22">genetics</searchLink> ; <searchLink fieldCode="MH" term="%22Bacterial+Proteins%22">Bacterial Proteins</searchLink>/<searchLink fieldCode="MH" term="%22Bacterial+Proteins+metabolism%22">metabolism</searchLink> ; <searchLink fieldCode="MH" term="%22Humans%22">Humans</searchLink> ; <searchLink fieldCode="MH" term="%22Microbial+Sensitivity+Tests%22">Microbial Sensitivity Tests</searchLink> ; <searchLink fieldCode="MH" term="%22DNA+Transposable+Elements%22">DNA Transposable Elements</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Carbapenem-resistant Acinetobacter baumannii isolate HUMC1 (USA, 2009), which is hypervirulent and extensively antibiotic resistant, has been used in many experimental studies. The complete sequence of the chromosome and two plasmids was determined, and the causes of the resistance phenotype were investigated. HUMC1 (ST2:ST1839:KL22:OCL3) is an unusual global clone 2 (GC2) isolate that lacks an AbGRI1 type resistance island interrupting the comM gene. However, a version of AbGRI2, which is present together with AbGRI1 in the oldest known GC2 isolate, and versions of AbGRI3 and the less common AbGRI4 were found in the chromosome. The oxa23 carbapenem resistance gene is carried by two copies of Tn2006. The remaining resistance gene complement is distributed among the three AbGRI, which each carry a sul1 type class 1 integron remnant bounded by IS26 with a gene cassette conferring resistance to useful aminoglycosides; aacC1 (gentamicin) in AbGRI2, aacA4 (gentamicin and tobramycin) in AbGRI3, and aadB (gentamicin and tobramycin) in AbGRI4. The armA gene (amikacin, gentamicin, tobramycin) was also in AbGRI3. The likely source of AbGRI4 was traced to an ST406 lineage. It was imported into HUMC1 or its ancestor, surrounded by a 23 Kbp ST406 segment that is not normally present in GC2 and incorporated into the chromosome by recombination in homologous flanking regions. The segment carrying AbGRI4 has also been acquired by the ST499 and ST229 lineages. The HUMC1 features highlight the importance of class 1 integrons, insertion sequences IS26 and ISAba1, and homologous recombination in the evolution of resistance in this species.<br />Importance: HUMC1 is a carbapenem-resistant Acinetobacter baumannii isolate belonging to the dominant globally disseminated GC2 clonal complex that is often used in experimental studies as a highly virulent and extensively antibiotic-resistant representative of the species. However, its resistance gene complement had not been examined. The complete genome reported here revealed that HUMC1 carries multiple genes conferring resistance to aminoglycoside antibiotics within chromosomally located resistance islands, including AbGRI4, which is not widespread in GC2 isolates. AbGRI4 appears to have been acquired from an ST406 type co-circulating with GC2 in the USA. The ST499 clonal group, also co-circulating in the USA, has also acquired AbGRI4 from the same source. HUMC1 is also unusual because it lacks an AbGRI1 resistance island found in the comM gene in most current GC2 isolates and in the earliest currently available GC2 isolates from Europe. Hence, it may represent a form that is a precursor of those isolates. – Name: Abstract Label: Competing Interests Group: Ab Data: The authors declare no conflict of interest. – Name: GrantInfo Label: Grant Information Group: Grant Data: GNT1194978 National Health and Medical Research Council; FT230100400 Australian Research Council – Name: SubjectMinor Label: Contributed Indexing Group: Data: <i>Keywords: </i>AbGRI4; Acinetobacter baumannii; aminoglycoside resistance; carbapenem resistance; global clone 2 – Name: NumberCAS Label: Substance Nomenclature Group: ID Data: 0 (Anti-Bacterial Agents)<br />0 (Carbapenems)<br />0 (Aminoglycosides)<br />0 (Bacterial Proteins)<br />0 (DNA Transposable Elements) – Name: DateEntry Label: Entry Date(s) Group: Date Data: <i>Date Created: </i>20260417 <i>Date Completed: </i>20260606 <i>Latest Revision: </i>20260726 – Name: DateUpdate Label: Update Code Group: Date Data: 20260726 – Name: PubmedCentralID Label: PubMed Central ID Group: ID Data: PMC13228073 – Name: DOI Label: DOI Group: ID Data: 10.1128/spectrum.00389-26 – Name: AN Label: PMID Group: ID Data: 41995356 |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1128/spectrum.00389-26 Languages: – Code: eng Text: English PhysicalDescription: Pagination: StartPage: e0038926 Subjects: – SubjectFull: Carbapenems pharmacology Type: general – SubjectFull: Integrons genetics Type: general – SubjectFull: Acinetobacter Infections microbiology Type: general – SubjectFull: Plasmids genetics Type: general – SubjectFull: Aminoglycosides pharmacology Type: general – SubjectFull: Bacterial Proteins genetics Type: general – SubjectFull: Bacterial Proteins metabolism Type: general – SubjectFull: Humans Type: general – SubjectFull: Microbial Sensitivity Tests Type: general – SubjectFull: DNA Transposable Elements Type: general – SubjectFull: Acinetobacter baumannii genetics Type: general – SubjectFull: Acinetobacter baumannii drug effects Type: general – SubjectFull: Acinetobacter baumannii isolation & purification Type: general – SubjectFull: Anti-Bacterial Agents pharmacology Type: general – SubjectFull: Drug Resistance, Multiple, Bacterial genetics Type: general – SubjectFull: Genomic Islands Type: general – SubjectFull: Homologous Recombination Type: general Titles: – TitleFull: Mobilization of the AbGRI4 resistance island in Acinetobacter baumannii: IS26 action and homologous recombination both contribute. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Harmer CJ – PersonEntity: Name: NameFull: Kenyon JJ – PersonEntity: Name: NameFull: Hall RM IsPartOfRelationships: – BibEntity: Dates: – D: 02 M: 06 Text: 2026 Jun 02 Type: published Y: 2026 Identifiers: – Type: issn-electronic Value: 2165-0497 Numbering: – Type: volume Value: 14 – Type: issue Value: 6 Titles: – TitleFull: Microbiology spectrum Type: main |
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