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Genomic analysis of Acinetobacter baumannii A118 by comparison of optical maps: identification of structures related to its susceptibility phenotype.

ABSTRACT: Acinetobacter baumannii A118, a naturally competent clinical isolate, is unusually susceptible to several antibiotics. Comparison of the optical map of strain A118 with in silico-generated restriction maps of sequenced genomes and sequence analyses showed that the AbaR region, commonly found inserted within the comM gene in other isolates, is missing in strain A118, which could in part explain the susceptible phenotype exhibited by this isolate. These comparative studies also showed differences in regions where genes coding for functions that may be involved in drug resistance or susceptibility are located. Further sequencing demonstrated that cat and bla(ADC), named bla(ADC-55), are present but that a tet(A) gene usually found in other strains is not. In addition, carO and pbp2, which may play a role in susceptibility to carbapenems, are present in strain A118. These findings support the idea that A. baumannii strains possess multiple mechanisms that contribute to antibiotic resistance, and the presence of some of them is not sufficient for a resistant phenotype. The results shown here indicate that optical mapping is a useful tool for preliminary comparative genomic analysis.

SUBMITTER: Ramirez MS

PROVIDER: S-EPMC3067174 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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Genomic analysis of Acinetobacter baumannii A118 by comparison of optical maps: identification of structures related to its susceptibility phenotype.

Ramirez Maria Soledad MS Adams Mark D MD Bonomo Robert A RA Centrón Daniela D Tolmasky Marcelo E ME

Antimicrobial agents and chemotherapy 20110131 4

Acinetobacter baumannii A118, a naturally competent clinical isolate, is unusually susceptible to several antibiotics. Comparison of the optical map of strain A118 with in silico-generated restriction maps of sequenced genomes and sequence analyses showed that the AbaR region, commonly found inserted within the comM gene in other isolates, is missing in strain A118, which could in part explain the susceptible phenotype exhibited by this isolate. These comparative studies also showed differences ...[more]

PMID: 21282446

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Project description:Acinetobacter (A.) baumannii is an opportunistic pathogen that causes severe infections in humans and animals, including horses. The occurrence of dominant international clones (ICs), frequent multidrug resistance, and the capability to form biofilms are considered major factors in the successful spread of A. baumannii in human and veterinary clinical environments. Since little is known about A. baumannii isolates from horses, we studied 78 equine A. baumannii isolates obtained from clinical samples between 2008 and 2020 for their antimicrobial resistance (AMR), clonal distribution, biofilm-associated genes (BAGs), and biofilm-forming capability. Based on whole-genome sequence analyses, ICs, multilocus (ML) and core-genome ML sequence types (STs), and AMR genes were determined. Antimicrobial susceptibility testing was performed by microbroth dilution. A crystal violet assay was used for biofilm quantification. Almost 37.2% of the isolates were assigned to IC1 (10.3%), IC2 (20.5%), and IC3 (6.4%). Overall, the isolates revealed high genomic diversity. We identified 51 different STs, including 22 novel STs (ST1723-ST1744), and 34 variants of the intrinsic oxacillinase (OXA), including 8 novel variants (OXA-970 to OXA-977). All isolates were resistant to ampicillin, amoxicillin/clavulanic acid, cephalexin, cefpodoxime, and nitrofurantoin. IC1-IC3 isolates were also resistant to gentamicin, enrofloxacin, marbofloxacin, tetracycline, and trimethoprim/sulfamethoxazole. All isolates were susceptible to imipenem. Thirty-one multidrug-resistant (MDR) isolates mainly accumulated in the IC1-IC3 groups. In general, these isolates showed less biofilm formation (IC1 = 25.0%, IC2 = 18.4%, IC3 = 15.0%) than the group of non-IC1-IC3 isolates (58.4%). Isolates belonging to the same ICs/STs revealed identical BAG patterns. BAG blp1 was absent in all isolates, whereas bfmR and pgaA were present in all isolates. At the level of the IC groups, the AMR status was negatively correlated with the isolates' ability to form a biofilm. A considerable portion of equine A. baumannii isolates revealed ICs/STs that are globally present in humans. Both an MDR phenotype and the capability to form biofilms might lead to therapeutic failures in equine medicine, particularly due to the limited availability of licensed drugs.

Dataset Information

Genomic analysis of Acinetobacter baumannii A118 by comparison of optical maps: identification of structures related to its susceptibility phenotype.

Publications

Genomic analysis of Acinetobacter baumannii A118 by comparison of optical maps: identification of structures related to its susceptibility phenotype.

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