April 21, 2020  |  

Dual Role of gnaA in Antibiotic Resistance and Virulence in Acinetobacter baumannii.

Acinetobacter baumannii is an important Gram-negative pathogen in hospital-related infections. However, treatment options for A. baumannii infections have become limited due to multidrug resistance. Bacterial virulence is often associated with capsule genes found in the K locus, many of which are essential for biosynthesis of the bacterial envelope. However, the roles of other genes in the K locus remain largely unknown. From an in vitro evolution experiment, we obtained an isolate of the virulent and multidrug-resistant A. baumannii strain MDR-ZJ06, called MDR-ZJ06M, which has an insertion by the ISAba16 transposon in gnaA (encoding UDP-N-acetylglucosamine C-6 dehydrogenase), a gene found in the K locus. The isolate showed an increased resistance toward tigecycline, whereas the MIC decreased in the case of carbapenems, cephalosporins, colistin, and minocycline. By using knockout and complementation experiments, we demonstrated that gnaA is important for the synthesis of lipooligosaccharide and capsular polysaccharide and that disruption of the gene affects the morphology, drug susceptibility, and virulence of the pathogen.Copyright © 2019 American Society for Microbiology.

April 21, 2020  |  

Relocation of Tn2009 and characterization of an ABGRI3-2 from re-sequenced genome sequence of Acinetobacter baumannii MDR-ZJ06.

Sir,Acinetobacter baumannii is becoming an important opportunistic Gram-negative pathogen and has shown extensive MDR to most first-line antibiotics in recent years. The acquisition of the MDR phenotype is a determining factor for the success of A. baumannii. For example, blaOXA-23is the most common acquired gene for car- bapenem resistance, and it is acquired via mobile element. Our previous studies identified six clones (clones A–F) of imipenem- resistant A. baumannii strains isolated from 16 cities in 2005 in China and clone C was the dominant clone in various cities.1 One isolate of clone C, MDR-ZJ06, which belonged to global clone 2, was sequenced by the 454 Genome Sequencer FLX system, Illumina sequencer and Sanger sequencing. The blaOXA-23 of MDR-ZJ06 was located in Tn2009, which was initially named as part of the analysis of MDR-ZJ06 and was mostly reported in isolates from China. In this study, we present the revised complete genome sequence of A. baumannii MDR-ZJ06, which is widespread in China. Materials and methods are available as Supplementary data at JAC Online. The sequence data for the revised genome of A. baumannii MDR-ZJ06 have been deposited in GenBank under the accession number CP001937.2.

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