In:
Microbiology Spectrum, American Society for Microbiology, Vol. 11, No. 3 ( 2023-06-15)
Abstract:
Aminoglycoside-modifying enzymes are among the most important mechanisms of resistance to aminoglycoside antibiotics, typically conferring high-level resistance by enzymatic drug inactivation. Previously, we isolated a multidrug-resistant Brucella intermedia strain ZJ499 from a cancer patient, and whole-genome sequencing revealed several putative novel aminoglycoside-modifying enzyme genes in this strain. Here, we report the characterization of one of them that encodes an intrinsic, chromosomal aminoglycoside nucleotidyltransferase designated ANT(9)-Ic, which shares only 33.05% to 47.44% amino acid identity with the most closely related ANT(9)-I enzymes. When expressed in Escherichia coli , ANT(9)-Ic conferred resistance only to spectinomycin and not to any other aminoglycosides tested, indicating a substrate profile typical of ANT(9)-I enzymes. Consistent with this, deletion of ant(9)-Ic in ZJ499 resulted in a specific and significant decrease in MIC of spectinomycin. Furthermore, the purified ANT(9)-Ic protein showed stringent substrate specificity for spectinomycin with a K m value of 44.83 μM and a k cat / K m of 2.8 × 10 4 M −1 s −1 , echoing the above observations of susceptibility testing. In addition, comparative genomic analysis revealed that the genetic context of ant(9)-Ic was conserved in Brucella , with no mobile genetic elements found within its 20-kb surrounding region. Overall, our results demonstrate that ANT(9)-Ic is a novel member of the ANT(9)-I lineage, contributing to the intrinsic spectinomycin resistance of ZJ499. IMPORTANCE The emergence, evolution, and worldwide spread of antibiotic resistance present a significant global public health crisis. For aminoglycoside antibiotics, enzymatic drug modification is the most common mechanism of resistance. We identify a novel chromosomal aminoglycoside nucleotidyltransferase from B. intermedia , called ANT(9)-Ic, which shares the highest identity (47.44%) with the previously known ANT(9)-Ia and plays an important role in spectinomycin resistance of the host strain. Analysis of the genetic environment and origin of ant(9)-Ic shows that the gene and its surrounding region are widely conserved in Brucella , and no mobile elements are detected, indicating that ANT(9)-Ic may be broadly important in the natural resistance to spectinomycin of Brucella species.
Type of Medium:
Online Resource
ISSN:
2165-0497
DOI:
10.1128/spectrum.00620-23
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2023
detail.hit.zdb_id:
2807133-5
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