Genetic Organization of Acquired Antimicrobial Resistance Genes and Detection of Resistance-Mediating Mutations in a Gallibacterium anatis Isolate from a Calf Suffering from a Respiratory Tract Infection

Antibiotics (Basel). 2023 Feb 1;12(2):294. doi: 10.3390/antibiotics12020294.

Abstract

Gallibacterium (G.) anatis isolates associated with respiratory diseases in calves and harboring acquired antimicrobial resistance genes have been described in Belgium. The aim of this study was to analyze the genetic organization of acquired resistance genes in the G. anatis isolate IMT49310 from a German calf suffering from a respiratory tract infection. The isolate was submitted to antimicrobial susceptibility testing, and a closed genome was obtained by a hybrid assembly of Illumina MiSeq short-reads and MinION long-reads. Isolate IMT49310 showed elevated MIC values for macrolides, aminoglycosides, florfenicol, tetracyclines, and trimethoprim/sulfamethoxazole. The acquired resistance genes catA1, floR, aadA1, aadB, aphA1, strA, tet(M), tet(B), erm(B), and sul2 were identified within three resistance gene regions in the genome, some of which were associated with IS elements, such as ISVsa5-like or IS15DII. Furthermore, nucleotide exchanges within the QRDRs of gyrA and parC, resulting in amino acid exchanges S83F and D87A in GyrA and S80I in ParC, were identified. Even if the role in the pathogenesis of respiratory tract infections in cattle needs to be further investigated, the identification of a G. anatis isolate with reduced susceptibility to regularly used antimicrobial agents in cases of fatal bovine respiratory tract infections is worrisome, and such isolates might also act as a reservoir for antimicrobial resistance genes.

Keywords: Gallibacterium anatis; antimicrobial resistance; cattle; multidrug resistance; respiratory disease; whole-genome sequencing.

Grants and funding

This research was supported by internal funding. We acknowledge support by the Open Access Publication Fund of the Freie Universität Berlin. T.S. was funded by the German Federal Ministry of Health (BMG) within the ZooSeq MinION-Zoo project, grant number ZMVI1-2519NIK704. S.S. was funded by the German Federal Ministry of Education and Research (BMBF) as part of the Research Network Zoonotic Diseases, project number 01KI2009D.