Gross, Natascha (2025). Genetic basis of β-lactam resistance in Corynebacterium auriscanis and association with otitis externa in dogs and cats. (Thesis). Universität Bern, Bern
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Abstract
Corynebacterium (C.) auriscanis is an opportunistic pathogen isolated from canine otitis externa. We found a surprisingly high prevalence of β-lactam resistant isolates (47%). To determine the genetic base of this phenotype a selection of isolates of C. auriscanis with high and low minimal inhibitory concentration values were subjected to whole genome sequencing. Comparative analysis revealed a gene cassette containing three genes (hdfR encoding a LysR-family transcriptional regulator, blaB encoding a β-lactamase related protein and pbp2c encoding a D,D-transpeptidase) as the likely resistance-encoding determinant. This locus had previously been described in C. jeikeium as well as C. diphtheriae. In our six C. auriscanis isolates the pbp2c locus was always associated with the same IS3 family transposase, an association also found on C. diphtheriae plasmid CP091096, indicating horizontal gene transfer between species. To elucidate the function of the three genes in the pbp2c locus we constructed plasmids with different combinations of these genes, transformed β-lactam sensitive isolates with the plasmids and tested resistance in the mutants phenotypically. We confirmed Pbp2c to be the primary factor conferring β-lactam resistance and HdfR and BlaB being important for expression and regulation. Interestingly, resistance to all β-lactams including carbapenems was mostly constitutive in C. auriscanis while an induction effect was visible for C. glutamicum and C. rouxii.
| Item Type: | Thesis |
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| Dissertation Type: | Single |
| Date of Defense: | 19 June 2025 |
| Subjects: | 600 Technology > 610 Medicine & health |
| Institute / Center: | 05 Veterinary Medicine > Department of Infectious Diseases and Pathobiology (DIP) > Institute of Veterinary Bacteriology |
| Depositing User: | Hammer Igor |
| Date Deposited: | 21 Dec 2025 09:47 |
| Last Modified: | 21 Dec 2025 09:47 |
| URI: | https://boristheses.unibe.ch/id/eprint/6984 |
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