INVESTIGATION OF ANTIMICROBIAL RESISTANCE IN Staphylococcus pseudintermedius
Date
2017-10-23
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
Staphylococcus pseudintermedius is a coagulase positive bacterium and found on the mucous membranes of approximately 90% of healthy dogs. This organism is an opportunistic pathogen in dogs and an increasingly recognized zoonoses. As in human medicine, the emergence of
antimicrobial resistance is a growing problem in companion animal practice. In the current investigation, we saught to 1. Identify the emergence of resistance among S. pseudintermedius
colonizing healthy dogs, 2. Determine whether there are strain specific tissue tropisms among isolates causing dermatological and urinary tract infections, 3. Perform a clinical and
bacteriological description of human S. pseudintermedius infections and 4. To describe the correlation of susceptibility of isolates to tetracycline, doxycycline and minocycline, and to
describe the mechanisms of tetracycline resistance. We found that methicillin-resistant S. pseudintermedius colonizes 7% of healthy dogs and that since a previous surveillance study
conducted in 2008, resistance has emerged in our region. S. pseudintermedius isolates from dermatological and urinary tract infections were genetically heterogeneous, suggesting that these
organisms are true opportunists and do not possess a strain specific tissue tropism. Despite this
genetic heterogeneity, antimicrobial resistance was found to be significantly higher in isolates from dermatological infections compared to those from the urinary tract. Human infections with S. pseudintermedius were relatively rare, comprising 0.05% of skin and soft tissue infections in a large Canadian health region. Among these human isolates, we found that all methicillin resistant
isolates were the European pandemic clones ST71 and ST181. We found that tetracycline is not a
satisfactory indicator for doxycycline and minocycline resistance, and that these phenotypic discrepancies could not be explained by the presence or absence of particular resistance genes.
Furthermore, factors related to tetM (which was the most commonly identified resistance gene including copy number, predicted amino acid sequence or expression level, were not significantly associated with the phenotypic diversity observed. Although numerically high association were found in high MIC category on tetM expression comparing to low MIC category, larger studies required for further conclusions. The genotypic evidence on MICs for
tetracycline and doxycycline is largely unknown and more studies are required.
Description
Keywords
Staphylococcus pseudintermedius, dog, antimicrobial resistance, tetracycline, MRSP, skin, UTI, Canada
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Veterinary Microbiology
Program
Veterinary Microbiology