De Abreu, Cipriano2024-01-052024-01-052023-08https://hdl.handle.net/11299/259527University of Minnesota M.S. thesis. August 2023. Major: Veterinary Medicine. Advisors: Maria Pieters, Monserrat Torremorell. 1 computer file (PDF); vii, 94 pages.Mycoplasma hyopneumoniae (M. hyopneumoniae) is a difficult bacterium to grow that is responsible for enzootic pneumonia (EP), a respiratory disease affecting pigs of all ages. High economic losses have been associated with M. hyopneumoniae infections mainly due to decreased performance, and an increased need for antibiotic treatments. Antibiotic therapy remains a significant approach to control and treat M. hyopneumoniae infections. Selection of antimicrobials in the field against M. hyopneumoniae is often based on veterinary expertise rather than on antimicrobial susceptibility testing (AST). Reports of decreased susceptibility in M. hyopneumoniae isolates have become available over time, raising concerns about its potential impact on the persistence of infections and the efficacy of treatment strategies applied in affected herds. Antimicrobial susceptibility testing of M. hyopneumoniae is not commonly performed, primarily due to the low success rate of the culture and isolation process for this bacterium. In this research, we assessed the presence of genetic mutations associated with decreased antimicrobial susceptibility in M. hyopneumoniae isolates as well as in clinical specimens as molecular tools such as PCR and sequencing. Amplification and sequencing of five different gene segments (gyrA, gyrB, parC, parE and 23S rRNA) was performed, and mutations were recorded and contrasted to previous reports. Findings revealed synonymous and non-synonymous mutations in the assessed gene segments. In the parC gene, a mutation previously associated with decreased susceptibility to fluoroquinolones (C248A) was detected in isolates and clinical specimens, whereas, in the 23S rRNA gene, a macrolide-susceptibility associated mutation (A2071G) was detected only in clinical specimens. Results underscore the potential utility of molecular-based methods for routine monitoring of the emergence of susceptibility-associated traits in M. hyopneumoniae, and its potential to guide treatment selection and consequently improve the treatment and control of EP.enantimicrobial susceptibilityantimicrobialsMycoplasma hyopneumoniaeMycoplasma infectionssusceptibility genessusceptibility surveillanceThesis or Dissertation