| dc.description.abstract | Staphylococcus pseudintermedius is a major opportunistic canine pathogen that has been associated with an increasing number of human infections. As an opportunist, S. pseudintermedius causes a wide range of infections, predominantly of skin and soft tissue but also device/implant related infections and systemic infections such as bacteremia. Increasing methicillin and multipledrug-resistance in the species complicate treatment of S. pseudintermedius infections, which are often already difficult to treat due to the bacteria’s ability to produce biofilms that hamper effective use of antimicrobial drugs. Biofilm formation and virulence factor expression in Staphylococcus is regulated, in part, by the accessory gene regulator (agr) operon. Polymorphisms in this operon result in four distinct agr groups (I, II, III, and IV) in S. pseudintermedius. In S. aureus, agr groups are associated with infection type, virulence factor carriage, and phylogenetic relationships. This operon has shown promise as a therapeutic target in S. aureus. Similar relationships remain largely unexplored in S. pseudintermedius. Furthermore, the pathogenic differences in infections caused by S. pseudintermedius between canines and humans and the characterization of isolates causing human infections in general are substantively lacking. Biofilm characterization was performed on 710 clinical isolates from healthy and diseased canines. We found that the majority of clinical isolates from dogs produce biofilm, while a type of biofilm utilizing slime was found to be associated with isolates causing disease. In order to explore the associations of agr groups of S. pseudintermedius, whole-genome-sequencing was performed on 160 isolates collected from four groups (pyoderma infections, surgical infections, urinary tract infections, and healthy colonization). We found that agr group II isolates were significantly associated with healthy colonization rather than disease, and were less likely to be multiple-drug-resistant or carry multiple toxin genes.
The predominant methicillin-resistant sequence types were identified for the geographic region (Texas) including ST64, St68, ST71, ST84, ST150, and ST155. Four isolates from human bacteremia infections and four from canine bacteremia infections were sequenced and complete, or near-complete, genome assemblies were achieved and published, allowing for the examination and comparison of virulence factors associated with both human and canine invasive infections. While statistical significance was not seen with the small sample size, pan-genomic analysis did allow us to identify genes unique to the isolates causing human infections. | en |
