Abstract:
Staphylococcus pseudintermedius is an important cause of clinical infections in small-animal-
veterinary medicine. Evolutionary changes of strains using multilocus sequence typing
(MLST) have been observed among S. pseudintermedius in European countries and the
United States. However, there are limited or no studies on the detection of methicillin resistant
Staphylococcus pseudintermedius (MRSP) and predominating MLST strains in South
Africa. Therefore, this study aimed to determine the molecular epidemiology of S. pseudintermedius
in South Africa. Twenty-six, non-duplicate, clinical isolates from dogs were
obtained as convenience samples from four provinces in South Africa. The Kirby Bauer disk
diffusion test was used to determine antimicrobial susceptibility. We used Resfinder and the
Comprehensive Antibiotic Resistance Database (CARD) to detect antimicrobial resistance
genes. Virulence genes were identified using the virulence factor database and Basic Local
Alignment Search Tool (BLASTN) on Geneious prime. geoBURST analysis was used to
study relationships between MLST. Finally, the maximum likelihood phylogeny was determined
using Randomized Axelerated Maximum Likelihood (RAxML). Twenty-three isolates
were confirmed as S. pseudintermedius of which 14 were MRSP. In addition to β-lactam
antimicrobials, MRSP isolates were resistant to tetracycline (85.7%), doxycycline (92.8%),
kanamycin (92.8%), and gentamicin (85.7%). The isolates harbored antimicrobial resistance
genes (tetM, ermB, drfG, cat, aac(6’)-Ie-aph(2”)-Ia, ant(6)-Ia, and aph(3’)-III) and virulence
genes (AdsA, geh, icaA, and lip). MLST analysis showed that ST2228, ST2229,
ST2230, ST2231, ST2232, ST2318, ST2326 and ST2327 are unique sequence types in
South Africa. Whereas, previously reported major STs including ST45, ST71, ST181,
ST551 and ST496 were also detected. The geoBURST and phylogenetic analysis suggests that the isolates in South Africa are likely genetically related to isolates identified in other
countries. Highly resistant MRSP strains (ST496, ST71, and ST45) were reported that could present challenges in the treatment of canine infections in South Africa. Hence, we have
gained a better understanding of the epidemiology of MRSP in the African continent, the
genes involved in resistance and virulence factors associated with these organisms.
