Emergence of methicillin resistant Staphylococcus pseudintermedius (MRSP) in dogs sampled in 2018 in the island nation of Grenada, West Indies

Josephine Azikuru Afema^1,2*Cristina Mastromonaco¹Margaret Alison Davis²Diana M Stone¹Lisa P Jones²Marta Lanza Perea¹Tara Paterson¹Brian P Butler^1,3

• ¹St. George's University, St. George's, Grenada
• ²Washington State University, Pullman, United States
• ³Clemson University, Clemson, United States

Staphylococcus pseudintermedius (SP) is a commensal bacterium, and an opportunistic pathogen of dogs. Emergence and global dissemination of methicillin resistant SP (MRSP), environmental contamination in veterinary clinical settings, and nosocomial infections are of concern to veterinary medicine. Furthermore, zoonotic infections impact public health. By 2014, only methicillin susceptible SP were detected in canine pyoderma cases in Grenada. We hypothesized MRSP might be introduced to Grenadian dogs via international movement of dogs owned by foreigners associated with St. George's University (SGU). We compared antimicrobial resistance patterns, and genotypes in SP from foreign-born and Grenadian-born dogs. Oral and perianal swabs were collected from 85 dogs owned by SGU faculty, staff, students, and SGU security dogs. Skin swabs were obtained from 25 of these dogs with cutaneous lesions consistent with pyoderma. Bacteria were isolated and identified using culture, PCR, and MALDI-TOF. Antimicrobial susceptibility testing was performed using disc diffusion assay, and genotypes determined by multi-locus variable number of tandem repeat analysis. A questionnaire was administered to investigate risk factors for MRSP infection. Dogs were classified as foreign-born (n = 58) or Grenadian-born (n = 27). Overall, MRSP prevalence was 9.4%, with no difference between foreign-born and Grenadian-born dogs. Univariable analysis indicated that antimicrobial use was associated with MRSP infection, however, other factors e.g. age, sex, hospitalization or country/region of birth were not. Staphylococcus pseudintermedius was isolated from 37.4% (73/195) of dog samples, and from 11.9% (10/84) of the environmental samples. Methicillin resistant SP constituted 13.3% of SP isolates, and MRSP was documented for the first time in Grenadian dogs. Detection of a similar MRSP strain in foreign-born and Grenadian born dogs suggests transmission occurred between these dogs. Genotypic, resistance, and epidemiologic data could be consistent with reports of MRSP dissemination via dog movements. Detection of a similar MRSP strain in foreign-born dogs and animal contact surfaces in the Small Animal Clinic supports the plausibility of environmental contamination and nosocomial transmission, and highlights the importance of disinfection procedures. Compared to the 2014 study, the frequency of resistance to most antimicrobials increased. Monitoring trends in antimicrobial resistance is important for making informed animal health decisions.