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Open Access Highly Accessed Research article

Carriage of methicillin-resistant Staphylococcus pseudintermedius in dogs--a longitudinal study

Ulrika Windahl1*, Elin Reimegård2, Bodil Ström Holst13, Agneta Egenvall3, Liselotte Fernström4, Mona Fredriksson4, Gunilla Trowald-Wigh4 and Ulrika Grönlund Andersson1

Author Affiliations

1 Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute, SVA, SE-751 89 Uppsala, Sweden

2 Södra djursjukhuset, Månskärsvägen 13, 141 75 Kungens kurva, Sweden

3 Department of Clinical Sciences, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden

4 Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Box 7009, SE-750 07 Uppsala, Sweden

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BMC Veterinary Research 2012, 8:34  doi:10.1186/1746-6148-8-34

Published: 23 March 2012

Abstract

Background

Methicillin-resistant S. pseudintermedius strains (MRSP) are reported with increasing frequency in bacterial cultures from dogs. The objectives of this study were to determine whether MRSP could be found in dogs several months after a clinically apparent infection and whether the length of carriage varied depending on systemic antimicrobial treatment, diagnosis at time of the first positive MRSP culture and the presence of skin disease or wounds. Thirty-one dogs previously diagnosed with a clinical infection were sampled repeatedly for a minimum of eight months or, with the exception of two dogs, until two consecutive negative results were obtained. Five specified locations were sampled, and the results were evaluated to determine future recommendations concerning sample strategies when screening for MRSP carriage. Information was collected from medical records and questionnaires to evaluate factors that may influence length of carriage.

Results

The overall median length of MRSP carriage was 11 months (48 weeks). The presence of wounds and signs of dermatitis did not influence length of carriage. Systemic treatment for three weeks or longer with antimicrobial agents to which the bacterium was resistant was associated with prolonged carriage compared to dogs treated for a shorter period of time. Three of five dogs treated with an antimicrobial to which their MRSP-isolates were susceptible (tetracycline) were found to still be MRSP-positive when sampled after the end of treatment. Wound samples had the highest positive MRSP yield (81%) for the positive sample sites, compared to less than 70% for each of the other four sample sites. Cultures from the nostrils were less likely to detect MRSP carriage relative to the pharynx, perineum, wounds and the corner of the mouth.

Conclusions

Dogs can carry MRSP for more than a year after a clinically apparent infection. Systemic antimicrobial treatment of infections with antimicrobial agents to which the MRSP-bacteria are resistant should be avoided when possible in dogs with possible or confirmed MRSP carriage or infection, since it may prolong time of MRSP carriage. Simultaneous sampling of pharynx, perineum, and the corner of the mouth as well as wounds when present is recommended when screening for MRSP. Cultures from nostrils were shown to be less likely to detect MRSP carriage.

Keywords:
MRSP; Methicillin resistant Staphylococcus pseudintermedius; Dog; Carriage; Bacterial infection