An investigation of household dogs as the source in a case of human bacteraemia caused by Staphylococcus pseudintermedius

Staphylococcus pseudintermedius is a commensal and an opportunistic pathogen in dogs, and is also an opportunistic pathogen in humans. Here we report about a case of bacteraemia with a fatal outcome in a 77-year-old co-morbid male likely caused by a S. pseudintermedius and the investigation into the possible transmission from the two dogs in the patient's household. The two dogs carried the same S. pseudintermedius strain, but this dog strain was unrelated to the strain from the patient. In contrast to the patient strain, the dog strain showed reduced susceptibility to several antibiotics and both dogs had received antibiotic treatment prior to sampling. So, it is conceivable that these treatments can have eliminated the patient's strain between the transmission event and the dog sampling. It is also worth noting that the patient strain was positive for the expA gene, which encodes an exfoliative toxin closely related to the S. aureus exfoliative toxin B. This toxin has been linked to canine pyoderma, but its effect on humans remains unknown. Transmission of S. pseudintermedius was confirmed in the household between the dogs. However, we could not verify that the dogs were the source for the S. pseudintermedius in the patient.