Sharing more than friendship--nasal colonization with coagulase-positive staphylococci (CPS) and co-habitation aspects of dogs and their owners

Abstract

Background: Since the relationship between dogs and their owners has changed, and dogs moved from being working dogs to family members in post-industrial countries, we hypothesized that zoonotic transmission of opportunistic pathogens like coagulase positive staphylococci (CPS) is likely between dogs and their owners.

Methodology/principal findings: CPS- nasal carriage, different aspects of human-to-dog relationship as well as potential interspecies transmission risk factors were investigated by offering nasal swabs and a questionnaire to dog owners (108) and their dogs (108) at a dog show in 2009. S. aureus was found in swabs of 20 (18.5%) humans and two dogs (1.8%), and spa types which correspond to well known human S. aureus lineages dominated (e.g. CC45, CC30 and CC22). Multilocus sequence typing (MLST) of the two canine strains revealed ST72 and ST2065 (single locus variant of ST34). Fifteen dogs (13.9%) and six owners (5.6%) harboured S. pseudintermedius, including one mecA-positive human isolate (MRSP). Pulsed field gel electrophoresis (PFGE) revealed that one dog/owner pair harboured indistinguishable S. pseudintermedius- isolates of ST33. Ten (48%) of the 21 S. pseudintermedius-isolates showed resistance towards more than one antimicrobial class. 88.9% of the dog owners reported to allow at least one dog into the house, 68.5% allow the dog(s) to rest on the sofa, 39.8% allow their dogs to come onto the bed, 93.5% let them lick their hands and 52.8% let them lick their face. Bivariate analysis of putative risk factors revealed that dog owners who keep more than two dogs have a significantly higher chance of being colonized with S. pseudintermedius than those who keep 1-2 dogs (p<0.05).

Conclusions/recommendations: In conclusion, CPS transmission between dog owners and their dogs is possible. Further investigation regarding interspecies transmission and the diverse adaptive pathways influencing the epidemiology of CPS (including MRSA and MRSP) in different hosts is needed.

Figure 1. Comparative PFGE analysis and strain characteristics of S. pseudintermedius from human and canine origin.

Dendrogram (percent similarity) showing DNA restriction pattern after digestion with SmaI for all 21 MSSP and MRSP isolates. PFGE analysis by use of bionumerics® (unweighted-pair group method using average linkages), dice coefficient, 1.2% tolerance and 0.5% optimization. Pair 36 comprised the isolates IMT18797 (canine) and IMT18798 (human), which show indistinguishable PFGE pattern. The canine isolate IMT18789 and IMT18828 (human) share an indistinguishable pulsotype as well, although they did not compose a dog/dog owner pair. ¹Strain collection number: IMT: Institute of Microbiology and Epizootics. RKI: Robert Koch-Institute (Wernigerode branch). ²Individual number for each of the participating dog/dog owner pairs. ³Determined by use of VITEK® 2 (bioMerieux) according to the manufacturers instructions. ⁴Allelic profile of the genes pta, cpn60, tuf, 16S rRNA and agrD. Abbreviations: PEN, Penicillin G; GEN, Gentamicin; KAN, Kanamycin; ENR, Enrofloxacin; MAR, Marbofloxacin; ERY, Erythromycin; CLI, Clindamycin; TET, Tetracycline; CHL, Chloramphenicol; i: susceptibility testing result: intermediate. Luk-I: Leukotoxin I (lukS and lukF), expA: Exfoliative toxin A (primer: this study), expB: Exfoliative toxin B.