Methicillin-resistant Staphylococcus pseudintermedius in a veterinary teaching hospital

Abstract

We surveyed methicillin-resistant coagulase-positive staphylococcus (MRCPS) strains from 57 (26 inpatient and 31 outpatient) dogs and 20 veterinary staff in a veterinary teaching hospital. From the staff, three MRCPS strains were isolated, and two were methicillin-resistant Staphylococcus aureus (MRSA). In contrast, 18 MRCPS strains were detected in both inpatient (12 of 26 [46.2%]) and outpatient (6 of 31 [19.4%]) dogs. Among them, only one strain was MRSA. Using direct sequencing of sodA and hsp60 genes, the 18 MRCPS strains other than MRSA from a staff and 17 dogs, were finally identified as Staphylococcus pseudintermedius, a novel species of Staphylococcus from a cat. All of the methicillin-resistant S. pseudintermedius (MRSP) strains were multidrug resistant to erythromycin, clindamycin, trimethoprim-sulfamethoxazole, and levofloxacin. Most of the MRSP strains showed high-level resistance to oxacillin (>/=128 mug/ml, 15 of 18 [83.3%]), and 10 of 15 (66.7%) high-level oxacillin-resistant MRSP strains carried type III SCCmec. DNA fingerprinting of MRSP strains by pulsed-field gel electrophoresis yielded eight clusters: clone A with four subtypes, clone B with four subtypes, clone C with three subtypes, and five other different single clones. MRSP strains from the staff and some inpatient and outpatient dogs shared three major clones (clones A, B, and C), but the strains of the other five different clusters were distributed independently among inpatient or outpatient dogs. This genetic diversity suggested that the MRSP strains were not only acquired in this veterinary teaching hospital but also acquired in primary veterinary clinics in the community. To our knowledge, this is the first report of MRSP in dogs and humans in a veterinary institution.

FIG. 1.

Phylogenetic tree (unrooted) based on partial sodA gene sequences of the S. intermedius group isolated in the present study. The tree was constructed by the neighbor-joining method using CLUSTAL X.

FIG. 2.

Phylogenetic tree (unrooted) based on partial hsp60 gene sequences of the S. intermedius group isolated in the present study. The tree was constructed by the neighbor-joining method using CLUSTAL X.

FIG. 3.

PFGE patterns of SmaI-digested MRSA strains in the veterinary hospital. Low-molecular-weight marker DNA λ is shown on the left side. The three lanes on the right display results obtained with strains. Each lane shows a different PFGE type.

FIG. 4.

PFGE patterns of MRSP strains digested with SmaI and AscI in the veterinary hospital. Low-molecular-weight marker DNA λ is shown on the left. The lanes on the right side display results obtained with strains. Each lane shows a different PFGE type.