Two major clonal MRSP lineages have disseminated in Europe (ST71-J-t02-II-III) and North America (ST68-C-t06-V). Regardless of their geographical or clonal origin, the isolates displayed resistance to the major classes of antibiotics used in veterinary medicine and thus infections caused by MRSP isolates represent a serious therapeutic challenge.

No abstract

Veterinarians should be aware of the potential for empiric drug treatment failures in instances where Staphylococcus spp infections are common (eg, pyoderma). Judicious use of bacterial culture and susceptibility testing is recommended.

f Staphylococcus pseudintermedius is an opportunistic pathogen in dogs. Four housekeeping genes with allelic polymorphisms were identified and used to develop an expanded multilocus sequence typing (MLST) scheme. The new seven-locus technique shows S. pseudintermedius to have greater genetic diversity than previous methods and discriminates more isolates based upon host origin. Staphylococcus pseudintermedius, recently classified as a member of the Staphylococcus intermedius group (SIG), is the most common opportunistic pathogen in dogs. In this host it is frequently associated with pyoderma and other infections, such as those of the urinary tract, wounds, and otitis externa (1-3). It has also been isolated from infections in cats (4, 5), has zoonotic potential (6-8), and is an important nosocomial pathogen causing postsurgical infections in veterinary clinics (9, 10, 33). The incidence of methicillin-resistant S. pseudintermedius (MRSP) has increased significantly in the past few years (1,5,(11)(12)(13)(14)(15)(16)(17)(18)(19). MRSP has emerged as an important problem worldwide because of multidrug resistance and the limited number of drug choices remaining to treat infections caused by this organism. Multilocus sequence typing (MLST) has been used extensively to define the population genetic structure of Staphylococcus aureus and other bacterial species. This information has been used to predict founder strains as well as track the spread of methicillin resistance and identify epidemic clones (2,20). Likewise, the widespread application of this technique to S. pseudintermedius should help to identify methicillin-sensitive S. pseudintermedius (MSSP) progenitors of MRSP clones and provide a mechanism to track their spatial and temporal distribution (21). The identification of successful and/or virulent clonal populations of S. pseudintermedius may facilitate research into characteristics which provide a selective advantage and inform efforts to develop alternative methods of treatment and control, such as vaccines or phage therapy targeting the major clonal populations of S. pseudintermedius associated with disease.MLST is well established as a valuable method for genotyping bacteria based on the sequence variation of housekeeping genes (9,22). It provides accurate, portable data useful for global epidemiology studies and studies of evolution and population genetics (22)(23)(24)(25)(26). MLST techniques applied to diverse species of bacteria generally use at least seven loci (22,(24)(25)(26)(27). Sequence typing based on four loci (MLST-4) has provided insight into the overall genetic structure of the SIG (1). The development of an MLST method expanded to seven loci (MLST-7) for S. pseudintermedius was undertaken to increase its discriminating power with the same number of loci used for other species of staphylococci (24,32).DNA extracts from 125 previously characterized isolates of S. pseudintermedius from dogs (114 isolates), cats (5 isolates), and human beings (6 isolates) from diverse geographical regions (N...