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...

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Staphylococcus pseudintermedius is the primary cause of canine pyoderma and has been associated with diseases in other animals, including human beings. A high prevalence of methicillin and multidrug resistance has been reported in this bacterium in some geographic regions of the United States. Multilocus sequence type (MLST) 68 was implicated, initially, as the major clonal genotype based on a limited number of samples. The objectives of this study were to determine the population genetics of S. pseudintermedius isolated from a cross-section of the United States using a seven-locus multilocus sequence typing method, to identify clonal complexes (CCs), and to correlate sequence types with antimicrobial susceptibility profiles. A total of 190 S. pseudintermedius with 86 different MLSTs were detected and the constituents of three major CCs of methicillin-resistant S. pseudintermedius (MRSP), CC68, CC71, and CC84, were identified. Different patterns of resistance were associated with each CC. CC71 from the United States had notable differences with CC71 studied on other continents with chloramphenicol, tetracycline, and trimethoprim/sulfamethoxazole resistance. Some isolates with resistance to the broadest range of drugs tested, including that to chloramphenicol, had STs unrelated to the major CCs, suggesting the potential for the emergence of new clonal populations of MRSP that are resistant to most therapeutically useful antimicrobials.

HighlightsRevealing the biodiversity of Red Sea marine invertebrates associated microorganisms by 16S rRNA sequence analysis.Isolation of bacteria and actinomycetes with antimicrobial activity from different Red Sea invertebrates.Detection of biosynthetic gene clusters (PKS and NRPS) in microorganisms associated with the Red Sea marine invertebrates.