Microbiological Description

S. aureus and other members of the genus Staphylococcus are gram-positive, catalase-positive, predominantly facultatively anaerobic, nonmotile, nonspore-forming, spherical-shaped bacteria, approximately 0.5-1.0 mm in diameter, which typically form irregular ''grapelike'' clusters and/or occasional configurations of single cells, pairs, tetrads, and short chains, and are differentiated from other closely related genera by their cell wall teichoic acids, susceptibility to lysostaphin, intrinsic bacitracin resistance, lack of cytochrome c (as determined by the modified oxidase test), and relatively low guanine plus cytosine DNA base composition.1-23-1 Approximately 35 species of staphylococci have been described to date. Based on the production of the enzyme and virulence factor coagulase (encoded by the coa gene), the staphylococci are classified as either coagulase-positive (S. aureus, and the veterinary pathogens Staphylococcus schleiferi subspecies coagulans, Staphylococcus lutrae, Staphylococcus delphini, Staphylococcus intermedius, and Staphylococcus hyicus) or coagulase-negative.[23] A positive tube (free) coagulase test serves as the basis for presumptive identification of S. aureus because the other coagulase-positive staphylococcal species are almost never encountered in human infections. However, rare strains of S. aureus may lack the coa gene and/or fail to produce coagulase.[23] Heat-stable nuclease (encoded by the nuc gene) is another virulence factor produced almost exclusively by the coagulase-positive staphylococci and serves as the basis for the DNase test.[23] The organism is also characterized by the presence of protein A on its cell surface, allowing for rapid, species-specific identification through the use of IgG-coated latex bead-based agglutination kits. S. aureus is a very hardy organism that grows well on most microbiological media and under a variety of incubation conditions. The morphology of S. aureus on solid agar media is somewhat distinctive; after 24 hr of growth, colonies are approximately 3-5 mm in diameter, creamy yellow to orange in color, smooth, and slightly raised. Strains frequently demonstrate beta-hemolysis on blood-containing agar media. Sequencing of the 16S rRNA gene can be used for definitive speciation of S. aureus. However, colonial features, biochemical tests, and 16S rRNA profiles do not differentiate MRSA from methicillin-sensitive S. aureus (MSSA).

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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