Answer to Question #219150 in Microbiology for Darlington Chimwar

Question #219150

Describe the steps you would take to identify Staphylococcus aureus from a patient’s blood sample:

Expert's answer

Staphylococcus aureus

The Gram-positive, round-shaped bacteria Staphylococcus aureus belongs to the Firmicutes family. It's a common microbe found in the body's microbiota, especially in the upper respiratory tract and on the skin. It is a facultative anaerobe that may grow in the absence of oxygen and is usually catalase and nitrate reduction positive, (Dinges et al., 2000). Staphylococcus aureus has ten main human lineages. There are a few minor lineages as well, but they are less prevalent in the population.

The genomes of bacteria within the same lineage are nearly similar, with the exception of mobile genetic components. In S. aurous, bacteriophages, pathogenicity islands, plasmids, transposons, and staphylococcal cassette chromosomes are all common mobile genetic elements. The two main steps are natural genetic changes and skin infections. Natural genetic transformation is a type of reproduction that involves the transfer of DNA from one bacterium to another through medium and homologous recombination to integrate the donor sequence into the recipient genome. aureus was found to be capable of natural genetic change under the experimental conditions employed, although only at a low frequency. Further study shows that, under the appropriate circumstances, the development of competence for spontaneous genetic transformation might be far more rapid. Skin infection is the most common form of S. aureus infection, (Dinges et al., 2000).

 This can include small benign boils, folliculitis, impetigo, cellulitis, and more severe, invasive soft-tissue infections. Because there is no evidence that antibiotics assist persons with atopic dermatitis, the presence of S. aureus in their bodies is not a justification to treat them with antibiotics. Topical corticosteroids in combination with topical analgesics have been shown to help with the symptoms of the illness. Colonization of S. aureus causes atopic dermatitis.

S. aurous is hypothesized to take advantage of the skin barrier defects that atopic dermatitis sufferers have, increasing cytokine production and therefore exacerbating symptoms.


Dinges, M. M., Orwin, P. M., & Schlievert, P. M. (2000). Exotoxins of Staphylococcus aureus. Clinical microbiology reviews13(1), 16-34.

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