**1.** *Staphylococcus aureus* **infections: introduction**

*Staphylococcus aureus* is a Gram‐positive staphylococci that can exist commensally with humans as a colonizer but can also exist as a pathogen. It is a major pathogen in bacteremia whether community acquired or hospital acquired. It has proven its versatility by continu‐ ing to be an important infectious pathogen that has contributed to increasing morbidity and mortality of patients over the years. Despite the advances in antibiotic therapy target‐ ing this pathogen, *S. aureus* remains a multipotent organism that causes infection using toxin production and nontoxin‐mediated pathways. This organism causes a wide array of

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

infections, from a simple skin infection to more dangerous situations such as bacteremia, endocarditis, pneumonia, bone and joint infections, and many others that may jeopardize the life of the patient. Bacteremia is one major cause of morbidity in both the inpatient and outpatient setting, and *S. aureus* is notorious for causing invasive infections that lead to bacteremia.

Patients with *S. aureus* bacteremia can be at risk for many complications that may increase morbidity, with mortality rates of 20–40% that have been described. The higher the level of resistance, the higher the mortality rates. This is why methicillin‐resistant *S. aureus* (MRSA) is expected to have a higher morbidity/morality, longer hospital stays, and higher health care costs when compared with methicillin‐sensitive *S. aureus* (MSSA) bacteremia [1]. Also, in cases of infection with MRSA, there is a higher rate of treatment failure that may include death within 30 days of receiving therapy, persistent positive blood cultures for more than 10 days after therapy, or recurrence of septicemia within 60 days after finishing therapy.
