The strategies of Staphylococcus aureus to develop a chronic infection

Staphylococcus aureus is a gram-positive coccal bacterium that is a member of the Firmicutes. S. aureus is a facultative pathogenic bacterium that can colonize the epithelial surfaces of humans and domestic animals and can also cause different types of severe tissue infections. Approximately 20% of individuals are persistently nasally colonized with S. aureus, and 30% of individuals are intermittently colonized [1, 2]. However, other sites can be colonized, including the axillae, groin, and gastrointestinal tract [3]. Colonization provides a reservoir from which bacteria can cause different types of infection [4]. In a study of bacteraemia, blood isolates were identical to nasal insolates in 82% of patients, suggesting that S. aureus can occasionally breach epithelial barriers and enter the bloodstream [5]. S. aureus is the main pathogen of osteomyelitis worldwide. Osteomyelitis is a bone infection that can be associated with high levels of inflammation and bone tissue destruction. The infection can sometimes develop into a chronic course and may become extremely difficult to treat with antimicrobials [6]. Osteomyelitis can be categorized into three groups, according to the route used by the infecting bacterium to gain access to the bone [7]. First, in haematogenous osteomyelitis, staphylococci access the bone tissue via the bloodstream. This form of osteomyelitis affects mainly prepubertal children. Second, osteomyelitis develops by way of a contiguous spread from a local infection after trauma, bone surgery, or joint replacement. Finally, osteomyelitis can be peripheral to vascular insufficiency. This form of osteomyelitis occurs mostly in diabetic patients and usually originates from an infected foot ulcer that spreads to the bone. All its forms can present in the acute or chronic phase and in virtually any bone. Osteomyelitis is the most frequent cause of non-traumatic limb amputation, as antimicrobial compounds often fail to clear the infection [6-9]. Despite the availability of effective antimicrobial agents to treat staphylococcal infection, it continues to be a major cause of morbidity and mortality worldwide [10]. Epidemiological studies due to the spread of successful clones continue to be reported from virtually every geographic region [11].