Staphylococci is group of gram-positive aerobic bacteria that are localized on the skin and nasal passages of about 20 to 30 percent of healthy adults. Staphylococci bacteria becomes pathogenic when it has systemic access to our organs and tissues, thereby causing skin infections characterized by abscess and pus and in severe cases, pneumonia, sepsis and endocarditis. Staphylococcus aureus is the most virulent of the staph species because of its ability to clot blood and its widespread resistance to penicillin class antibiotics. Three main antibiotics are used in the treatment of Staphylococcus aureus infections include flucloxacillin for normal staph infections, vancomyin for methicillin resistant Staphylococcus aureus, or MSRA, infections and linezolid for vancomyin resistant Staphylococcus aureus, or VRSA, infections.
Flucloxacillin
Flucloxacillin is an antibiotic used for the treatment of Staphylococcus aureus infections acquired outside the hospital. Flucloxacillin is classified as a penicillinase resistant beta lanctam because of its resistance to penicillinase, an enzyme secreted by Staphylococcus strains to destroy the antibacterial properties of antibiotics such as penicillin, according to the Merck Manual. Flucloxacillin's mechanism of action involves binding to the penicillin-binding proteins inside the cell walls. This effectively prevents the cross-linkage of sugar and amino acid monomers and thus, the bacterial cell is forced to release enzymes such as autolysins, which disrupt the cellular membrane and consequently destroys the bacteria. Flucloxacillin is an effective treatment for bone, skin and soft tissue infections, as well as more serious infections such as meningitis and sepsis caused by Staphylococcus aureus.
Vamcomyin
Methicillin resistant Staphylococcus aureus are hospital strains of Staphylococcus aureus that are extremely resistant to beta-lactam antibiotics such as methicillin and flucloxacillin and are considered to be extremely dangerous . MSRA are considered life threatening infections because the individuals most at risk are already undergoing some sort of surgical procedure or have a weakened immune system and thus are at greater risk for bloodstream infections, pneumonia or surgical sepsis. Most strains of MSRA are resistant to most penicillin class antibiotics and only sensitive to vancomycin. According the Microbelibrary.org, vancomycin inhibits the formation of the bacteria's cell wall by binding to a chain of five amino acids in the cell wall and effectively prevents the addition of amino acid and sugar monomers to the cell wall. This inhibition of the amino acid and sugar cross chains weakens the bacterial cellular wall and ultimately, autolysins are released to destroy the cell wall.
Linezolid
Linezolid belongs to a class of antibiotics called oxazolidinones. It is prescribed as an intravenous treatment for specific strains of Staphylococcus aureus that have developed a resistance to penicillinase resistant beta lactam antibiotics as well as vancomycin. According to the Centers for Disease Control and Prevention, these vancomycin resistant Staphylococcus aureus strains were first reported in Japan in 1993 and as of 2003, there have been eight clinical infections in the USA. Since these strains of Staphylococcus aureus are resistant to antibiotics that lyse the cell walls, linezolid works by inhibiting the formation of the assembly initiation complex required for protein synthesis, thus preventing the synthesis of proteins needed by the bacteria to multiply and divide. By inhibiting the ability of Staphylococcus aureus to grow and replicate, linezolid effectively contains the bacterial infection and the remaining colonies die or are destroyed by the immune system.
