Staphylococcus Aureus - Group of Bacteria

Staphylococcus Aureus

Flucloxacillin

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Section 1

Staphylococcus aureus is a group of bacteria that can cause a number of diseases as a result of infection to various tissues of the body. It appears grape like in structure when seen under the microscope and can survive in salty, low moisture and under high osmotic conditions(Lee & Bishop, 2010). Staphylococci can infect humans, but most infections are caused by Staphylococcus aureus. Staphylococcus aureus is a gram-positive, non motile, non spore producing bacteria which has a polysaccharide cell capsule . S. aureus is a gram positive bacteria, which means that the cell wall of this bacteria consists of a very thick peptidoglycan layer. Peptidoglycan layer of S. aureus is heterogeneous, highly cross-linked polymer of unknown tertiary structure and is typically 20-30 nm thick(Schaefer, Singh, Sharif, & Kim, 2009). Attached to the peptidoglycan are negatively charged other complex polysaccharides called teichoic acid which influence the passage of materials in and out of the cell(Lee & Bishop, 2010). Peptidoglycan also surrounds a cell membrane containing penicillin binding protein called transpeptidase and also contains protein A which prevents phagocytosis(Galdwin & Trattler, 2009).

Staphylococcus aureus can grow in both aerobic and anaerobic conditions with a temperature range of 10-42oC. It prefers 37oC which is the normal temperature of the human body(Elliot, Worthington, Osman, & Gill, 2007). Most of the time S. aureus grows in moist conditions but can also survive drying(Ahmad, Plorde, & Lawrence, 2010).S. aureus is usually spread through direct contact with a person who has a skin infection or is carrying the bacteria on their skin or in their nose. This can occur in the community where there is close skin to skin contact, sharing items such as clothes or towels or touching articles which are already been infected. Staph can affect anyone, going in crowded places such as hospitals, cinemas, schools or other public places where there is frequent skin to skin contact can increase the chances of infection. People who have poor immune systems and other health issues such as diabetes and skin problems are at higher risk of getting the infection. The skin of up to 100% of patients with atopic dermatitis is colonized with Staphylococcus aureus . Of all S. aureus strains isolated from lesional skin, up to 65% have been shown to produce exotoxins with superantigenic properties(HÄussler, Werfel, Kapp, & Breuer, 2002).

Although it is estimated that 20-30% of the general human population are carriers of Staphylococcus aureus, this bacterium is one of the most important etiological agents responsible for healthcare-associated infections(Wegrzyn, Rosato, & Plata, 2009). Because of its ability to combat host defences and resistance to treatment to many antibiotics is the cause of many diseases. It can easily adhere to the cells with the help of different proteins it produces, spread in the tissue, form abscesses and produce exotoxins. Staphyloccous aureus has a wide range of microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) which helps adherence to host cells. These include Protein A and Coagulase which protects the organism from phagocytosis and increases its ability to invade tissue. Haemolysin, leukotoxin and leukocidin are some of the exotoxins that lyses erythrocytes and white blood cells and damage platelets, membranes and susceptible cells. It also produces heat stable Enterotoxins unaffected by gastrointestinal enzymes which causes food poisoning. A S. aureus strain which produces toxin A and B releases a diffusible toxin that have distant effects on neonates with local infections or older children with skin infections(Galdwin & Trattler, 2009). It is also a superantigen like Epidermolytic toxin and Toxic shock syndrome toxin(TSST) which bind non-specifically to specific white cells resulting in over production of cytokines giving rise to toxic shock like presentation. Many strains of staphylococcus aureus are resistant to the antibiotic methicillin which are called methicillin resistant staphylococcus aureus(MRSA) which is because of an additional penicillin binding protein encoded by an acquired mecA gene which makes it even more pathogenic and resistant to treatment(Ahmad, et al., 2010).

Methicillin Resistant Staphylococcus Aureus is a major pathogen in the Australian hospitals and other health care settings and is the major cause of morbidity and mortality in populations at higher risk of infections. MRSA is endemic in the majority of Australian hospitals and there is a high patient morbidity and mortality in association with health care-associated MRSA(Jessica, 2004). The reason Staphylococcus aureus has developed resistance to glycopeptides may be because of the prolonged use of antibiotics to treat MRSA, but it is important to prevent it from transmission while providing adequate treatment. Compliance with standard precautions like handwashing and skin antisepsis and aseptic technique, droplet precautions for patients with MRSA in their sputum, judicious antibiotic prescribing practice, practices that encourage covering skin infections with waterproof dressings and not handling of food if having skin infections that cannot be covered can help us in managing the effects and exposure of Staphylococcus aureus(Health, 2010).

Section 2

Antibacterials are bacterial or fungal in origin (Bullock, E., & Galbraith, 2007) and inhibit the growth of bacteria in four different ways, by inhibiting cell wall synthesis, as exhibited by Beta-lactams or glycopeptides, by inhibiting protein synthesis essential to maintain life functions of the bacteria, as with Amino glycosides and Macrolides. Antimetabolites prevent cellular metabolism as with sulphonamide or those which inhibit nucleic acid synthesis as with fluoroquinolone(Smith, 1999). Flucloxacillin is an important antimicrobial drug in the treatment of infections with Staphylococcus aureus and therefore is often used in staphylococcal infections(Heinz, et al., 2003). It is a narrow spectrum Beta lactam antibiotic which is stable group of penicillin with antistaphyloccol activity and is used as a first line of defence against sensitive strains of staphylococcus