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MRSA - page 3
Keywords: MRSA, infection hospital superdrug infection methicillin resistant staphylococcus aureus
By Einstein10 on 30/12/2009
Level: Foundation Degree
Page Number: 3 of 6 pages: 1 2 3 4 5 6out. 12 However, today’s reports show the presence of Vancomycin resistant staphylococcus Aureus (VRSA) 12
The majority of the SA bacterial cell wall is made of peptidoglycans, the most important component. B-lactam antibiotics contain D-Cycloserine and O-Carbamylserine which inhibit the biosynthesis of the nucleopeptide precursors of the cell wall. 15
Vancomycin, ristocetin and bacitracin prevent use of these precursors for the synthesis of the peptidoglycans.16 Vancomycin and ristocetin account for the accumulation of lipid intermediates which consequently inhibit the transfer of disaccharide-peptide into glycopeptides. Both of these antibiotics bind to the cell walls of SA and form complexes with the nucleotide-peptide precursors of peptidoglycan and weaken the bacterial cell wall. 16 The cell wall collapses and the intracellular components leak out the cell, killing the bacteria. 13 Figure 2 shows an overview on antibiotic action against bacteria, especially SA.
Figure 2. Sites of action of different antibiotics 17
Antibiotic Resistance in SA
The overuse of antibiotics is due to a number of factors and both doctors and patients are guilty of indiscriminate use.5 Resistance to antibiotics has long-term effects as the synthesizing of new antimicrobials is outmatched by production of new ones.27 Counter selling and sharing of antibiotics in developing countries like Pakistan and Bangladesh means untrained individuals are self medicating.28 Unregulated production of antibiotics by manufacturers to reduce costs leads to poor doses of toxic in the antibiotic.28 After analysis of a 500-mg tablet of ciprofloxacin it contained only 20mg of ciprofloxacin. Poverty remains a major cause in antimicrobial resistance.28
The routine use of antibiotics in animal husbandry, not for their anti-bacterial action but rather for their accelerated growth properties is proposed to select for antibiotic-resistant bacteria that cause diseases in humans. 18 However, whilst there is undoubtedly a risk from eating undercooked and contaminated meat, the risk of antibiotic-resistant bacteria of animal origin causing serious human diseases has been evaluated to be minimal. 19
Bacterial resistance occurs in one of two ways, acquired or natural. 27 In transformation the bacterial cell take in naked DNA becomes part of its genetic material. 20 The DNA that is taken up might be of a dead bacterium which had the resistant gene. 14 In Transduction bacterial viruses are attached to DNA that is taken up by the bacterium and the viral DNA will be incorporated into the bacterial DNA and cause resistance to the antibiotic.14 Finally in conjugation there is direct contact with between
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