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MRSA stands for methicillin-resistant Staphylococcus aureus. These are strains of S. aureus that are resistant to methicillin and to the other β-lactam antibiotics, including penicillin and amoxicillin. Many strains are also resistant to several other groups of antibiotics.
How it is resistant. Methicillin was developed because it is not broken down by the β-lactamase enzymes that make many staphylococci resistant to penicillin. MRSA got round this by gaining a gene, mecA, that codes for an altered transpeptidase enzyme (a penicillin-binding protein) in the cell wall. β-lactam antibiotics cannot bind to its active site, so the bacterium keeps building cross-linked peptidoglycan and its wall stays strong.
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Key terms in this lesson
- transpeptidase
- A bacterial enzyme that forms the peptide cross-links between peptidoglycan chains in the cell wall.
More in Bacteria and Disease
- Protein synthesis Inhibitors
- Cell Wall Agents
- Cell Membrane Agents
- DNA Gyrase Inhibitors
- Antibiotic Resistance
- Creating Drug-Resistant Bacteria
- Clostridium difficile
- Prevention and Control of Infection
All 30 lessons in Bacteria and Disease · All Edexcel A-level Biology topics