Answer
Antibiotic resistance develops when strains of bacteria are exposed to antibiotics to a point that is not sufficient to eradicate them but enough for them to develop mutations that enable them to counteract the impact of antibiotics on them. The methicillin-resistant Staphylococcus aureus that Andrea was infected with was able to overcome the beta-lactam antibiotics which she was prescribed.
Work Step by Step
1. Antibiotic resistance can only occur if bacteria have exposure to the antibiotics which they develop resistance against.
2. This exposure must not be strong enough to wipe out the bacteria, but sufficient for the bacteria to become 'familiar' with the antibiotic, and thus develop mutations which nullify the effects of the antibiotic.
3. Methicillin-resistant Staphylococcus aureus, or MRSA, is one such example of antibiotic-resistant bacteria.
4. MRSA, or the strain of Staphylococcus aureus from which it originated, was exposed to beta-lactam antibiotics, but not to a point that proved lethal to the bacteria.
5. MRSA was able to develop a mutation that enabled it to produce the enzyme beta-lactamase, which can destroy beta-lactam antibiotics.
6. Andrea was infected with MRSA and prescribed beta-lactam antibiotics. Because MRSA is resistant to these antibiotics, Andrea's infection was not cured, and indeed became worse.
