Final answer:
The statement about Staphylococcus aureus becoming resistant to methicillin due to mutation is true, resulting in MRSA, which is of great concern to medical professionals due to its ability to be highly resistant to multiple antibiotics and its potential to become a 'superbug'.
Step-by-step explanation:
The statement that the bacterium Staphylococcus aureus became resistant to methicillin because the Staphylococcus mutated so that methicillin was no longer harmful is true. Methicillin-resistant Staphylococcus aureus (MRSA) occurred due to the acquisition of a new low-affinity penicillin-binding protein (PBP), along with other resistance genes, which has made these bacteria resistant to all β-lactam antibiotics, including methicillin. This resistance has resulted from the imprudent use of antibiotics, which has accelerated the natural selection of these resistant forms.
Medical professionals are extremely concerned about MRSA because it represents a significant challenge in treating bacterial infections due to its resistance to multiple antibiotics. Some reasons for their concern include: a) MRSA can transfer methicillin-resistance to other bacteria, b) patients are often not treated with the correct antibiotics rapidly enough to prevent serious illness, and c) MRSA could acquire additional antibiotic resistance genes from other bacteria to become a 'superbug'. This makes MRSA strains some of the most difficult to treat because they exhibit resistance to nearly all available antibiotics.