Question

In 1959, doctors began using the powerful antibiotic methicillin to treat infections of Staphylococcus aureus, but within two years, methicillin-resistant strains of S. aureus (MRSA) appeared. How did the resistant strains of S. aureus emerge?A) In response to treatment of Staphylococcus aureus infections with methicillin, some bacteria began to synthesize cell walls using a protein that was not affected by methicillin. These bacteria survived the methicillin treatments and reproduced at higher rates than did other individuals. Over time, these resistant individuals became increasingly common.B) In response to treatment of Staphylococcus aureus infections with methicillin, bacterial populations gradually began to synthesize cell walls using a protein that was not affected by methicillin.C) Staphylococcus aureus bacteria that were able to synthesize cell walls using a protein that was not affected by methicillin survived the methicillin treatments and reproduced at higher rates than did other individuals. Over time, these resistant individuals became increasingly common.

Answer 1

The correct answer will be option-B

Step-by-step explanation:

Staphylococcus aureus is a gram-positive, spherical and one of the first described pathogens by scientific communities. The S. aureus is known to cause a number of infections to humans in homes and hospitals and is able to adapt to the environmental conditions.

When Methicillin antibiotic was given to treat the infections caused by the S. aureus, within two years they became resistant to methicillin. This adaptability is the result of the due to the incorporation of the mecA gene at specific sites in their chromosomes.

This gene coded for an alternative penicillin-binding protein which has low affinity for the methicillin including other antibiotics. This gene spread to the S. aureus population and the species became resistant to methicillin.

Thus, Option-B is the correct answer.