Penicillin was the first antibiotic to be developed, and the first antibiotic treatment which selected for resistance in S. aureus. Since then, more antibiotics have been developed and used in medical treatment of bacterial infections. Methicillin was developed around 1960 and soon after it was widely used to treat bacterial infections including S. aureus. 11. A circle appears on the graph above 1960. Starting from that point, draw a line that shows what percent of S. aureus you would expect to show methicillin resistance over time, between 1960 and 2000 Penicillinase-producing S. aureus 100 80 60 1 Antimicrobial-resistant isolates, % 40 - 20 0 1940 1950 1960 1970 1980 1990 2000 Year L. Clifford McDonald Clin Infect Dis. 2006:42 565-571 2006 by the infectious Diseases Society of America Clinical Infectious Diseases 12. Which of the following statements is true? (Circle one) Explain your reasoning below. a) the use of methicillin caused the appearance of the genetic mutation for methicillin resistance b) the use of methicillin caused the increase in frequency of methicillin-resistant S. aureus (MRSA) c) both of the above 3. How do you think information on the evolution of S. aureus resistance to antibiotics could be used to inform future medical treatment of bacterial infections