A female patient was admitted to her city hospital with a high fever (>103oF) and urinary tract infections (UTI). A blood sample and lab culture analysis also revealed a blood infection (bacteremia). The physician on call suspected the most common UTI pathogen, Gram-negative bacteria, and immediately started the patient on methicillin treatment. The patient was discharged after two days when she showed signs of recovery and no fever. A week later, the patient returned to the emergency ward with a very high fever. Upon testing, no UTI infection was detected. Further testing with blood culture revealed the presence of Gram-negative bacilli that matched the colony characteristics with the original blood culture sample. Kirby-Bauer antimicrobial susceptibility test on the second isolate showed resistance.

Why was the Methicillin treatment chosen?
When the colony characters matched with the first isolated culture, what does it indicate?
Is the second isolate identical to the first isolate?
Discuss how the bacterial culture became resistant to the antibiotic that showed recovery upon administration?