Answer
Polymyxin antibiotic has no effect on these viruses that are found in the nerves cells of cold sore patients.
Work Step by Step
Coldsores are caused by virus while polymyxin antibiotic is effective against bacteria particularly against gram negative bacteria. It acts by disrupting cell membrane of the bacteria. Lui was successful in treating cut on his hand using topical polymyxin cream earlier because the cut might have been infected with bacteria which were sensitive to polymyxin antibiotic. Thus application of polymyxin caused death of infection causing bacteria. The coldsore on the upper lip of Lui did not respond to polymyxin cream just because it was ineffective against coldsore causing organism which is virus (Herpes Simplex Virus) mostly by type HSV-1 and sometimes also by HSV-2. Polymyxin antibiotic has no effect on these viruses that are found in the nerves cells of cold sore patients.
