BIOM 4090 Lecture Notes - Lecture 6: Cefalexin, Pharmacovigilance, Bioavailability

• School: University of Guelph
• Department: Biomedical Sciences
• Course: BIOM 4090
• Professor: Laura Favetta

Document Summary

Unit 6: principles of antibacterial therapy & beta-lactams. Gram stain first step used to identify a type of bacteria by applying a purple dye (allows visualization of bacteria). The decolourization step will identify if the bacteria is positive or negative . Gram positive bacteria- purple cells (ex. rods from cocci) A counterstaining step (add red dye) makes it easier to visualize the gram negative cells. The basic steps involved with staining are outline: fixation of the cells, addition of crystal violet, iodine treatment which binds to crystal violet and traps it in the cells, decolourization with alcohol, counterstain with safranin. Gram positive bacteria retain the stain and appear purple. Gram negative bacteria lose the stain and appear pink from the subsequently applied safranin counterstain. Gram negative bacteria possess an outer membrane, an asymmetric bilayer in which the outer leaflet is comprised of lipopolysaccharide.