Here we have some lovely Eschericia coli and Staphylococcus saprophyticus, spread on plates to test for UTIs, that are clearly all dressed up and ready to hit the town for New Year’s Eve. E. coli is rocking the metallic glam look! And S. sapro is oh-so pretty in hot pink.
Actually, to test for UTIs, bacteria are spread on special plates with dyes in them. The dyes keep gram positive bacteria from growing (bacteria that cause UTIs are gram negative, so if a patient sample grows on these plates it means there is likely a UTI. A gram stain is a type of differential test, and bacteria are either positive or negative). The plates also have lactose in them, and only certain types of bacteria can ferment (digest) lactose. Fermenters show up as pink/purple, except E. coli, which turns that awesome metallic green color. You can see on the first plate that opposite from the E. coli and S. sapro, there is growth, but no fermentation. This means those bacteria are likely either part of the normal growth in the urethra, or, if they are not, are at least not causing the UTI. On the second plate, you can see that PV (which stands for Proteus vulgaris) is growing but not fermenting, and SE (which stands for Staphylococcus epidermis) isn’t even growing.
These are definitely the coolest/prettiest plates we worked on this semester! Sadly (or happily, depending on how much you like looking at pictures of bacteria), this is the last photo I took from Microbiology. Next semester, my only lab is Food Science, so the pics should at least be more appetizing.