Question

mixed unknown. the goal of this assignment is to identity each organism. so this attachement or picture has both organism seperated by gram stanin and result of each on macConkeys Agar and Columbia CNA. so in order to identify the genus and specise both organsims, i have to order 2 additional test per. MY questions to you is what kinds of test do have to requesd or do in oder to identity  the organism ?

N (No Title) Gram + Gram - 3 Columbia CNA Agar MacConkey's Agar Gram + Gram - 0 Slide 2 of 3 English (United States) Notes Comments A P W

Answer 1

The first one is a Gram + coccus, and the second one is a Gram - bacillus. Let us address how could we proceed to reach identification for each one:

- Gram + coccus: We should proceed to make a catalase test, Sthaphylococcus tests positive while Streptococcus tests negative. If the catalase tests points at Sthaphylococcus I would recomend to proceed with a Mannitol agar test, this fermentation test will tell us if the species is S. aureus or not.

- Gram - bacillus: In this case it would be good to apply a TSI test, which is an agar that contains three sugars: glucose, sucrose and lactose. Different gram - bacilli ferment different of these sugars, some produce gas while doing it and some other don't. This agar also contains iron so it tests for H2S production too. This test is specially made to differentiate between Enterobacteriace, which are all Gram - bacilli. In this casse a second test is not required, since this previous one already gives a huge step in indentifying your species.