3. Could you differentiate between S. aureus and s. epidermidis with any of the

Question

3. Could you differentiate between S. aureus and s. epidermidis with any of the tests? How? 4. Some species of Streptococcus are normal microbiota of the throat. Using techniques from this lab, how would you determine whether someone with a sore throat has strep throat? 5. Which of the media types used in this lab would you predict is used to detect possible fecal contamination of drinking water and meat products by identifying coliforms like Escherichia coli? 6. Let's say you culture an unknown bacterial species on EMB media. The organism grows well, and the colonies do not appear dark. Based on these results, what can you conclude about this bacterial species (circle all that apply): a) The organism is likely Gram-positive b) The organism can ferment mannitol c) The organism is a halophile d) The organism cannot ferment lactose e) The organism is likely Gram-negative f The organism cannot ferment glucose 8) The organism is cocci-shaped 7. Let's say you culture an unknown bacterial species on MSA media. The organism grows well, and the media turns yellow near the bacterial growth. Based on these results, what can you conclude about this bacterial species?

Explanation / Answer

3. Biochemical tests can be used to differentiate. S.aureus is a coagulase positive bacteria. But S.epidermidis is a coagulase negative bacteria. In addition S.aureus is a hemolytic bacteria but S.epidermidis is a non hemolytic bacteria.

4.strep throat is caused by Streptococcus pharyngitis. In lab, rapid strep test or rapid antigen detection testing (RADT) can be used to determine whether a person with sore throat has strep throat or not.

5.chromogenic coliform agar is used to identify E.coli in fecal coliform in drinking water and meat. E.coli produces dark blue to purple Color after 24hrs of incubation.

6.d. organism cannot ferment lactose. Because lactose fermenter will produce colored colonies

E. Organism is a gram negative. Cause eosine and methylene blue inhibits gram positive bacteria.

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