Gram-Positive Cocci Lab Report

Gram-positive cocci are an interesting group of bacteria to study. Some common species include Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Streptococcus pyogenes, and Sarcina lutea. Gram-positive cocci have a gram positive cell wall, cocci morphology and many different styles of grouping. Some species have begun to exhibit a resistance to fluoroquinolone by the use of altering the drug binding site and the use of a membrane pump (Hooper 2002). Thanks to the resistance to this antibiotic, this opens the door to superinfections. Superinfections occur when an antibiotic eliminates competing bacteria and allows the mutant and resistant survivors to repopulate. Superinfections can be dangerous especially in immunocompromised …show more content…
I will start with Tube A which was examined under a microscope and found to be a gram-positive staphylococcus cocci. Upon receiving the tube, I looked over the results from our cocci report. I chose to streak a Sheep’s Blood Agar plate first. My thinking was if I were to observe weak beta hemolysis then I would have either Staphylococcus aureas or Streptococcus pyogenes. If the results were gamma then I would eliminate Staphylococcus aureas and Streptococcus pyogenes and narrow down my organism to Staphylococcus epidermidis, Enterococcus faecalis, or Sarcina lutea. After two days I returned to the lab to discover my organism exhibits gamma …show more content…
For my first plate I decided to use an Eosin Methylene Blue. This plate gives a variety of different results that are easy to interpret. A metallic green color indicates either Escherichia coli or Citrobacter freundii, purple can indicate Enterobacter aerogenes, and a pink color occurs when Serratia marcescens is plated on an Eosin Methylene Blue plate. Upon entering the lab, I discovered metallic green colonies on the plate. I then knew I had either Escherichia coli or Citrobacter freundii. To find out which I chose to inoculate a tryptophan broth with my