ANTIMICROBIAL CHEMICALS
Disinfectants, Antiseptics, and Spices
Many herbs and spices MAY have (some documented, some just hearsay) antimicrobial
activity: thyme, cinnamon, garlic, ginger, chamomile, oregano, sage, echinacea, wasabi,
etc. We are going to try some out in this lab: fresh or dried, leaf or powder. In addition, you
will be running various antimicrobial chemicals against your bacteria. To save on time, for the
identification of antibacterial spices, each group will extract a different plant tissue and prepare
enough herb/spice extract for each group. Each table will run 2 bacterial organisms with the 4
disinfectants and antiseptics along with the spice extract for their table plus 1 from another
table. Therefore, each table will be running 6 chemicals against 2 bacterial organisms.
OBJECTIVES:
Compare the antimicrobial capabilities of different antiseptic and disinfectant chemicals.
Identify which categories of chemicals are most effective.
Identify antimicrobial properties of some plants.
MATERIALS NEEDED: per table
broth cultures of Staphylococcus and E. coli or other bacteria
TSA plates
sterile cotton swabs
sterile paper disks
an herb or spice extract (1 per table)
antiseptic and disinfectant chemicals (at least 4 per table)
small beakers for antiseptics and disinfectants
forceps and beakers of ethanol
1ml pipettes + pi-pump
PROCEDURES:
Prior to the Lab
Pick an antimicrobial chemical (NOT an antibiotic) that you have at home or work, or bring a chemical from the
store. Bring the following information on your chemical:
the brand name of the antiseptic/disinfectant
the active chemical ingredient (not the inert chemicals such as glucose or water)
The herb extracts
1. The herb extracts have already been made for you, using about a half-dozen kinds of
herbs. Your table will receive 1 or 2 of these extracts to use along with your
antimicrobial chemicals.
2. The herbal extracts will be added to small cotton discs which will be placed on the
placed containing the bacterial. The discs may already be saturated with the herbal
extract, or you may have to do that in lab. You will be directed by your instructor.
Using The Spice/herb Extracts and Antimicrobial Chemicals
1. Inoculate a TSA plate with 1 bacterium, using a sterile cotton swab to pick up an
inoculum from the broth and then covering the agar plate thoroughly. Use a tight zigzag procedure to cover the ENTIRE AGAR SURFACE with the inoculum.
2. Your table can choose 4-5 antimicrobial chemicals plus 2 spices/herbs to test each
organism against. That will be 6 discs on each agar plate.
3. Pour a small amount of each of your antiseptics and disinfectants, plus 1-2 spice/herb
extracts into each of the beakers.
4. Using alcohol-flamed forceps, pick up a sterile paper disk and dip it halfway into one of
the antimicrobial solutions, then place the disk on the inoculated media.
5. Repeat the procedure with the other chemicals. Both organisms will be tested with the
same chemicals.
6. Incubate the plates at room temperature, 25 oC or 37 oC, depending on what your
instructor says.
7. AFTER INCUBATION, measure the zone of inhibition for each chemical in
millimeters . If there is no zone around the disk, call it 0.
8. Record the results for the entire class in the table on this handout.
INTERPRETATION:
Record the results for the various chemicals and spices used in this exercise.
DIAMETER ZONE OF INHIBITION
(in mm)
Chemical (brand name) or Spice
Active Ingredient
Staph
E. coli
QUESTIONS:
1. The space created around the chemical disc is called the ________________.
2. The most effective active ingredients found in the store-bought chemicals was:
LAB MANUAL: TABLE OF CONTENTS
Fall 2015 – Jackie Reynolds, Richland College, BIOL 2421