The antimicrobial spectrum of different antibiotics is different, some antibiotics only have antibacterial effects on a few bacteria, polymyxin only has an effect on Gram-negative bacteria, this type of antibiotic is called a narrow-spectrum antibiotic; while other antibiotics have an effect on a wide range of bacteria, for example, tetracycline, oxytetracycline, and hyoscyamine have an effect on many gram-positive and gram-negative bacteria, this type of antibiotic is called a broad-spectrum antibiotic.

Operation method

Influence of biological factors on microorganisms

Principle

If a bacterium producing a certain antibiotic is inoculated in a straight line on a plate of bean sprout juice glucose agar medium, after incubation, a band of bacteria will grow and produce a certain antibiotic to spread around the band. And then with this band perpendicular to the straight line inoculation of some different test bacteria, will produce different lengths of the inhibition band. According to the length of the inhibitory band, the effect of the antibiotic on different microorganisms can be judged. This experiment illustrates the inhibitory effect of penicillin produced by Penicillium chrysogenum on Escherichia coli, Staphylococcus aureus and Bacillus subtilis.

Materials and Instruments

Penicillium chrysogenum, Escherichia coli, Staphylococcus aureus Bacillus subtilis
Soybean sprout juice dextrose agar medium
Flat dish Inoculation ring

Move

1. Dissolve bean sprout juice dextrose agar medium, cool to about 45℃ and pour the plate, solidify and wait for use.
2. Pick the spores of A. flavus with an inoculating loop and draw a straight line on the plate.
3. After inoculation, invert and incubate in a greenhouse at 28°C for 2 to 3 days.
4. After the formation of fungal moss on the above plate, then use the inoculation ring to inoculate Escherichia coli and Staphylococcus aureus by drawing a straight line vertically outward from the edge of the band of Penicillium xanthum, but do not touch the fungal moss, respectively,
Bacillus subtilis.
5. Place upside down in a greenhouse at 37°C for 24 hours.
6. Observations.

For more product details, please visit Aladdin Scientific website.

https://www.aladdinsci.com/