Antibiotics are medicines that kill harmful germs or stop them from growing, and cattle producers sometimes add them to animal feed. Traces can remain in the meat and keep killing bacteria long after. To test this, you swab agar dishes with juice from standard and natural ground beef brands, then incubate all six plates for five days. Natural beef averaged 31 percent bacterial coverage versus 30 percent for standard beef — suggesting natural beef carried fewer antibiotic residues, leaving more bacteria alive to grow.

Antibiotics kill harmful germs or stop them from growing, and their strength can be measured by how wide a clear ring forms around a treated disk. This project puts that to the test, comparing prescription antibiotics, over-the-counter acne creams, and plant extracts like oregano oil and tea tree oil against Propionibacterium acnes. Disks soaked in each treatment go onto agar plates with the bacteria, and after incubation you measure the inhibition zone — the clear ring where bacteria cannot grow. The prescription antibiotics produced the largest zones overall, though oregano oil ranked third, an unexpected result among the store-bought and plant-based options.

Antibiotics kill harmful bacteria or stop them from growing, but repeated exposure can leave some bacteria alive — and those survivors keep growing anyway. This two-part project tests that dynamic directly. First, you press everyday objects onto agar plates, one containing an antibiotic in the medium, and compare growth after a week. Then you streak E. coli across a fresh plate and place disks of penicillin G and tetracycline on it. After incubation, the clear zone around each disk reveals whether E. coli is sensitive or resistant to that antibiotic.

Antibiotics kill harmful germs or stop them from growing, but not all antibiotics stop the same germ with equal strength. To find out which works best, you swab the hands of ten people and grow the bacteria on blood agar plates. After identifying coagulase-negative staphylococcus through gram staining and catalase testing, you spread it on Mueller Hinton plates and place discs soaked in different antibiotics on each plate. After overnight incubation, measuring the death zone around each disc with a caliper reveals which antibiotic destroys this common skin bacterium most effectively.

Antibiotics kill harmful germs or stop them from growing, and different medications can halt the same bacterium across very different distances. This project tests three acne treatments against Propionibacterium acnes — the skin bacterium that triggers inflammation when it multiplies too fast. You spread P. acnes across three agar plates, then place a filter paper disk soaked in Tetracycline, Clindamycin, or Benzoyl peroxide on each. After four days, measuring the inhibition zone around each disk shows which stopped bacterial growth across the widest area. Tetracycline produced the largest zone at 48mm, followed by Clindamycin at 44mm and Benzoyl peroxide at 27mm.