The antibiotic, tetracycline was serially diluted (2-fold dilutions), starting with tube #1 (100 g/ml) and ending with

The antibiotic, tetracycline was serially diluted (2-fold dilutions), starting with tube #1 (100 µg/ml) and ending with tube #9 (tube #10 = Control).

Tetracycline is a yellow powder that is freely soluble in water. To prepare the tetracycline solution, dissolve the powder in water, with heating, to make 50 mg/ml.

1. A constant amount of bacteria was added to all tubes and they were incubated at 37°C for 18-24 hours.
2. Mix each tube and examine them for growth, comparing each tube to the Control. The MIC is the lowest concentration of antibiotic that still inhibits growth. Refer to Fig.4 and 5  and fill out the table below. Put a checkmark on those with growth (5 points).

Tube #	1	2	3	4	5	6	7	8	9	10
Tetracycline concentration
Growth (tube)
Growth (plate)

Figure 4.

Figure 5.

THE MIC OF TETRACYCLINE FOR THIS STRAIN OF E. coli IS _____µg/ml.

5. From each of the NEGATIVE tubes (tubes in which no growth is apparent) and the Control tube, samples were swabbed onto the surface of a TSA plate.
6. The plate was incubated at 37°C for 18-24 hours.
7. The MBC is the least concentration of antibiotic that does not permit growth.

THE MBC OF TETRACYCLINE FOR THIS STRAIN OF E. coli IS _____µg/ml. 

With which kind of antibiotic (static or cidal) would you expect the MIC and MBC to be about the same concentration and to be vastly different concentrations?

Transcribed Image Text:

4 5 6 7 to 4 5 6 7 to

Answer rating: 100% (QA)

Testube 1 2 3 4 5 6 7 8 9 10 Dilution microgram ml 100 50 25 125 625 3125 15625 078125 0390 Con... View the full answer