Videos
Is the disk-diffusion technique measuring bacteriostatic or bactericidal activity? Briefly explain.
To write:
The nature of the activity of the disc-diffusion technique.
Introduction:
The disc-diffusion method is also called Kirby-Bauer test. It is a technique that tests the effectiveness of the antibiotics on a specific microorganism. An agar plate is spread with bacteria and then, paper discs of antibiotics are added to it. The bacteria are allowed to grow on the agar media and inhibition zones are observed.
Explanation of Solution
Antibiotics eliminate the bacteria completely. They are categorized as bactericidal, that is potent and bacteriostatic, which hampers growth. Bactericidal antibiotics kill the bacteria directly while the bacteriostatic antibiotics inhibit the bacteria from growing. The disc-diffusion technique works both by inhibiting the growth as well as by killing the bacteria.
The zone of inhibition is formed around the antibiotic discs. Bigger is the area, maximum will be the activity of the antibiotic. Similarly, lesser is the area, the minimum will be the activity of the antibiotic. Around the antibiotic discs, bacteria are not grown in any case nor the bacteria have been killed. They kill the bacteria as well as inhibit the growth also. They act both ways of the action.
Thus, disc-diffusion technique measured both the ways of bactericidal as well as bacteriostatic activity as they inhibit bacterial growth and killed the bacteria as well.
Want to see more full solutions like this?
Chapter 25 Solutions
Laboratory Experiments in Microbiology (11th Edition)
- Differentiate the growth curve exhibited by the same inoculum under the following conditions. Draw and label the parts of your growth curve. A). If it is exponentially growing and inoculated in the same nutritious medium under the same optimum conditions. B). If it is taken from an old culture and inoculated into the same nutritious medium and incubated under the same optimum conditions in (A). C). If it is taken from an old culture and inoculated to a different and less nutritious medium and incubated under the same optimum conditions as (A).arrow_forwardThe ribosome is the target for many important antibiotics. These drugs must discriminate between bacterial and eukaryotic ribosomes to achieve drug specificity and toxicity. For the two common antibiotics below, what is their mechanism of action and why are they more toxic to bacteria than eukaryotes? a) Tetracycline b) Erythromycinarrow_forward1) The inactivation of Staphylococcus aureus was studied in pomegranate juice heated at 75°- 95°C. The slopes for the inactivation of this bacteria were calculated from the linear lines in semi-log graphical paper. The slope values were presented in Table 1. a) Determine the temperature change needed to inactivate this bacteria by 90%. b) Temperature change to inactivate Bacillus cereus in pomegranate juice by 90% at the same temperature range was 29°F. At 75°-95°C temperature range, which bacteria will be more affected by the temperature changes? Commend on your answer in one sentence Table 1- Slope values for the inactivation of Staphylococcus aureus in pomegranate juice heated at various temperature Temp. (°C) 75 80 85 95 -Slope x 10² (min-¹) 2.222 3.704 5.000 13.158arrow_forward
- Explain why the growth of both the strains A and C in medium III is not similar to that of strain B. Use the appropriate vocabulary and provide one putative explanation for strain A.arrow_forwardWhat is the mode of action for kanamycin? Is it bacteriostatic or bactericidal? https://pubchem.ncbi.nlm.nih.gov/compound/Kanamycinarrow_forwardWhat is an IgAase and why would a bacterial pathogenproduce one?arrow_forward
- 1.). a.) What particular pathways or enzymes appear distinct for sulfate reducing bacteria in order to harness energy (create ATP)? b.) What interesting structures or unique characteristics allowed sulfate reducing bacteria to solve physical and/or chemical challenges/problems in conserving energy?arrow_forwardCompare and contrast bacteriocidal, bacteriostatic and bacteriolytic agents. What are their effects on the optical density (OD) and viable count of a bacterial culture, respectively?arrow_forwardIn Methicillin resistant bacteria, what have the bacteria developed that allows them to stay alive in the presence of Methicillin?arrow_forward
- In a certain culture of bacteria, the rate of increase is proportional to the number present. (a) if it is found that the number doubles in 6 hours, how many may be expected at the end of 18 hours? (b) If there are 10^2 at the end of 4 hours and 8(10^2) at the end of 8 hours, how many were at the beginning?arrow_forwardStrain X. spp. is a rod-shaped, anaerobic, Gram-positive bacterium with peritrichous flagella andpili that could use glucose and dye as its sole carbon source. Answer the following sections (a, band c).a) With a doubling time of 240 minutes and a starting population size of 10 bacteria cells. Howmany bacteria cells will be present after 72 hours, assuming no cell death?b) Draw the diagram and describe motility required for the bacteria to gradient concentrationof attractant (food)?arrow_forwardAssume that you counted 67 plaques on a bacterial plate where 0.1ml of a 10-5 dilution of phage was added to bacterial culture. What is the initial concentration of the undiluted phage? Show your calculations and give your answer in pfu/ml (pfu = plaque-forming units)arrow_forward
