Microbiology Lab HW Help Please?

microman

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12 years ago

Is the disk-diffusion technique measuring bacteriostatic or bactericidal activity? Briefly explain.

In which growth phase is an organism most sensitive toa chemotherapeutic agent?

Thanks for any help

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firestorm

wrote...

12 years ago

It depends on the antibiotic. Some are bactericidal, some are bacteriostatic.

During the exponential growth phase, bacteria are most vulnerable since many metabolic pathways are switched on, the cell wall is at its most plastic, and replication is occurring.

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askal

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12 years ago

It measures how affective anti-biotics are at stopping/killing bacteria.
It really only affects bactericidal activity, which kills the bacteria. bacteriostatic stop the bacteria from growing and breeding.

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askollmeyer

wrote...

12 years ago

It depends on which antibiotics you use. Some are bacteriostatic (they inhibit the growth of microorganisms but not completely kill them) others are bactericidal (they kill microorganisms). So it depends on which antibiotics one uses. Disk-diffusion technique can be used to measure both.

In the exponential phase, microorganisms are more sensitive to a chemotherapeutic agent. It's because the bacterial cells are rapidly undergoing growth in this phase. Cells are very metabolically active in this phase. Synthesis of cell walls, DNA replication and other cellular processes are very active during this phase. So, it is easy to inhibt the growth if proper antibiotic is used during the exponential phase.

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tommyt_

wrote...

12 years ago

Disk Diffusion test or Kirby-Bauer Test is "useless when a bactericidal drug is required, since the diskdiffusion test measures only bacteriostatic activity".

Broth dilution susceptibility tests are used to determine the minimal inhibitory (MIC) and bactericidal (MBC) concentrations of antibiotics.

Orgamisms are most susceptible in the LOG phase a.k.a EXPONENTIAL Phase.

Good Luck!

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