Chapter 7 On The Rate Of Microbial Death

Front 1

What is the relation between bacterial populations and the treatment of antimicrobial chemicals or heat? Give an example.

Back 1

The relation is that bacterial populations usually die at a constant rate. For example a microbial exponential death rate: 1,000,000 microbes have been treated for a minute and 100,000 is left. If treated for another minute; only 10,000 is left. So 90% of the remaining population is killed every minute.

Front 2

If the death curve is plotted logarithmically, the death rate is constant. What will the log scale look like in a graph?

Back 2

The log scale will be a straight line.

Front 3

What is the relation of the number of microbes and time the population takes to eliminate fully?

Back 3

The more microbes there are to begin with, the longer it takes to eliminate the entire population.

Front 4

Give an example of the relation between microbes and environmental influences.

Back 4

The presence of organic matter inhibits the actions of chemical microbials. Blood, vomit and feces influences the selection of disinfectants. Biofilms are difficult for biocides to reach effectively because the effectiveness is due to a certain temperature; disinfectants work better under warm conditions. Fats and proteins are especially protective to microbes. Heat works better in an acidic condition.

Front 5

Give an example between time of exposure and chemical antimicrobials applied on microbes.

Back 5

Chemical antimicrobials require extended exposure to affect more resistant microbes or endospores.

Front 6

Give an example of the relation between microbial characteristics, disinfectants and antiseptics.

Back 6

Gram negative bacteria are more resistant than gram positive bacteria to disinfectants and antiseptics. Mycobacteria, endospores, protozoan cyst and oocyst are very resistant to disinfectants and antiseptics. Nonenveloped viruses are more resistant than enveloped viruses. Prions are resistant to disinfectants and autoclaving.