Chapter 5: Control of Microbial Growth. Important Point:. If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!. Methods are employed to destroy, remove, and/or inhibit the growth of microorganisms.
If you are having trouble
understanding lecture material:
Try reading your text
before attending lectures.
And take the time to read it well!
I’m not sure why these Ss are missing!
“Minimizing the numbers of microorganisms in a hospital is particularly important because of the danger
of hospital-acquired, or nosocomial, infections. Hospitalized patients are often more susceptible to
infectious agents because of their weakened condition. In addition, patients may be subject to invasive
procedures such as surgery, which breaches the intact skin that would otherwise help prevent infection.
Finally, pathogens are more likely to be found in hospitals because of the high concentration of patients
with infectious disease. These patients may shed pathogens in their feces, urine, respiratory droplets, or
other body secretions. Thus, hospitals must be scrupulous in their control of microorganisms. Nowhere
is this more important than in the operating room, where instruments used in invasive procedures must
be sterile to avoid introducing even normally benign microbes into deep body tissue where they could easily establish infection.”Nosocomial Infections
“It takes more time to kill a large population of bacteria than it does to kill a small population, because only a fraction of organisms die during a given time interval.Exponential Death
10 min boiling (at sea level).
121°C for 15 min to kill endospores (but must be penetrating, moist heat, and 15 min at 121°C)
But don’t use scented chlorine bleach to purify water!
Note that temperature can affect rate of water purification (i.e., cold water purifies slowly).
Today iodine is more often used as an iodophore which is a less-irritating, slow-release form of iodine.
Iodine typically is used as a tincture (i.e., dissolved in alcohol).
Watch out because Pseudomonas spp. can live and grow in some iodophores!
However, HOOH is still useful for supplying oxygen to otherwise anaerobic environments.
Bacteria removal is not quite equivalent to sterilization. than it does to kill a small population, because only a fraction of organisms die during a given time interval.Membrane Filtration of Liquids
Bacteria removal is easier than removal of viruses.