MB 351 - Lecture 19 Flashcards
destruction of pathogens on living tissue
antisepsis
study of distribution and determinants of health-related states. the branch of medicine that deals with the incidence, distribution, and possible control of diseases and other factors relating to health.
epidemiology
17th C hospitals for childbirth become common, and doctor’s would not _________, and would not __________ in between. This caused high numbers of childbed fever/puerperal fever. The most common infection causing puerperal fever is _____________, caused by what?
-wash hands between patients, and would not change clothes -genital tract sepsis (bacterial contamination) caused by contaminated medical equipment or unhygienic medical staff who contaminate the mother’s genital tract during the delivery. -other types of infection that can lead to sepsis after childbirth include urinary tract infection, breast infection (mastitis) and respiratory tract infections -resulted in high death rates of women giving birth in America and Europe prior to the late 1800s.
Hungarian physician who is called the “saviour of mothers.” What did he do? Before Robert Koch and Louis Pasteur
Ignaz Philipp Semmelweis (one of the pioneers of antiseptic procedures) -discovered in 1847 that the incidence of puerperal fever could be drastically cut by use of hand washing standards in obstetrical clinics. -introduced washing hands with chlorinated lime solutions, and this reduced the incidence of fatal puerperal fever from about 10 percent to about 1-2 percent
At first he was ridiculed for his hypothesis that there was only one cause, that all that mattered was cleanliness. Why was his hypothesis considered extreme?
Ignaz Philipp Semmelweis. He was dismissed from the hospital and harassed by the medical community. Semmelweis’ practice only earned widespread acceptance years after his death, when Louis Pasteur and Robert Koch provided evidence for the germ theory of disease.
A British surgeon who was also a pioneer in the control of microbial growth. Awareness of Semmelweis’s work and together with Pasteur’s work, realized the true nature of infectious disease, and used this to help his surgery patients. What did he use to reduce the number of microorganisms on wounds and incisions? He also started doing what in his operating room?
Lord Joseph Lister (1867) -bandages treated with phenol (aka carbolic acid) -started washing everything in his operating room
an aromatic organic compound that kills microorganisms by denaturing their proteins and disrupting the cell membrane, used by Lister. How would Lister apply this? The use of this greatly reduced…
phenol (carbolic acid) -spraying the wound with a fine mist of phenol -reduced the rate of infection and mortality of surgery patients, lending further credence to the germ theory of disease.
HOW DOES PHENOL KILL MICROBES?
CREDITED for developing the use of antiseptics (compounds used on living tissue to kill microbes), and aseptic surgery (techniques used to minimize microbial contamination). Earned a reputation as the world’s safest surgeon.
Lord Joseph Lister
Major problem with phenol?
IRRITATING to eyes and skin, and bad odor. Some forms may cause brain damage in infants.
How is phenol still used today?
In throat lozenges and in throat sprays
Inspiration for the modern antiseptic mouthwash product _________ . This does not contain _______ , but does contain what?
Listerine - LISTER. Did not develop it, but a way to recognize his work. -does not contain phenol, but does contain eucalyptol, methanol, thymol, etc. which in combination have antiseptic effect
Lister introduced these ________ : these are techniques to prevent microbial contamination of what? Where are these techniques also applied?
aseptic techniques: prevent microbial contamination of instruments, lab benches and workstations, patients, surgical rooms. -in work at research labs, the food industry, and pharmaceutical companies that produce medicines and other health products
Very specific meaning, which is the complete destruction or removal of ALL viable (living) microorganisms. Frequently achieved by ________ or ________ treatments.
Sterilization. -chemical and physical treatments
Most common method used for killing microbes
HEAT
Cells that are actively growing or dividing
vegetative cells
Highly resistant dormant forms of microbes
endospores
Bacteriostatic compounds often have a reversible effect since they do not kill the bacteria, but inhibit growth. What does this growth graph look like? And explain.
It is often reversible, if you remove the bacteriostatic compound, the organism will start to grow again. In this graph, it shows that bacteriostatic compounds when used on a growing population of cells (y axis represents log cell number is increasing) and at a specific point in time (indicated by the arrow), a bacteriostatic agent is used, then the number of microbial cells cease to increase or decrease, it stays the same, your total cell count using a direct microscopic count is the same as the viable cell count (using the plate count method).
Bacteriocidal agents will prevent growth by killing the cells, it does not destroy/lyse the cells. So what does the graph look like, and explain.
Microbes are still physically there and can be counted, but there is no cell lysis (cells are still intact), so if you were to do a total cell count using a direct microscopic count, it would appear that there was no change in cell number. However, the viable cell count goes down-meaning the number of cells you plate out on an agar plate will decrease since you have killed the cells with your agent, so they will not grow.
Bacteriolytic agents will induce killing by cell lysis. Growth graph, and explain. What is an example of a bacteriolytic agent, and what does it do?
During lysis, the cell components are released into the media and there appears to be a dramatic decrease in the total cell count (when a cell lyses, there is no microbial “body” left, and the culture media starts to look less cloudy or turbid). The viable cell count also goes down since there are fewer living cells and thus fewer will grow up on a viable plate count.
-penicillin, it stops the enzyme that crosslinks peptidoglycan, the cell wall structure becomes compromised, and the cell goes through osmotic lysis (too much water coming into the cell).
When bacterial populations are heated or treated with antimicrobial chemicals, they usually die at a _______ ________ . Rates are generally constant on a _____ _____ ______ .
- constant rate
- on a semi log plot
When bacterial populations are heated or treated with antimicrobial chemicals, they usually die at a constant rate. For example, suppose a population of 1 million microbes has been treated for 1 minute and 90% of the population has died. We are now left with 100,000 microbes. If the population is treated again for another minute, 90% of those microbes die, and we are left with 10,000 survivors. In other words, for each minute the treatment is applied, 90% of the remaining population is killed (Table 7.2). Rates are generally constant on a semi log plot: (ie 90% of survivors die per unit time)
If the microbial death curve is plotted logarithmically, the death rate is ______ , as shown by the graph. What is the length of time it takes for an antimicrobial treatment to decrease the population by 1 log called? There is a name for this.
- death rate is constant
- decimal reduction time (D)
- plotting arithmetically is impractical
The kinetics of death are very similar to the kinetics of growth, it is influenced by: Population size, the more microbes there are to begin with, the longer it takes to eliminate the entire population (Fig. 7.1, right, high vs. low population load). If the rate of killing is the same, it will take longer to kill all members of a larger population than a smaller one. This is true in both heat and chemical treatments. Another factor that influences the death rate are environmental influences: such as temperature, age of cells (old cells are harder to kill, so are endospores). Eg. The presence of organic matter often inhibits the action of chemical antimicrobials. Microbes in surface biofilms are difficult for microbiocides to reach effectively. A third factor is the time of exposure, chemical antimicrobials often require extended exposure to more resistant microbes or endospores to be affected.
What is the D-value for 50, 60, 70 degrees celcius?
70C D = 3 mins
60C D = 12 mins
50C D = 42 mins
Check your understanding:
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Learning Objectives
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