Resistance in microbes
0
Concepts in antimicrobial control
Sterilization- Destroys and removes all viable microbes, including viruses and endosporesDisinfection- Physical process or chemical agent that destroys vegetative pathogens, but not spores. Also removes toxinsSanitization/Decontamination- Cleaning process that physically removes microbes and other debris from objects Antisepsis/Degermination- Reduces the number of microbes on human skin. Decontamination of living tissue
For the above, what types of chemical and physical agent could be used to achieve them?
Sterilization- Reserved for use on inanimate objects. Examples include heat, autoclave, and chemical sterilantsDisinfection- Used on inanimate objects because it is too harsh for human skin. Examples include bleach, iodine, and boilingSanitization/Decontamination- Useful in the food and beverage industry. Can be used to clean large amounts of objects Antisepsis/Degermination- Involves both scrubbing of the skin and use of antiseptic chemicals. Examples include alcohol sanitizer, surgical hand scrubs, soaps
What are normal skin biota?
Not harmful to us and in some cases can be beneficial, but are in constant competition with transient organismsEx: M luteus, S epidermidis, S aureus, Corynebacterium, Propionibacterium acnes
What are transient organisms?
Transient organisms are found on our skin, but do not normally grow there and are usually acquired through contact with a contaminated surface
3 major components of handwashing
- Soap or detergent- Friction- Incorporation of antiseptic into soap
How does a surfactant (i.e. soap) work to rid us of transients?
- Surfactant insert into the lipid bilayer, disrupt it, and create abnormal channels that alter permeability and cause leakage both into and out of the cell. Emulsifies skin oils that have transient bacteria trapped in them. - Binds to oils in skin that contain bacteria - Emulsify oils and allow them to be scrubbed off - Can disrupt the cell membrane
What are some of the limits of surfactants like soap?
- Some bacteria (mycobacteria) have waxy cell walls that resist surfactants - Endospores are usually not affected
Why is it so important for clinicians to wash their hands between patients?
- So they do not transfer one patient's bacteria to another
In general, what are the most difficult and least difficult organisms to kill?
- Most difficult: organisms containing prions (Ex: Bacillus cereus - 7 day culture)- Least difficult: enveloped viruses (Ex: Micrococcus luteus - 24 hour culture)
How does UV radiation kill bacteria? What does it do to the DNA of the cells?
UV (non-ionizing) radiation kills by damaging the DNA and creating thymine dimers between adjacent thymine or cytosine in the DNA
What are some of the limitations of using UV light to kill microbes?
- Can't penetrate plastic, glass- Can only be used on surfaces, air, and water- Not good on living tissue
Results of Lab
Most resistant to killing by UV: Bacillus cereus, because it has the ability to produce endosporesWhy wouldn't UV inhibit growth? Not on long enough, plastic covering
Know the difference between disinfectants and antiseptics
Disinfectants- are chemicals used on inanimate objects Antiseptics- are chemicals used on living tissues
Know the difference between bactericidal and bacteriostatic agents
Bactericidal agents- kill bacteriaBacteriostatic agents- can inhibit growth for a period of time
Why do we have to leave most disinfectants on surfaces for at least 10-20 minutes in order to be most effective? What is the time called?
Dwell time- it is how long a compound must be left on a surface in order for it to be effective
Antimicrobial
Anything that kills or inhibits the growth of microorganisms (can be a drug, natural substance, chemicals, etc)
Antibiotics
A chemical made by microorganisms to kill or inhibit other microorganisms (think about penicillin and cephalosporin from fungi)
Difference between broad and narrow spectrum antibiotics
Broad- work well against a variety og bacterial typesNarrow- work only against specific types of bacteria
What is the zone of inhibition when we do the Kirby-Bauer method?
The zone of inhibition is the area/ring around the disk where the bacteria did not grow
What does it mean for a bacteria to be sensitive, intermediate, or resistant to an antibiotic in the K-B test?
Sensitive- antibiotic would be effective to use against the bacteria Intermediate- antibiotic has some effect against the antibiotic Resistant- antibiotic is not effective against the bacteria
Questions for results of lab
Three types of organisms used: Escherichia coli (Ec), Pseudomonas aeruginosa (Pa), Staphylococcus aureus (Sa)Most sensitive: SaMost resistant: Pa
Choices if organism was intermediately sensitive to certain antibiotics
If the organism is only intermediately sensitive, then you could use two antibiotics in order to help further the process. If you have a sensitive, always go with that
Ways infectious diseases can be transmitted
- There are several routes by which pathogens can be introduced into the body (air, water, food, vectors, fomites)- Several ways in which epidemics can be propagated (direct contact, airborne, fecal-oral, and droplet)
What is a fomite and a vector in terms of disease transmission?
Fomites- inanimate objects that carry infection Vector- an organism (alive) that does not cause disease itself, but spreads infectious agent/toxin from the same source
How was our infection transmitted?
Through direct contact
Define prevalence and incidence rate
- Incidence is the number of new cases being reported in a time period. This is divided by the population at risk at a given point in time- Prevalence is the number of people who are sick at any given time. Also known as the burden of disease
Index case
First patient(s)
Calculate incidence rate and prevalence for our disease
Incidence = (# of new cases in a time period / size of population at specific time) x 10^n Prevalence = (# of new cases in a time period/ size of population at a specific time) x 10^n
How do we interpret non- Serratia growth on the plates?
Direct contact
What are MMWR reports?
Morbidity and mortality weekly report. It is produced by the Center for Disease Control and Prevention. Epidemiological tracking system for infectious diseases
Resistance in microbes
0
Concepts in antimicrobial control
Sterilization- Destroys and removes all viable microbes, including viruses and endosporesDisinfection- Physical process or chemical agent that destroys vegetative pathogens, but not spores. Also removes toxinsSanitization/Decontamination- Cleaning process that physically removes microbes and other debris from objects Antisepsis/Degermination- Reduces the number of microbes on human skin. Decontamination of living tissue
For the above, what types of chemical and physical agent could be used to achieve them?
Sterilization- Reserved for use on inanimate objects. Examples include heat, autoclave, and chemical sterilantsDisinfection- Used on inanimate objects because it is too harsh for human skin. Examples include bleach, iodine, and boilingSanitization/Decontamination- Useful in the food and beverage industry. Can be used to clean large amounts of objects Antisepsis/Degermination- Involves both scrubbing of the skin and use of antiseptic chemicals. Examples include alcohol sanitizer, surgical hand scrubs, soaps
What are normal skin biota?
Not harmful to us and in some cases can be beneficial, but are in constant competition with transient organismsEx: M luteus, S epidermidis, S aureus, Corynebacterium, Propionibacterium acnes
What are transient organisms?
Transient organisms are found on our skin, but do not normally grow there and are usually acquired through contact with a contaminated surface
3 major components of handwashing
- Soap or detergent- Friction- Incorporation of antiseptic into soap
How does a surfactant (i.e. soap) work to rid us of transients?
- Surfactant insert into the lipid bilayer, disrupt it, and create abnormal channels that alter permeability and cause leakage both into and out of the cell. Emulsifies skin oils that have transient bacteria trapped in them. - Binds to oils in skin that contain bacteria - Emulsify oils and allow them to be scrubbed off - Can disrupt the cell membrane
What are some of the limits of surfactants like soap?
- Some bacteria (mycobacteria) have waxy cell walls that resist surfactants - Endospores are usually not affected
Why is it so important for clinicians to wash their hands between patients?
- So they do not transfer one patient's bacteria to another
In general, what are the most difficult and least difficult organisms to kill?
- Most difficult: organisms containing prions (Ex: Bacillus cereus - 7 day culture)- Least difficult: enveloped viruses (Ex: Micrococcus luteus - 24 hour culture)
How does UV radiation kill bacteria? What does it do to the DNA of the cells?
UV (non-ionizing) radiation kills by damaging the DNA and creating thymine dimers between adjacent thymine or cytosine in the DNA
What are some of the limitations of using UV light to kill microbes?
- Can't penetrate plastic, glass- Can only be used on surfaces, air, and water- Not good on living tissue
Results of Lab
Most resistant to killing by UV: Bacillus cereus, because it has the ability to produce endosporesWhy wouldn't UV inhibit growth? Not on long enough, plastic covering
Know the difference between disinfectants and antiseptics
Disinfectants- are chemicals used on inanimate objects Antiseptics- are chemicals used on living tissues
Know the difference between bactericidal and bacteriostatic agents
Bactericidal agents- kill bacteriaBacteriostatic agents- can inhibit growth for a period of time
Why do we have to leave most disinfectants on surfaces for at least 10-20 minutes in order to be most effective? What is the time called?
Dwell time- it is how long a compound must be left on a surface in order for it to be effective
Antimicrobial
Anything that kills or inhibits the growth of microorganisms (can be a drug, natural substance, chemicals, etc)
Antibiotics
A chemical made by microorganisms to kill or inhibit other microorganisms (think about penicillin and cephalosporin from fungi)
Difference between broad and narrow spectrum antibiotics
Broad- work well against a variety og bacterial typesNarrow- work only against specific types of bacteria
What is the zone of inhibition when we do the Kirby-Bauer method?
The zone of inhibition is the area/ring around the disk where the bacteria did not grow
What does it mean for a bacteria to be sensitive, intermediate, or resistant to an antibiotic in the K-B test?
Sensitive- antibiotic would be effective to use against the bacteria Intermediate- antibiotic has some effect against the antibiotic Resistant- antibiotic is not effective against the bacteria
Questions for results of lab
Three types of organisms used: Escherichia coli (Ec), Pseudomonas aeruginosa (Pa), Staphylococcus aureus (Sa)Most sensitive: SaMost resistant: Pa
Choices if organism was intermediately sensitive to certain antibiotics
If the organism is only intermediately sensitive, then you could use two antibiotics in order to help further the process. If you have a sensitive, always go with that
Ways infectious diseases can be transmitted
- There are several routes by which pathogens can be introduced into the body (air, water, food, vectors, fomites)- Several ways in which epidemics can be propagated (direct contact, airborne, fecal-oral, and droplet)
What is a fomite and a vector in terms of disease transmission?
Fomites- inanimate objects that carry infection Vector- an organism (alive) that does not cause disease itself, but spreads infectious agent/toxin from the same source
How was our infection transmitted?
Through direct contact
Define prevalence and incidence rate
- Incidence is the number of new cases being reported in a time period. This is divided by the population at risk at a given point in time- Prevalence is the number of people who are sick at any given time. Also known as the burden of disease
Index case
First patient(s)
Calculate incidence rate and prevalence for our disease
Incidence = (# of new cases in a time period / size of population at specific time) x 10^n Prevalence = (# of new cases in a time period/ size of population at a specific time) x 10^n
How do we interpret non- Serratia growth on the plates?
Direct contact
What are MMWR reports?
Morbidity and mortality weekly report. It is produced by the Center for Disease Control and Prevention. Epidemiological tracking system for infectious diseases