Micro Lab Exam 3 Study Guide

Q: Difference between Sterilization, Disinfection, Sanitization and Antisepsis

Sterilization (heat) : destroys and removes all viruses and endospores (inanimate objects) Disinfection (bleach) : physical process or a chemical agent to destroy vegetive pathogens (inanimate, damaging to human tissue) Sanitization (soap) : cleansing technique that mechanically removes microbes as well as other debris (household use) Antisepsis (alcohol) : Reduces the number of microbes on the human skin

Q: How does UV radiation kill bacteria?

Gamma (ionizing ): radiation kills by creating free radicals within the cells. UV (nonionizing) : radiation kills by damaging the DNA and creating dimers between adjacent thymine or cytosine in the DNA.

question

What is the least resistant to more resistant microbes?

answer

- Enveloped viruses
- Most-gram positive bacteria
- Fungi and fungal spores
- Most gram-negative bacteria
- Protozoan trophozoites
- Protozoan cysts
- Staphylococcus and pseudomonas
- Mycobacterium
- Bacterial endospores
-Prions

question

Difference between Sterilization, Disinfection, Sanitization and Antisepsis

answer

Sterilization (heat): destroys and removes all viruses and endospores (inanimate objects)
Disinfection (bleach): physical process or a chemical agent to destroy vegetive pathogens (inanimate, damaging to human tissue)
Sanitization (soap): cleansing technique that mechanically removes microbes as well as other debris (household use)
Antisepsis (alcohol): Reduces the number of microbes on the human skin

question

What are normal skin biota?

answer

M luteus, S epidermidis, S aureus, Cornyebacterium, Propionibacterium acnes

question

What are transient organisms?

answer

found on our skin, but do not normally grow there and are usually acquired through contact with a contaminated surface.

question

What is the most effective way of getting transients off of our skin?

answer

hand washing

question

What are the 3 major components of handwashing?

answer

1. soap or detergent
2. friction
3. incorporation of antiseptic into soap

question

How does a surfactant (i.e. soap) work to rid us of transients?

answer

Emulsifies skin oils that have transient bacteria trapped in them which allow them to scrub off

question

What are some of the limits of surfactants like soap?

answer

some bacteria (mycobacteria) have waxy cel walls that can be resistant to surfactants

endospores are usually not affected

question

Why is it so important for clinicians to wash their hands between patients?

answer

Stops the spread of any disease or new diseases to the patient

question

In general what are the most difficult and least difficult organisms to kill?

answer

Prions are the most difficult and enveloped viruses are the least difficult

question

How does UV radiation kill bacteria?

answer

Gamma (ionizing): radiation kills by creating free radicals within the cells.
UV (nonionizing): radiation kills by damaging the DNA and creating dimers between adjacent thymine or cytosine in the DNA.

question

What does it do to the DNA of cells?

answer

radiation kills by damaging the DNA and creating dimers between adjacent thymine or cytosine in the DNA

question

What are some of the limitations of using UV light to kill microbes?

answer

- Can't penetrate plastic, glass.
- Can only be used on surfaces, air, water.
- Not good on living tissue.

question

Which bacteria was more resistant to killing by UV and why?

answer

Bacillus cereus was most resistant to killing by UV because it forms endospores which allow it to grow better in the dark

question

Think about places where UV use would work well.

answer

Hospitals

question

If your experiment didn't work, think about some reasons why the UV didn't inhibit growth.

answer

The UV light section was too tiny

question

Know the difference between bateriocidal and bacteriostatic agents

answer

Bacteriocidal: kill bacteria
Bacteriostatic: can inhibit growth for a period of time

question

Know the difference between disinfectants and antiseptics.

answer

Disinfectants: chemicals used on inanimate objects
Antiseptics: chemicals used on living tissues

question

Why do we have to leave most disinfectants on surfaces for at least 10-20 minutes in order to be most effective?

answer

To kill all the bacteria it is suppose to kill, different bacteria takes different time to kill

question

What is this time called when leaving disinfectant on surfaces?

answer

Dwell time

question

What is an antimicrobial, an antibiotic?

answer

Antimicrobials: anything that kills or inhibits the growth of microorganisms (drug, natural substance, chemicals, etc.)

Antibiotic: a chemical made by microorganism to kill or inhibit other microorganism ( penicillin and cephalosporin)

question

What's the difference between broad and narrow spectrum antibiotics?

answer

Broad spectrum antibiotics: work well against a variety of bacterial types

Narrow spectrum antibiotics: work only against specific types of bacteria.

question

What is the zone of inhibition when we do the Kirby-Bauer method?

answer

around the disk where the bacteria didn't grow

question

What does it mean for a bacteria to be sensitive, intermediate or resistant to an antibiotic in the K-B test?

answer

Sensitive - antibiotic would be effective to use against the bacteria

Intermediate - antibiotic has some effect against the bacteria.

Resistant - antibiotic is not effective against the bacteria.

question

Think about the three types of organisms that your patients were infected with in this exercise.

answer

Escherichia coli (Ec)

Pseudomonas
aeruginosa (Pa)

Staphylococcus epidermidis (Se)

question

Which bacteria was most sensitive to the antibiotics?

answer

Staphylococcus aureus

question

Which bacteria was the most resistant to the antibiotics?

answer

Pseudomonas aeruginosa

question

Think about the choices you would have to make if your organism was only intermediately sensitive to certain antibiotics.

answer

You would have to administer multiple drugs

question

Also think about what you would do if you wanted to add an additional antibiotics to your treatment plan but only had one susceptible and one intermediate?

answer

question

Also think about what you would do if you only have two intermediate antibiotics and no sensitive ones?

answer

question

Ways in which infectious diseases can be transmitted

answer

ingestion, inhalation, direct skin contact, bodily fluid contact (wounds, blood or during sex), bites, scratches.

question

What is a fomite and a vector in terms of disease transmission?

answer

Fomite: a non-moving object such as a doorknob, tissue, or used needle

Vector: a living organism such as a mosquito, fly, or tick

question

How was our infection transmitted last week?

answer

direct contact

question

Be able to define prevalence and incidence rate.

answer

Prevalence: number of people who are sick at any given time

Incidence rate: the number of new cases being reported in a time period

question

Be able to define index case

answer

First case of the disease

question

You should be able to calculate incidence rate and prevalence for our disease based upon our in class results.

answer

Incidence rate= # of new cases in a time period/size of risk population X K

Prevalence= # of existing cases at a point in time/ size of risk population X K

question

What is K in epidemiology?

answer

K varies depending on what the incidence is

question

How do we interpret non-Serratia growth on the plates (if there is growth that is not evidence of the epidemic)?

answer

That represents normal flora form our hands

question

What are the MMWR reports?

answer

Morbidity and Mortality Weekly Report

question

Who produces them?

answer

Centers for Disease Control and Prevention

question

What are two common trends we see incidence spikes for Chlamydia and Lyme disease like we discussed in class?

answer

Both increase in warmer months and mode of transmission

question

What months are the spikes likely to happen during and why?

answer

Summer months because more people are outdoors and social with one another

question

Staphylococcus aureus - S aur.

answer

- G+ cocci
- found in the nasal passages and on the skin (part of normal skin biota)
- most pathogenic of Staph (hemolysins, enterotoxins)
- food poisoning (enterotoxins)
- causes MRSA, pneumonia, meningitis, endocarditis, toxic shock syndrome, bacteremia, and sepsis

question

Escherichia coli - E coli

answer

- G- rod
- found in GI tracts of humans + animals
- can cause pneumonia, urinary tract infections, and diarrhea (gastroenteritis)

question

Pseudomonas aeruginosa - P aeru.

answer

- G- rod
- commonly inhabits soil, water, and vegetation
- opportunistic pathogen
- causes urinary tract infections, respiratory system infections, dermatitis, soft tissue infections, bacteremia, bone and joint infections, gastrointestinal infections and a variety of systemic infections (esp. in immunocompromised patients)

question

Bacillus cereus - B cer.

answer

- G+ rod
- found on soil, on plants*, and in the enteric tract of insects and mammals
- a foodborne pathogen that can produce toxins, causing two types of gastrointestinal illness: the emetic (vomiting) syndrome and the diarrhoeal syndrome

question

Micrococcus luteus - M lut.

answer

- G+ cocci
- found in soil, dust, water and air, and as part of the normal microbiota of the mammalian skin
- generally considered non pathogenic

question

Serratia marcescens - S mar.

answer

- G- short rod
- occurs naturally in soil and water
- hospital-acquired infections caused respiratory tract infections, urinary tract infections (UTI), septicaemia, meningitis, pneumonia, conjunctivitis wound and eye infections, osteomyelitis, keratoconjunctivitis, keratitis, endophthalmitis and endocarditis

question

Gram staining procedure

answer

Heat Fix
1. Primary stain- Crystal violet (1 minute)
Wash off stain with di-water
2. Mordant- Gram's Iodine (1 minute)
Wash off the iodine
3. Decolorization- Acetone-alcohol (hold slide at 45 degree angle and apply decolorizer, do this until it runs clear)
Stop decolorization by washing slide with gentle stream of di-water
4.Counterstain- Safranin (1 minute)
Wash off gently for only a few seconds
5. Blot dry with bibulous paper & air dry
6.Examine slide under oil immersion

question

Good aseptic technique

answer

flame loop, flame tube lips, hold plate lid at 45 degree angle, don't set stuff down on benches

question

Selective and differential media

answer

Allows only certain bacteria to grow, with a component that also differentiates among the species that survive.

question

How you could identify an unknown using the different tests we did this term.

answer

1. Sampling, growth, and isolation streaking
2. Gram staining
3. Presumptive tests like catalase, oxidase, or starch hydrolysis.
4. Use of differential and selective media like blood agar, MSA, EMB

question

Catalase Test (presumptive)

answer

distinguishes G+ cocci (bubbling is positive)
+ = Micrococcus, Staphylococcus, many Bacilli
- = Enterococcus and Streptococcus (use peroxidase instead)

question

Oxidase test (presumptive)

answer

differentiating among G- rods (must be rough with bacteria to break cell wall - purple is positive)
+ = Pseudomonas aeruginosa, Neisseria, some Bacillus
- = E coli and many other facultative anaerobes of Enterobacteria group

question

Starch agar (presumptive)

answer

differential (for species of Clostridium, Enterococcus, and Bacillus)

question

Blood agar (differential and selective)

answer

important for hemolytic bacteria because it allows for differentiation of types and can be crucial for choosing the correct antibiotic (Beta = S. pyogenes, Alpha = S. sanguinis, Gamma = E. faecalis)

question

MSA plate (differential and selective)

answer

differential: phenol red dye and mannitol nutrient - bacteria that can ferment mannitol will produce acid byproduct that lower pH and turns agar from red to yellow (usually only S. aureus)selective: high salt content, selects for G+ organisms (halophiles) and inhibits growth of G- organisms

question

EMB plate (differential and selective)

answer

differential: with fermentation of lactose (strong fermentors = metallic green and weak fermentors = bubblegum pink)selective: with eosin-methylene dye (against G+, for G-)

1 of 58

question

What is the least resistant to more resistant microbes?

answer

question

Difference between Sterilization, Disinfection, Sanitization and Antisepsis

answer

question

What are normal skin biota?

answer

M luteus, S epidermidis, S aureus, Cornyebacterium, Propionibacterium acnes

question

What are transient organisms?

answer

found on our skin, but do not normally grow there and are usually acquired through contact with a contaminated surface.

question

What is the most effective way of getting transients off of our skin?

answer

hand washing

question

What are the 3 major components of handwashing?

answer

1. soap or detergent
2. friction
3. incorporation of antiseptic into soap

question

How does a surfactant (i.e. soap) work to rid us of transients?

answer

Emulsifies skin oils that have transient bacteria trapped in them which allow them to scrub off

question

What are some of the limits of surfactants like soap?

answer

some bacteria (mycobacteria) have waxy cel walls that can be resistant to surfactants

endospores are usually not affected

question

Why is it so important for clinicians to wash their hands between patients?

answer

Stops the spread of any disease or new diseases to the patient

question

In general what are the most difficult and least difficult organisms to kill?

answer

Prions are the most difficult and enveloped viruses are the least difficult

question

How does UV radiation kill bacteria?

answer

question

What does it do to the DNA of cells?

answer

radiation kills by damaging the DNA and creating dimers between adjacent thymine or cytosine in the DNA

question

What are some of the limitations of using UV light to kill microbes?

answer

- Can't penetrate plastic, glass.
- Can only be used on surfaces, air, water.
- Not good on living tissue.

question

Which bacteria was more resistant to killing by UV and why?

answer

Bacillus cereus was most resistant to killing by UV because it forms endospores which allow it to grow better in the dark

question

Think about places where UV use would work well.

answer

Hospitals

question

If your experiment didn't work, think about some reasons why the UV didn't inhibit growth.

answer

The UV light section was too tiny

question

Know the difference between bateriocidal and bacteriostatic agents

answer

Bacteriocidal: kill bacteria
Bacteriostatic: can inhibit growth for a period of time

question

Know the difference between disinfectants and antiseptics.

answer

Disinfectants: chemicals used on inanimate objects
Antiseptics: chemicals used on living tissues

question

Why do we have to leave most disinfectants on surfaces for at least 10-20 minutes in order to be most effective?

answer

To kill all the bacteria it is suppose to kill, different bacteria takes different time to kill

question

What is this time called when leaving disinfectant on surfaces?

answer

Dwell time

question

What is an antimicrobial, an antibiotic?

answer

question

What's the difference between broad and narrow spectrum antibiotics?

answer

Broad spectrum antibiotics: work well against a variety of bacterial types

Narrow spectrum antibiotics: work only against specific types of bacteria.

question

What is the zone of inhibition when we do the Kirby-Bauer method?

answer

around the disk where the bacteria didn't grow

question

What does it mean for a bacteria to be sensitive, intermediate or resistant to an antibiotic in the K-B test?

answer

Sensitive - antibiotic would be effective to use against the bacteria

Intermediate - antibiotic has some effect against the bacteria.

Resistant - antibiotic is not effective against the bacteria.

question

Think about the three types of organisms that your patients were infected with in this exercise.

answer

Escherichia coli (Ec)

Pseudomonas
aeruginosa (Pa)

Staphylococcus epidermidis (Se)

question

Which bacteria was most sensitive to the antibiotics?

answer

Staphylococcus aureus

question

Which bacteria was the most resistant to the antibiotics?

answer

Pseudomonas aeruginosa

question

Think about the choices you would have to make if your organism was only intermediately sensitive to certain antibiotics.

answer

You would have to administer multiple drugs

question

Also think about what you would do if you wanted to add an additional antibiotics to your treatment plan but only had one susceptible and one intermediate?

answer

question

Also think about what you would do if you only have two intermediate antibiotics and no sensitive ones?

answer

question

Ways in which infectious diseases can be transmitted

answer

ingestion, inhalation, direct skin contact, bodily fluid contact (wounds, blood or during sex), bites, scratches.

question

What is a fomite and a vector in terms of disease transmission?

answer

Fomite: a non-moving object such as a doorknob, tissue, or used needle

Vector: a living organism such as a mosquito, fly, or tick

question

How was our infection transmitted last week?

answer

direct contact

question

Be able to define prevalence and incidence rate.

answer

Prevalence: number of people who are sick at any given time

Incidence rate: the number of new cases being reported in a time period

question

Be able to define index case

answer

First case of the disease

question

You should be able to calculate incidence rate and prevalence for our disease based upon our in class results.

answer

Incidence rate= # of new cases in a time period/size of risk population X K

Prevalence= # of existing cases at a point in time/ size of risk population X K

question

What is K in epidemiology?

answer

K varies depending on what the incidence is

question

How do we interpret non-Serratia growth on the plates (if there is growth that is not evidence of the epidemic)?

answer

That represents normal flora form our hands

question

What are the MMWR reports?

answer

Morbidity and Mortality Weekly Report

question

Who produces them?

answer

Centers for Disease Control and Prevention

question

What are two common trends we see incidence spikes for Chlamydia and Lyme disease like we discussed in class?

answer

Both increase in warmer months and mode of transmission

question

What months are the spikes likely to happen during and why?

answer

Summer months because more people are outdoors and social with one another

question

Staphylococcus aureus - S aur.

answer

question

Escherichia coli - E coli

answer

- G- rod
- found in GI tracts of humans + animals
- can cause pneumonia, urinary tract infections, and diarrhea (gastroenteritis)

question

Pseudomonas aeruginosa - P aeru.

answer

question

Bacillus cereus - B cer.

answer

question

Micrococcus luteus - M lut.

answer

- G+ cocci
- found in soil, dust, water and air, and as part of the normal microbiota of the mammalian skin
- generally considered non pathogenic

question

Serratia marcescens - S mar.

answer

question

Gram staining procedure

answer

question

Good aseptic technique

answer

flame loop, flame tube lips, hold plate lid at 45 degree angle, don't set stuff down on benches

question

Selective and differential media

answer

Allows only certain bacteria to grow, with a component that also differentiates among the species that survive.

question

How you could identify an unknown using the different tests we did this term.

answer

1. Sampling, growth, and isolation streaking
2. Gram staining
3. Presumptive tests like catalase, oxidase, or starch hydrolysis.
4. Use of differential and selective media like blood agar, MSA, EMB

question

Catalase Test (presumptive)

answer

distinguishes G+ cocci (bubbling is positive)
+ = Micrococcus, Staphylococcus, many Bacilli
- = Enterococcus and Streptococcus (use peroxidase instead)

question

Oxidase test (presumptive)

answer

question

Starch agar (presumptive)

answer

differential (for species of Clostridium, Enterococcus, and Bacillus)

question

Blood agar (differential and selective)

answer

important for hemolytic bacteria because it allows for differentiation of types and can be crucial for choosing the correct antibiotic (Beta = S. pyogenes, Alpha = S. sanguinis, Gamma = E. faecalis)

question

MSA plate (differential and selective)

answer

question

EMB plate (differential and selective)

answer

differential: with fermentation of lactose (strong fermentors = metallic green and weak fermentors = bubblegum pink)selective: with eosin-methylene dye (against G+, for G-)

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Micro Lab Exam 3 Study Guide

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