Module 8 - Notes Flashcards
What are the 3 main methods of microbial control?
Physical
Mechanical Removal
Chemical
What are the 2 categories of physical microbial control?
Heat
Radiation
What are the 2 categories of Heat to control microbial infection?
Dry Heat - Like oven
Moist Heat - Like Boiling of autoclave
What types of microbial controls do you use on inanimate items (non-living)
Sterilization
Disinfection
Sanitization
What types of microbial controls do you use on living tissues?
Antiseptics
Degerming
What is sterilization?
Completely eliminate all vegetative cells, endospores and viruses
Eliminates all microbial risk
Only used on inanimate items.
What is Disinfection?
Reduces or destroys microbial load using heat or chemicals.
(there can still be some bacterial life)
Only used on inanimate items
What is Sanitization?
Reduces microbial loads to a safe public health level using heat or chemicals
Only used on inanimate items
What is Antisepsis?
Reduces microbial load using antimicrobial chemicals on living tissues
What is degerming?
Reduces microbial load using scrubbing and mild chemicals on living tissues.
You have injured your arm and your sibling tells you that you must sterilize your would. Why are they wrong?
A) Sterilization is a process that uses scrubbing and you could damage the wound
B) Sterilization is a process exclusively used on inanimate objects
C) Sterilization will only reduce the microbial load without killing the pathogen.
D) Sterilization absolutely requires heat to completely destroy the microbes.
B) Sterilization is a process exclusively used on inanimate objects
What are the 2 categories of radiation for the physical methods of microbial control?
Nonionizing - UV
Ionizing - Xray
Dry heat methods for microbial control include a dry oven and incineration (flame). What level of microbial control is achieved with either method?
Sterilization
Moist heat methods for microbial control include autoclave (steam & pressure) and boiling water or pasteurization. What level of control is achieved with autoclaves?
Sterilization
but only if held at 121 degrees Celcius for 15 minutes or more.
15 minutes is how long it takes to kill spores
Moist heat methods for microbial control include autoclave (steam & pressure) and boiling water or pasteurization. What level of control is achieved with boiling water of pasteurization?
Disinfection
Reduces bacterial loads but only eliminates heat-sensitive pathogens.
Not sterile
What is HTST Pasteurization of milk?
High temp short time
milk is heated to 72 degrees celsius for 15 seconds then bottled and refrigerated.
Shorter shelf life
What is UHT pasteurization for milk?
Ultra High Temperature
Milk is heated to 138 degrees celsius or more for 2 or more seconds, then sealed in airtight containers for up to 90 days without refrigeration. (tetra pack milk)
What other physical methods of microbial control can be used besides heat or pressure?
Cold - Refrigeration or freezing
Dessication - Drying
Both methods just control growth. They do not reduce the population by killing.
For a research project, you pasteurized your growth medium. Once the process is complete, you leave your flask on the bench to cool down. After a few days, you notice growth in your medium, what is the best explanation?
The aim of pasteurization is to reduce the microbial population to a safe level; therefore you do not sanitize your growth medium.
What is an example of a mechanical process to control microbial growth?
Filtration.
Effectiveness depends on pore size
HEPA filters have a 0.3 micron pore size. (used to remove microbes from air)
Membrane filters have a 0.2 micron pore size or smaller. (Used in liquid solutions)
What are the 2 categories of chemical microbial control?
Gases
Liquids
Gases used in chemical methods of microbial control can achieve what level of control?
sterilization or disenfection
What are the examples of liquid chemical controls used on living tissues?
Chemotherapy (taken internally)
- Antibiotics
- antivirals
- Antiparasitic
- Antifungal
Antisepsis (Applied topically)
What are the 3 main categories of antimicrobial agents?
Static (stops growth)
Cidal (kills)
Lytic (Lyses)
examples
bacteriostatic/cidal/lytic -targets bacteria
fungistatic/cidal - targets fungi
viricistatic/dal - targets viruses
sporocidal - targets spores
How do we determine the effects of antimicrobial agents?
Use plate counts and optical denisty
With a static agent, the optical density and number of colony forming units will plateau once the agent is applied
With a cidal or lytic agent, the optical density and the number of colony forming units will decrease once the agent is applied.
How do we test the effectiveness of antiseptics and disinfectants?
Use the disc diffusion assay method
A plate is inoculated with various antimicrobial discs.
The zone of inhibition around each disc indicates how effective that antimicrobial is against the particular species being tested.
The larger zone = more it kills
can only tell you how much it kills
How do we test the efficacy of germicides?
logarithmic scale - overtime how much is decreasing. The steeper the curve, the more effective it is.
How many bacteria can a compound with 99.999% efficacy kill?
A) 10 000 and above
B) 100 000 and below
C) 100 000 and above
D) 1 million
E) 1 billion
B) 100 000 and below
Count the number of 9’s and then count the number of 0’s
5 nines = 5 zeros
Something that kills 99.9% is not as effective as something that kills 99.99%
99.9% is up to 1000
What is the difference between physical methods, chemical methods and filtration to control microbes?
Physical methods and chemical methods reduce populations and/or inhibit growth. Filtration removes microbes
You work with a food-borne human pathogen that is psychrotolerant bacteria. What storage temperature would you use to make sure the food stays safe?
Below refrigeration temperature
Psychrotolerants are mesophiles that can grow at refrigeration temperature
Human pathogen must grow at body temperature
What are the considerations when using a chemotherapy?
Toxicity towards the host - dosage and route of administration
- Kill or inhibit pathogen without damaging the host
- Easier for bacteria, harder for viruses and very hard for eukaryotic pathogen
What is a broad-spectrum vs narrow-spectrum antibody?
Broad-spectrum - kills many different groups, indiscriminate - kills the good and bad bacteria
Narrow-spectrum - kills specific groups of bacteria
What is an antibiotic?
chemical substance that kills bacteria or prevents bacterial growth
the familiar/current definition is an umbrella term for antibacterial compounds but classically:
1. antibacterial
2. produced naturally by microorganisms
3. a chemical not a protein
What are the targets of antibiotics?
Cell wall
Plasma membrane
Ribosomes
Metabolic pathways
DNA synthesis
RNA synthesis
If we use an antibiotic to inhibit cell wall biosynthesis what are the targets?
Penicillin-binding proteins
Peptidoglycan subunits
Peptidoglycan subunit transport
If we use an antibiotic to inhibit biosynthesis of proteins what are the targets?
30S ribosomal subunit
50S ribosomal subunit
If we use an antibiotic to disrupt membranes what are the targets?
Lipopolysaccharide, inner and outer membranes
If we use an antibiotic to inhibit nucleic acid synthesis what are the targets?
RNA
DNA
If we use an antibiotic for antimetabolites what are the targets?
Folic acid synthesis enzyme
Mycolic acid synthesis enzyme
If we use an antibiotic as a mycobacterial adenosine triphosphate (ATP) synthase inhibitor what are the targets?
Mycobacterial ATP synthase
A patient wth a pneumonic receives a beta lactam but their condition does not improve, the patient is given a macrolide and they fully recover. What is the explanation?
The patient was infected with a mycoplasma pneumoniae.
What antibiotics target the cell wall
Beta-lactams
- penicillins
- cephalosporins
- monobactams
- carbapenems
Glycopeptides
- vancomycin
Bacitracin
What antibiotics target the plasma membrane?
Polymyxins
- polymixin B
- colistin
Lipopeptide
- daptomycin
What antibiotics target the Ribosomes?
30S subunit
- aminoglycosides
- tetracyclines
50S subunit
- macrolides
- lincosamides
- chloramphenicol
- oxazolidinones
What antibiotics target DNA synthesis?
Fluoroquinolones
- ciprofloxacin
- levofloxacin
- moxifloxacin
What antibiotics target RNA synthesis?
Rifamycins
- rifampin
What antibiotics target Metabolic pathways?
Folic acid synthesis
- sulfonamides
- sulfones
- trimethoprim
Mycolic acid synthesis
- izoniazid
You are trying to prevent fungus infection in the hospital. What type of activity should your antimicrobial agent have if it is used to sterilize surfaces in a hospital room?
A) Bactericidal
B) Fungistatic
C) Fungicidal
D) Viricidal
C) Fungicidal
What mechanisms do antifungal drugs use?
inhibit ergosterol synthesis
bind ergosterol in the cell membrane and create pores that disrupt the membrane
inhibit cell wall synthesis
inhibit microtubules and cell division
Lots of fungal infections are skin-based or nail-based so we can use fairly caustic chemicals to treat them
Your patient asks you to explain why Ivermectin cannot be used to treat SARS-CoV-2 infections and can only be used against parasitic worms. How do you respond?
The target of Ivermectin are present in invertebrate nerve and muscle cells, and are not present in viruses.
How do antiviral drugs work?
You want to target viral enzymes that modify their nucleotides
By adding nucleotide analogues, we’re able to prevent synthesis of micro RNAs or other things made by the virus
What mechanisms of action do antivirals depend on?
Nucleotide analog inhibition of nucleic acid synthesis
Non-nucleoside noncompetitive inhibition
Inhibt escape of virus from endosomes
Inhibit neuraminadase
Inhibit viral uncoating
Inhibition of protease
Inhibition of integrase
Inhibition of membrane fusion
What are some antimicrobial susceptivity tests?
Dilution Test
the lowest dilution that inhibits turbidity (cloudiness) is the MIC. minimal inhibitory concentration
In this example, the MIC is 8 μg/mL.
Broth from samples without turbidity can be inoculated onto plates lacking the antimicrobial drug.
The lowest dilution that kills ≥99.9% of the starting inoculum is observed on the plates is the MBC. minimal bactericidal concentration
What is a microdilution tray?
A microdilution tray can also be used to determine MICs of multiple antimicrobial drugs in a single assay.
In this example, the drug concentrations increase from left to right and the rows with clindamycin, penicillin, and erythromycin have been indicated to the left of the plate.
For penicillin and erythromycin, the lowest concentrations that inhibited visible growth are indicated by red circles and were 0.06 μg/mL for penicillin and 8 μg/mL for erythromycin.
For clindamycin, visible bacterial growth was observed at every concentration up to 32 μg/mL and the MIC is interpreted as >32 μg/mL.
What is an E-Test?
The E-test can be used to determine the MIC of an antibiotic.
In this E-test, vancomycin is shown to have a MIC of 1.5 μg/mL against Staphylococcus aureus.
When measuring the activity of antimicrobial compounds, what is the difference between efficacy and susceptibility?
A) There is no difference
B) How fast it fills vs. how much it inhibits growth
C) How much it kills vs. how much it inhibit growth
D) How fast it kills and how much it kills vs. the concentration required to kill/inhibit growth.
D) How fast it kills and how much it kills vs. the concentration required to kill/inhibit growth.
Efficacy = how fast and how much
Susceptibility = the concentration required
What are the 7 mechanism of antibiotic resistance?
Efflux pump
Blocked penetration
Inactivation of enzymes
Target modification
Overproduction of target
Production of alternate enzymes
Target mimicry
You sequenced an antibiotic resistant gram-negative bacterium that is a lysogen. You observed that the antibiotic is quickly degraded by the bacterial cells. What type of mechanism is mediating the antibiotic resistance and how was it acquired?
A) Enzymatic inactivation acquired via conjugation
B) ABC efflux pump acquired via transduction
C) Enzymatic inactivation acquired by transduction
D) Target modification acquired via conjugation
C) Enzymatic inactivation acquired by transduction
What is a superbacteria?
bacteria resistant to most antibiotics used to treat infections
What is antibiotic stewardship?
an effort to follow evidence-based antibiotic usage to stop antimicrobial overuse and slow antimicrobial resistance
What is epidemiology?
the study of the occurrence, distribution, and determinants of health and disease in a population
goal - identify the nature of disease and transmission
surveillance and reporting to trace the spread of a disease
What is public health concerned with?
Health of the population as a whole
Their goal is to keep the population healthy
- slow or stop the spread of infectious disease.
What is mortality?
incidence of death in a popultion
What is morbidity?
incidence of disease (fatal, non-fatal, severe, mild)
What is DALY (Disability-adjusted life year)
disease burden in terms of lost years due to disease, disability and/or premature death
What is the effect of morbidity on the Disease-adjusted life year (DALY)?
It has a negative effect as it decreases the quality of life of individuals.
What does prevalence mean in terms of epidemiology
it’s the total number of cases (new and existing) in a given time
What does incidence mean in terms of epidemiology
it’s the total number of new cases in a given time.
What does epidemic mean in terms of epidemiology?
a large number of people in a population are affected
What does pandemic mean in terms of epidemiology?
A widespread, usually worldwide population is affected.
What does endemic mean in terms of epidemiology?
It is constantly present in a population. Presence of a reservior.
The presence of a constant reservoir in a given population.
A) What is an epidemic?
B) What is a pandemic?
C) What is endemic?
D) What is prevalence?
E) What is incidence?
C) What is endemic
What is a reservoir?
“Normal/natural” habitiat of an infectious microbe
- Animal Reservoir = zoonotic disease
- Environmental Reservoir = sapronosis
(present in water, soil, erc) - Human Reservoir = human only disease
What is zooanthroponosis?
humans can give disease to animals
ie. mastitis in dairy cows
What are mechanisms of transmission for disease?
- Contact Transmission
- direct (physical)
- indirect (via an intermediate carrier)
vehicles like food
fomites like door knobs
vectors like mosquitos - Droplet Transmission
- travel less than 1m from the source
sneezing - Airborne Transmission
- travel more than 1m and stay suspended for hours
microbes that freely float
How can we prevent the spread of infectious diseases?
- Eliminate the reservior
- Animal (immunize or slaughter)
- Environment (Decontaminate or avoid)
- Human (identify, isolate & treat infected host) - Limit the availability of new hosts
- improve living condition, general health & safety
- Vaccination - Block routes of transmission
- Indirect contact
clean water, prevent food contamination
remove vectors
clean fomites
- Airborne
flow system to prevent dispersal
- Droplets & direct contact
wash hands
Barriers like gloves, gowns, masks
What are asymptomatic individuals?
Individuals who are affected by microbial infection but show no symptoms.
What is the swiss cheese method of controlling microbes?
Using multiple strategies to reduce the risks of infection.
What are the challenges associated with preventing the spread of infectious disease?
Natural progression of an infection
- asymptomatic carriers vs. pre-symptomatic
Vaccine compliances
Reservoirs
Social Pressure
- working while sick
What are the most effective methods to decrease infectious disease incidence?
- Clean drinking water supply
- Clean food supply
- Promoting sanitization and personal hygiene
- Controlling insect vectors
- Public education about STIs and respiratory disease
What are the current issues in public health practices?
- Global disparity in preventing infectious disease
- New infectious disease continue to appear
- microbes mutate and evolve
- spillover events (zoonosis)
- global warming and travel
