Control of microorganisms Flashcards
How many bacteria are present on one square inch of skin
32,000,000
What environment will microorganisms perfer to proliferate in?
Areas with high levels of nutrients
remote < floor < sponge < skin
What microorganisms need to be controlled within the environement?
Bacteria, fungi, viruses (global term: microbes)
Areas that need to have microbial control?
Surgical suite (tools, living tissue)
food and water
airborne biohazards
How does food spoilage occur?
Bacterial and mold growth (bacterial contamination by pathogens)
Common food poising oubreaks?
Salmonella, listeria, E. coli
Common source of E. Coli infections in food?
Lettuce, kimchi, centralized kitchens, onions, ground beef
Recent cause of salmonella outbreaks?
cantaloupe
snakes and rodents (raw pet food)
affecting predominantly children
What does nosocomial mean?
Hospital aquired
Why do we need antimicrobial therapy?
Need for steril or disinfected environemnts for surgey
Treatment against infectious disease
Control of airbrone biohazards for immuno compromised hosts and/or nosocomial transmission of infections
Why is biohazard control important?
Safe disposal of biohazard waste from hospitals and labs
For laboratory safety
Transmission prevention
Safe disposal of blood and other biological products (assumption of contamination)
Why is biohazard control for public health?
Prevention of outbreaks (ebola, dengue, norovirus, TB…)
epidemics and pandemics (influenza, covid…)
Or rapid control
difference between epidemic and pandemics
While an epidemic is large, it is also generally contained or expected in its spread, while a pandemic is international and out of control
Need for environmental microbial control?
Potable and filtered water
Waste and water management
Keeping the two very separate to provide safe sources of water is essential
Four main avenues of microbial control? In increasing order of effectiveness or decrease in microbial density
Antisepsis: application of a medicated compound to the skin
Sanitization: more for inanimate surfaces
Disinfection: hospitals - not complete removal but high enough (wiping down surface with antiseptic compound)
**above clears out vegetative cell, but NOT spores
Sterilization: most aggressive, also deals with spores (heat, chemicals, radiation or mechanically by filter)
Role of sanitation and disinfection in society?
Reduces total microbial population to a “safe” public health standard
Difference between bacteriostatic and bactericidal?
Stops growth vs kills cells
What is antimicrobial potency
measure of how effective an antimicrobial agent is at killing microorganisms or stopping them from growing.
How is population death measured?
Logarithmically
What is the D-value
Decimal reduction time (10 to the 9 down to 10 to the 8)
How do we quantify the efectiveness of an antimicrobial agent?
More effective killing agent = faster killing = lower D-value
What factors influence the ability of an antimicrobial to carry out microbial control?
-population size
-microbial composition (cell vs spores, bacteria vs virus)
-concentration and potency of microbial agents
-contact time
-temp
-local environment (pH, organic matter)
What are the 3 microbial control methods?
Physical, chemical, mechanical
What are the two physical control methods? (+subcategories)
Heat: dry (incineration - sterilize) or moist (sterilize by steam autoclave or disinfect by boiling or pasteurization)
Radiation: ionizing (X-ray or gamma) or non-ionizing (UV) disinfects or sterilizes
How does the autoclave work? Pros and cons, quality control
Uses steam at high pressure to sterilize liquids and solid materials - kills spores over 15-30min
Its efficient, cheap, simple and has no waste, but can damage materials
Spore biological indicators test, heat indicator strip
How does pasteurization work? Whats it for? Standard vs UHT?
Used for heat sensitive products: controlled disinfection below boiling point
Reduces spoilage and food borne illnesses but does not sterilize (not good enough for spore forming pathogens)
Dairy products, eggs, wine, beer
Standard: 60 celsius for 30min
Ultra high temp: 135-140 for 2-5sec
How do we recognize food spoilage?
-Visible mold growth
-gas/odour from microorganism overgrowth
-Softening and rotting due to enzyme production and pigments
-Growth of pathogenic bacteria (not always recognizable - hence the possibility of food borne disease)
Properties of UV radiation?
Kills microorganisms in short range but does not penetrate glass, water or plastic well
Disinfects or sterilizes (dependent on dose, intensity and distance from UV source)
No damage to product, but toxic to humans
How does gamma radiation works? Pros and cons? What for
Photons at extremly high frequency and energy
Biologically hazardous due to possible DNA damage
But highly penetrating
Used for sterilization of medical supplies in highly specialized sterilization facilities
Categories of chemical microbial control methods? (2+ subcategories)
Gases - sterilize or disinfectant
Liquids - antiseptics (animate), chemotherapy (animate) or disinfectant (inanimate
How do antiseptics work? What for? Application?
Kills or inhibits growth of microorganisms but does not sterilize
Precents infection and contamination
Applied to skin/tissue surfaces to decrease toxicity
Why are biocides in soap a problem? And what is a biocide
a chemical or microorganism that destroys, deters, or controls harmful organisms
Can activate multidrug resistance pumps that eject all sorts of compounds that are chemically distinct
How do disinfectants work? Application
Kills or inhibits the growth of microoragnisms - more pontent than antiseptics, but still do not sterilize
Applied on inanimate surfaces - often toxic (bleach, chlorine…)
4 classes of antiseptics/disinfectants?
alcohols, phenolics, aldehydes, halogens
How do alcohols work?
+practical use
antiseptic/disinfectant
denature proteins, dissolve lipids in membranes
ethanol at 60-70% for 10-15minutes
How do phenolics work?
antiseptic/disinfectant
disrupt cell membranes and denature proteins
How do aldehydes work?
antiseptic/disinfectantHighly reactive molecule that crosslinks with nucleic acids and proteins to deactivate them
highly toxic
How do halogens work?
+practical use
antiseptic/disinfectant
forms hypochlorous acid (HOCl) - highly reactive oxidant that reactss with molecules by oxidization (leads to sterilization)
Cheap but toxic
10%bleach for 10min
What are disinfectants and sterilizers commonly used for?
2 examples?
Heat sensitive items - most are very toxic
Ethylene oxide: highly reactive ring structure - strong alkylating agent that reacts with nucleic acids and proteins (potent, toxic and flammable)
Vaporized hydrogen peroxide: no damage to non living materials as it creates no toxic by-products
What are some modern approaches to surface contamination?
Self sterilizing surfaces:
-copper and other antibacterial material coated surfaces
-nanopillar mediated killing of bacteria
Two mechanical microbial control methods?
Air filtration and liquid filtration (both sterilize)
How do liquid filtration systems work?
Sterilize heat-sensitive liquids via porous membranes (<0.45-0.2 micron, removes bacteria fungi and spores but not viral particles)
How do air filtration systems work?
HEPA : high efficiency particulare air filter
has pores of 0.1-0.3 micron
filters fungi and bacteria, absrobs virus
Why does antimicrobial control fail?
-Use of suboptimal methods of microbial control
-High bacterial load
-Highly virulent pathogens
-Resistant microorganisms (resistance to antiseptics or biofilm formation)
What are biofilms?
Multicellular bacterial communitites with cells aggregated within and extracellular matrix and adherent to a surface
Where cna we find biofilms?
Natural environments, medical devices & within accumulation of biological waste
Why do biofilms protect microorganisms?
Cause poor penetration, trap or inactivate toxi molecules and slows growth of microbes (reducing effectiveness of disinfectants and antiseptics)
How do biofilms form?
Formed from individual bacteria on abiotic surfaces
Forms mushroom like structures
What factors influence choice of antimicrobial method for microorganism control?
-disinfection vs sterilization
-material being disinfected
-duration of methods
-sensitivity of method (to temp, chemicals)
-toxcity
-packaging of material
-availability
Name all antimicrobial control methods?
Air filtration & liquid filtration
Gamma, UV, boiling, pasteruization, steam autoclave, incineration & dry oven
gas sterilants, antiseptics, chemotherapy & antiseptics
What are the 4 biosafety levels? Whats the point?
BSL-1: non-pathogens
BSL-2: opportunistic pathogens (not contagious through aerosol) - most dangerous to immunocompromised people
BSL-3: Pathogens (infectious through aerolols)
BSL-4: deadly pathogens (no treatment or cure)
Defines the level of biocontrol methods needed for safety in lab settings
Biocontrol methods used for BSL-1
Decontamination + filtering of waste
Biocontrol methods used for BSL-2
Restricted acces, use of biological safety cabinets, safety when using sharp objects + BSL1 methods
Biocontrol methods used for BSL-3
All air in lab is controlled and filtered, everything is decontaminated, self contained lab unit (2 door system, gown….)
+ BSL-1&2
Biocontrol methods for BSL-4
Entrance and exit to the lab involves hazmats, showers, UV vacuum room
What factors must be considered in the reduction of transmission of infectious microorganisms?
-Mode of transmission
-Infectious dose
-Mortality / morbidity, whetehr there is an available treatment
-Vectors and non human reservoirs
-Who the pathogen can affect (AKA LSB2 or LSB3-4)
How is the ebola virus transmitted?
through blood, semen, saliva (droplets)
