Control of microorganisms

Question 1

How many bacteria are present on one square inch of skin

Answer 1

32,000,000

Question 2

What environment will microorganisms perfer to proliferate in?

Answer 2

Areas with high levels of nutrients
remote < floor < sponge < skin

Question 3

What microorganisms need to be controlled within the environement?

Answer 3

Bacteria, fungi, viruses (global term: microbes)

Question 4

Areas that need to have microbial control?

Answer 4

Surgical suite (tools, living tissue)
food and water
airborne biohazards

Question 5

How does food spoilage occur?

Answer 5

Bacterial and mold growth (bacterial contamination by pathogens)

Question 6

Common food poising oubreaks?

Answer 6

Salmonella, listeria, E. coli

Question 7

Common source of E. Coli infections in food?

Answer 7

Lettuce, kimchi, centralized kitchens, onions, ground beef

Question 8

Recent cause of salmonella outbreaks?

Answer 8

cantaloupe
snakes and rodents (raw pet food)
affecting predominantly children

Question 9

What does nosocomial mean?

Answer 9

Hospital aquired

Question 10

Why do we need antimicrobial therapy?

Answer 10

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

Question 11

Why is biohazard control important?

Answer 11

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)

Question 12

Why is biohazard control for public health?

Answer 12

Prevention of outbreaks (ebola, dengue, norovirus, TB…)
epidemics and pandemics (influenza, covid…)
Or rapid control

Question 13

difference between epidemic and pandemics

Answer 13

While an epidemic is large, it is also generally contained or expected in its spread, while a pandemic is international and out of control

Question 14

Need for environmental microbial control?

Answer 14

Potable and filtered water
Waste and water management
Keeping the two very separate to provide safe sources of water is essential

Question 15

Four main avenues of microbial control? In increasing order of effectiveness or decrease in microbial density

Answer 15

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)

Question 16

Role of sanitation and disinfection in society?

Answer 16

Reduces total microbial population to a “safe” public health standard

Question 17

Difference between bacteriostatic and bactericidal?

Answer 17

Stops growth vs kills cells

Question 18

What is antimicrobial potency

Answer 18

measure of how effective an antimicrobial agent is at killing microorganisms or stopping them from growing.

Question 19

How is population death measured?

Answer 19

Logarithmically

Question 20

What is the D-value

Answer 20

Decimal reduction time (10 to the 9 down to 10 to the 8)

Question 21

How do we quantify the efectiveness of an antimicrobial agent?

Answer 21

More effective killing agent = faster killing = lower D-value

Question 22

What factors influence the ability of an antimicrobial to carry out microbial control?

Answer 22

-population size
-microbial composition (cell vs spores, bacteria vs virus)
-concentration and potency of microbial agents
-contact time
-temp
-local environment (pH, organic matter)

Question 23

What are the 3 microbial control methods?

Answer 23

Physical, chemical, mechanical

Question 24

What are the two physical control methods? (+subcategories)

Answer 24

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

Question 25

How does the autoclave work? Pros and cons, quality control

Answer 25

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

Question 26

How does pasteurization work? Whats it for? Standard vs UHT?

Answer 26

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

Question 27

How do we recognize food spoilage?

Answer 27

-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)

Question 28

Properties of UV radiation?

Answer 28

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

Question 29

How does gamma radiation works? Pros and cons? What for

Answer 29

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

Question 30

Categories of chemical microbial control methods? (2+ subcategories)

Answer 30

Gases - sterilize or disinfectant
Liquids - antiseptics (animate), chemotherapy (animate) or disinfectant (inanimate

Question 31

How do antiseptics work? What for? Application?

Answer 31

Kills or inhibits growth of microorganisms but does not sterilize
Precents infection and contamination
Applied to skin/tissue surfaces to decrease toxicity

Question 32

Why are biocides in soap a problem? And what is a biocide

Answer 32

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

Question 33

How do disinfectants work? Application

Answer 33

Kills or inhibits the growth of microoragnisms - more pontent than antiseptics, but still do not sterilize
Applied on inanimate surfaces - often toxic (bleach, chlorine…)

Question 34

4 classes of antiseptics/disinfectants?

Answer 34

alcohols, phenolics, aldehydes, halogens

Question 35

How do alcohols work?
+practical use

Answer 35

antiseptic/disinfectant
denature proteins, dissolve lipids in membranes
ethanol at 60-70% for 10-15minutes

Question 36

How do phenolics work?

Answer 36

antiseptic/disinfectant
disrupt cell membranes and denature proteins

Question 37

How do aldehydes work?

Answer 37

antiseptic/disinfectantHighly reactive molecule that crosslinks with nucleic acids and proteins to deactivate them
highly toxic

Question 38

How do halogens work?
+practical use

Answer 38

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

Question 39

What are disinfectants and sterilizers commonly used for?
2 examples?

Answer 39

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

Question 40

What are some modern approaches to surface contamination?

Answer 40

Self sterilizing surfaces:
-copper and other antibacterial material coated surfaces
-nanopillar mediated killing of bacteria

Question 41

Two mechanical microbial control methods?

Answer 41

Air filtration and liquid filtration (both sterilize)

Question 42

How do liquid filtration systems work?

Answer 42

Sterilize heat-sensitive liquids via porous membranes (<0.45-0.2 micron, removes bacteria fungi and spores but not viral particles)

Question 43

How do air filtration systems work?

Answer 43

HEPA : high efficiency particulare air filter
has pores of 0.1-0.3 micron
filters fungi and bacteria, absrobs virus

Question 44

Why does antimicrobial control fail?

Answer 44

-Use of suboptimal methods of microbial control
-High bacterial load
-Highly virulent pathogens
-Resistant microorganisms (resistance to antiseptics or biofilm formation)

Question 45

What are biofilms?

Answer 45

Multicellular bacterial communitites with cells aggregated within and extracellular matrix and adherent to a surface

Question 46

Where cna we find biofilms?

Answer 46

Natural environments, medical devices & within accumulation of biological waste

Question 47

Why do biofilms protect microorganisms?

Answer 47

Cause poor penetration, trap or inactivate toxi molecules and slows growth of microbes (reducing effectiveness of disinfectants and antiseptics)

Question 48

How do biofilms form?

Answer 48

Formed from individual bacteria on abiotic surfaces
Forms mushroom like structures

Question 49

What factors influence choice of antimicrobial method for microorganism control?

Answer 49

-disinfection vs sterilization
-material being disinfected
-duration of methods
-sensitivity of method (to temp, chemicals)
-toxcity
-packaging of material
-availability

Question 50

Name all antimicrobial control methods?

Answer 50

Air filtration & liquid filtration
Gamma, UV, boiling, pasteruization, steam autoclave, incineration & dry oven
gas sterilants, antiseptics, chemotherapy & antiseptics

Question 51

What are the 4 biosafety levels? Whats the point?

Answer 51

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

Question 52

Biocontrol methods used for BSL-1

Answer 52

Decontamination + filtering of waste

Question 53

Biocontrol methods used for BSL-2

Answer 53

Restricted acces, use of biological safety cabinets, safety when using sharp objects + BSL1 methods

Question 54

Biocontrol methods used for BSL-3

Answer 54

All air in lab is controlled and filtered, everything is decontaminated, self contained lab unit (2 door system, gown….)
+ BSL-1&2

Question 55

Biocontrol methods for BSL-4

Answer 55

Entrance and exit to the lab involves hazmats, showers, UV vacuum room

Question 56

What factors must be considered in the reduction of transmission of infectious microorganisms?

Answer 56

-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)

Question 57

How is the ebola virus transmitted?

Answer 57

through blood, semen, saliva (droplets)