MGY277H1 Lecture Notes - Lecture 6: Surgical Mesh, Glutaraldehyde, Antibiotics

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Unit 6 Controlling Microbial Growth
Overview of Microbial Control
Sterilization  removal or destruction of all organisms so they can no longer
multiply or revive
Sterile item is FREE of microbes including endospores and viruses but …
DOE S NOT consider prions (not destroyed by standard sterilization)
Disinfection  elimination of most or all pathogens
Some viable microbes may remain
Disinfectant/biocides/germicide/bactericides used on inanimate objects
Antiseptics used on living tissue
Pasteurization brief heating to reduce number of spoilage
Foods and inanimate objects
Decontamination reduced pathogens to levels considered safe to handle
Sanitization  Substantially reduced microbial population that meets accepted
health standard (NOT a specific level of control)
Preservation process of delaying spoilage of foods and other perishable products
Pasteurization may assist this process
Adjust condition to slow microbial growth
Add bacteriostatic preservative (growth-inhibiting but DO NOT KILL)
Microbial control methods depends upon situation and level of control required
Daily Life
Routine control washing and scrubbing with soaps and detergents
Soap remove surface organisms
Beneficial skin microbiota reside deeper in skin = No effect
Pores typically has NO contact with soap and bacteria here are in BIOFILM
Hospitals & Health care Facilities
Healthcare associated infection = Nonsocomial infections
Patients more susceptible to infection due to weakened condition
High concentration of infectious disease in confined area (pathogens)
Instruments must be sterilized
Laboratories
routinely work with microbial cultures
Must eliminate microbial contamination to both experiment sample and
environment (Aseptic Techniques)
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Careful sterilization before and after
COC and PHAC guidelines for labs working with
microbes
oBiosafety levels range from BSL-1 to
BSL-4 to each type of microbe
Food Production Facilities
Contamination microbes must be
destroyed, removed, inhibits
Heat treatment is most common (alter flavour and appearance)
Chemical additives or Irradiation for certain foods (high energy ray)
CFIA-CAD/FDA-USA regulates use of irradiation and chemical additives due
to risk of toxicity
Facilities must KEEP surface clean and relative free of microbes
Water Treatment Facilities
Ensure drinking water free of pathogens
Chlorine is traditionally used to disinfect water
oSave live from water born disease
oCan react with naturally occurring chemicals to form disinfection by
products (DBPs)but linked to long term health risks
Some organisms resistant to (traditional) chemical disinfectants
oCryptosporidium parvum (cause diarrhea)
oRegulation require facilities to minimize DBPs and C.parvum in
treated water
Selection of an Anti-microbial procedure
All method has advantage and limitation (NO multipurpose methods)
Depends on factors include:
1. Types of microbe
2. # of contaminating microbes
3. Environmental condition
4. Risk for infection
5. Composition of the item
Types of Microbes
Products potentially contaminated with highly resistant microbes require more
rigorous treatment
Bacterial endospores
Most resistant form of life encountered
(Only kill by extreme heat or chemical)
Spore/Endospores produced by gram positive cell
Contain hard shell that protect DNA and metabolic inert
E.g bacillus, Clostridium sp
Protozoan cysts and oocysts
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Excreted in feces and cause diarrheal disease if ingested
Also content hard shell that surround DNA and inert
Resistant to disinfectant but EASILY destroyed by boiling
E.g Giardia lambia
Micobacteirum species
Waxy cell walls make resistant to many chemical treatments
Stronger, more toxic chemical is used to disinfect
But susceptible to ultra violate light
Pseudomonas species
Common environmental organisms that can cause serious healthcare
associated infection
Opportunistic pathogens (problematic for cystic fibrosis or burn patient)
Resistant to and can ACTUALLY GROW in some disinfectants
Naked viruses
Lack lipid envelope (Contain protein shell) and MORE RESISTANT to
disinfectant sand detergents but still susceptible to chlorine (i.e Polio virus)
Noro-virus the MOST common food poisoning pathogen
(Kill weak people by dehydration of diarrhea)
Envelope viruses (i.e HIV) are sensitive to these chemicals
Number of Microbes
Time for heat of chemicals to kill if affected by population
size since only a fraction of population dies during given
time interval
Large population = more time
Decimal reduction time(D value) gauges commercial
effectiveness
D value depends on type of treatment for decimal
reduction rate and type of microbe (susceptibility)
Time required to kill 90% of population under specific
condition= “Logarithmic killing”
Environmental Condition
Dirt, grease, body fluids can interfere with heat penetration, action of
chemicals
pH, temperature can influence effectiveness of microbial death
oSodium hypochlorite (household bleach) solution can kill suspension
of M.tuberculosis at 55 C in ½ time as at 50 CMore effective at low pH
Risk for Infection
Medical instruments categorized according to risk for transmitting infectious
agent [greater threat = more rigorous procedure]
Critical items come in contact with body tissues
Include needles and scalpels, MUST be sterile
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