Transcript Factors Affecting Foodborne Disease

Laboratory Control
• BSCs
• Centrifuge containment
• HVAC
Class I
• Personnel and
Environmental
Protection
• No Product Protection
• Similar to fume hood
with HEPA exhaust
• 75 LPM
• Hard-ducted to BLDG
exhaust
• 0.5 inches water
Class I
• Some have integral
blower
• Must be turned off in
case of BLDG
exhaust failure
• Good design to
surround all positive
pressure plenums
with vacuum
Class IIA/B3 (Now Class II A2)
• 30/70 exhaust/recirculation
• HEPA filtered on exhaust
and recirculation
• 75 LPM
• Hard-ducting not
recommended
• Not rated for volatiles or
toxics
Class IIB1
• Originated with NCI designed
cabinet
• 70/30 exhaust/recirculation
• HEPA filtered on exhaust,
recirculation and inflow
• Personnel, environment and
product protection
• 100 LPM
• 70% downflow through rear
grill; 30% front grill
• Hard-ducted; preferably
dedicated
Class IIB2
• Total exhaust
• Personnel, environment and
product protection
• HEPA filtered on inflow and
exhaust
• 100 LPM
• Hard-ducted;1.5 inches
water; must be interlocked;
ideally dedicated
• With internal blower may not
be hard-ducted
Class III
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Designed for work with BSL 4 agents
Interchange box
Heavy duty rubber gloves
HEPA filtered on supply and exhaust (double or
incinerator)
• Hard-ducted; dedicated exhaust 0.5 inches water
BAG-IN BAG-OUT (BIBO)
• Additional layer of
protection
• Between BSC and
BLDG exhaust
• HEPA
• Required for
BSL3/BSL4 laboratories
Respirators/PAPRs
Fit Testing
Before an employee uses any respirator with a
negative or positive pressure tight-fitting
facepiece, the employee must be fit tested with
the same make, model, style, and size of
respirator that will be used.
Qualitative Fit Test (QLFT)
A pass/fail fit test to assess the adequacy
of respirator fit that relies on the
individual’s response to the test agent.
Quantitative Fit Test (QNFT)
An assessment of the adequacy of respirator
fit by numerically measuring the amount of
leakage into the respirator.
Control of Foodborne Disease
Today
• Review of classes of food-borne disease,
types of contamination, sources and
factors affecting growth
• HACCP
• Types of controls
– Physical Methods
– Chemical Methods
– Biological Methods
Classes of Food-borne Disease
• Infection
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Foodhandler
Food Concentration
Direct Contamination
Water-washed
• Toxico-infection
• Intoxication (food poisoning)
– Bacterial and Fungal Toxins
– Shellfish Toxins
– Metals, Chemicals, etc.
• Allergy
Types of Contamination
• Viral
• Bacterial
– Cells
– Products
• Fungi
– Products
• Protozoa and Helminths
• Other (Cyanobacteria??)
Microbial Growth in Food
• Bacteria and Fungi
• Complex Ecology
– Interaction with multiple environmental factors
controls whether an organism can grow in a
given environment
• Food Preservation
– Ecology of zero growth
Microbial Growth in Food
• Intrinsic Factors:
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pH
Water Activity
Salt Concentration
Nutrients
Etc.
• Extrinsic Factors
– Temperature
– Gaseous Conditions
– Presence of Other
Microbes
Heterogeneity
- Question of scale
- Food items may have several distinct
microenvironments
HACCP
• Hazard Analysis and Critical Control Point
– Framework to identify risks and control hazards
• Preliminary steps
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Gain management support
Assemble HACCP team
Describe the food and method of distribution
Identify the intended use and consumers
Develop a flow diagram
Verify the flow diagram
• Establish plan-specific objectives and performance
criteria
7 Principles of HACCP
1) Conduct a Hazard Analysis
a.
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Hazard identification
Hazard evaluation
Identification of control measures
Determine influence of prerequisite
programs
2) Determine the Critical Control Points
a. Consideration for product type
b. Use of decision trees
7 Principles of HACCP
3) Establish Critical Limits
a. Defined as “ a maximum or minimum value
to which a biological, chemical, or physical
parameter must be controlled at the CCP to
prevent, eliminate, or reduce to an
acceptable level the occurrence of a
significant food safety hazard
b. Typically process based rather than
microbiological
7 Principles of HACCP
4) Establish Monitoring Procedures
a.
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What is being monitored
How often
Procedures to collect data
Responsibility
5) Establish Corrective Actions
a. Fix or correct problem
b. Determine disposition of product
c. Re-evaluate HACCP plan
7 Principles of HACCP
6) Establish Verification Process
a. Methods, procedures, and/or tests used to
verify compliance to HACCP plan in addition
to monitoring
b. Essentially QA/QC
7) Establish Record-Keeping and
Documentation Procedures
a. HACCP Plan and supporting documentation
b. Records obtained during operation of plan
Control of Food-borne Microbes
• Poor- No control over food production,
distribution, or consumption
• Good- Prevent degradation of product by
control of shelf-life and environmental
factors
• Better- Chemical, Physical or Biological
Treatment
• BEST- PREVENT CONTAMINATION
Physical Controls
• Water Activity
– Dehydration
• Drying- air
• Freeze-Drying (vacuum sublimation of ice content)
– Minimal aw needed for growth
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Bacteria
Yeasts
Molds
Halophilic bacteria
Xerotolerant molds
Xerotphilic molds and osmophilic yeasts
0.91-0.88
0.88
0.80
0.75
0.71
0.62-0.60
Physical Controls
• Temperature Controls
– Cool Storage (4-12ºC)
• Controlled-Atmosphere Storage
• MAP/VP
– Freezing and Frozen Storage (-15 to -40ºC)
– Heat Treatments
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Autoclaving
Dry Heat Sterilization
Pasteurization/Flash Pasteurization
Tyndalization
Microwave heating
Ohmic Heating
Physical controls
• Ultrasound
– Synergy with heat
• Irradiation
– UV Radiation
– High-Intensity Pulsed Light
• Xenon lamps
– Ionizing Radiation
• Gamma
• E-Beam
• Hydrostatic Pressure
• Electric Field Effects
• Magnetic Field Effects
Chemical Controls
• Organic Acids and Esters
– E.g. acetic, lactic, propionic, sorbic, benzoic
– Related to pH (used in foods with pH<5.5)
• Dimethyl Dicarbonate
– Highly reactive with wide range of compounds
– Primarily targeted at yeasts, but also bacteriocidal
– Inactivates enzymes
• Lysozyme
– Targets peptidoglygan causing hydrolysis
– Egg albumin
– Increased effectiveness with pretreatment chelators
Chemical Controls
• Nitrites
– Particularly good against C. botulinum
– Inactivates enzymes; better under anaerobic
conditions, and low pH
• Parabens
– Antimicrobial activity related to length of chain
– Better against molds and yeast than bacteria; but more
effective against Gram + than Gram –
– Inhibit nutrient uptake (e.g. amino acids line serine)
Chemical Controls
• Phenolic Antioxidants
– E.g. BHA, BHT, propyl gallate, and TBHQ
– Function: Delays auto-oxidation of
unsaturated lipids
• Interupts free-radical chain mechanism of
hydroperoxide formation
– Similar antimicrobial mechanism to Parabens
and other phenolics; higher levels required
Chemical Controls
• Phosphates
– E.g. sodium acid pyrophosphate (SAPP),
TSPP, STPP, SHMP, TSP
– Gram + more susceptible than Gram –
– Mechanism: metal chelation
• Inhibits cell division
– Interference with Mg2+-dependent enzyme.
• Salt (NaCl)
– Water activity
Chemical Controls
• Sulfites and Sulfur salts
– Targets spoilage and fermentative yeasts,
molds, acetic acid bacteria, and malolactic
bacteria
– Act as antioxidants; inhibit enzymatic activities
Natural Chemical Compounds
• Lactoperoxidase System
– Enzyme in milk
– Better against Gram –
• Lactoferrin and Other Iron Binding
Proteins
• Avidin (glycoprotein in egg albumin)
– Binds biotin (a co-factor for enzymes)
• Spices and Oils
• Phenolics
Biological Controls
• Controlled Acidification
– E.g. lactobacilli and lactococcal bacteria
• Bacteriocins
– E.g. Nisin (temp-dependent)