Transcript GEHS-6030 Env.MICRO1

Tulane University
School of PH&TM
Global
Environmental Health Sciences
Environmental Microbiology
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Lecture Outline
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Role of Microorganisms in the
Environment
– Algae, Fungi, Viruses and Bacteria
Microbial growth
– Optimum conditions : pH, Oxygen,
Temperature, Nutrients,
– Microbial Growth Curve
Microorganisms in Water
Microorganisms in Food
Microorganisms in Waste
Microorganisms in Soil, the Nitrogen,
Sulfur and Carbon Cycles
Management of Microorganisms in Health
care facilities
*Control of Nosocomial Infections
*CDC Manual for Infections
*Universal Precautions
*Disinfection techniques
*Sterilization
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Environmental Microbiology
ALGAE
Chlorella
FUNGI
Basidiomycete
BACTERIA
Gram Negative Bacilli
Algae
Algae
Algae
Environmental Benefits
 Algae uses photosynthesis to capture sunlight
energy and carbon dioxide to produce oxygen
and carbohydrates. It grows so quickly and can
produce 15-50 times more Biofuel per acre
than any other crop such as soy beans and corn
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Food for humans (sea weed) and fish.
Algae-Based BioFuel
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Algae a new energy source that has been
getting a lot of attention lately. Certain
types of algae contain natural oils that can
be readily distilled into a vegetable oil or a
number of petroleum-like products that
could serve as drop-in replacements for
gasoline, diesel, and jet fuel.
National Algae Association
Benefits of Algae
It can thrive in nutrient poor environment .
Algae farms can be located near carbon
dioxide producing industries and help clean
the air by utilizing carbon dioxide to grow.
Algae can grow in fresh and salt water , in
sewage and the high quality protein which
can be harvested and converted to livestock
feed
Algae
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Environmental Impact
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Oxygen depletion
Clogging water filters
Algal Blooms/Eutrophication
Color, taste and odors in Drinking water
Red tide caused by Dinoflagellates (Algae), produce
toxins
FUNGI
Basidiomycete
Fungi
Bacteria
Bacteria
Salmonella
Vibrio cholera
Diplococci
Spirochetes
Microbial Growth
Factors:
Temperature
Oxygen
pH
Moisture
Osmotic Pressure
Food
Growth Factors(conti.)
Temperature
Cryophilic
< 20 0 C
Mesophilic
20 – 45 0 C
Thermophilic
46 - 65 0 C
Thermoduric
> 66 0 C
Growth Factors (conti.)
Oxygen
Oxygen:
Aerobic:
requires free
Oxygen
Anaerobic : combined oxygen
Facultative : free or combined
pH
Optimum pH 6.5-8.5
Moisture
Osmotic Pressure
Food
Growth Curve
 Lag
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phase
Log phase
Stationary phase
Decline phase
GROWTH CURVE
Number of organisms
7
6
5
4
3
2
1
0
2.5
5
7.5
Time
10
12.5
15
Microorganisms In Water
Water Contamination
Water Treatment:
Filtration: slow sand filters
Rivers and Stream and ponds
Microorganisms In Wastewater
Biological Treatment of Sewage
activated sludge
trickling filters
biodiscs
Biological Treatment of solid waste
Biological Treatment of toxic chemicals
Microorganisms In Food
Food Contamination:
diseases
disinfection
pasteurization
sterilization
Food Industry: cheese, fermentation
Microorganisms in Soil
Most are present in the top 3 inches
Aerobic, anaerobic and facultative
Degrade and in many cases detoxify toxic
chemicals.
Sulfur, nitrogen and carbon cycles
Sediment microbial population .
THE NITROGEN CYCLE
Animal
Metabolism
Nitogen
Fixation by
Azotabacter and
Rhizobium
Complex
Nitrogenous
Compounds
in
Plants
Complex
Nitrogenous
Compounds
in
Animals
Loss of NH3 into
the Atmosphere
Decomposition
by Microorganisms
in the Soil
Decomposition and
Reduction of Nitrogenous
Compounds to Ammonia
by Organisms in the Soil
Ammonia
(NH3)
in the
Soil
Oxidation by
Microorganisms
(Nitrosomonas)
in the Soil
Plant
Metabolism
Nitric
Acid Salts
(NaNO3)
Industries,
commercial
fertilizer,
volcanic
DENITRIFICATION
Oxidation by
Microorganims
(Nitrobacter)
in the Soil
LIGHTNING
Nitrous
Acid Salts
(NaNO2)
THE SULFUR CYCLE
Organic Compounds
(cystine, methionine, glutathione,etc)
in plants and animals
Putrefactive
microorganisma
(use S as H-acceptor)
Sulfate-reducing
microorganims :
Desulfovibrio, etc.
Food of plants
and animals
H2SO4
Sulfur oxidation by
Thiobacillus,
Thiorhodaceae, etc
Sulfur oxidizing bacteria :
Thiorhodaceae, etc.
H2 S
S
Sulfur compounds
from non-living
source: mines, waters,
volcanic gases, etc.
THE CARBON CYCLE
PHOTOSYNTHESIS
Organic
compounds
in plants
(Green plants,
Combustion;
Metabolism;
Decomposition by
Microorganims
Atmospheric or
free CO2
Microbial
reduction
to
Organic
compunds
in animals
Microbial oxidation
CH4
Management of Hospital
Environment
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Areas Covered:
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Hazardous Materials
Waste/solid /gas and liquid
Food / water/air
Emergency Preparedness
Safety
Security
Medical Equipment
Microbiology Of Health Care
Institutions
Equilibrium :Host, agent and the
environment. Any misbalance might
increase or decrease the chance of
diseases .
 Control the agent, protect the Host and
clean the environment.
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CDC Manual:
In 1970 the CDC published a detailed
manual “Isolation Techniques For Use In
Hospitals”
 In 1985 the CDC issued the “Universal
Precautions Standard”
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Designed to protect employees from
exposure to the blood and fluids of AIDS
Patients.
Universal Precautions
Standard (conti.)
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The standard contains Six Components:
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administrative controls
work control practices
personal protective equipment
housekeeping
employee health issues
Engineering control
I- Administrative Controls
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It places the responsibility on the
institution (hospital) to establish An
Infection Control Program which should
include policies and procedures
,surveillance and staff education. These
describe patient care practices, cleaning,
disinfection, and sterilization .
II- Work Control Practices
Handling patients ,
 Handling specimens,
 hand washing practices is the single most
important practice to prevent the spread
of infections in a hospital.
 Laboratory employees.
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III- Personal Protective
Equipment (PPE)
These are extra covering put on the
employee /patient when handling patients
.They include gowns, cloves, masks, eye
protection, and face shields.
 In 1983 CDC manual, Category-Specific
Isolation Precautions was developed to
assist employees in selecting appropriate
protective equipment to use .
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III-Personal Protective
Equipment (conti.)
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In 1995 the CDC published new document
“Guideline for Isolation Precautions in
Hospitals” It has two parts: the old
Universal Precautions: gloves, masks,
gowns, eye protection and the new part
(Transmission-Based Precautions) covers
Airborne, droplet and Contact.
IV- Housekeeping
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Routine and terminal cleaning of surfaces
as well as linen and laundry. Selection of
detergents and disinfectants for cleaning
surfaces such as beds, bedrails, over-bed
tables, chairs, floors, walls in patient rooms
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Laundry facilities in hospitals are
monitored by the local health agencies.
The water and dryer temperatures are
important to clean and sterilize soiled
linen.
V- The Employee Health
Program
To prevent disease transmission from
patient to employee and from employee
to patient.
 Most programs include screening and
post exposure evaluation. Vaccination
against Rubella, Influenza, Mumps etc .
vary according to hospitals.
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VI- Engineering Controls:
Consist of cleaning patient care
equipment sterilization or disinfection
 Handling and disposal of infectious
waste, air conditioning / ventilation,
positive or negative air flow.
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Sterilization
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In considering methods for sterilization
procedures, it is important to differentiate
between sterilization and disinfection.
* Sterilization kills all viable
microorganisms.
* Disinfection only reduces the number
of viable microorganisms.
Disinfection
It is a process that kills most pathogens ,
rarely kills spores.
 Three major methods are used:
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1- Ultra violet irradiation
2. pasteurization
3. liquid chemicals.
1- Ultraviolet Irradiation
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Both viruses and bacteria are susceptible.
UV light does not penetrate large dust
particles, mucus and large droplets . It
might cause skin and eye burns.
2- Pasteurization
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It is hot water disinfection at
temperatures about 75 C0.
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Washer-Rinser-dryer
It is simple ,nontoxic, and no chemical
residue .
It does not kill spores
3- Liquid Chemical Disinfection
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Disinfection will destroy pathogens except the
spores which they are more resistant .
Major categories the commonly used
disinfectants are
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Halogens
Phenols
Quaternary ammonia (QUUATS)
Aldehydes
These are NOT sterilants
Sterilization
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The preferred methods of sterilization are high
pressure steam/temperature (in autoclaves) for
items that can with stand high temperature,
and ethylene oxide gas for items that cannot
withstand high temperature. However, cold
chemical sterilants may be used effectively for
many items.
Sterilization
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Two Major Methods:
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1) Thermal : steam and dry
2) Chemical : Ethylene Oxide(C2 H4 O)
ETO mixed with CFC 12/88 , used for heat
sensitive articles
Chloroflourocarbons
ETO: is flammable, toxic air contaminant ,
probable carcinogen and CFC is an Ozone
depleter
Other Sterilization Methods
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Ozone / oxidizes metals, plastics
Radiation/ Gamma
Plasma: Hydrogen peroxide
Microwave Radiation ( Promising )
All react with microorganism cell membrane
and destroy cell proteins and DNA
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Cidex: Active ingredient: 2% Glutaraldehyde. The
manufacturer's instructions indicate that a
minimum of 10 hours is required for sterilization.
Cidex comes in two formulations, Cidex and
Cidex-7 (long-life). The shelf life of activated
Cidex is 15 days and of activated Cidex-7 is 28
days.
Clidox: Active ingredient: Chlorine dioxide. 1:5
mixture must be mixed daily. 1:18 mixture is good
for 14 days. 1:5 is a good sterilant; 1:18 is a
disinfectant.
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Alcide: Active ingredient: Sodium hypohlorite 1.37%. The
manufacturer's instructions indicate that a minimum of 6
hours is required for sterilization. The shelf life of the
activated solution is 14 days.
Other acceptable sterilants are the following chemicals
classified as sterilants by the Centers for Disease Control
(CDC). These are the chemical ingredients of some of the
commercial sterilants:
– Glutaraldehyde (2%) for a minimum of 10 hours.
– Formaldehyde (8%) / Alcohol (70%); minimum of 18 hours.
– Stabilized hydrogen peroxide (6%) for a minimum of 6 hours.
Dispersants
Corexit EC 9527A
 2-butoxyethanol
 Organic Sulfonic acid
 Propylene Glycol
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Specific Gravity
30%
10%
1%
0,98-1.02