1. Ch 7 - Microbial Growth and Control
Stephanie Lanoue

2. The Terminology of Microbial Control
Learning Objective 7-1 Define the following key terms related to microbial control: sterilization, disinfection, antisepsis, degerming, sanitization, biocide, germicide, bacteriostasis, and asepsis.

3. The Terminology of Microbial Control
Google now. What do the terms sepsis and asepsis mean?
Sepsis refers to bacterial contamination
Asepsis is the absence of significant contamination
Aseptic surgery techniques prevent the microbial contamination of wounds

4. The Terminology of Microbial Control
Sterilization: ________ and destroying all microbial life
Sanitization: __________ microbial counts on eating utensils to safe levels
Commercial sterilization: killing C. botulinum endospores from canned goods
Disinfection: destroying harmful microorganisms
Antisepsis: destroying harmful microorganisms from _____________ tissue
Biocide (germicide): treatments that kill microbes
Bacteriostasis: inhibiting grow, not killing, microbes

5. The Rate of Microbial Death
Learning Objective 7-3 Describe the effects of microbial control agents on cellular structures.

6. The Rate of Microbial Death
Effectiveness of treatment depends on:
________ of microbes
______________ (organic matter, temperature, biofilms)
Time of exposure
Microbial characteristics

7. Actions of Microbial Control Agents
Alteration of cell _____________ permeability
Damage to cell ______
Damage to proteins (enzymes)
Damage to nucleic acids

8. Physical Methods of Microbial Control
Learning Objectives 7-4 Compare the effectiveness of moist heat (boiling, autoclaving, pasteurization) and dry heat. 7-5 Describe how filtration, low temperatures, high pressure, desiccation, and osmotic pressure suppress microbial growth. 7-6 Explain how radiation kills cells.

9. Microbial Control Physical: ________ _______ temperature Filtration
Moist heat sterilization (autoclave)
Dry heat sterilization
_______ temperature
Filtration
High pressure
Desiccation
Osmotic pressure
Radiation

10. Moist Heat Sterilization
Autoclave: steam under ______________
121 C at 15 psi for 15 min
Kills _______ organisms and endospores
Steam must contact the item's surface

11. Figure 7.2 An autoclave. Exhaust valve (removes steam
after sterilization)
Operating valve
(controls steam from
jacket to chamber)
Steam to
chamber
Safety
valve
Pressure gauge
Steam
Door
Steam
chamber
Air
Perforated shelf
Sediment
screen
Steam jacket
Thermometer
Automatic ejector valve
(thermostatically controlled;
closes on contact with
pure steam when air is
exhausted)
Pressure regulator
for steam supply
To waste line
Steam supply

12. Heat Pasteurization ___________ spoilage organisms and pathogens
Equivalent treatments
63 C for ____ ________
High-temperature short-time (HTST): 72 C for 15 sec
Ultra-high-temperature (UHT): 140 C for 4 sec
Thermoduric organisms survive

13. Dry Heat Sterilization
Dry Heat Sterilization kills by ______________
– Flaming
– Incineration
Oven,
170˚C, 2 hr
Review Question – What is oxidation? Google now.

14. Low temperature Filter Sterilization __________ microbial growth
Refrigeration
Deep freezing (-20oC or -80oC)
Lyophilization
Filter Sterilization
Passing of a substance through a filter resulting in a sterile filtrate

15. Passage of ___________ through a screen-like material (filter)
Figure 7.4 Filter sterilization with a disposable, presterilized plastic unit.
Passage of ___________ through a screen-like material (filter)
Used for heat-sensitive materials
Membrane filters remove microbes >0.22 µm
Flask of
sample
Cap
Membrane filter
Cotton plug in
vacuum line
ensures sterility
Vacuum line
Sterile
filtrate

16. Microbial Control - Physical (cont’d)
High pressure denatures ____________
Desiccation _________ metabolism
Osmotic pressure causes plasmolysis (shrinkage of cytoplasm)
Radiation damages DNA
Microwaves kill by heat

17. Chemical Methods of Microbial Control
Learning Objectives 7-7 List the factors related to effective disinfection. 7-8 Interpret the results of use-dilution tests and the disk-diffusion method.

18. Microbial Control Chemical Effective disinfection
________ microbial growth
Effective disinfection
– ________________ of disinfectant
– pH
– Time

19. Evaluating a disinfectant • Disk-diffusion method
• Particular species are evaluated in ________ test
• Zone of inhibition must be at or beyond a certain diameter
Zone of inhibition
Chlorine
Chlorine
Chlorine
O-phenylphenol
O-phenylphenol
Hexachlorophene
Hexachlorophene
Hexachlorophene
O-phenylphenol
Quat
Quat
Quat
Staphylococcus aureus
(gram-positive)
Escherichia coli
(gram-negative)
Pseudomonas aeruginosa
(gram-negative)

20. Microbial Control - Chemical (cont’d)
Phenolic
______________ of the plasma membrane, causing leakage

21. Microbial Control - Chemical (cont’d)
Halogens
Tincture of _________ (I2 ); iodine denatures proteins
Sodium hypochlorite (NaOCl) in bleach is a strong oxidizing agent.

22. Microbial Control - Chemical (cont’d)
4. Alcohol
Ethanol, isopropanol
Denatures proteins, dissolves __________
No effect on endospores and non-enveloped viruses
Ethanol and isopropanol
Require water

23. Microbial Control - Chemical (cont’d)
Heavy metals
Denature proteins by ______________ disulfide bonds
Mercurachrome, antiseptic for wounds
Figure 7.8 Oligodynamic action of heavy metals.

24. Microbial Control - Chemical (cont’d)
___________ active agents
Soaps
Detergents

26. Chemical Food Preservatives
Sulfur dioxide ___________ wine spoilage

27. Antibiotics
Bacteriocins—proteins produced by one ______________ that inhibits another
Penicillin

28. Biofilms
Learning Objective 6-7 Describe the formation of biofilms and their potential for causing infection.

29. Biofilms Microbial communities
Form __________ or hydrogels that adhere to surfaces
Share nutrients
Shelter bacteria from harmful environmental factors

30. Water currents move, as shown by the blue arrow, among
Figure 6.5 Biofilms.
Clumps of bacteria
adhering to surface
Migrating
clump of
bacteria
Surface
Water currents
Water currents move, as shown by the blue arrow, among
pillars of slime formed by the growth of bacteria attached to
solid surfaces. This allows efficient access to nutrients and removal of
bacterial waste products. Individual slime-forming bacteria or bacteria in
clumps of slime detach and move to new locations.

31. Biofilms
Found in digestive system and sewage treatment systems; can clog pipes
1000x _____________ to microbicides
Involved in ___% of infections
Catheters, heart valves, contact lenses, dental caries