1. MLAB 2434 –MICROBIOLOGY KERI BROPHY-MARTINEZ
Chapter 4 – Control of Microorganisms

2. Control of Microorganisms (cont’d)
Sterilization vs. Disinfectant
Sterilization
Removes all forms of life, including spores
“All or nothing” process
Chemical or physical

3. Control of Microorganisms (cont’d)
Disinfection
Removes all pathogenic organisms but not necessarily all spores
“Disinfectants” are chemicals applied to inanimate objects
“Antiseptics” are disinfectants applied to living tissue. They do not kill spores.

4. Control of Microorganisms (cont’d)
Factors Influencing Degree of Killing
Types of organisms - Bacterial spores, mycobacteria, nonlipid viruses, fungi, bacteria, lipid viruses (most resistant to least resistant)

5. Control of Microorganisms (cont’d)
Number of organisms – microbial load
The higher the number of organisms, more exposure to the killing agent is required.
Concentration of disinfecting agent
Presence of organic material
Affects killing activity by inactivating disinfecting agent
Nature of the surface to be disinfected
Contact time
Temperature

6. Control of Microorganisms (cont’d)
Methods of Disinfection & Sterilization
Physical Methods: mainly for sterilization
Moist Heat – autoclave = 15 psi at 121° C for 15 minutes
Dry Heat o
Bacticinerator
Hot air ovens ( glassware)
Boiling & pasteurization
Do NOT sterilize or remove spores

7. Control of Microorganisms (cont’d)
Radiation: used to sterilize disposable medical supplies (catheters, syringes)
Filtration
Liquids: liquid is pulled through cellulose acetate or cellulose nitrate membrane with a vacuum. Used for heat sensitive liquids such as serum, antibiotic solutions, toxic chemicals and vaccines
Air: use high-efficiency-particulate air (HEPA) filters. Designed to remove organisms larger than 0.3 µm from isolation rooms, biological cabinets and respirators

8. Control of Microorganisms
Quality control for Sterilization Procedures
For each load:
Temperature & duration of cycle should be checked and recorded
Indicator tape is attached to each item
Weekly:
Check biological indicators
Bacterial spores are used as indicator of sterilization
Sporestrips are placed in the center of the load to be sterilized. After the cycle, the strips are cultured to demonstrate complete kill.
Spores used
Bacillus stearothermophilus- moist steam
Bacillus subtilis- dry heat

9. Control of Microorganisms
Chemical Methods: used in disinfection

10. Control of Microorganisms (cont’d)
Microbiology Laboratory Safety Program
Address biological hazards
Describe safe handling, storage and disposal of biological hazards & chemicals
MSDS: Material Safety Data Sheets
Biohazard bags & sharps containers
Correct techniques for lifting and moving heavy objects
Procedures in event of fire, natural disasters, and bomb threats
Fires: R= rescue A= alarm C= contain E=extinguish
Electrical: grounded 3-pronged plugs, check for frayed cords

11. Control of Microorganisms (cont’d)
Occupational Safety and Health Administration (OSHA)
Safety training for potentially exposed employees
Goal is to protect workers

12. Control of Microorganisms (cont’d)
Exposure Control Plan
Required by OSHA
Determine tasks that may result in hazards
A plan to investigate exposure and prevent reoccurrences
Methods of compliance with universal precautions
Engineering and work practice controls
Personal protective equipment (PPE)
Workplace cleanliness
Handling and disposal of waste
Active hazard training programs

13. Control of Microorganisms (cont’d)
Universal/standard precautions
Developed in 1985, redone in 1996
All blood and body fluids are treated as infectious
Lone exception is sweat
Precautions address
Hand washing
Gloves, mask, eye protection
Lab coats
Appropriate sharps disposal
Environmental controls
Employers are required to provide appropriate PPE

14. Control of Microorganisms (cont’d)
Engineering controls
Controls designed to remove hazards from the workplace
Some examples are eye wash stations, safety showers, eye shields

15. Control of Microorganisms (cont’d)
Handling Biological Hazards
Two sources of hazards:
Patient specimens
Actively growing cultures of microorganisms

16. Control of Microorganisms (cont’d)
Biosafety levels (BSL)
BSL-1
Well classified and not known to cause disease
Standard PPE
BSL-2
Moderate potential hazard
PPE and BSC class I

17. Control of Microorganisms (cont’d)
BSL-3
Potential aerosol transmission
Agents may have serious lethal consequences
PPE, BSC Class II or III, negative-pressure rooms
BSL-4
Dangerous and exotic pathogens
PPE, BSC Class III, negative-pressure rooms
Decontamination of room and personnel after use

18. Control of Microorganisms (cont’d)
Safety Cabinets (Hoods)
Class I – exhaust fan moves the air inward through the open front. Air passes through HEPA filter. Example = chemical fume hood
Class II – air pulled inward and downward and then passes through HEPA filter before reaching work surface. Example = most common microbiology laboratory hood

19. Control of Microorganisms (cont’d)
Class III
Self-contained, ventilated system for highly infectious microorganisms
Provides highest level of personal protection
Closed front contains attached gloves for work on bench

20. Safety Cabinets (Hoods)

21. References
Engelkirk, P., & Duben-Engelkirk, J. (2008). Laboratory Diagnosis of Infectious Diseases: Essentials of Diagnostic Microbiology . Baltimore, MD: Lippincott Williams and Wilkins.
Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.