Microbial Growth Control Chapter 5

Chapter 5: Control of Microbial Growth

• Microbial control methods vary depending on the situation and desired level of control.
• Joseph Lister's work revolutionized surgery by introducing methods to prevent wound infections.
• Lister utilized carbolic acid (phenol) and sterilized instruments to prevent infections.
• Modern hospitals utilize strict procedures to prevent microbial contamination.

Principles of Control

• Sterilization: Eliminates all microorganisms, including endospores and viruses (but not prions).
• Disinfection: Eliminates most or all pathogens; some viable microbes may remain.
• Disinfectants: Used on inanimate objects.
• Antiseptics: Used on living tissues.
• Pasteurization: Brief heating to reduce spoilage organisms and pathogens.

Approaches to Control (continued)

• Decontamination: Reduces pathogens to safe levels.
• Sanitization: Reduces microbial population to meet health standards.
• Preservation: Delays spoilage of perishable food and other products.
• Add bacteriostatic (growth inhibiting) preservatives.

Daily Life

• Washing and scrubbing with soaps and detergents is a common method to reduce microbial populations.
• Soap mechanically removes organisms.
• Beneficial skin microbiota reside deeper, so regular handwashing is not adversely affected.

Hospitals

• Minimizing microbial populations is crucial for preventing healthcare-associated infections.
• Patients undergoing invasive procedures are more susceptible to infections.
• Hospital settings frequently contain pathogens like fecal, urine, respiratory droplets and bodily secretions.
• Instruments must be sterilized to prevent introducing infections to deep tissues.
• Prions are a new concern because they are difficult to destroy.

Food and Food Production Facilities

• Perishables retain quality longer when microbes are removed, destroyed, or inhibited.
• Heat treatment is a common method.
• Irradiation is used to control certain foods.
• Chemical additives can control spoilage.
• Facilities must maintain clean surfaces to minimize microbes.

Water Treatment Facilities

• Ensuring safe drinking water involves removing pathogens.
• Chlorine is traditionally used to disinfect water, although it can react with naturally occurring chemicals to create disinfection by-products (DBPs).
• Some DBPs are linked to long-term health risks.
• Some organisms, like Cryptosporidium parvum, are resistant to chemical disinfectants.
• Regulations require minimization of DBPs and C. parvum in treated water.

Selection of an Antimicrobial Procedure

• Selecting effective procedures can be challenging due to the existence of various factors involved in the process.
• Factors like the type and number of microbes, environmental conditions, risk of infection, and the composition of the infected item are important considerations.
• Multiple highly resistant microbes, like bacterial endospores and protozoan cysts, require extreme conditions to completely destroy them.
• The time needed for heat or chemicals to kill microbes depends on microbial population size.
• Environmental conditions like dirt, grease, body fluids can interfere with effective microbial control, and factors like pH and temperature influence chemical effectiveness.

Composition of Item

• Certain sterilization and disinfection methods are inappropriate for certain items like plastics.
• Irradiation provides a viable alternative to heat for moisture-sensitive materials.

Using Heat to Destroy Microorganisms and Viruses

• Heat treatment is a safe and relatively fast method.
• Moist heat, a reliable method for denaturing proteins and destroying microorganisms, includes boiling, pasteurization, and sterilization using pressurized steam (autoclaving) and flash sterilization.
• Dry heat is less effective than moist heat, but can be used for sterilization in hot air ovens.

Using Other Physical Methods to Remove or Destroy Microbes

• Filtration methods remove microbes from fluids and is extensively used in both liquids and air.
• Membrane filters with small pore sizes are frequently used.
• HEPA (high-efficiency particulate air) filters remove nearly all microbes from air.
• Radiation, including ultraviolet light and gamma rays, can be used to destroy microbes, but have limitations pertaining to penetrating power.

Chemical Methods to Remove or Destroy Microbes

• Sterilants destroy all microorganisms, whereas high-level disinfectants typically destroy viruses, vegetative cells, and some fungi.
• Intermediate and low-level disinfectants target different microorganisms.
• Chemical disinfectants have limitations based on the nature of the material being sanitized, organic matter, or the chemical residue left behind after use.

Preservation of Perishable Products

• Chemical preservatives must be non-toxic for safe consumption.

• Weak organic acids and nitrites are commonly used as preservatives.

• Nitrates and nitrites inhibit microbial growth, particularly in processed meats.

• They preserve the color and increase the safety of processed meats but are known carcinogens.

• Low-temperature storage of perishable products slows or stops enzyme reactions. Avoiding microbial growth is crucial to preserving the quality and safety of perishable products.

• Reducing available water through salting, adding sugar, and drying food reduces microbial growth based on the removal of water from bacterial cells.

Explore the key concepts of microbial control methods covered in Chapter 5. Learn about sterilization, disinfection, and the historical impact of Joseph Lister’s contributions to surgery. This quiz will test your understanding of how various techniques are applied in modern healthcare settings.