CHAPTER 5 — Control of Microbial Growth

terms

Sterilization

Removal/destruction of all microorganism and viruses

Does sterilization consider prions?

No

Disinfection

Elimination of most or all pathogens

Kill Bacteria

Bactericide

Kill Fungi

Fungicide

Virucide

Interactive Viruses

Antiseptic

Non-toxic, used on skin/tissues

Sanitization

Substantially reduces microbial population to meet health standards

Preservation

Delaying a spoilage of perishable products

Bacteriostatic

Inhibits Bacterial growth

Pasteurization

brief heating without changing products characteristics

hand washing with soap and H20

Most important daily step against infectious disease spread

HAI stands for

Healthcare associated infection (nosocomial infection)

more susceptible to infections in hospital

Immunocompromised patients

Aseptic technique

procedure to prevent contamination of personal/samples/environments

Extreme heat or chemical treatment

Destroys bacterial endospores

destroys protozoan cysts/oocysts

Boiling

Mycolic acids

Gives Mycobacterium chemical resistence

pseudomonas

Resistance to some disinfectants can grow in them

Non-enveloped viruses

lack a lipid envelope more resistant to disinfectants

d value ( decimal reduction time)

time to kill 90% microbial population

removes biofilm, reduces sterilization time

scrubbing

Two environmental factors affecting disinfectant efficacy

Temperature and pH

direct contact with body tissues; must be sterile

critical instruments

contact with mucous membranes; must be disinfected

semicritical instruments

contact with unbroken skin; little infection risk

non-critical instruments/surfaces

Boiling destroys most microorganisms in

5 minutes

What boiling does not kill

Endospores

What is Milk HTST temperature time?

72° C for 15 seconds

What is ice cream HTST temperture/time?

82°C for 20 seconds

UHT milk temperture

140°C , then rapidly cooled

UHT pasterurization

Used for shelf-stable boxed juice

Autoclave pressure/temp/time

15 PSI, 121°C, 15 min

PSI stands for

Pounds per square inch

Destruction by burning to ashes

Incineration

Dry heat ovens

Less efficient that moist heat, needs longer/hotter

Lab glassware dry heat temp/time

160-170°C for 2-3 hours

Dry heat equivalent to auto-claving

200°C for 90 min

Pore size for fluid filtration (bacteria removal)

0.2 µm

Pathogen size HEPA filters remove

0.3 µm or larger

determines type of irradiation cell damage

wavelength

Gamma radiation destroys

DNA (possibly cytoplasmic membrane)

Two reactive oxygen species from irradiation

Superoxide (O₂⁻) and hydrogen peroxide (H₂O₂)

Converts superoxide to O₂ and H₂O₂

Superoxide dismutase

Converts H₂O₂ to O₂ and H₂O

Catalase

Most resistant microbial form to gamma irradiation

Bacterial endospores

Most susceptible genera to gamma irradiation

Pseudomonas and Salmonella

UV radiation damages

DNA

Why UV can’t kill in solids/turbid liquids

Poor penetration

Alcohol effective concentration range

60% - 80%

What alcohol is NOT reliable against

Endospores and some non-enveloped viruses

chlorine effective dilution in water

1:100

what iodine doesn’t readily kill

Endospores

What iodine may be more effective against

Giardia lamblia cysts