Control refers to sterilization, disinfection and antisepsis.
    ·Sterilization: Eliminates all forms of life including spores and viruses from a place or object.
   · Disinfection: killing, inhibition or removal of disease-causing organisms from an object.
   · Sanitation: microbial population is reduced to safe health standards.
   · Antisepsis: killing or inhibition of disease-causing organisms on living tissue - since should not
      damage tissue, less toxic than disinfectants. Generally topical treatment

I. Sufix CIDAL vs STATIC
   · CIDAL (to kill): bactericidal, fungicidal, etc.
   · STATIC (to stop): bacteriostatic.

II. BACTERIAL DEATH
· Death: microorganisms won't grow when inoculated into culture medium that will normally
    support its growth.
· Microbial death is logarithmic, just like growth. Population decreases by same fraction at constant
    intervals, so a plot of log survivors over time is linear. Consequently, a larger population takes
    longer to die. If you mix bacteria with a lethal agent you will get a 90% reduction after 1 minute,
    after another 1 minute you will have 90% reduction, and so forth. [e.g. 10, 000 (log 4) ® 1,000
    (log 3) ® 100 (log 2) ® 10 (log 1)].

III. Factors that influence effectiveness:
    · Population size
    · Temperature- low T, more time; high T, shorter time
    · Population composition - different species have different sensitivities. Vegetative cell,
        endospores, type of waxy cell wall of Mycobacteria, cysts of protozoa, type of virus
        (enveloped or just a capsid)
    · Local environment - organic matter neutralizes many disinfectants - this is especially a
        problem with chlorine compounds.
    · Concentration of the disinfecting agent are also important considerations.
    · Duration of the exposure

Moist Heat - Protein denaturant (breaks hydrogen bonds) and DNA denaturant. Moist heat (hot
    water, boiling water, steam) is more effective than dry heat
· Boiling - 10 minutes will kill vegetative cells and viruses. Not endosporocidal or virucidal
· Autoclave - 121 C, 15 psi steam pressure, 15 min. Kills everything.
· Pasteurize - mild heating to reduce populations in heat-sensitive liquids (milk, beer, wine). In milk the
    goal is to reduce pathogenic microbes. Old version: 63^o C (145 F) for 30 min.  New version: 72^o C
    (162 F) for 15 sec.
· Dry heat - Flaming - you will do this with your loop. Oven set at 170^o C (338 F) for 3 hours. Good
     for glassware. Kills endospores.
· Filtration - 0.2 - 0.4 mm pore size membranes. Good for sterilizing liquids. Viruses are not
    excluded. Used for heat-sensitive solutions. Receptacle and filter membrane must be sterile
    (obviously!). New filters with size of 0.01 mm will retain viruses.
· Low temperature - doesn't kill, it preserves. Bacteriostatic. Refrigerators from 2-6^o C
· Radiation – non-ionizing VS ionizing.
    · UV light: at 260 nm. Lamps for treatment of air and exposed surfaces --> cannot penetrate glass,
 water, dirt, etc.
    ·Ionizing radiation (gamma rays, X rays) - ionizes water --> OH- radicals that react with organic
        molecules, in particular DNA: gamma radiation from a Cobalt 60 source. Good penetrating power.
        Used on solutions, plastic syringes, etc. Expensive to operate and lots of safety precautions.
 

b) Phenol coefficient: uses Salmonella (G [-]), Staph. aureus (G[+]).
    - Dilutions of phenol standard and chemical "X"
    - Dip disks containing bacteria and place them in chemical for 10 min, 20 C.
    - Plate and incubate
    - PC = chemical "X"/ Phenol. >1 better than phenol; <1 worst than phenol.

Types of Disinfectants:

1. Phenolic compounds: Phenol (carbolic acid), Lysol, Cresols,  All are powerful
    disinfectants. Not inactivated by organic matter. Hexachlorophene-skin infections and triclosan -soaps
    (Bisphenols).

2. Alcohols: Remove lipids and disrupt cell membrane. Also a dehydration effect (denatures
    proteins). Good for washing skin - antiseptic. Kills vegetative bacterial cells and enveloped viruses
     well.
Not effective on endospores and non-enveloped viruses. Isopropyl slightly better than ethanol,
    70% more effective than higher concentrations. Denaturation requires water.

3. Halogens:
    Chlorine: widely used as a disinfectant to treat water and in dairy industry.
    · Strong oxidizing agents. Oxidazes the S-H group on cysteine and S-S bridges on enzymes.
    · Chlorine gas or sodium hypochlorite.
    · Active ingredient: HOCl - hypochlorous acid
    · Chlorine + H₂O ® hypochlorous acid (HClO).
    · Sodium hypochlorite - house hold disinfectant - bleach

    Iodine: used as a skin disinfectant. Halogens have the disadvantage of being inactivated by
    organic materials. Tincture: iodine solution + alcohol (1% iodine + 70% etahnol). Iodophore: 2%
     iodine + detergent - (release iodine very slowly, e.g. Betadine, Isodine).

4. Alkylating agents (attach methyl or ethyl groups to proteins or DNA)
    · formaldehyde and glutaraldehyde (37% formaldehyde is called formalin). Very effective
        agents, these kill everything, but they are highly toxic.
    · Ethylene oxide: A good sterilizing agents but it is a very toxic gas. Mixed with inert gas such
        as freon or CO₂
5. Heavy metals (bind to SH groups of proteins ® denature)
    Olygodynamic action: diffucion of very amounts of metals.
· Mercury- mercuric chloride - control of mildew in paints. Mercurochrome such as merthiolate-
     antiseptic.
· Silver- 1% silver nitrate used in newborn's eyes and as antiseptic in burn patients. Silver impregnated
    dressings for wound dressings.
· Copper- copper sulfate used in agriculture to control algae. Used in paint and used to treat swimming
    pools and fish tanks. Toxic to invertebrates.
· Zinc - Zinc chloride common in mouth washes and zinc oxide is a good antifungal ingrdient in paints and
    in foot powders.

6. Antimicrobial detergents
· Surface active agents - not good microbicidal agents. E.g. soaps and detergents. They function
    mainly as wetting agents.
· Ionic (pos. charged) detergents - they my affect the cell membrane.. These are the most effective.
    Among these, the quaternary ammonium compounds (QUATS)- benzalkonium chloride (Zephiran),
    cetylpyridium chloride (Cepacol). Good against gram (+) not so good against gram (-). Soap and
    organic matter will inactivate QUATS.
· disrupt membranes and affects selective permeability.
· not tuberculocidal or sporicidal.
· clean away organic matter as well as disinfecting

7. Organic acid - function as food preservatives.
· Sodium benzoate, calcium propionate, sorbic acid

8. Alkylating Agents - Aldehydes
· Attach alkyl groups (CH3-, CH2-) to functional groups in proteins: -NH2, -OH, -COOH, -SH.
· Examples are: formaldehyde (formalin, 37%), gluteraldehyde, ethylene oxide gas.
 

Reaction of microorganisms to chemicals:
More resistant                                                           Less Resistant
- Prions                                                                            -  Viruses with lipid envelopes
- Endospores                                                                    - Gram (+) bacteria
- Mycobacteria                                                                 - Viruses without envelopes
- Cysts of protozoa                                                           -  Fungi