13.1 and 13.3 Control of Microbial Growth

Terminology (3)

-cidal: kills the microbial population; the organism that come into contact with this are going to die; can be toxic and can hurt the individual that comes into contact with that so that is why -static might be used instead of -cidal i. Fungicides: kills fungus -static: prevents the growth/reproduction of microorganisms, but does not necessarily kill the microbes already there, less toxic, safer than -cidal i. Fungistatic: targets only fungus so won't kill bacteria

Fomite

1. A physical object that serves to transmit an infectious agent from person to person; harbors pathogen 2. Nonporous surfaces: pathogen cannot stay on surface very long 3. Porous surface: can stay on surface very long

Alcohols

1. Denature proteins and dissolves lipids 2. No effect on endospores and nonenveloped viruses 3. Ethanol and isopropanol a. Require water to dilute them; more isn't actually better. Less effective more more concentration of alcohol; average is 70% b. Ethyl alcohol, intoxicating ingredient found in alcoholic drinks, is also used commonly as a disinfectant. c. Isopropyl alcohol, also called rubbing alcohol, has a related molecular structure and is another commonly used disinfectant.

Chemical Methods for Controlling Microbial Growth: Phenolic Compounds

1. Joseph lister used carbonic acid to disinfect surgical instruments but it is no longer used because irritates skin. 2. Contains benzene ring and external hydroxyl group 3. Works by disrupting the growth of microorganisms by denaturing proteins and disrupting their membranes; injure lipids of plasma membranes, cause leakage; control microbial growth a. o-Phenylphenol, a type of phenolic, has been used as a disinfectant as well as to control bacterial and fungal growth on harvested citrus fruits. b. Hexachlorophene, phenol, known as a bisphenol (two rings), is the active ingredient in pHisoHex. Was a popular antibacterial compound used in otc soap such as Dial. However there were reports of deaths in infants associated with the compound, so the FDA banned its use in otc products in 1971. Any product that has greater than 0.1% hexachlorophene had to either reformulate or become available through prescriptions

Heavy Metals

1. Oligodynamic action—very small amounts of these metals exert antimicrobial activity This means you won't need to use a lot of metals for them to be effective 2. Denature proteins 3. Ag, Hg, Cu, Zn a. Silver nitrate is used to prevent ophthalmia neonatorum. Used to be routinely applied to newborns (eyelids) because infant being exposed to microbial flora during the process of birth b. Mercuric chloride prevents mildew in paint c. Copper sulfate is an algicide d. Zinc chloride is found in mouthwash

Halogen: Chlorine

1. Oxidizing agents; shut down cellular enzyme systems 2. Bleach: hypochlorous acid (HOCl) 3. Chloramine: chlorine + ammonia

Surfactants (fancy name for soaps)

1. Surface acting agents 2. Lower the surface tension of water 3. Emulsions of oils and grease allow the physical removal of organisms from the surface of the skin 4. A carbon-hydrogen rich compound is an example of a surfactant 5. Soaps are the salts (sodium salt in the illustration) of fatty acids and have the ability to emulsify lipids, fats, and oils by interacting with water through their hydrophilic heads and with the lipid at their hydrophobic tails.

Factors That Affect the Efficacy of Disinfectants

1. Time of exposure 2. Population being treated Target Virus? bacteria? 3. Surface being treated Non-porous or porous surface, tension of surface? 4. Presence of other"stuff", organic matter, biofilms etc. These may make some disinfectants less effective 5. Concentration of the disinfectant i. For example, ethanol. You don't want to disinfect surfaces with 100% ethanol because ethanol will evaporate and not effectively penetrate bacterial cells ii. Water is actually necessary to complex with the ethanol and get it to penetrate the target organisms

Halogens: Iodine

1. Used as disinfectants and antiseptics, very effective 2. Iodine: works by oxidizing cellular components including proteins, nucleotides, and fatty acids i. Tincture: solution in aqueous alcohol ii. Iodophor: combined with organic molecules 3. Compound of iodine complex with an organic molecule which stabilizes the iodine A. Betadine is a solution of the iodophor povidone-iodine. B. It is commonly used as a topical antiseptic on a patient's skin before incision during surgery. 5. Impairs protein synthesis and alters membranes

Commercial "sterilization"

1. Uses heat at a temperature low enough to preserve food quality but high enough to destroy Clostridium botulinum endospores. a. Especially In their canned products C. botulinum is a spore former and also found in the soil 2. Is commercial sterilization really sterilization? No It is meant to remove one type of organism specifically, a spore former. a. Effective at removing a lot of organisms, but does not remove ALL organisms Endospore formers can still be present

How do you determine the appropriate way to clean something?

1. What is the object used for? For surgery, then obviously you would want to sterilize it 2. What type of pathogens might be on this object? Performing surgery on someone who has gangrene is considered a potentially infectious organism that i don't want to transmit to somebody else

Clostridium botulism

1. anaerobe, endospore former 2. canned food; home canned vegetables are the most common cause of botulism outbreak in the US but does not commonly occur

Triclosan

1. phenol, a common ingredient in antibacterial soaps despite evidence that it poses environmental and health risks and offers no significant health benefit compared to conventional soaps 2. Targeted the fatty acid synthesis pathway, which was unique to bacteria. 3. Microorganisms became resistant to it by having mutated enzymes in that pathway so it became less effective as it was used more widely. Up until 2016, you can find this in everything like deodorant and toothpaste and soaps. Because it was widely used, it ended up making its way into the water treatment systems and accumulate, which ended up killing a lot of microorganisms which are necessary for the function of the water treatment plant It was also being released into freshwater systems and being consumed by freshwater organisms (fish) and we would consume the fish and therefore the triclosan accumulates in our tissues

Alkylating agents

1. synthetic chemicals containing alkyl groups that attack DNA, causing strand breaks 2. Alkylating agents replace hydrogen atoms with alkyl groups. Here, guanine and oxygen is alkylated, resulting in its hydrogen bonding with thymine, instead of cytosine; because guanine and oxygen is alkylated and ethylated, this affected the base pairing properties of guanine and makes it base pairs to thymine instead of cytosine 3. ex: formaldehyde, Glutaraldehyde, o-phthaladehyde, ethylene oxide, beta-propionolactone

Terminology (2)

For Fomites a. Disinfection: reduces the number of microorganisms on the surface of an inanimate object (countertop, keyboard, etc). A disinfected surface is NOT considered sterile! b. Sanitization: cleaning of fomites to decrease microorganisms to a safe level. > Food industry c. Sterilization: the complete removal or killing of all vegetative cells, endospores, and viruses; term used commonly but not correctly For Living Tissue a. Antiseptics: reduces the number of microorganisms on living tissue. One thing you can use as an antiseptic and a disinfectant: rubbing alcohol c. Degerming: the removal of microorganisms on skin through scrubbing and the use of chemicals.

Halogen: Fluorine

Incorporated into toothpaste and tap water in order to promote oral health

Why don't we sterilize everything?

It's not practical to sterilize everything we come into contact with; sterilizing something is quite difficult; we dont have autoclaves in our home

How do we sterilize something?

Physical methods a. autoclave Chemical methods (sterilants) a. sterilants are often toxic, have to be careful of how we dispose it

Silver-Embedded Clothing

Small, nanoparticles of silver in clothing items like socks. This is because we sweat and odor causing bacteria can grow in the socks and the silver can kill odor and prevent the growth of microorganisms

Biosafety levels

a. BSL-1: non-infectious agents, standard protective equipment (goggles), standard aseptic technique BSL-4: agents are infectious and potentially fatal, microbes may be "exotic", highest degree of protective equipment, most restricted access, very few labs are BSl-4 b. Different microorganisms pose different levels of risk, so it is important that you understand the risk associated with that microorganism, and that you also have the equipment necessary to deal with that microorganism c. 4 Biological Safety Levels are based upon: infectivity, ease of transmission, potential disease severity, purpose, whether there are treatment available or not

Terminology

a. Aseptic Technique: Precautionary measures taken to avoid contamination of a sterile surface or solution. i. Flames lips of the tubes and loops before and after loops b. Sterile field/suite: a designated area that is kept free of all vegetative microbes, endospores, and viruses. c. Sepsis: refers to bacterial contamination; When a bacteria is introduced somewhere they should not be Often associate sepsis with infections of the blood; blood is somewhere the microorganism should not be d. Asepsis: is the absence of significant contamination; opposite of sepsis

Different Types of Equipment Require Different Types of Treatment

a. Critical: must be sterile, will be used to penetrate tissues (scalpels, surgical scissors) Sterile through radiation or autoclave b. Semicritical: must be well disinfected, may encounter mucus membranes but will not penetrate tissue (endoscope) c. Noncritical: may contact skin but will not penetrate skin (stethoscope)

Heavy metals (2)

a. denature proteins, impairing cell function and, thus, giving them strong antimicrobial properties. b. Copper in fixtures like this door handle kills microbes that otherwise might accumulate on frequently touched surfaces. c. Eating utensils contain small amounts of silver to inhibit microbial growth. d. Copper commonly lines incubators to minimize contamination of cell cultures stored inside. e. Antiseptic mouthwashes commonly contain zinc chloride. This patient is suffering from argyria, an irreversible condition caused by bioaccumulation of silver in the body.

Food preservatives

a. inhibit enzyme activities and decreasing intracellular ph (specifically benzoic acid), which can lead to the disruption of oxidative phosphorylation because it dissipates the proton motive force so that cells cannot make atp that way b. Benzoic, propionic and sorbic acid Sulfur dioxide Nitrites

Microbial Death Curve

a. plotted logarithmically shows a constant death rate as a straight line b. helps us determine the amount of time necessary to keep a disinfectant on a surface in order for it to be effective c. D-value (decimal reduction value): tells us the amount of time required for that compound or chemical to reduce the number of cells by one order of magnitude d. On the table, at 0 minute is 10^10 number of cells. At 5 minutes, the number went down one order of magnitude (10^9)

Quaternary Ammonium Compounds

a. quats, has long carbon-hydrogen rich tail (Lysol, purell) b. Two common quats: benzalkonium chloride and cetylpyridinium chloride. Note the hydrophobic nonpolar carbon chain at one end and the nitrogen-containing cationic component at the other end. Because they look like phospholipids, Quats are able to infiltrate the phospholipid plasma membranes of gram-negative bacterial cells and disrupt their integrity, leading to death of the cell. c. Pros: stable, non-toxic, inexpensive, colorless, odorless, and tasteless. Also active against fungi, protozoans, and envelope viruses

Biguanides

cationic compounds (ex: chlorhexidine, alexidine) a. effective against yeast and bacteria, used in surgical hand scrubs b. Disrupt plasma membranes, which can be bacteriostatic at low concentrations, bactericidal and sporicidal at high concentrations; effective against enveloped viruses but have not found to be effective against non-enveloped viruses

Peroxygens

ex: hydrogen peroxide, benzoyl peroxide a. Strong oxidizing agents Lipids, proteins, nucleic acids b. Disinfectants or antiseptics c. Produces free oxygen radicals that can damage lipids, proteins and DNA d. A lot of organisms contain an enzyme called catalase, which can detoxify hydrogen peroxide. However, if they are exposed to relatively uncommon amounts, then it will overwhelm the ability of catalase to do that