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Chapter 9 Lecture 5 (Halogens (They are widely used in numerous…
Chapter 9 Lecture 5
Halogens
Are the four very reactive, nonmetallic chemical elements: iodine, chlorine, bromine, and fluorine
Intermediate-level antimicrobial chemicals that are effective against vegetative (active) bacterial & fungal cells, fungal spores and some bacterial endospores and protozoan cysts and lots of viruses
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Halogens use their antimicrobial effect by unfolding damaging (denature) proteins including the enzymes.
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Iodine- used to put iodine tablets in water to drink (hikers) but now have found out that some protozoan cysts (amoebic dysentery and Giardia) can survive the iodine treatment to water.
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Betadine is an example of an iodophor (we use to prepare skin for surgery) and contains halogen, the chemical agent
Heavy metals
Are ions of relatively high-density metals like arsenic, zinc, mercury, silver and copper that are toxic at low concentrations
They are antimicrobial because they combine with sulfur atoms in molecules of cysteine, which denatures (destroys) proteins, stopping their function
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Many eyes of newborns were treated with 1% silver nitrate to prevent blindness caused by Neisseria gonorrhoeae which can enter babies' eyes while traveling through the birth canal- today we use something different
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Thimerosal, a mercury containing compound was used to preserve vaccines for over 70 years. In 1999 US Public Health Service recommended alternatives because mercury is a metabolic poison
Today, children’s vaccines are free of mercury and considered safe
The only exception is the flu vaccines that are distributed in multidose vials as well as the adult vaccines (whole-cell pertussis, tetanus, fly and meningococcal meningitis.
Surfactants
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One of the ways they act is to reduce surface tension of solvents like water because it decreases the attraction among molecules.
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Use-dilution test
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Cylinders removed, washed, and placed into tube of medium
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Alcohols
Are bactericidal, fungicidal , and virucidal against enveloped viruses(Influenza, HCV, and HIV) But make note- THEY ARE NOT EFFECTIVE AGAINST FUNGAL SPORES, OR BACTERIAL ENDOSPORES
Alcohols are considered intermediate level disinfectants and the denature (breakdown) proteins and disrupt /damage the cytoplasmic membrane – Remember that phenolics are disinfectants that do this too.
Pure alcohol is not an effective antimicrobial agent because the breakdown of proteins (denaturing) requires water so solutions of 70-90% alcohol are used to control microbes
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Disadvantage
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Alcohol based antiseptics are more effective than soap in removing bacteria from the hands but not effective against some viruses like the noroviruses
Chlorine
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Calcium hypochlorite- used to disinfect utensils and the medical field will use to disinfect hemodialysis systems
Chlorine dioxide is a gas used to disinfect large spaces (federal building contaminated with anthrax spores
Gaseous Agents
Many heart and lung machine components, sutures, plastic lab ware, mattresses, pillows, artificial heart valves and dried or powered foods cannot be sterilized easily with heat or water-soluble materials
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Used in hospitals and dental offices. NASA uses to sterilize spacecraft designed to land on other worlds.
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Disadvantages include highly explosive, and they are extremely poisonous and carcinogenic
Enzymes
Many organisms produce chemicals that inhibit or destroy fungi, bacteria or viruses. These are called antimicrobial enzymes
Human tears contain lysozyme, which is a protein that digests the peptidoglycan cell walls of bacteria (bacteria end up rupturing)
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Antimicrobial Drugs
Include, antibiotics, semisynthetic, and synthetics
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Chloramines
Are a combination of chlorine and ammonia used in wound dressings, skin antiseptics, and in some municipal water supplies
Less effective antimicrobial agents than other forms of chlorine but are longer lasting because they are released slowly
Bromine is effective disinfectant in hot tubs (evaporates more slowly) as well as pools, cooling towers and water containers
Fluorine in the form of Fluoride is an antibacterial in drinking water and toothpaste (it disrupts the metabolism in the biofilm in dental plaque)
Ozone
A reactive form of oxygen that is generated when molecular oxygen is subjected to an electrical discharge
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Aldehydes
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Function in microbial control by cross-linking organic functional groups to denature (damage) proteins and inactivating nucleic acids (damage DNA)
Hospitals and scientists can use 2% solutions of glutaraldehyde to kill bacteria, viruses, and fungi- when exposed for 10 hours it sterilizes
Morticians use formaldehyde dissolved in water to make a 37% solution called formalin(used for embalming and to disinfect hospital rooms, instruments and machines. This is a carcinogen
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Quats
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Quats are bactericidal, fungicidal and virucidal against enveloped viruses, mycobacteria, or endospores.
Some pathogens like Pseudomonas aeruginosa thrive in quats; so quats are considered as low-level disinfectants
Oxidizing agents
Peroxides, ozone and peracetic acid kill microbes by oxidizing(releasing oxygen radicals) their enzymes
They are known to be high-level disinfectants and antiseptics and we use them in health care because they are effective in killing anaerobic microorganisms in deep puncture wounds
Hydrogen Peroxide
Household chemical we use that can disinfect and even sterilize the surfaces of inanimate objects like a contact lens
Many people will mistakenly use it for open wounds but it does not make a good antiseptic because catalase (an enzyme released from damaged human cells) will neutralize H2O2 by breaking it down into water and oxygen gas (escaping bubbles)
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