Chemical Methods Flashcards
(28 cards)
A disk of filter paper is soaked with a chemical and placed in an agar plate previously inoculated with test organism
Disk Diffusion Method
irritates the skin and has disagreeable odor; are often used in throat lozenges for its local anesthetic effect but has little antimicrobial effect at low concentrations
Phenols
are derivatives of phenols that has been chemically altered to reduce its irritating qualities or increase its antibacterial activity in combination with a soap or detergent
Phenolics
Derivatives of phenol
✦ E.g. hexachlorphene ingredient of a prescription lotion used for surgical and hospital microbial control
Bisphenols
Have a broad spectrum of activity
✦ MOA: affects the bacterial cell membranes
✦ Especially effective against gram positive bacteria and also gram negative bacteria except of most pseudomonas
Biguanides
Mixture of hydrocarbons extracted from plants; Used in traditional medicine and preserving foods
Essential Oils
one of the oldest and most effective antiseptics; active against all kinds of bacteria (many endospores, various fungi, some viruses)
Iodine
As a gas or in combination with other chemicals; Liquid form of compressed chlorine gas for disinfecting swimming pools and sewage
MOA: hypochlorous acid HOCl ) that forms when chlorine is added to water
Chlorine
used to disinfect dairy equipment and restaurant eating utensils
Calcium hypochlorite
component of a household disinfectant (e.g bleach)
Sodium hypochlorite
Effectively kill bacteria and fungi but not endospores and nonenveloped viruses; Denatures protein, disrupt membranes and dissolve many lipids including lipid component of enveloped viruses
Alcohols
70% recommended optimum concentration; this is less effective than aqueous solutions because denaturation requires water
Ethanol
Often sold as rubbing alcohol; slightly superior to ethanol as an antiseptic and disinfectant; Less volatile, less expensive, more easily obtained than ethanol
Isopropanol
Inorganic mercury compounds (mercuric chloride bacteriostatic, broad spectrum but now is limited because of toxicity and ineffectiveness in organic matter
Heavy Metals
Can decrease surface tension among molecules of a liquid
Surface Active Agents
Most widely used; cationic detergents
Quaternary Ammonium compounds (Quats)
prevent molds from growing in cheese and soft drinks
Sodium benzoate
added to meat products like ham, bacon, hotdogs and sausage
Sodium nitrate and sodium nitrite
often added to cheese to inhibit the growth of certain endospore forming spoilage bacteria
Nisin
antifungal antibiotic mostly used in cheese
Natamycin (pimaricin)
aqueous solution used to preserve biological specimens and inactivate bacteria and viruses in vaccines
Formaldehyde
Less irritating and more effective than formaldehyde; Used to disinfect hospital instruments 2% solution is bactericidal, tuberculocidal and virucidal in 10 min and sporicidal in 3 to 10 hours
Glutaraldehyde
Gaseous chemosterilants are frequently used as substitutes for physical sterilization processes; Requires a closed chamber similar to a steam autoclave
Chemical Sterilization
Kills all microbes and endospores but requires a lengthy exposure period of several hours; It is toxic and explosive in its pure form so it is usually mixed with nonflammable gas such as CO2
Ethylene oxide
