Control of Microorganisms

Scientific Control Louis Pasteur Joseph Lister: 1) hand washing 2) aseptic surgery techniques What are the implications for the embalmer?

Readings question #1: What is the difference between sterilization, disinfection, and antisepsis?

Actions of Microbial Control Agents 2 basic ways: 1) alteration of membrane permeability 2) damage to proteins and nucleic acids

Physical Methods Scrubbing Heat: heat resistance varies among microbes Dry heat: incineration, cremation, hot-air sterilization Moist heat: kills by coagulation of proteins (denaturation) boiling, free flowing steam (unpressurized), steam under pressure Pasteurization: mild heating

Physical Methods (cont’d) Cold: bacteriostatic effect Radiation: ionizing radiation -gamma rays, x-rays, electron beams nonionizing radiation -UV light Microwaves: solid foods heat unevenly due to uneven distribution of moisture Pork: trichinosis

Chemical Methods living tissue and inanimate objects few achieve sterility reduce microbial populations to safe levels or remove vegetative forms of pathogens from objects no single disinfectant is appropriate for all circumstances

Germicides Bactericides Fungicides Viricides Insecticides Larvicides Sporicides

Factors Influencing Chemical Agents Read the label!!!! nature and concentration of disinfectant nature of material to be disinfected number and type of microorganisms present length of exposure temperature and pH during exposure

Halogens Readings question #2: What are halogens and how do they work? Chlorine: hypochlorites (bleaches) Iodine: iodophore e.g. polyvinylpyrrolidone

Alcohols Readings question #3: How do alcohols control microbial growth? Two of the most commonly used: ethanol isopropanol

Aldehydes Readings question #4: What are aldehydes and how do they work? 2 examples: formalin glutaraldehyde

Phenolic Compounds Readings question #5: Give two examples of phenolic compounds, and explain how each control microbial growth. carbolic acid (phenol) cresols hexachlorophene

Quaternary Ammonium Compounds Readings question #6: What are “quats”? How do surfactants effect cells? Zephiran, Cepacol bactericidal: gram-positive bacteria fungicidal, amoebicidal, virucidal (enveloped viruses) do not kill endospores or mycobacteria Pseudomonas grow in quats