Answers on Micro bio – Microbiology Flashcards
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Unlock answers| Sterilization |
| Destruction of all forms of microbial life inc. endospores |
| Commercial Sterilization |
o destruction of endospores of Clostridium botulinum in canned food but not all endospores § Some thermophile endospores survive but can’t grow in canned foods due to room temp
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| Disinfection |
| Destruction of vegetative pathogens |
| Antisepsis |
| Destruction of vegetative pathogens on living tissue |
| Degerming |
| removal of microbes from limited area like injection site |
| Sanitization |
| lowering of microbes on eating and drinking utensils to safe levels |
| Germicide |
| chemical that rapidly kills vegetative cells but not necessarily endospores |
| Bacteriostasis |
| condition where bacteria growth and multiplication are inhibited, but the bacteria are not killed |
| Asepsis |
o absence of microorganisms from object or area
§ Air filters, UV lights, masks, gloves, sterile instruments all useful in achieving this
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| Sepsis |
| prescense of bacterial contamination |
Rate of Microbial Death
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o Microbes of a single type treated with antimicrobial agent die at constant rate o Microbial death curves can be constructed § Straight line if logarithm of population plotted versus time. thus the bacteria die at a constant rate § After 6 min of 90% dying/min 1 of 1 million microbes would be alive o Large populations take longer to kill o Factors affecting kill time § Bacterial load § Time of exposure |
Mechanism of Action of Antimicrobial Agents
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· Kill in 2 ways o Disrupt integrity of cell § Cell wall maintains shape and integrity and protects from osmotic pressure § No wall à cell bursts § Water leaks in, cellular components leak out § These microbicidal agents also inactivate lipid enveloped viruses · Lipid envelope mediates attachment to host cell · Without envelope – no attachment or infection · Naked viruses much harder to inactivate (more resistant) o Disrupt cellular metabolism and reproduction by damaging proteins or nucleic acids § Proteins have native conformation destroyed by heat and chemical agents · Denaturation – egg example · Denatured proteins – nonfunctional DNA destruction – lethal |
Factors to Consider in Choosing an Antimicrobial Agent
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o Nature of site to be treated
o Susceptibility of microbes
o Environmental conditions that apply to treatment |
Nature of site to be treated
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o Instruments penetrating skin § High potential for infection § Critical items § Must be clean or sterile o Instruments touching mucous membranes or skin with out penetrating § Low potential for infection § Semi-critical items § Need to be clean and disinfected unless patient is immunocompromised o Items not touching membranes or skin § Non critical § Need to be cleaned and disinfected Harsh chemicals or extreme heat cannot be used on humans, animals, sensitive material |
| Susceptibility of microbes |
· Depends on microbe and physiological state · Dormant forms like endospores and protozoan cysts more resistant than vegetative cells o Antimicrobials have difficulty penetrating them o Actively growing cells are more susceptible to killing than non-replicating cells because DNA, protein, and cell wall damage only affects growing cells · Mycobacteria are more resistant to killing because of lipid mycolates on cell wall o Difficult to penetrate · Spectrum o Endospores o Mycobacteria o Protozoan Cysts o Vegetative Protozoans o Gram-negative bacteria o Fungi o Non-enveloped viruses o Gram-positive bacteria o Enveloped viruses Choose method to kill the most resistant microbe possible in population – should kill least in population |
Environmental conditions that apply to treatment
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§ Must be able to kill microbes under environmental conditions · Temperature · pH · Organic materials · Dirt · Grease § Organic matter, dirt, and grease · Can interfere with killing action · Must be cleaned to ensure contact § Antimicrobials more effective at low pH § Antimicrobials more effective in warm solutions · Reactions increase § Use at manufacturer’s recommended temperature and condition |
| Puerperal sepsis |
| an infection of the uterus also called childbirth fever. 25% of women giving birth in hospital died from this. |
