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MMG 101 Exam 1 Study Guide

by: Katarina Fielding

MMG 101 Exam 1 Study Guide MMG 101

Marketplace > University of Vermont > Microbiology > MMG 101 > MMG 101 Exam 1 Study Guide
Katarina Fielding
GPA 3.4

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This study guide inclUdes all the materials for Exam 1!
Microbiology and Infectious Diseases
Douglas Johnson and Brenda Tessman
Study Guide
mmg101, UVM, Microbiology
50 ?




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This 57 page Study Guide was uploaded by Katarina Fielding on Monday September 19, 2016. The Study Guide belongs to MMG 101 at University of Vermont taught by Douglas Johnson and Brenda Tessman in Winter 2016. Since its upload, it has received 72 views. For similar materials see Microbiology and Infectious Diseases in Microbiology at University of Vermont.


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Date Created: 09/19/16
Control of Microbial Growth • there are numerous physical, chemical, and mechanical methods that can destroy or reduce undesirable microbes in a given area (decontamination) Fig. 8.1 Microbial Control Terminology • antimicrobial agent: either inhibits growth or kills microbe (sterilization) – antibiotic: produced by microbe that can kill or inhibit another microbe; naturally occurring – chemotherapeutic agent: used internally to kill or inhibit microbe; can be antibiotic or chemically synthesized Fig. 8.2 Microbial Death Rates • microbes die at constant death rate D: decimal reduction time • most susceptible cells die first, - 10-fold reduction in growth followed by hardier (resistant) cells – therefore, must use antimicrobial agent until all cells are dead!!! Fig. 8.3 • effectiveness of anti-microbial agents: – high-level: kills all pathogens, including endospores – intermediate-level: kills fungal spores, protozoan cysts, viruses and pathogenic bacteria – low-level: kills growing bacteria, fungi, protozoa, and some viruses Rise of Antibiotic Resistance Factors that Affect Death Rates • number of microbes 109 7 High load 10 105 • nature of microbes in the population 3 10 Low 109 101 load 7 –1 10 Spores 10 105 10–3 3 –5 10 10 101 –1 10 Vegetative cells Log of Number of Viable Cells 10–3 10 14 –5 10 (b) Time for Sterilization Log of Number of Viable Cells Talaro Agent added Fig. 11.2 (c) Time 109 7 10 • temperature and pH of environment 105 Microbistatic agent 3 10 • concentration or dosage of agent 101 –1 10 Microbicidal agent 10–3 • mode of action of the agent 10–5 • presence of solvents, organic matter, Log of Number of Viable Cells or inhibitors (d) Time Lecture 9 5 -static vs. -cidal Inhibition • - static: reversibly inhibits growth – bacteriostatic, fungistatic, viristatic • - cidal: kills microbes – bacteriocidal, fungicidal, viricidal • - lytic: kills by lysing cells – bacteriolytic, fungilytic Brock Fig. 20.9 • external (host) control methods: physical and chemical • internal (host) control methods: chemotherapeutic agents/antibiotics General Mechanisms of Action • four categories of cellular targets: - cell wall: antibiotics (penicillins), alcohols, detergents - cell membrane: detergents, surfactants - protein and nucleic acid synthesis: block replication, transcription, and/or Fig. 11.3 translation  antibiotics, radiation, formaldehyde, etc. - protein structure and function: disrupt or denature (unfold) proteins  loss of secondary, tertiary, and quaternary structures but not primary  alcohols, phenols, heavy metals Talaro Fig. 11.4 Physical Methods Bauman Physical Control – Heat • most widely used method of sterilization; moist and dry heat - moist heat is most efficient; steam heat (autoclave) • high temperature melts cellular membranes and denatures proteins • efficacy depends on time and temperature Bauman Fig. 9.3 • dry heat: usually carried out in some type of oven O O O O – requires 160 - 180 C (320 - 356 F) for 1-2 hours – metals, glass, powders, and oils Steam Heat – Autoclave • uses steam under pressure - pressure causes water to boil at higher temperatures o - usually 121 C for 15 min. or more • kills (sterilizes) all pathogenic bacteria, including endospores!! • plastics or perishables, such as proteins or other heat-labile chemicals, cannot be autoclaved except for disposal Fig.8.7 Reduced Heat – Pasteurization • used for milk, beer, wine, ice cream, yogurt, fruit juices • NOT sterilization … heat-tolerant and thermophilic microbes survive – these microbes do not cause spoilage prior to consumption and are generally non-pathogenic Bauman flash pasteurizer Physical Control – Radiation • electromagnetic radiation: – microwaves, UV light, gamma-rays, X-rays, high energy electrons (particles) UV water treatment  microwaves – thermal effects • non-ionizing radiation: UV light - makes thymine dimers; blocks DNA replication - surface sterilization; doesn’t penetrate solids • ionizing radiation: X-rays, gamma rays, electrons – cause DNA and protein damage + X-rays; - X-rays; 5 days later 5 days later – sterilizing liquid and solid material that is heat-labile, such as growth serum, antibiotics, tissues, surgical supplies, some foods Talaro Fig. 11.9 Physical Control – Filtration • physically removes microbes … NOT viruses – porous material traps microbes while allowing fluids or gases to flow through pores … pore size determines efficacy – not totally sterile … viruses and small molecules can pass through Fig. 8.4 Salmonella trapped on membrane filter Chemical Control – Disinfectants and Antiseptics • disinfectant: used on inanimate objects – e.g., floors, tables, bench tops, walls – dangerous if used internally! • antiseptics: used on skin but not internally – sufficiently non-toxic to tissues • non-specific: usually have one, or both, of the these mechanisms: – disrupt cell membranes  remove or interact with lipids  e.g., detergents and lipid solvents – alter proteins irreversibly  oxidants, alkylating agents, sulfhydryl-reacting reagents  e.g., alcohols, phenols, heavy metals Chemical Control – Disinfectants and Antiseptics Bauman Fig. 8.10 Phenols and Alcohols • phenols: first antiseptic used – Joseph Lister – denatures proteins and disrupts membranes – phenol is too caustic; phenolics are used  hexachlorophene (hex in pHisoHex), Lysol, amphyl, staphene, triclosan Fig. 11.13 • alcohols: – denatures proteins and disrupts membranes – ethanol and isopropyl alcohol  most effective as 70% solution – effective against viruses but not endospores Halogens • halogens: iodine, chlorine, bromine, fluorine – denatures proteins by disrupting disulfide bonds – chlorine and bromine: water treatment; fluoride in drinking water – iodine: 2% tincture in alcohol (7% is toxic)  iodophores (Wescodyne, Betadine): iodine carried by detergents • iodine is released by dilution in water and detergent enhances its action Bauman Talaro Table 11.7 Fig. 9.13 Surfactants • surfactants: “surface active” chemicals – reduce solvent surface tension; more effective dissolving solutes – soaps: cleansing action – wash off microbes (degerming)  germicidal soaps give persistent effects Fig.11.18 – detergents: amphipathic – disrupts membrane permeability  cationic (+) quaternary ammonium ions (quats) are used most  most Gram-negative and Gram-positive bacteria are susceptible; fungi are moderately affected Bauman Fig. 9.14 Oxidizing Agents • oxidizing agents: – peroxides, ozone, and peracetic acid produce ROS that oxidize proteins – hydrogen peroxide: disinfect and sterilize objects  neutralized by catalase, so not useful for treating open wounds – ozone: treatment of drinking water – peracetic acid: effective sporocide used to sterilize equipment peroxide sterilizing medical equipment Talaro Fig.11.14 Heavy Metals • heavy metal ions: – alter 3-D shape of proteins, inhibiting their function – e.g., 1% silver nitrate: used to prevent blindness caused by N. gonorrhoeae; replaced by antibiotics – thimerosal (mercury): used to preserve vaccines – mercurials: bind to SH groups of enzymes  merthiolate and mercurichrome – copper: controls algal growth in reservoirs, fish tanks, swimming pools, etc.  interferes with chlorophyll Talaro Fig. 11.19 Aldehydes and Gaseous Agents • aldehydes: contain terminal –CHO groups – denature proteins and inactivate nucleic acids  cross-links amino, hydroxyl, sulfhydryl, and carboxyl groups – glutaraldehyde: cross-links proteins • gaseous agents: – denature proteins and DNA Fig. 8.11 – ethylene oxide (ETO): used in chambers to sterilize items in hospitals; dental office – hazardous to people; explosive, poisonous, and potentially carcinogenic


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