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176 Cards in this Set
- Front
- Back
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Reasons for controlling growth
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1. to prevent spoilage of food n 2. to prevent microbes from causing n disease n 3. to prevent microbial contamination & n undesirable alteration of materials
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microbicidal agents
bactericidal agents fungicidal agents virucidal agents |
Killing microbes
kill bacteria kill fungi Kill Viruses |
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microbistatic agents
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Preventing microbial growth – microbistatic agents effect is temporary & growth resumes when agent or microbes removed inhibit bacterial n growth
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3 Approaches for controlling microbial growth
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Killing microbes
Microbistatic agents Removal of microbes |
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Antimicrobial agents
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agents that kill microbes or inhibit their growth
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Sterilization
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removal or destruction n of all forms of microbial life
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Commercial sterilization
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exposure to sufficient heat to kill spores of Clostridium botulinum used to process canned foods
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Disinfection
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destruction of vegetative pathogens present
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Disinfectant
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(germicide)– chemical used to kill vegetative pathogens on nonliving surfaces
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Antisepsis
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destruction of vegetative pathogens on skin and living tissues
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Antiseptic
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chemical used to kill n vegetative pathogens on living tissues
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Degerming
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removal of microbes n from an area (such as skin)
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Sanitization
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reduction of microbes present to safe levels
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Asepsis
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absence of microbes from an area
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Physical Methods of Control
Targets of physical methods |
1. plasma membrane n cause leakage and lysis n 2. cell proteins n enzymes are particularly sensitive n 3. nucleic acids n results in disrupted function & death
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Physical Methods Used
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1. heat 4.desiccation
2. filtration 3. cold 5. radiation |
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Two types of heat
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Moist heat - involves steam coagulates cell components
dry heat - bakes or oxidizes cell components |
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thermal death point
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lowest temp. that kills all bacteria in liquid medium in 10 mins.
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thermal death time
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minimal time required to kill all bacteria in a liquid suspension at a n given temperature
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decimal reduction time
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time required to n kill 90% of bacteria at a given temp.
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Boiling
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heating to 1000C for 30 mins. can be used for disinfection
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Autoclave
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uses pressurized steam for sterilization typical conditions – 15 psi. steam pressure, 1210C for 15 minutes used to sterilize media & various heatresistant items
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Pasteurization
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Use of high temperatures to kill all pathogens in foods disinfection process
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Pasteurization processes
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1. classic method – 630C for 30 mins. 2. HTST – 720C for 15 sec. 3. ultra-high temperature – 1400C for less than 1 sec.
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Equivalent treatments
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using different exposure or dosage to achieve same result
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Dry Heat
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Requires higher temp. & longer exposure for sterilization
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Methods using dry heat
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1. dry air oven typical conditions – 1700C for 2 hrs. used for glassware
2. incineration – burning microbes used to sterilize transfer loops |
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Filtration
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Physical removal of microbes from a suspension using porous barrier
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Types of filters
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1. HEPA filters- removes microbes from n air of homes, OR’s & special rooms 2. membrane filters remove bacteria from fluids can sterilize heat-sensitive fluids
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Low temperatures are
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microbistatic
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1. refrigerators
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temp. = 00C – 70C inhibit growth of most microbes but not psychrophiles or psychrotrophs
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freezers
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temp.= (-50C) – (-250C) inhibit growth of most microbes many microbes survive
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lyophilization freeze
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drying of microbial cultures common way of storing microbes
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Desiccation
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Removal of water Microbistatic
Least sensitive microbes are molds & yeasts |
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Methods that remove water
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1. drying 2. hypertonic environments 10% - 15% NaCl used in pickling 50% - 70% sugar in jams
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Radiation
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Energy of radiation inversely related to wavelength
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Types of microbicidal radiation
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1. ionizing radiation X-rays, gamma rays & high – energy electrons 2. Nonionizing radiation – ultraviolet light
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Ionizing Radiation
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Action produces high-energy ions called free radicals which react with DNA and other components killing microbes
Uses 1. cold sterilization of plastics & other items n 2. killing microbes to preserve foods |
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Nonionizing Radiation
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Ultraviolet Light n wavelength - 10 nm – 400 nm n target – DNA n most damaging wavelength – 260 nm
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Ultraviolet Light
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action causes formation of pyrimidine dimers n abnormal bonds between adjacent DNA bases n major disadvantage – poor penetration
use – disinfection to kill airborne microbes in hospital rooms, OR’s and other areas |
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Factors Affecting Use of Chemical Agents
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1. type of infectious agent
2. concentration of agent 3. number of microbes 4. Time of exposure 5.Environmental conditions |
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Prions
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Most difficult type of infectious agent destroy.
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sporeformers
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most difficult living microbes to kill
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mycobacteria
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most difficult nonsporeformers to kill
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concentration of agent
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lowest effective concentration is cheapest, least toxic and best
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number of microbes
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greater numbers require higher conc. of n agent or increased exposure washing & scrubbing reduce number
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time of exposure
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time required for n chemical to kill microbes or inhibit their growth n varies with number of microbes and conc. of agent
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environmental conditions
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a. pH acidity increases activity of some agents b. temperature heat generally increases activity c. organic molecules present combine with some agents reducing activity
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High-level germicides
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kill endospores, n all vegetative bacteria & viruses (sterilize)
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Intermediate-level germicides
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kill all vegetative bacteria & viruses but not endospores most agents used in disinfection
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Low-level germicides
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kill enveloped viruses & some vegetative cells but not endospores, naked viruses or some vegetative cells n
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Alcohols
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Group of germicide:
action – denature proteins & damage membranes level – intermediate-level types – 1. ethyl alcohol (grain alcohol) 2. isopropyl alcohol (rubbing alcohol)most effective concentration – 70% |
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Uses of Alcohols
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1. solvent for other chemical n agents tincture – alcoholic solution 2. disinfection of skin & instruments 3. degerming skin
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Groups of Germicides - Phenolics
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derivatives of phenol action – denature proteins & damage membranes level – intermediate-level use – 1. standard for new agents phenol coefficient test
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Phenolics
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use – 1. standard for new agents phenol coefficient test
2. 1% phenol used in antiseptic surgery & chlorseptic throat spray 3. hexachlorophene – bisphenol effective antibacterial in phisohex now available only by prescription 4. lysol – cresol containing phenol 5. triclosan –antibacterial agent in soaps |
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Groups of Germicides:Halogens
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include chlorine & iodine Action – alter proteins Level- intermediate-level Groups – chlorine and iodine agents
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Halogens
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Chlorine Agents use – 1. chlorine gas used to disinfect water supplies 2.hypochlorites used to disinfect restaurant equipment & swimming pools 10% Clorox kills HIV & HBV
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Halogen Iodine agents
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use – 1. tincture of iodine – I2 in alcohol effective but irritating 2. iodophors – antiseptics with I2 attached to organic carrier betadine & others less irritating
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Groups of Germicides: Biguanidines (chlorhexidine)
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Biguanidines action - damage membranes level - low-level example – hibiclens use – 1. contact lens solutions 2. surgical hand scrubs 3. preoperative skin prep
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Groups of Germicides Hydrogen Peroxide
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Hydrogen Peroxide Level – low concentrations are intermediate-level higher concentrations may be high-level Action – forms hydroxyl (free) radicals
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Peroxide uses
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use – 1. 3% H2O2 used cleanse & disinfect wounds 2. 35% H2O2 used to sterile reusable equipment such as endoscopes
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Groups of Germicides Heavy Metals
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include silver, mercury, zinc & copper action – alter proteins level – intermediate-level oligodynamic action – ability of low concentrations to inhibit bacterial growth
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Groups of Germicides – Heavy Metals silver
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1% AgNO3 placed in eyes of newborns to prevent gonococcal infections n replaced by antibiotic salves that inhibit Chlamydia also
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Groups of Germicides – Heavy Metals Mercury
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use – mercurochrome used as skin antiseptic
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Groups of Germicides – Heavy Metals Zinc
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use – zinc oxide used as antifungal agent in paints
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Groups of Germicides – Heavy Metals Copper
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use – copper sulfate is algicidal
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Groups of Germicides Quaternary Ammonium Compounds (QUATS)
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detergents containing ammonium ions action – damage surface membranes level – low-level more effective against Gram+ bacteria use – found in mouth wash & contact solutions example – Ceepryn in cepacol mouthwash Roccal – common disinfectant
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Groups of Germicides - Aldehydes
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Action – alter proteins Level – high-level & intermediate-level 1. Formaldehyde formalin - 37% solution use – 1. preserve specimens 2. embalming fluid suspected carcinogen use – 1. preserve specimens 2. embalming fluid suspected carcinogen 2. Glutaraldehyde sporocidal at extended exposures Cidex – 2% solution is good disinfectant
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Groups of Germicides Chemosterilizers
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chemicals that can be used in sterilization 1. Ethylene oxide - used for plastics & other heat-sensitive 2. Hot 30% H2O2 used to sterilize food packaging 3. Betapropiolactone used to sterilize tissues and vaccines suspected carcinogen materials instrument called chemiclave requires 90 mins. – 3 hrs.suspected carcinogen
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Chemotherapeutic Agents
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Chemicals used to treat diseases; may also be used to prevent infection and either kill pathogens or inhibit their growth.
First chemotherapeutic agent – salvarsan, an arsenical compound developed by Paul Erlich (1910) to treat syphilis |
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Properties of Chemotherapeutic Agents
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Spectrum – groups of microbes against which an agent is effective 1. narrow-spectrum drug – kills or inhibits Selective toxicity – ability of drug to kill or inhibit pathogen without harming patient side effects result from lack of selective toxicity Gram+ or Gram- species but not both example – penicillin G & streptomycin 2. broad- spectrum drug – kills or inhibits both Gram+ and Gram- species example - tetracycline
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Synergistic effect
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one drug enhances action of another described as 1+1 = 3 combined effect greater than sum of individual effects example –carbenicillin & gentamycin used in problem infections
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Antagonistic effect
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one drug decreases action of another obviously undesirable example – tetracycline & penicillin milk & tetracycline
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Allergy
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immune response to drug may cause anaphylactic shock & death common response in patients example – penicillins
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Elimination of normal flora
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due to long-term use of broad-spectrum agents
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superinfection
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overgrowth & infection by microbes that survive
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Antibiotics
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produced by microbes n major antibiotic producers
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Penicillium
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terrestrial molds a. natural penicillin(Penicillin G) broken down by penicillinases produce by Staph & other bacteria b.griseofulvin (antifungal drug)
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Cephalosporium
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aquatic molds produce cephalosporins such as cephalothin & keflex
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Bacillus
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soil bacteria that produce bacitracin & polymyxins
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Streptomyces
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filamentous soil bacteria n produce many antibiotics including: a. streptomycin b. erythromycin c. tetracyclines d. nystatin – antifungal drug
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Synthetic agents
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produced in the lab first group – sulfa drugs developed in 1930’s many others since including: 1. quinolones (Cipro) 2. rifampin used to treat tuberculosis
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Semisynthetic drugs
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Basic structure synthesized by microbes & additional groups or chains added in lab Semisynthetic penicillins used for many infections some can be given orally have broader spectrum than penicillin G examples – ampicillin & carbenicillin
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Actions of Chemotherapeutic Agents
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1. inhibit cell wall synthesis 2. inhibit or damage plasma membranes 3. inhibit protein synthesis 4. inhibit nucleic acid metabolism 5. antimetabolites – competitive inhibitors of enzymes
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Drugs That Inhibit Cell Wall Synthesis
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prevent synthesis of peptidoglycan tend to have gram+ spectrum examples:
1. penicillins 2. cephalosporins 3. Vancomycin |
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Drugs That Damage Plasma Membranes
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Damage plasma membranes or inhibit their synthesis examples:
1. polymyxins – Gram-spectrum 2. amphotericin B – antifungal 3. ketoconazole – antifungal inhibits synthesis of plasma membrane |
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Drugs That Inhibit Protein Synthesis
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Have several different specific actions n examples:
1. streptomycin - Gram - spectrum 2. erythromycin - Gram + spectrum 3. tetracyclines - broad - spectrum |
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Drugs That Inhibit Nucleic Acid Metabolism
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1. rifampin inhibits RNA synthesis used to treat tuberculosis 2. quinolones (Cipro)inhibits DNA synthesis broad-spectrum agents frequently used for urinary infections
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Drugs That Are Antimetabolites
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Competitive inhibitors of enzymes examples: 1. sulfa drugs - broad-spectrum drugs that inhibit folic acid synthesis in bacteria 2. Isoniazid (INH) – inhibitor of mycolic acid synthesis used to treat tuberculosis
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Actions of Antiviral Drugs
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. Block uncoating of viruses n example – amantadine used for influenza 2. Inhibit viral replication example – interferons n3. Inhibit synthesis of viral nucleic acids example – acyclovir (Zovirax) used for infections by herpesviruses
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Disk-Sensitivity Test
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Used to determine effectiveness of antibiotics
Steps 1. saturate agar plate with broth culture or suspension of sample 2. place several disks each with specific concentration of different antibiotic on the plate 3. incubate plate at 37OC for 22 hrs. 4. measure clear zone of inhibition around each disk 5. compare measurements with information from standard table to determine sensitivity |
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Antibiogram
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sensitivity profile for the microbe obtained by using representatives n from different groups of drugs
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Resistance to Antibiotics
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Definition - ability of microbes to develop a tolerance forchemotherapeutic agents Major problem in treatment of diseases 1. mutation – change in gene that makes microbe resistant exposure to antibiotic eliminates sensitive cells &
allows resistant cells to increase producing resistant population |
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Genetic mechanisms of resistance
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1. mutation – change in gene that makes microbe resistant exposure to antibiotic eliminates sensitive cells &
allows resistant cells to increase producing resistant population 2. transfer of plasmids called R factors by conjugation R factors contain genes for resistance resistance spreads from cell to cell through population |
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Antibiotic Resistance
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Cellular changes that produce resistance 1. enzyme that breaks down drugpenicillinase 2. decreased permeability to drug keeps drug from entering cells 3. altered target site no longer inhibited by drug
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Minimizing Resistance to Antibiotics
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1. Use proper dosage for infections patient should take all of prescription
2. Avoid unnecessary use of drugs antibacterial drug for viral infections antibiotics in animal feed 3.Use drug combinations for some infections sulfasoxazole & trimethoprim |
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genetics
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study of transmission & expression of genes
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gene expression
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includes transcription & translation
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transcription
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copying of DNA to mRNA
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transanslation
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using mRNA to synthesize polypeptide
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genome
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one copy of all genes in a cell
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gene
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amount of DNA required to synthesize mRNA & its polypeptide
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genotype
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genetic makeup or genes of an organism
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phenotype
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appearance of organism results from expression of genotype
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Unique Characteristics of Bacterialgenetics
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1. one circular chromosome 2. haploid – one gene for each trait mutation frequently changes phenotype 3. no introns or noncoding DNA 4. E. coli has about 5, 000 genes human genome contains about 30,000 genes
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Operon
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Definition – a group of genes involved in the transcription of several related enzymes Function – regulates transcription of enzymes which function in same metabolic pathway
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Operon components
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1. structural genes – sequence of genes
transcribed to produce enzymes that function in a common metabolic pathway 2. promoter – DNA sequence to which RNA polymerase binds at beginning at transcription 3. operator – DNA sequence that initiates transcription of the structural genes along with the promoter forms the control site (control locus) of the operon 4. regulator gene – codes for a protein called a repressor that when active combines with the operator repressing it, blocking transcription & enzyme synthesis |
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Inducible operons
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a. operon is turned off because the regulator gene codes for an active repressor b.substrate combines with the repressor inactivating it & turns the system on transcription of structural genes and synthesis of enzymes proceeds c. operon turned back off by breakdown of substrate regulates catabolic pathways example – lactose operon
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Two Types of Operons
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Repressible operons
Inducible operons |
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Repressible operons
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a. regulator gene codes for inactive repressor b. operon is on with transcription of the structural genes and synthesis of enzymes c. end product combines with repressor to make it active & stop transcription d. operon turned on again as end product is used upregulates synthetic pathways example – arginine operon
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Units of DNA transferred between bacteria
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1. plasmids
2. sections of the donor’s chromosome DNA transfer always one-way from donor to recipient |
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Possible Results of DNA Transfer
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Donor DNA degraded nDonor DNA remains separate from n recipient chromosome & expressed transfer of plasmids such as F factor Recombination - donor DNA replaces section of recipient chromosome recipient may gain new traits
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conjugation
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one-way transfer of DNA from donor to recipient
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transformation
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uptake of free DNA by competent recipient cells
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transduction
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transfer of DNA from n donor to recipient by phage
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Requirements for Conjugation
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Donor with F factor - plasmid with genes coding for sex pilus to initiate transfer two types of donors
1. F+ donor – has independent F factor 2. Hfr donor – F factor attached to its chromosome Recipient lack F factor designated F - cannot initiate DNA transfer n receive DNA from donor nContact between donor and recipient |
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Types of Conjugation
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F+ x F-
1. donor’s F factor replicated 2. copy of F factor transferred to recipient 3. F- recipient converted to F+donor Hfr x F- 1. donor’s chromosome & attached F factor n replicate with F factor replicating last 2. replicating unit begins to move across pilus 3. pilus or chromosome breaks so only 1st section of chromosome is transferred 4. recombination may occur between donor DNA and recipient’s chromosome recipient remains F-Hfr – high frequency of recombination |
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Transformation
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Uptake of free donor DNA by recipient Requirements
1. Free Donor DNA 2. Competent recipient – cell wall permeable to donor DNA Frequently used to introduce foreign DNA in genetic engineering Griffiths experiments |
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Transduction
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General process
1. phage injects DNA into donor 2. Replication produces some transducing phage contain donor DNA 3. released transducing phage injects DNA into recipient 4. attachment of donor DNA or recombination occurs in recipient |
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Generalized transduction
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uses lytic phage any section of donor chromosome transferred
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Specialized transduction
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uses lysogenic phage only genes next to attachment site transferred
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genetic engineering
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introduction of foreign DNA into microbe & its replication or expression to produce specific product
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Recombinant DNA
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DNA made up of DNA from different sources (species)
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cloning vector
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self-replicating unit containing recombinant DNA examples – plasmids & phage
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cloning host
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cell in which n recombinant DNA can be expressed examples – bacteria & yeasts
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Key enzymes – restriction endonucleases
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discovered in 1970 cut any DNA so that pieces can be joined together to form recombinant DNA
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Steps in Genetic Engineering
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1.Isolated gene introduced into cloning vector by restriction endonucleases
2. vector with gene inserted into cloning host 3. Foreign gene is replicated & expressed in host producing specific product 4. Product collected and purified |
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variation
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change in phenotype not due to change in genotype
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mutation
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change in the genotype or genes
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mutant
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altered phenotype resulting from mutation
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Prototroph
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organism with all nutritional properties of the species
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auxotroph
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mutant with additional nutritional requirement
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genetic code
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organization of DNA bases for protein synthesis
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Genetic code has 64 sets of triplets called
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Codons
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Two types of Codons
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1. sense codons – 61 codons for 20 different amino acids redundancy of genetic code – 2 or more codons for most amino acid mutation can occur without producing mutant
2. nonsense codons – stop signals |
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Substitution
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change of one DNA base to different one
1. neutral (silent) mutation –altered codon codes for same amino acid 2. missense mutation – altered codon codes for different amino acid example – sickle cell anemia 3. nonsense mutation – altered codon is stop signal produces incomplete protein |
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Insertion
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addition of 1 or more DNA bases
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Deletion
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loss of one or more DNA bases insertions or deletions produce frameshift mutations which change subsequent mRNA codons
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Point Mutation
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addition, deletion or n substitution of only one DNA base
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Types of Mutagens:Spontaneous mutation
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no identifiable cause fixed rate in each species about 1 in 106 replicated genes in bacteria
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Types of Mutagens:Induced mutations
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due to abnormal environment abnormal environments called mutagens
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Types of Mutagens:Nonionizing radiation
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UV light produces pyrimidine dimers in DNA bacteria can repair some UV damage mutations cause errors in replicating and copying DNA
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Types of Mutagens:Ionizing Radiation
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examples – gamma rays & x-rays produces free radicals that alter DNA code & cause breaks in DNA high doses bactericidal, lower doses mutagenic
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Types of Mutagens:Chemicals
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a. base pair mutagens – alter DNA bases cause base substitution during replication example – nitrous acid
b. nucleoside (base) analogs –replace normal DNA bases pair differently & change genetic code example – 2-aminopurine |
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Ames Test
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Identifies mutagenic chemicals
About 85% of mutagens are carcinogens Useful screening test for carcinogens |
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Characteristics of Fungi
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1. Eucaryotes
2. Nutrition by absorption most are saprotrophs(saprobes) – get nutrients from dead or decaying matter some are parasites 3. haploid 4. Most have cell walls of chitin 5. Aerobes or facultative anaerobes |
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mycology
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study of fungi
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hyphae
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tubular filaments that comprise muticellular fungi
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mycelium
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growth of mold containing all its hyphae
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thallus
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body of a mold or fleshy fungus
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Morphological Groups of Fungi
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Yeasts – unicellular fungi Molds – produce wooly growths comprised of hyphae Fleshy fungi – produce large fruiting bodies made of compacted hyphae examples – mushrooms & puffballs Dimorphic fungi – grow as mold in environment & yeast in body example – Histoplasma capsulatum
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Structural types of Hyphae
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1. septate hyphae – have partitions called septa 2. nonseptate (coenocytic)hyphae – have no partitions hypha contains multinucleated cytoplasm
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Functional types of Hyphae
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1. vegetative hyphae found close to substrate absorb nutrients 2. aerial hyphae involved in reproduction spores give mold color
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Types of Reproduction in Fungi
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1. mitosis – in fission yeasts
2. fragmentation – in filamentous fungi n piece of hypha forms new fungus 3. spore formation each spore can germinate to produce a new fungus not as resistant as endospores |
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Types of Fungal Spores
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Asexual spores -formed by mitosis in cells or hyphae of one fungus germination produces fungus genetically identical to the parent
Sexual spores requires donor & recipient strains fungus from germination has properties of both mating strains |
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Formation of Sexual spores
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Steps in formation of sexual spores
1. Haploid nucleus of donor cell (+)penetrates cytoplasm of recipient cell (-) 2. Karyogamy – + and – nuclei fuse to from diploid zygote 3. Meiosis – division of diploid nucleus producing haploid nuclei & sexual spores |
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teleomorphs
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fungi that produce both sexual & asexual spores
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Anamorphs
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fungi that produce only asexual spores
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Sporangiospores
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formed in saclike sporangium at end of aerial hyphae example - Rhizopus nigricans
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Conidiospores (conidia)
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free spores not enclosed in a sac formed by pinching off of tips of aerial hyphae or segmentation of existing hyphae several different specific types
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Arthrospores
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Asexual rectangular spores formed by segmentation of septate hyphae example – Coccidioides immitis
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Blastospores
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Asexual buds of budding yeasts example – Saccharomyces cerevisiae n pseudohyphae – chains of blastospores
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Types of Sexual Spores
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Basidiospores – formed at tips of club shaped hyphae (basidia)
Ascopores – formed in a sac called an ascus Zygospores – develop from zygote |
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Zygomycota
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A division of the fungi called “conjugation fungi” nonseptate hyphae example – Rhizopus nigricans which is black bread mold
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Basidiomycota
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septate hyphae called “club fungi” produce basidiospores n examples – mushrooms & puffballs
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Deuteromycota
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called “fungi imperfecti” n no sexual spores contains some human pathogens example – Candida albicans Phytophthora infestans – aquatic fungus that causes potato blight
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Beneficial Effects of Fungi
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1. Some are edible
2. Some produce antibiotics 3. Decomposers that recycle nutrients 4. Some produce products of fermentation 5. Some are mycorrhizae mutualistic relationship absorbing water & minerals on roots of plant |
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Harmful Effects of Fungi
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1. Some cause infections in humans
2. Cause diseases in plants 3. Produce toxins |
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mycosis
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fungal infection true pathogens – cause infection under usual conditions
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opportunistic pathogens
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cause infection only under unusual conditions
Candida albicans – thrush & vaginitis Pneumocystis carinii – pneumonia in AIDS patients (PCP) |
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toxins
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Aspergillus – aflatoxins Claviceps purpurea (ergot) – LSD & St. Anthony’s fire
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Types of Mycoses
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Superficial mycoses
Cutaneous mycosis Subcutaneous mycoses Systemic mycoses |
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Superficial mycoses
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involve hair & outer skin example – tinea versicolor
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Cutaneous mycosis
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involve skin, hair & nails n dermatophytes – fungi involved in cutaneous mycoses examples– tinea capitis ( ringworm)& tinea pedis ( athlete’s foot)
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Subcutaneous mycoses
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involve tissues below skin example – sporotrichosis
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Systemic mycoses
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involve internal organs example - histoplasmosis
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