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Microbiology > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

factors that affect microbial growth (7)

A
  • availability of nutrients
  • moisture
  • temperature
  • pH
  • osmotic pressure and salinity
  • biometric pressure
  • gaseous atmosphere
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2
Q

availability of nutrients

A
  • all living things require nutrients to live
  • nutrients are energy sources
  • organisms obtain energy by breaking chemical bonds
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3
Q

moisture

A
  • water is essential for life and to carry out metabolic processes
  • certain microbial stages (bacterial endospores and protozoal cysts) can survive drying process
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4
Q

temperature

A
  • every organism has optimum growth temperature

- optimum temperature and pH is determined by optimum temperature and pH of its enzymes

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5
Q

thermophiles

A
  • microorganisms that grown best at high temperatures

- less likely to be pathogenic

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6
Q

mesophiles

A
  • microbes that grow best at moderate temperatures (37C body temp)
  • more likely to be pathogenic
  • why we develop fever, to prevent pathogen reproduction
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7
Q

psychrophiles

A
  • microbes that prefer cold temperatures (deep ocean water)
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8
Q

psychrotrophs

A
  • group of psychrophiles

- prefer refrigerator temperature (4C)

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9
Q

psychroduric organisms

A
  • prefer warm temperatures but can endure cold/freezing temperatures
  • can sustain itself in unideal environment
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10
Q

pH

A
  • acidity or alkalinity of a solution

- most microorganisms prefer a neutral or slightly alkaline growth medium (7.0-7.4)

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11
Q

acidophiles

A
  • prefer acidic pH of 2-5
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12
Q

alkaliphiles

A
  • prefer alkaline/basic pH of >8.5
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13
Q

osmotic pressure

A
  • pressure that is exerted on a cell membrane by solutions both inside and outside the cell
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14
Q

osmosis

A
  • the movement of H2O (solvent) through a permeable membrane from a low solute concentration to a high solute concentration
  • moves from high H2O to low H2O
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15
Q

hypertonic solution

A
  • concentration of solutes in the external environment of a cell is greater than that of the internal environment of the cell
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16
Q

plamolysis

A
  • when the cell membrane and cytoplasm of a cell shrink away from cell wall
  • when bacteria with rigid cell walls are placed in hypertonic solution
  • H2O moves from inside to outside
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17
Q

crenation

A
  • shrinkage of human cell from hypertonic solution
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18
Q

hypotonic solution

A
  • concentration of solutes in the external environment of a cell is less than that of the internal environment of the cell
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19
Q

plasmoptysis

A
  • bacterial cell is placed in hypotonic solution and does not burst due to rigid walls
  • if it does burst, the cytoplasm escapes
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20
Q

hemolysis

A
  • explosion of human cell from hypotonic solution
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21
Q

isotonic solution

A
  • concentration of solutes outside a cell is equal to the concentration of solutes inside the cell
  • why saline is used in an IV so cells don’t burst or shrink
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22
Q

halophilic organisms

A
  • organisms that prefer to live in salty environments
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23
Q

haloduric organisms

A
  • organisms that prefer to live in a less salty environment but are capable of surviving salty environments
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24
Q

barometric pressure

A
  • microbes that can survive in high atmospheric pressure (>14.6 psi) are called piezophiles
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25
Q

gaseous atmosphere

A
  • microorganisms vary with respect to the type of gaseous atmosphere that requires
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26
Q

obligate aerobes

A
  • prefer the same atmosphere that humans do
  • 20-21% O2
  • 78-79% N
  • <1% other gases
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27
Q

microaerophiles

A
  • require reduced concentrations of O2

- 5% O2

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28
Q

obligate anaerobes

A
  • killed by presence of O2`
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29
Q

capnophiles

A
  • require increased concentrations of CO2

- 5-10% CO2

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30
Q

bacterial growth

A

in terms of number, not size

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31
Q

binary fission

A
  • how bacteria divide
  • continue through many generations until a colony is produced on solid culture media
  • continues as long as there is sufficient nutrients, water, and space
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32
Q

generation time

A
  • time is takes for one cell to become 2 cells

- e coli = 20 mins

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33
Q

media

A
  • used in microbiology labs to culture/grow bacteria
  • media prepared in he labs are referred to as artificial or synthetic media
  • can be liquid or solid
  • multiple categories of media can be used at same time
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34
Q

chemical defined medium

A
  • a media in which all ingredients are known
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35
Q

enriched medium

A
  • a broth or solid containing a rich supply of special nutrients that promote its growth
  • chocolate agar, blood agar
36
Q

selective medium

A
  • medium that has added inhibitors that discourage the growth of certain organisms while allowing the growth of a desired organism
  • MacConey agar, phenylethyl alcohol (PEA) agar, colistin-nalidixic (CNA) agar, Thayer-martin agar, martin-lewis agar, mannitol salt agar
37
Q

differential medium

A
  • medium that permits the differentiation of organisms that grow on the medium
  • colour changes
  • macConkey agar, mannitol salt agar, blood agar
38
Q

thioglycollate broth (THIO)

A
  • popular liquid medium in bacteriology labs
  • supports the growth of all categories of bacteria from obligate aerobes to obligate anaerobes
  • concentration gradient of dissolved O2 in tube
  • organism only grows in part of tube where O2 concentration meets its needs
39
Q

inoculation of culture medic

A
  • culture media are inoculated within clinical specimens
  • involves adding a portion of a specimen to the medium with a sterile inoculating loop
  • creates individual colonies
40
Q

septic technique

A
  • practiced when it is necessary to exclude microbes from a particular area
  • sterility of media must be maintained before inoculation
  • inoculating media within a biologic safety cabinet minimizes contamination and protects laboratories
  • airflow in the cabinet presents airborne bacteria from getting into agar
41
Q

contaminants

A
  • unwanted organisms

- growth medium/plate is said to be contaminated

42
Q

media incubator

A
  • after media are inoculated they must be placed in incubator which will maintain atmosphere, temperature, and moisture level the organism requires
43
Q

3 types of incubators

A

1) CO2 incubator - 5-10% CO2
3) non-CO2 incubator - room air
3) anaerobic incubator - atmosphere is devoid of O2

44
Q

bacterial population counts

A
  • microbiologists sometimes need to know how many bacteria are present in a particular liquid at a given time
  • ex: determine bacterial contamination of drinking water
  • can determine either total number of cells or total number of viable cells
45
Q

spectrophotometer

A
  • can be used to determine growth by measuring the turbidity of the medium
46
Q

viable plate count

A
  • used to determine the number of viable bacteria in a liquid sample by making dilutions of the liquid and inoculating onto nutrient agar
  • after overnight incubation number of colonies from diluted sample are counted
47
Q

population growth curve

A
  • may be determined by growing a pure culture of the organism in a liquid medium at a constant temperature
  • samples are collected at fixed intervals
  • graph prepared by plotting the logarithmic number of viable organisms against incubation time
48
Q

population growth curve points

A
  • lag phase = slow bacterial growth
  • log (exponential) phase = fast bacterial growth
  • stationary phase = grow to fill space and use available nutrients but no longer increase in number
  • death phase = nutrients are used up or toxic waste increases and bacteria start to die
49
Q

chemostat

A
  • used for continuous cultures
  • to have bacteria continue growing and not hit a plateau or death phase
  • can introduce fresh medium and sterile air
  • can collect samples with collection vessel
50
Q

obligate intracellular pathogens

A
  • microbes that can survive and multiply only within living cells
  • include viruses and 2 groups of gram - bacteria (rickettsias and chlamydias)
  • culturing these is hard, must be grown in embryonate chicken eggs, lab animals, or cell cultures
51
Q

fungi culturing

A
  • including yeasts, mould, and dimorphic fungi
  • grow on and in a variety of solid and liquid culture media
  • no single medium that is best for all medically important fungi
  • caution when culturing fungi as some are highly infectiou
52
Q

examples of culture media for fungi

A
  • brain heart infusion (BHI) agar
  • BHI with blood
  • sabouraud dextrose agar (SDA) - selective for fungi because low pH
53
Q

protozoa culturing

A
  • not done often
  • protozoa that can be cultured in vitro: amebae, giardiasis lambila, leishmania, toxoplasma gondii, trichomonad vaginalis, trypanosome Cruz
  • due to severity of disease they cause it is of greatest importance to culture amebae: acanthamoeba, balamuthia, naegleria fowleri
54
Q

sterilization

A
  • complete destruction of all microbes including cells, spores, and viruses
  • accomplished by dry heat, autoclaving, gas, various chemicals, and certain radiation
55
Q

disinfection

A
  • destruction/removal of pathogens from nonliving objects by physical or chemical methods
  • ex: pasteurization
56
Q

disinfectants

A
  • chemical substances that eliminate pathogens on inanimate objects
57
Q

antiseptics

A
  • solutions used to disinfect skin and living tissue
  • reduce number of organisms on surface of skin
  • do not penetrate pores and hair follicles
  • antiseptic soaps and scrubbing used in healthcare
58
Q

chemicals that kill microbes

A
  • germicidal agents
  • biocidal agents
  • microbicidal agents
59
Q

bactericidal agents

A
  • chemical that specifically kill bacteria, but not necessarily endospores
60
Q

sporicidal agents

A

kill bacterial endospores

61
Q

fungicidal agents

A

kill fungi, including fungal spores

62
Q

algicidal agents

A

kills algae

63
Q

viricidal agents

A

kills viruses

64
Q

microbistatic agent

A
  • drug or chemical that inhibits growth/reproduction of microbes
65
Q

bacteriostatic agent

A
  • specifically inhibits metabolism and reproduction of bacteria
66
Q

lyophilization

A
  • process that combines dehydration and freezing

- widely used to preserve foods, antibiotics, microorganisms, and other biologic materials

67
Q

sepsis

A
  • the presence of pathogens in blood or tissues
68
Q

asepsis

A

absence of pathogens

69
Q

antisepsis

A

prevention of infection

70
Q

use of heat to kill organisms

A
  • two factors: temperature and time

- determine effectiveness of heat for sterilization

71
Q

thermal death point (TDP)

A
  • lowest temperature that will kill all of the organisms in a standardized pure culture within a specified time
72
Q

types of heat used for sterilization

A
  • dry heat - oven, electrical incinerator, flame

- moist heat - boiling, autoclave

73
Q

autoclave

A
  • large metal pressure cooker that uses steam under pressure to destroy microbial life
  • increase pressure raises the temp above boiling (100C) and forces steam into materials
  • autoclaving at pressure of 15 psi at 121.5C for 20 mins destroys vegetative microorganisms, bacterial endospores, and viruses
74
Q

method to ensure proper autoclaving

A
  • pressure sensitive tape (stiles on tape)
  • spore strips
  • solutions (colour change)
75
Q

methods to inhibit microbial growth (6)

A
  • cold
  • desiccation
  • radiation
  • ultrasonic waves
  • filters
  • gaseous atmosphere
76
Q

cold

A
  • most microorganisms are not killed, but metabolic activities are slowed
77
Q

desiccation

A
  • drying/dehydrating

- many dried microorganisms remain viable, but they cannot reproduce

78
Q

ultrasonic waves

A

used in hospital and medical and dental clinics to clean equipment

79
Q

radiation

A
  • a UV lamp is useful for reducing number of microbes in the air
80
Q

filters

A

used to separate cells/microbes from liquids or gases

81
Q

chemical disinfectants

A
  • use of chemical agents to inhibit growth of pathogens

- temporarily or permanently

82
Q

things that affect disinfectants (7)

A
  • prior cleaning
  • organic load (faces, blood, pus)
  • bioburden (type/number of microbes)
  • concentration of disinfectant
  • contact time
  • physical nature of object being cleaned
  • temperature and pH
83
Q

characteristics of an ideal chemical antimicrobial agent (9)

A
  • broad antimicrobial spectrum
  • fast acting
  • not affected by organic matter
  • nontoxic to human tissues and noncorrosive
  • should leave residual antimicrobial film on surface
  • soluble in water and easy to apply
  • inexpensive and easy to prepare
  • stable as concentrate and a working solution
  • odourless
84
Q

inhibiting pathogen growth in kitchens

A
  • many food brought in are contaminated with pathogens
  • problems arise before cooking
  • be aware of pathogens when preparing food
  • clean hands frquently
  • thoroughly clean things that had raw meat on them with hot soapy water
  • antibacterial kitchen sprays controversial
  • ex: e coli, salmonella, campylobacter
85
Q

antimicrobial agents and animal feed

A
  • 40 % of antibiotics are used in animal feeds, efforts underway to reduce
  • drug resistant organisms are transmitted in animal food products and poop
  • use of antimicrobial agents is widespread in many areas which can create resistance microbes that survive antimicrobial agents and thrive

Microbiology (18 decks)

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