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
2
Q
availability of nutrients
A
- all living things require nutrients to live
- nutrients are energy sources
- organisms obtain energy by breaking chemical bonds
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
4
Q
temperature
A
- every organism has optimum growth temperature
- optimum temperature and pH is determined by optimum temperature and pH of its enzymes
5
Q
thermophiles
A
- microorganisms that grown best at high temperatures
- less likely to be pathogenic
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
7
Q
psychrophiles
A
- microbes that prefer cold temperatures (deep ocean water)
8
Q
psychrotrophs
A
- group of psychrophiles
- prefer refrigerator temperature (4C)
9
Q
psychroduric organisms
A
- prefer warm temperatures but can endure cold/freezing temperatures
- can sustain itself in unideal environment
10
Q
pH
A
- acidity or alkalinity of a solution
- most microorganisms prefer a neutral or slightly alkaline growth medium (7.0-7.4)
11
Q
acidophiles
A
- prefer acidic pH of 2-5
12
Q
alkaliphiles
A
- prefer alkaline/basic pH of >8.5
13
Q
osmotic pressure
A
- pressure that is exerted on a cell membrane by solutions both inside and outside the cell
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
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
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
17
Q
crenation
A
- shrinkage of human cell from hypertonic solution
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
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
20
Q
hemolysis
A
- explosion of human cell from hypotonic solution
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
22
Q
halophilic organisms
A
- organisms that prefer to live in salty environments
23
Q
haloduric organisms
A
- organisms that prefer to live in a less salty environment but are capable of surviving salty environments
24
Q
barometric pressure
A
- microbes that can survive in high atmospheric pressure (>14.6 psi) are called piezophiles
25
gaseous atmosphere
- microorganisms vary with respect to the type of gaseous atmosphere that requires
26
obligate aerobes
- prefer the same atmosphere that humans do
- 20-21% O2
- 78-79% N
- <1% other gases
27
microaerophiles
- require reduced concentrations of O2
| - 5% O2
28
obligate anaerobes
- killed by presence of O2`
29
capnophiles
- require increased concentrations of CO2
| - 5-10% CO2
30
bacterial growth
in terms of number, not size
31
binary fission
- 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
32
generation time
- time is takes for one cell to become 2 cells
| - e coli = 20 mins
33
media
- 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
34
chemical defined medium
- a media in which all ingredients are known
35
enriched medium
- a broth or solid containing a rich supply of special nutrients that promote its growth
- chocolate agar, blood agar
36
selective medium
- 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
differential medium
- medium that permits the differentiation of organisms that grow on the medium
- colour changes
- macConkey agar, mannitol salt agar, blood agar
38
thioglycollate broth (THIO)
- 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
inoculation of culture medic
- 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
septic technique
- 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
contaminants
- unwanted organisms
| - growth medium/plate is said to be contaminated
42
media incubator
- after media are inoculated they must be placed in incubator which will maintain atmosphere, temperature, and moisture level the organism requires
43
3 types of incubators
1) CO2 incubator - 5-10% CO2
3) non-CO2 incubator - room air
3) anaerobic incubator - atmosphere is devoid of O2
44
bacterial population counts
- 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
spectrophotometer
- can be used to determine growth by measuring the turbidity of the medium
46
viable plate count
- 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
population growth curve
- 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
population growth curve points
- 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
chemostat
- 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
obligate intracellular pathogens
- 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
fungi culturing
- 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
examples of culture media for fungi
- brain heart infusion (BHI) agar
- BHI with blood
- sabouraud dextrose agar (SDA) - selective for fungi because low pH
53
protozoa culturing
- 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
sterilization
- complete destruction of all microbes including cells, spores, and viruses
- accomplished by dry heat, autoclaving, gas, various chemicals, and certain radiation
55
disinfection
- destruction/removal of pathogens from nonliving objects by physical or chemical methods
- ex: pasteurization
56
disinfectants
- chemical substances that eliminate pathogens on inanimate objects
57
antiseptics
- 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
chemicals that kill microbes
- germicidal agents
- biocidal agents
- microbicidal agents
59
bactericidal agents
- chemical that specifically kill bacteria, but not necessarily endospores
60
sporicidal agents
kill bacterial endospores
61
fungicidal agents
kill fungi, including fungal spores
62
algicidal agents
kills algae
63
viricidal agents
kills viruses
64
microbistatic agent
- drug or chemical that inhibits growth/reproduction of microbes
65
bacteriostatic agent
- specifically inhibits metabolism and reproduction of bacteria
66
lyophilization
- process that combines dehydration and freezing
| - widely used to preserve foods, antibiotics, microorganisms, and other biologic materials
67
sepsis
- the presence of pathogens in blood or tissues
68
asepsis
absence of pathogens
69
antisepsis
prevention of infection
70
use of heat to kill organisms
- two factors: temperature and time
| - determine effectiveness of heat for sterilization
71
thermal death point (TDP)
- lowest temperature that will kill all of the organisms in a standardized pure culture within a specified time
72
types of heat used for sterilization
- dry heat - oven, electrical incinerator, flame
| - moist heat - boiling, autoclave
73
autoclave
- 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
method to ensure proper autoclaving
- pressure sensitive tape (stiles on tape)
- spore strips
- solutions (colour change)
75
methods to inhibit microbial growth (6)
- cold
- desiccation
- radiation
- ultrasonic waves
- filters
- gaseous atmosphere
76
cold
- most microorganisms are not killed, but metabolic activities are slowed
77
desiccation
- drying/dehydrating
| - many dried microorganisms remain viable, but they cannot reproduce
78
ultrasonic waves
used in hospital and medical and dental clinics to clean equipment
79
radiation
- a UV lamp is useful for reducing number of microbes in the air
80
filters
used to separate cells/microbes from liquids or gases
81
chemical disinfectants
- use of chemical agents to inhibit growth of pathogens
| - temporarily or permanently
82
things that affect disinfectants (7)
- 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
characteristics of an ideal chemical antimicrobial agent (9)
- 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
inhibiting pathogen growth in kitchens
- 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
antimicrobial agents and animal feed
- 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
