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mcim lab exam > exam > Flashcards

exam Flashcards

1
Q

3 types of potential hazards

A

chemical, physical, microbial

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2
Q

governed by 3 levels of legislation

A

provincial, municipal, federal

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3
Q

this lab is at which containment level (bioavailability)

what our greatest risk

A

2- can potencialy cause illness but unlikekly to be serious, low posibility of spreading

aerosols- air borne can be from anything

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4
Q

sterilization

A

complete destructionby chemical or physical means. can be done by steam autoclave, gas sterilization, dry heat, boiling, filtration

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5
Q

disinfection (decontamination

A

treatment of inanimate objects wo reduce the level of microorganisms. this does not always affect spores, effectiveness depends on the nautre of the contaminatin microorganism, the concentration of chemical , the amount of organic material

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6
Q

whmis

A

workplace hazardous material information system- 3 key elements: labels(alert emplyers to the danger of the product), material safety data sheets (detailed hazard and precautionairy info on the product), worker education (instruction on hazards and training in work procesures)

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7
Q

labels

A

supplier label: must have the distinctive hatched borderand contain product identifier…
workplace label: less detailed , flexible

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8
Q

MSDS

A

must have 9 sections

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9
Q

worker education

A

info and instruction must be provided to all worker who work with controlled substances

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10
Q

brightfield microscopy typically has — lenses- called —- microscopes

A

2 lenses: occular and objective- compound microscope

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11
Q

the function of a microscope depends on 2 parameters

how is magnification calculated

A

magnification and resolution. total magnification is determined by multiplying ocular magnification (marked on the eye peice) by the magnification of the objective lense (marked on side of the lense 10x, 40x, 100x

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12
Q

equivalent focal distance

A

distance in mm between speciment and the objective lens

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13
Q

oil immersion

A

prevents the scattering of light rays that would normally occur if light had to pass through air before it reached the lens- improve resolution by allowing more light to pass through the specimen

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14
Q

example of a differential stain

A

gram stain- a stain used to distinguish one type of bacteria from another

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15
Q

staphylococcus aureus

A

gram positive, spherical- purple

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16
Q

e coli

A

gram negative rod- pink

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17
Q

asepsis

A

aseptic techniques or strile techniques

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18
Q

purpose of staining

A

increase contrast btw bacteria and background

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19
Q

what does a properly prepared smaer ensure

A

bacteria are kills- no infectious risk
bacteria surface is altered to readily accept the stain
bacteria become firmly stuck to the glass

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20
Q

simples stain

A

methylene blue

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21
Q

2 examples of differential stains

A

gram stain and spore stain(need to flame it wih malchite green - safarin

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22
Q

Bacillius sereus

A

spore, gram positive rod

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23
Q

agar

A

complex carbohydrate extracted from red algae- added to solidify (1.5-2%- not used nutritionally for bacteria

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24
Q

chemically defined media vs. complex media

A

exact chemical formula is known vs. not known

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25
Q

Basic media

A

for bacteria with relatively simple nutritional needs , can be minimal or complex (nutrient agar)

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26
Q

Enriched media

A

complex media to which additional coponents such as blood, serum or meat infusion have been added

supports gorwth of fastidious bacteria- often used for clinical laboratories because many human pathogens have complexe nutritional needs

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27
Q

selective media

A

substances have been added that inhibit the growth of certain bacteria while allowing others- can be chenically defined or complex

used to isolate specific species in mixed populations

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28
Q

differential media

A

allo all bacteria to grow but certain substances can be added that allow for differentiation

can be chemically defined or complexe

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29
Q

nitrogen free mannitol

A

lack n and is used to grow bacteria that can acquire n from some other sources such as air

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30
Q

minimal essential medium

A

basic, chemically defined contain only mineral salts and glucose. E coli can grow on it because it can syntheis all their cellular components by metabolizing simple organic compounds (sugar)

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31
Q

nutrient agar

A

basic, complex media contains salt, beef extract, peptones (hydrolysed protein

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32
Q

blood agar

A

like nutrient agar but contain 5% defibrillated sheep blood- this provides extra cofactors, vit, ect. that necessary for some fastidious bacteria

33
Q

mannitol salt agar

A

used to differentiat s aureus from s. epidermidis
contain mannitol and 7.5% sodium chloride. the high salt concentration inhibits the growth of most organism except staphylococci

also contain indicator , phenol red, which changes colours from red to yellow when there is an acid end product
s. aureeus turns the plate yellow

34
Q

Macconkey’s agar

A

has bile salt, crytal violet, sugar lactose and the ph indicator neutral red
the bile inhibits most organisms except those that are in the GI and crystal violet inhibits intestional cocci

generally , gram negative rods are the only thing that grow
main purpose is to isolate enterobacteriaceae way from other bacteria in mixed population such as stool sample and to differentiate lactose fermenters(pink or purple colonies) from non fermentors(no colour change)-
used to determine cause of diaheas

selective and differentialr

35
Q

Turbidity

A

(absorbance) is proportional to the # of bacterial cells present counts dead and alive bacteria

36
Q

how to determine bacterial population count

A

measuring turbidity

enumeration of bacteria by plate count

37
Q

plate count method

A

each viable bacteria will form a colony
2 ways to do this: pour plate and the spread plate
both need the bacteria to be diluted so that there is between30-300 colobies
do dilution by 1ml into a 99ml blnk (saline )

only living

38
Q

CFU

A

colony forming units

multiply the average number of colonies per plate by the reciprical of the dilution used

39
Q

coliform bacteria

A

group of gram negative bacteria which are found in GI tract . can be found in waste and soil, exmaple E.coli
sometimes refered to as “indicator organism” alert tha the food has be contaminated

40
Q

serological pipette

A

meant to be emptied to deliver the total volume- graduation stop abovve the tip

41
Q

the measuring pipette

A

delivers the volume read on the graduations- pipette is not emptied- we only used the serological pipetter

42
Q

there are two basic sensitivity test

which determines the MIC

A

diffusion technique in solid media- easy to perform but give only an indication of whether the organism is sensitive or resistant

serial dilution techniques in tubes of liquid broth- determines the minimal inhibitory concentration (MIC)( FOR AN ANTIBIOTIC

43
Q

MIC

A

the lowest drug concentration which will still have an antimicrobial effect

44
Q

an organism is considered resistant

A

if the concentration required in vitro exceeds that which can be obtained in vivo

45
Q

disc diffusion technique (kirby bquer method)

A

paper discs impregnated with known concentration of an antibiotic are placed on the surface of an agar plate previously streaked with with the test bacteria, during incubation a concentration gradient is created

resistance is determined by zome size obtained to a standardized interpretation chart

46
Q

what can affect zone size

A

solubility rate of diffusion of the antibiotic, rate of growth of the bacteria, concentration of bacteria, media composition therefore a standard consistent technique is important- we need to ensure the same number of bacteria are added to the plate each time so we need to estimate by using the mcfarland turbidity standard

47
Q

what is more accurate disc diffusion or tube dilution

A

tube dillution

48
Q

MIC

A

minimum inhibitory concentration
after incubation in tube dilution sensitivity test, tubes are examined for growth, the highest dilution (lowest drug concentration of antibiotics showing no growth of the test tube

49
Q

minimal bactericidal concentration

A

a second parameter that can be nmeasured with the tube dilution test, not possible with the disc diffusion assay

can determine if the bacetria in the tube or dead or inhibited,from each tube showing no visible growth a standardized amount of broth is removed and plated on antibiotic-free media to determine wether the bacteria are dead or alive

sometimes an entibiotic can be bacteriostatic at low concentrations but bacteriocidal at very high concentration- if this occurs, the tube dilution method allows us to determine a numerical value for the bacteriocidal concentration-the so called MCB

50
Q

synergism effects of antibiotic aombination

A

rationale: proper combos might lower the incidence of bacteriale resistance, reduce host toxicity, or enhance the agents antimicrobial activity

51
Q

an examble of synergism

A

sulfasoxazole and trimethoprim becuase they inhibit different components of the same metobolic pathwat folic acid biosynthesis

52
Q

antisepsis

A

the treatment of living tissue to reduce the number of viable microbes. the same chemical may be used in both disinfectants and antiseptics but they are not interchangeble

53
Q

use dillution method

A

small glass rods on which test organisms are dried

54
Q

resident flora

A

permanent bacteria on the skin

55
Q

transient flora

A

only present for a few hours

56
Q

oligodynamic action

A

ability of small amounts of heavy metals to exert a lethal effect on bacteria

57
Q

how do heavy metals kill bacteria

A

due to the high affinity of membrane and other cellular proteins for the metallic ions, leading to protein denaturation or interferance with protein action- cells die due to cimulative effect of ions within the cell- can be used in water treatment, ointmentsm bandages and fabric

58
Q

what does uv light do to bacteria

A

optimal wavelenghs of 260-265 nanometers, is lethal to most bacteria, this is because uv light induces the formation of covalent bonds between adjacent thymine bases in DNA -> thymine dimers- dimers distort the conformation of the DNA interfering with transcription-> mutation- if enough mutation accumulate-> die

59
Q

where is uv light effective

A

killing organisms on surfaces and in the air

it does not penetrate proteinaceous material such as blood or sputum and does not pass through glass or plastic

60
Q

the effectiveness of filtration is most dependant on

A

size of the pores

the most common filter used has a size of 0.2 uM and holds back most bacteria but lets viruses and rickettsia
there are smaller sizes but fdifficult because water passes through them very slowly

61
Q

filters are use to

A

seperate bacteria from viruses , toxins from bacterial broth culture and to sterilize material that are adversily affected by heat ex. preparation of nutrient media

62
Q

lipolytic organism

A

normal flora bacteria that metabolize sebum

yeast, bacteria, mold
they are beneficial because they lower the ph of the skin preventing potentially harmful bacteria but if the skin pores are blocked the acidic by products of propionibacteria are trapped under the skin and if sebum production is high, the organism may release enough acid to inflame the skin causing acne

63
Q

what does staph aureus do to the skin

A

it produces coagulase (clots fibrin in the bood) is associated with boils, carbunkcles and other pus producing skin diseases- not all s. aureus are disease causing and can be further tested

64
Q

what is used to distinguish pathogenic s. aureus

A

usinf delective and differential medium such as manitol salt agar

65
Q

strep throat

A

streptococcus salivarius

66
Q

blood agar

A

should have the most colonies as it is rich non selective media

67
Q

alpha hemolysis

A

partial breakdown of red blood cells in the agar causing a greening of the media immediately surronding the colonies

68
Q

beta hemo;lysis

A

total breakdown of the red blood cells in tha agar causing a complete clearing of the media around the colonies

69
Q

gamma hemolysis

A

is no change

70
Q

catalase test

A

add drop of h2o2 onto the smeared glass- if gas is produced = catalase positive= staphylococcus species
if no gas is produced= catalase negative = streptococcus species

71
Q

the coagulase test can be used to distinguish

A

s aureus from s. epidermidis

72
Q

what i s a quick way to determine if s. aureus is present

A

use mannitol salt agar because it is selective (high salt) and differential (s. aureus will metabolise the sugar while epidermidis will not, turns yellow

73
Q

what is wrights stains

A

combo of acidic stains such as eosin and a basic stain such as methylene blue, the giemsa component contains azure dyes with intensify nuclear features as well as cellular granulation

they are all contained in an alcoholic solvent for the fization of the stain to cellular components

the cells present in blood show a range of colors: bright red of their acids components to the depp blue of the basic cellular components- neutrals are lilac

74
Q

which cells contain granules

A

neutrophiles eosinofils and basophils

lymphcytes and monocytes do not- have round or kidney shaped nucleus

75
Q

agllutination reaction- why do it

A

demonstrates an antibody-antigen interaction

agglutination is a term that describes what happens when an antibody interacts with a particular antigen
an immune complex is formed which consists of many cells cross-linked to each other by antibody molecules- forms aggregates

if a serum contains antibodiesagglutination will occur- this proves that the person has been exposed to this before

you can also mix unknown bacteria with known antibodies to determine which organism it is

76
Q

mycology

A

is the study of yeast and molds- fungi

77
Q

yeast

A

unicellular fungi - spherical or oval reproduce by budding- large

78
Q

mold

A

multicellular ofrms of fungi have filamentous structure- hyphae- densely packed as mycelliumaerial hyphae arise from mycelial mat and asexualy produce spores- fuzy

79
Q

what media most commonly used to isolate and grow fungi

A

sabourauds agar- reduces ph to inhibit bactera and high level of dextrose- readily fermented by fungi

mcim lab exam (1 decks)

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