exam Flashcards

Question

Basic media

Answer 1

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

Answer 2

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

Answer 3

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

Answer 4

allo all bacteria to grow but certain substances can be added that allow for differentiation can be chemically defined or complexe

Answer 5

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

Answer 6

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)

Answer 7

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

Answer 8

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

Answer 9

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

Answer 10

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

Answer 11

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

Answer 12

measuring turbidity | enumeration of bacteria by plate count

Answer 13

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

Answer 14

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

Answer 15

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

Answer 16

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

Answer 17

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

Answer 18

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

Answer 19

the lowest drug concentration which will still have an antimicrobial effect

Answer 20

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

Answer 21

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

Answer 22

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

Answer 23

tube dillution

Answer 24

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

Answer 25

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

Answer 26

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

Answer 27

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

Answer 28

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

Answer 29

small glass rods on which test organisms are dried

Answer 30

permanent bacteria on the skin

Answer 31

only present for a few hours

Answer 32

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

Answer 33

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

Answer 34

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

Answer 35

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

Answer 36

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

Answer 37

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

Answer 38

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

Answer 39

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

Answer 40

usinf delective and differential medium such as manitol salt agar

Answer 41

streptococcus salivarius

Answer 42

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

Answer 43

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

Answer 44

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

Answer 45

is no change

Answer 46

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

Answer 47

s aureus from s. epidermidis

Answer 48

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

Answer 49

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

Answer 50

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

Answer 51

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

Answer 52

is the study of yeast and molds- fungi

Answer 53

unicellular fungi - spherical or oval reproduce by budding- large

Answer 54

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

Answer 55

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