Lab Quiz 4 revised Flashcards
33: what media is used in skin culture
Mannitol salt agar plate
33: What ingredient makes skin media selective and how is it selective
contains 7% salt which allows only salt tolerant organisms to grow
33: what ingredient make skin media differential and how is it
mannitol sugar
organisms that ferment mannitol grow yellow agar
non fermenting organisms remains red agar
33: what tests are used to determine if colony is a staph species
- gram + cocci
- catalase +
33: what test are used to identify staph species isolated
- mannitol fermentation
- coagulate
33: what is the reaction of coagulase
coagulase enzyme metabolizes fibrinogen into a fibrin clot
33: appearance of coagulase result
- liquid media: -
- clot formed: +
33: what species of staph produces coagulase
staph aureus
33: phenol red fermentation test explained and results
- sugar fermented, acids produced, ph decreases, phenol red changes from red to yellow
- yellow: +
- red: -
- phenol red indicator
35: what media are used for the mouth culture
- Mitis-salivating agar
- chrom agar candida
35: purpose of MSB agar
only allows growth of strep species which are prevalent in the mouth
35: How is MSB selective
crystal violet and telluride inhibit gram + and gram - growth excerpt for streptococcus
35: How is MSB differential
- contains tryptan blue and sucrose
- strep species blue black in color
- differences in colony appearance identify species
35: purpose of chrom agar candida
isolation of candida species from saliva
35: how is chrom agar selective
chloramphenicol inhibits all gram + and gram - bacterial which allows candida yeast to grow
35: how is chrom agar differential
chromagenic granules metabolized differently by different species and appear different colors on agar
35: what species is commonly isolated on chrom agar and what is the appearance
- candida albicans
- apple green
35: what strep species is responsible for dental carie’s
strep mutans
35: what is the appearance of the 4 major types of strep on MSB agar
strep mitis: small, blue
enterococcus: small, black
strep salivarius: large, blue, gumdrop
strep mutans: blue, glass or burnt sugar
35: appearance of yeast cells under microscope
rain droplet like colonies with green tint
36: what medias are used for urine culture
- 5% sheep blood agar
- MacConkey agar
36: purpose of 5% sheep blood agar
- good rich media that is non selective
- determine total bacterial count per ml of urine
36: purpose of Macconkey agar
- determine gram - bacteria count per ml of urine which is used to determine UTIs
36: how is macconkey agar selective
crystal violet and bile salts inhibit gram + growth and allow only gram - growth
36: how is macconkey agar differential
contains lactose. lactose fermenting organisms produce dark pink/ purple colonies while non lactose fermenting organisms appear colorless/ yellow on agar
36: calculation for bacteria per ml of urine
amount of colonies x 100
36: criteria for a UTI
> 10,000 organisms/mL urine and pure culture
36: criteria for minor and major contamination
- minor: < 10,000 bacteria/ml
- major: >10,000 bacteria/ml with multiple colony types
36: what does growth on macconkey agar mean
- there is gram - organisms in urine but this does not mean UTI unless it meets uti criteria
36: what are UTIs caused by
gram - rods
36: define cystitis
UTI confined to bladder
36: Define pyelonephritis
UTI spread to kidneys
37: medias used in intestinal culture
- Bile Esculin hydrolysis media
- Macconkey agar
- EMB agar
37: purpose of bike esculin hydrolysis test
detect enterococcus fecalis in sample
37: Reaction of + bike esculin test
- esculin fecalis present in media and hydrolyses esculin to esculetin and dextrose
- esculetin combines with ferric citrate indicator and turns black
37: How is bile esculin media selective
sodium azide and bile inhibit gram + and gram - growth except for enterococcus faecalis
37: gram stain of enterococcus faecalis
gram + cocci
37: purpose of macconkey agar
isolation of lactose fermenting, non pathogenic, gram - rod
37: how is macconkey agar selective
crystal violet and bile salts inhibit gram + bacteria and allow only gram - bacteria to grow
37: how is macconkey agar differential
lactose fermenting organisms appear pink/ purple and non lactose fermenting organisms appear colorless/ yellow
37: what tests are done to identify gram - rod isolated
- citrate
- Urease
- SIM
- EMB agar plate
37: how is EMB agar selective
eosin/methylene blue inhibit gram + bacteria and allow only gram - bacteria to grow
37: How is EMB agar differential
organisms can be differentiated based on colony appearance
37: what is the appearance of E. coli on EMB agar
green, metallic sheen
38: what test is for antimicrobial drug and antibiotics
kirby bauer test
38: what is the purpose of kirby bauer test
assess the effectiveness of different drugs and antibiotics against specific microorganisms
38: what are the standardized features of kirby bauer test
- Muller Hinton agar media
- 1+ turbidity of broth culture
- concentrations of agent
- method of measurement of zones of inhibition
- charts used for interpretation: SIR
38: what media is used for kirby bauer test
Muller Hinton agar
38: process of kirby bauer test
- agar plate swabbed with broth culture
- antibiotic disks placed on agar plate
- zones of inhibition measured after incubation
38: why is it also called disk diffusion assay
gradient of highest concentration near the disk to lowest concentration away from the disk as the agent diffuses outward
38: define zone of inhibition
- clear are of no bacterial growth surrounding disk
- formed when agent destroys pathogen
- the bigger the size the more effective
38: how are kirby bauer results reported
- Sensitive
- Intermediate
- Resistant
39: What 3 organisms were tested against the agents
- E. coli
- Staph aureus
- pseudomonas
39: how was the effectiveness of each agent determined
- disk diffusion assay
- zones of inhibition measured
39: does gram stain influence effects of agents
gram + bacteria is much more susceptible to affects of antiseptics and disinfectants than gram - bacteria
39: difference between antiseptic and disinfectant
antiseptic is used in the body while disinfectants are used on surfaces
40: alcohol mechanisms of action
- disruption of plasma membrane
- denaturation of proteins
40: why are aqueous solutions superior to pure alcohols
denaturation of proteins more effective in presence of water
40: is alcohol effective as antiseptic or disinfectant
- both because it can be used in both surfaces and people
- kills bacteria and fungi but not endospores or non enveloped
- quadrant with alcohol thumb had no bacterial growth
41: take home lessons of hand washing
- extremely important in eliminating transmission of pathogen
- sanitizer is very effective
- need to wash hands for long time with soap while scrubbing to be super effective
