microblabquiz Flashcards
(20 cards)
Family micrococcaceae
genera includes Stapylococcus and Micrococcus
Found on human body
- Gram positive coci
- micrococcus–tetrads
- staphylo-clusters
- Do not produce endospores
- adapted to salty 7.5%NaCl
- Uses O2 in aerobic resp.
- Micrococcus–strict aerobes and Staphylo are facultative
- Catalase positive good for distinguishing form other gram pos
Staphylococcus
S. aureus
S. epidermidis
S. saprophyticus
Micrococcus
M. luteus
How to distinguish Staphyl/Micro from Strepto/Entero
- Gram stain (clusters/tetrads) verse (chains) respectively
- Catalase assay (pos) vs. (neg)
- Salt tolerance (Staphylo and Micro will grow)
Mannitol salt agar
highly selective for gram pos ^^
also differential b/c sugar mannitol and pH indicator phenol red–test for ability to ferment mannitol helps to identify staphylococcus species
phenol red carb assay
pos for acid by fermentation: broth will be bright yellow indicating Staphylo species
neg for acis by ferm: any orange or red color indicating Micrococcus
Identifying within Staphylo
- Fermentaion of mannitol
- resistance to antibiotic novobiocin
- production of coagulase
Mannitol Salt agar
Pos for acid ferm: if medium around colonies has a bright yellow color could be S. aureus or S.saprophytuicus
Neg for acid ferm: medium will be orange-red to pink red color. this could be S. epidermidis or any number of Micrococcus
Novobiocin sensitivity and resistance
S. saprophyticus is resistant while micro-and other staphylo are sensitive
zone of inhibition 18mm or 9mm radius
Coagulase assay
Positive rxn: appears blue grains suspended in colorless liquid within 30-60 sec can be identified as S. aureus
Neg rxn: absence of blue aggregates and retention of homogenous opaque blue appearance after 30-60 sec
false pos possible if wait too long
Enteric species characterized by
- Gram neg rods
- Do not produce spores
- species are all faculatitive anaerobes produce organic acids and gases
- All enterics ferment glucose to produce organic acids and gas
Lactose fermentaion
Coliform and non-coliform enterics
able to ferm lactose-coliform
not able to ferm lactose- non coliform
MacConkey agar
Selective for gram neg enterics by inhibiting gram pos with crystal violet and bile salts
Differential seperates enteric isolates into lactose fermentor and non fermentors. contins 1% lactose and neutral red as pH indicator
Pos rxn: medium surounding colonies and colonies are bright red = coliform ~ E.coil and Citrobacter freundii
Neg rxn: remains unchanged or becomes pale yellow as aposed to brick red
EMB agar
selective for gram neg–inhibits gram pos with dyes eosin and methylene blue
Differential 1% lactose as substrate for ferm. dyes act as pH indicators
Pos rxn: medium surrounding colonies/conolies are dark red-purple to purple black = coliform… high concentrations will produce metalic green sheen typical of E.coli
Neg rxn: remains colorless or yellow purple noncoliform
Pseudomonas species typically non-pathogenic
- gram neg rods
- do not produce endospores
- possess flagella and are motile
- many produce blue, hello, green and or red pigments which are water soluble and diffuse into bacteriological media
- strictly respiratory–relies on ETS NO ferm pathways
- Some are strict aerobes
- others can live anaerobically if nitrate is available
Oxidative/Fermentation Assay
glucose medium designed to detect conversion of glucose to organic acids either oxidatively or fermentatively
At pH 6.0–uncharged bromthmol blue molecules outnumber neg charged–clearly yellow–significant quantities of organic acids are produced from glucose–medium will be yellow
6.5-7.5pH 7pH neutral even color molecules will appear green
8.0pH shortage of free protons or H+ neg chraged blue alkaline
open tube yellow at top green at bottom and closed tube green throughout: Ps. aeruginosa
- opentube yellow from t to b and closed tube is yellow from t to b: enterobacteriaceae family
- open tube green to blue at top and green at botom and closed tube is gren from t to b: can be a diff pseu species or enterio
Methyl red assay/ MRVP
detecting range of acid produced
Pos for high conc of organic acids: orange to red indicator only turns orange elow 5PH indicates cells must be E.coli
-Neg rxn: yellow could be E. aerogenes
Citrate assay
Simmons citrate agar
diffierentiate Ecoli from E. aerogenes
Pos rxn:visable evidence of growth is a deep or royal blue color indicates ability to use citrate as the sole carbon source must be E. aerogenes
Neg rxn: no evidence of growth medium is green must be e.coli and are likely of fecal origin
a heavy innoculated agar might appear slimy and produce false pos
Urease assay
urea broth
Pos: if broth turns bright pink most likely proteus
Neg:unchanged or orange in color no more than 24hrs after in.
SIM assay
sulfide production
indole
motility
sulfide:
pos-black shit could be salmonella, proteus or citrobacter
neg- no black shit could be alot of shit
indole- kovac’s reagent added after-
pos if butanol react and produce cherry red could be E.coli and E. aerogenes
neg- yellow or unchaged could be E.aerogene and klebsiella pneumonia
motility:
pos: disperas all enterics expe klebsiella and shigella
neg still see line
