Introduction to Microbiology Techniques Flashcards
non selective, nutrient media, supports large number of organisms, ex t-soy and sheep blood agar
Primary Isolation Media
Known amounts of pure chemical substances, predictable and reproducible, ideal for all media
Defined
contains inhibitors to retard some organisms, ex MAC, HEK, XLD
selective isolation media
indicators allow recognition of certain biochemical reactions, ex MAC (those that utilize lactose and those that do not)
Differential Media
Promote growth of some organisms, contains enrichments, ex CHOC, often incubated in CO2 incubator for growth of fastidious organisms
Enrichment Media
allows survival of organisms for extended periods, limit sugars (or add extra buffer to counteract acids in sugar fermentation) and avoid selective agents
Maintenance media
inhibit growth of unwanted organisms (usual flora), only used in selective media, mostly used in specimens with mixed normal flora, selectivity is also concentration dependent
Selective Agents
selective agent dye that inhibits GP and fastidious GN
Brilliant Green
selective agent DYES that inhibit GP
Eosin, Methylene Blue, Basic Fuchsin
Heavy metal that inhibits GP and most GN
Bismuth
used for isolation of salmonella (GN)
Bismuth Sulfide Agar
Dyes, Heavy Metals, antimicrobials, and other chemicals are used as _____
Selective Agents
chemical that inhibits GP, Blue
Citrate
chemical that inhibits GP, Bile Salts
Sodium desoxycholate
Chemicals that inhibit GN
Phenylethyl alcohol and Azide
high conc. of this are inhibitory to most organisms (except staphylococcus)
NaCl
this agar is used to isolate staph
Mannitol Salt Agar
binds O2 in anearobic medium
reducing agents
oxidation-reduction potential in anearobic medium
Eh indicators
areas with flora usually require use of what kind of media?
Selective and Differential
this media is often added on specimens from normally sterile areas
enrichment media
used in most laboratories on ALL routine specimens, best medium for colonial morphology, only medium used for determination of hemolysis
Sheep Blood Agar
most frequently used liquid medium for cultivation of organisms from original specimens (swabs, CSF fluids, etc), enriched but will NOT support growth of many fastidious organisms, anaerobes will grow in lower levels in this because of less O2 tension
Thioglycollate Broth
selective agar, antibiotics inhibit most GN organisms, appearance is similar to SBA
Colistin Nalidixic Acid (CNA) Agar
selective and differential agar, GP organisms INHIBITED (crystal violet and bile salts), used for isolating and differentiating GNR’s
MacConkey Agar (MAC)
Lactose positive colonies are _______
Dark Pink
Lactose Negative colonies are _______
very light pink
Selective and differential agar, GP organisms INHIBITED, used for isolating and differentiating GNR’s (lactose and other CHO’s), used primarily for isolating pathogens in stool
Xylose, Lysine, Desoxycholate Agar (XLD)
color of CHO positive on XLD plate
yellow
color of CHO negative on XLD plate
clear/red (color of original medium)
color of H2S producing organism on XLD plate
Black
Selective and differential agar, GP organisms inhibited by bile salts, used for isolating and differentiating GNR’s (Lactose and other CHO’s), used primarily for isolating pathogens in stool
Hektoen Agar (HE or HEK)
color of CHO positive organisms on HE or HEK plate
orange
color of CHO negative organisms on HE or HEK plate
clear/green (color of original medium)
color of H2S producing organisms on HE or HEK plate
black
Selective and differential agar, Inhibits GP organisms, often used for E. coli identification (green sheen)
Eosin Methylene Blue Agar (EMB)
enrichment media, no selective agents, supports growth of most organisms and many fastidious organisms, particularly Haemophilus and Neisseria, used for spinal fluid
chocolate agar
selective enrichment agar, chocolate agar with antimicrobials, primarily used on genital or rectal specimens for isolation of Neisseria gonorrhoeae or Neisseria meningitidis while inhibiting usual flora
Martin-Lewis, Thayer Martin Media
Used to disinfect non-metallic surfaces, effective against HIV and HBV
sodium hypochlorite (bleach) for table tops
Autoclave temp, psi , and time
121’C, 15 psi, and 15-20 min (not for large volumes)
List 3 Aerobes…
obligate aerobe, microaerophile, facultative anaerobe
List 3 anaerobes…
aerotolerant anaerobes, moderate obligate anaerobes, strict obligate anaerobes
Incubation condition for ambient air or non-CO2 incubator
21% O2, 0.03% CO2 (room air), aerobic
incubation conditions for CO2 incubator
15% O2, 5-10% CO2 (room air w/ extra CO2 pumped in) , aerobic
Incubation conditions for microaerophilic incubator
5% O2, 10%CO2, aerobic
Incubation conditions for anaerobic incubator
0% O2, 5-10% CO2
where do we put biochemicals, differential media, and antimicrobial susceptibility tests?
ambient air incubators
where do we put primary plates and fastidious organisms?
CO2 Incubators (capnophilic)
these provide initial clue to cause of infection, may dictate therapy decisions, evaluate quality of specimen, tells us if we need additional media, determines if we should QC for culture results
Direct Smears
primary stain in gram stain (add Na Bicarbonate buffer)
crystal violet
mordant in gram stain, complexes with crystal violet inside cell and makes it difficult to wash out
Iodine
decolorizer in gram stain
acetone/alcohol
counterstain in gram stain
safranin
Have increased peptidoglycan in cell wall which retains crystal violet and will stain dark blue-purple
Gram positive
Have increased lipid content ,dissolved with acid/alcohol allowing crystal violet to flow out of cell, stains pink-red
Gram negative
stain useful for high lipids in cell wall where acidified alcohol is used, stains mycobacteria including M. tuberculosis and related bacteria, Ziehl-Neelsen and Kinyoun Methods, stain red=positive blue=negative
Acid Fast (AF) stains
stains nucleic acid, fluorescent dye, bacteria stain fluorescent yellow, used most often in blood smears
acridine orange
these methods can be spot tests, chromogenic or fluorogenic substrates by enzymes, slide agglutinations or ELISA, nucleic acid methods, or automated systems
Rapid Methods
What does MALDI-TOF stand for ?
Matrix Assisted Laser Desorption Ionization-Time of Flight
