Introduction to Microbiology Techniques Flashcards
Known amounts of pure chemical substances, predictable and reproducible, ideal for all media
Defined media
Nonselective, nutrient media, supports large number of organisms (ex. TSA, SBA)
Primary (nonselective) isolation media
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 don’t)
Differential media
Promotes 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, limits sugars (or adds extra buffer to counteract acids in sugar fermentation) and avoids selective agents
Maintenance media
Inhibits growth of unwanted organisms (usual flora), only used in selective media, mostly used in specimens w/ mixed normal flora, selectivity is also concentration dependent
Selective agents
Selective agent dye that inhibits GP and fastidious GN
Brillian green
Selective agent DYES that inhibit GP
Eosin, methylene blue, basic fuchsin
Heavy meatl 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 concentration of ____ is inhibitory to most organisms (except Staphylococcus)
NaCl
This agar is used to isolate Staphylococcus
Mannitol Salt agar (MSA)
Binds O2 in anaerobic medium
Reducing agents
oxidation-reduction potential in anaerobic medium
Eh indicators
Areas w/ flora usually require use of what kind of agar?
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 (SBA)
The most frequently used liquid medium for cultivation of organisms from original specimens (swabs, CSF, etc.), enriched will NOT support growth of many fastidious organisms, anaerobes will grow in lower levels in this b/c of less O2 tension
Thioglycollate broth
Selective agar, antibiotics inhibit most GN organisms, appearane 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 GNRs
MacConkey Agar (MAC)
Lactose positive colonies are ____
Dark pink
Lactose negative colonies are ____
Very ligth pink
Selective and differential agar, GP organisms INHIBITED, used for isolating and differentiating GNRs (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 CHOs), 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 (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 w/ 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)
Autoclave temp, PSI, and time
121C, 15 PSI, 15-20 minutes (not for large volumes)
List 3 aerobes
Obligate aerobe, microaerophile, facultative anaerobe
List 3 anaerobes
Aerotolerant anaerobes, moderate obligate anaerobes, strict obligate anaerobes
Incubation ccondition 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 infecction, 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 Biocarbonate)
Crystal violet
Mordant in Gram stain, complexes w/ crystal violet inside cell and makes it difficult to wash out
Iodine
Decolorizer in Gram stain
Acetone/Alcohol
Counterstin in Gram stain
Safranin
Have increased peptidoglycan in cell wall which retains crystal violet and will stain dark blue-purple
Gram positive
Have incrased lipid content, dissolved w/ acid/alcohol allowing crystal violet to flow out of cell, stains pink-red
Gram negative
Stain useful for high lipis in cell wall where acidified alcohol is used, stains mycobacteria includingM, tuberculosis and related bacteria, Ziehl-Neelsen and Kinyoun Methods, stain red = positive, blue = negative
Acid fast (AF)
Stains nucleic acid, fluorescent dye, bacteria stain 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 and methods, or automated systems
Rapid methods
What does MALDI-TOF stand for?
Matrix Assisted Laser Desportion–Time of Flight
