Lab & diagnostics
Lab & diagnostics in PetriKey
Stains, media, and biochemical tests — what they show and how to read them.
45 reference cards
16S rRNA sequencing
Bacterial gene sequencing ID concept
Acid-fast stain
Mycolic-acid wall staining concept
Antigen test concept
Detects microbial protein or polysaccharide target
Bacitracin (A disk) test
A-disk: Group A strep sensitive, Group B resistant
Gram +Bile solubility test
Pneumococcus dissolves in bile; viridans does not
Gram +Blood agar hemolysis
Alpha, beta, and gamma hemolysis vocabulary
Calcofluor white stain
Fluorochrome binding fungal chitin
CAMP test
Arrowhead synergy = Group B strep / Listeria
Gram +Catalase test
Staph vs strep study branch
Chocolate agar X/V factors
Enriched media vocabulary for fastidious bacteria
Citrate utilization test
Prussian blue = citrate positive (Klebsiella)
Gram −Coagulase test
S. aureus clue among staphylococci
Direct antiglobulin (Coombs) test
Detects antibody/complement coating red cells
DNase test
Clearing on DNA agar = S. aureus positive
Gram +ELISA
Antigen-antibody assay concept
EMB agar concept
Green metallic sheen = E. coli
Gram −Germ tube test
Sprout with no constriction = C. albicans
Giemsa stain
Romanowsky stain for blood and intracellular organisms
GMS silver stain
Silver stain making fungi and Pneumocystis black
Gram stain
First-pass bacterial sorting tool
Gram +Hippurate hydrolysis test
Purple color = GBS, C. jejuni, Listeria, Gardnerella
Gram +Immunofluorescence assay
Fluorophore-tagged antibody detection
India ink preparation
Negative stain that reveals a capsule halo
Indole test
Cherry-red ring = E. coli (indole positive)
Gram −Kirby-Bauer disk diffusion
Susceptibility testing concept
KOH preparation
Alkali clears keratin to reveal fungal elements
Lactophenol cotton blue
Mounting stain for mold morphology
Lateral flow assay
Rapid immunochromatographic strip test
MacConkey agar concept
Lactose-fermentation sorting vocabulary
Gram −MALDI-TOF MS
Protein fingerprint ID concept
Methyl red / Voges-Proskauer test
MR+ E. coli vs VP+ Klebsiella
Gram −Minimum inhibitory concentration
MIC susceptibility vocabulary
Motility test concept
Diffuse growth from the stab = motile
NAAT
Nucleic acid amplification test concept
Nitrate reduction test
Red after reagents = nitrate reduced
Gram −Optochin test
P-disk: pneumococcus sensitive, viridans resistant
Gram +Oxidase test
Cytochrome c oxidase clue
Gram −PCR
Amplifies target nucleic acid
PYR test
Red = Group A strep and Enterococcus
Gram +Quellung reaction
Antibody-induced capsular swelling
Thayer-Martin agar concept
VCN-selective chocolate agar for Neisseria
Gram −Triple sugar iron agar
Slant/butt fermentation + H2S blackening
Gram −Urease test concept
Urea hydrolysis and pH-change vocabulary
Western blot
Protein-specific antibody detection by size
Wright stain
Romanowsky blood-film stain, kin to Giemsa