| Question | Answer |
| Bile Esculin Agar (BEA) components | Nutrient, ferric citrate; Esculin hydrolysis by group D strep turns media brown; sodium desoxycholate inhibits many bacteria |
| Bile Esculin Agar (BEA) purpose | Differential isolation and presumptive ID of group D step and enterococci |
| Bile Esculin Azide Agar with Vancomycin components | Azide (inhibit GNs); vanco (select for resistant GPs); Bile Esculin (differentiate Enterococci from other vanco-resistant bacteria) |
| Bile Esculin Azide Agar with Vancomycin purpose | Selective and differential for vanco-resistant enterococci |
| Blood agar components | Tryptocase soy agar, Brucella agar, or beef heart infusion with 5% sheep blood |
| Blood agar purpose | Non-inhibitory, non-enriched; fastidious microorganisms, determination of hemolytic reactions |
| Bordet-Gengou agar components | Potato-glycerol-based medium enriched with 15-20% defibrinated blood; contaminants inhibited by methicillin (2.5 um/mL) |
| Bordet-Gengou agar purpose | Isolation of Bordetella pertussis |
| Buffered Charcoal-Yeast Extract (BCYE) agar components | Yeast extract, agar, charcoal, and salts supplemented with l-cysteine HCl, ferric pyrophosphate, ACES buffer, and a-ketoglutarate |
| Buffered Charcoal-Yeast Extract (BCYE) agar purpose | Enrichment for Legionella spp. |
| Buffered Charcoal-Yeast Extract (BCYE) agar with Antibiotics components | BCYE supplemented with polymyxin B, vanco, and ansamycin, to inhibit GNs, GPs, and yeast (respectively) |
| Buffered Charcoal-Yeast Extract (BCYE) agar with Antibiotics purpose | Enrichment and selection for Legionella spp. |
| Campy-Blood agar components | Contains vanco (10 mg/L), trimethoprin (5 mg/L), polymixin B (2500 U/L), amphotericin B (2 mg/L), and cephalothin (15 mg/dL), in a Brucella agar base and sheep blood |
| Campy-blood agar purpose | Selective for Campylobacter spp. |
| Campylobacter Thioglycollate broth components | Thioglycollate broth supplemented with increased agar concentration and antibiotics |
| Campylobacter Thioglycollate broth purpose | Selective holding medium for recovery of Campylobacter spp. |
| Cefoperazone, Vancomycin, Amphotericin (CVA) medium components | Blood-supplemented enrichment medium containing cefoperaozn, vanco, and amphotericin to inhibit GNs, GPs, and yeast (respectively) |
| Cefoperazone, Vancomycin, Amphotericin (CVA) medium purpose | Selective medium for isolation of Campylobacter spp. |
| Cefsulodin-Irgasan-Novobiocin (CIN) agar components | Peptone base with yeast extract, mannitol, and bile salts; supplemented with cefsulodin, irgasan,and novobiocin; neutral red and chrystal violet indicators |
| Cefsulodin-Irgasan-Novobiocin (CIN) agar purpose | Selective for Yersinia spp.; may be useful for isolation of Aeromonas spp. |
| Chocolate agar components | peptone base, enriched with solution of 2% hemoglobin or IsoVitaleX (BBL) |
| Chocolate agar purpose | Selective isolation of GP cocci |
| Columbia colistin-nalidixic acid (CNA) agar components | Columbia agar base with 10 mg colistin per liter, 15 mg nalidixic acid per liter, and 5% sheep blood |
| Columbia colistin-nalidixic acid (CNA) agar purpose | Selective isolation of GP cocci |
| Cystine-tellurite blood agar components | Infusion agar base with 5% sheep blood. Reduction of potassium tellurite by Corynebacterium diphtheriae produces black colonies |
| Cystine-tellurite blood agar purpose | Isolation of C. diphtheriae |
| Eosin methylene blue (EMB) agar (Levine) components | Peptone base with lactose and sucrose; Eosin and methylene blue as indicators |
| Eosin methylene blue (EMB) agar (Levine) purpose | Isolation and differentiation of lactose-fermentating and non-lactose-fermenting enteric bacilli |
| Gram-negative broth (GN) agar components | Peptone base broth with glucose and mannitol. Sodium citrate and sodium desoxycholate act as inhibitory agents |
| Gram-negative broth (GN) agar purpose | Selective (enrichment) liquid medium for enteric pathogens |
| Hektoen enteric (HE) agar components | Peptone base agar with bile salts, lactose, sucrose, salicin,a nd ferric ammonium citrate.; indicators include bromthymol blue and acid fuchsin |
| Hektoen enteric (HE) agar purpose | Differential, selective medium for the isolation and differentiation of Salmonella and Shigella spp. from other GN enteric bacilli |
| MacConkey agar components | Peptone base with lactose; GP organisms inhibited by crystal violet and bile salts; neutral red as indicator |
| MacConkey agar purpose | Isolation and differentiation of lactose fermenting and non-lactose-fermenting enteric bacilli |
| MacConkey sorbitol agar components | A modification of MacConkey agar in which lactose agar has been replaced with d-sobitol as the primary carbohydrate |
| MacConkey sorbitol agar purpose | For the selection and differentiation of E. coli O157:H7 in stool specimens |
| Mannitol salt agar components | Peptone base, mannitol, and phenol red indicator; salt concentration of 7.5% inhibits most bacteria |
| Mannitol salt agar purpose | Selective isolation of staphylococci |
| New York City (NYC) agar components | Peptone agar base with cornstarch, supplemneted with yeast dialysate, 3% hemoglobin, and horse plasma; antibiotic supplement includes vancomycin (2ug/ml), colistin (5.5 ug/ml), amphotericin B (1.2 ug/ml), and trimethoprim (3 ug/ml) |
| New York City (NYC) agar purpose | Selective for Neisseria gonorrhoeae |
| Phenylethyl alcohol (PEA) agar components | Nutrient agar base; phenylethanol inhibits growth of GN organisms |
| Phenylethyl alcohol (PEA) agar purpose | Selective isolation of GP cocci and anaerobic GN bacilli |
| Regan Lowe agar components | Charcoal agar supplemented with horse blood, cephalexin, and amphotericin B |
| Regan Lowe agar purpose | Enrichment and selective medium for isolation of Bordetella pertussis |
| Salmonella-Shigella (SS) agar components | Peptone base with lactose, ferric citrate, and sodium citrate; neutral red as indicator; inhibition of coliforms by brilliant green and bile salts |
| Salmonella-Shigella (SS) agar purpose | Selective for Salmonella and Shigella spp. |
| Schaedler agar components | Peptone and soy protein base agar with yeast extract, dextrose, and buffers; addition of hemin, l-cysteine, and 5% blood enriches for anaerobes |
| Schaedler agar purpose | Nonselective medium for the recovery of anaerobes and aerobes |
| Selenite broth components | Peptone base broth; sodium selenite toxic for most Enterobacteriaceae |
| Selenite broth purpose | Enrichment of isolation of Salmonella spp. |
| Skirrow agar components | Peptone and soy protein base agar with lysed horse blood; vancomycin inhibits GP organisms; polymyxin B and trimethoprim inhibit most GN organisms |
| Skirrow agar purpose | Selective for Campylobacter spp. |
| Streptococcal selective agar (SSA) componnets | Contains crystal violet, colistin, and trimethoprim-sulfamethoxazole in 5% sheep blood agar base |
| Streptococcal selective agar (SSA) purpose | Selective for Streptococcus pyogenes and Streptococcus agalactiae |
| Tetrathionate broth components | Peptone base broth; bile salts and sodium thiosulfate inhibit GP organisms inhibited and Enterobacteriaceae |
| Tetrathionate broth purpose | Selective for Salmonella and Shigella spp. |
| Thayer-Martin agar components | Blood agar base enriched with hemoglobin and supplement B; contaminating organisms inhibited by colistin, nystatin, vancomycin, and trimethoprim |
| Thayer-Martin agar purpose | Selective for N. gonorrheae and N. meningitidis |
| Thioglycollate broth components | Pancreatic digest of casein, soy broth, and glucose enrich growth of most microorganisms |
| Thioglycollate broth purpose | Supports growth of anaerobes, aerobes, microaerophilic, and fastidious microorgansims |
| Thiosulfate citrate-bile salts (TCBS) agar components | Peptone base agar with yeast extract, bile salts, citrate, sucrose, ferric citrate, and sodium thiosulfate; bromthymol blue acts as indicator |
| Thiosulfate citrate-blue salts (TCBS) agar purpose | Selective and differential for vibrios |
| Todd-Hewitt broth supplemented with antibiotics components | Todd-Hewitt, an enrichment broth for streptococci, is supplemented with naladixic acid and gentamicin or colitin for greater selectivity Thioglycollate and agar reduce redox potential |
| Todd-Hewitt broth supplemented with antibiotics purpose | Selection and enrichment for Streptococcus agalactiae in female genital specimens |
| Trypticase soy broth (TSB) components | All-purpose enrichment broth that can support the growth of many fastidious and nonfastidious bacteria |
| Trypticase soy broth (TSB) purpose | Enrichment broth used for subculturing various bacteria from primary agar plates |
| Xylose lysine desoxycholate (XLD) agar components | Yeast extract agar with lysine, xylose, lactose, sucrose, and ferric ammonium citrate; sodium desoxycholate inhibits GP organisms; phenol red as indicator |
| Xylose lysine desoxycholate (XLD) agar purpose | Isolation and differentiation of Salmonella and SHigella spp. from other GN enteric bacilli |
| Mueller-Hinton agar components | Horse blood, X, V, X and V |
| Mueller-Hinton agar purpose | Selective for Haemophilus |
| Acetamide Utilization principle | Determines if the orgamism uses acetamide as the sole source of carbon; bacteria that can grow on this medium deaminate acetamide to release ammonia; the production of ammonia results in a pH-driven color change of the medium from green to royal blood |
| Acetamide Utilization quality control organisms | Positive: Pseudomonas aeruginosa
Negative: Stenotrophomonas maltophilia |
| Acetate Utilization principle | Determines if an organism uses acetate as its sole source of carbon; breakdown of the sodium acdtate causes the pH of the medium to shift toward the alkaline range, turning the indicator from green to blue |
| Acetate Utilization quality control organisms | Positive: Escherichia coli
Negative: Shigella flexneri |
| Bacitracin principle | Determines the effect of a small amount of bacitracin (0.04 U) on an organism; Streptococcus pyogenes is inhibited by the small amount of bacitracin in the disk; other beta-hemolytic streptococci usually are not |
| Bacitracin quality control organisms | Positive: Streptococcus pyogenes
Negative: Streptococcus agalactiae |
| Bile Esculin agar principle | GPs other than some strep and entero and inhibited by bile; growth in 40% bile and hydrolysis of esculin turns ferric ammonium citrate dark brown (resulting from the combination of esculetin and ferric ions to form a phenolic iron complex) |
| Bile Esculin quality control | Positive: Enterococcus faecalis
Negative: Streptococcus mitis |
| Bile Solubility principle | Differentiates Streptococcus pneumoniae (positive) from alpha-hemolytic streptococci (negative); |
| Bile Solubility quality control | Positive: Streptococcus pneumoniae
Negative: Enterococcus faecalis |
| Butyrate Disk principle | A rapid test for the detection of the enzyme butyrate esterase in identifying Moraxella catarrhalis; If bromo-chloro-indolyl butyrate impregnated in the disks is hydrolyzed by the enzyme, a blue-colored indigo compound is formed |
| Butyrate Disk quality control | Positive: Moraxella catarrhalis
Negative: Neisseria gonorrhoeae |
| CAMP test principle | Certain organisms (including group B strep) produce a diffusible extracellular protein (CAMP factor) that acts synergistically with the beta-lysin of Staph aureus to cause enhanced lysis of red blood cells |
| CAMP test quality control | Positive: Strep agalactiae
Negative: Strep pyogenes |
| Catalase test principle | Catalase mediates the breakdown of H2O2 into O2 AND H2. If the organism has the enzyme, the specimen will bubble when placed in the H2O2 |
| Catalase quality control | Positive: Staphylococcus aureus
Negative: Streptococcus pyogenes |
| Cetrimide test principle | Determines the ability of an organism to grow in the presence of cetrimide, a toxic substance that inhibits the growth of many bacteria |
| Cetrimide quality control | Positive: Pseudomonas aeruginosa
Negative: Escherichia coli |
| Citrate utilization principle | Determines the abiliyt of an organism to utilize sodium citrate as its only carbon source and inorganic ammonium salts as its only nitrogen source; bacteria that grow turn the bromthymol blue indicator from green to blue |
| Citrate utilization quality control | Positive: Klebsiella pneumoniae
Negative: Escherichia coli |
| Coagulase test principle | Differentiate Staphylococcus aureus from coagulase-negative staphyococci; Sa produces 2 coags: bound and free; Bound is the "clumping factor" and reacts directly with fibrinogen. Fibrinogen precipitates on the cell, causing clumping |
| Coagulase test quality control | Positive: Staphylococcus aureus
Negative: Staphylococcus epidermidis |
| Decarboxylase test (Moeller's Method) principle | Measures the enzymatic ability of an orgnanism to decarboxylate (or hydrolyze) an amino acid to form an amine; this results in an alkaline pH change |
| Decarboxylase test quality control | Positive:
Lysine: K. pneumoniae
Ornithine: Enterobacter cloacae
Arginine: E. cloacae
Negative:
Lysine: E. cloacae
Ornithine: K. pneumoniae
Argainine: K. pneumoniae
Base: K. pneumoniae |
| DNA hydrolysis (DNase) test principle | Determins the abiliyt of an organism to hydrolyze DNA; the medium is pale green due to DNA-methyl green complex; if the organism growing hydrolyses DNA, the green color fades, leaving a colorless zone |
| Esculin Hydrolysis test principle | Determines whether an organism is able to hydrolyze the glycoside esculin |
| Esculin Hydrolysis test quality control | Positive: Klebsiella pneumoniae
Negative: Shigella flexneri |
