Microbiology Study Guide for Media, Tests and Specimen Processing

Microbiology Media, Tests and Specimen Processing
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-fermenting 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, and 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-sorbitol 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, supplemented 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	Non selective 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) components	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 microorganisms
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 colistin 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 non fastidious 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 organism 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 S. 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; S. aureus produces 2 coagulases: 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 organism 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	Determines the ability 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