Additional Info For Culture Media Flashcards
EKE (rapid lactose fermenters)
- Escherichia
- Klebsiella
- Enterobacter
is characterized by a clear, colorless zone around the bacterial colony due to complete lysis of red blood cells.
Beta-hemolysis
Common bacteria that show beta-hemolysis include
Streptococcus pyogenes (Group A Streptococcus)
Streptococcus agalactiae (Group B Streptococcus).
results in a greenish zone around the colonies, caused by the partial reduction of hemoglobin to methemoglobin.
Alpha-hemolysis
Examples of alpha-hemolytic bacteria include
Streptococcus pneumoniae
various species of viridans streptococci like Streptococcus mutans.
shows no visible hemolysis around the colonies, indicating no lysis of red blood cells.
Gamma-hemolysis (or non-hemolysis)
Bacteria like______display gamma-hemolysis
Enterococcus faecalis
McCoy’s Cells
Use
Primarily used for the isolation and culture of Chlamydia trachomatis and other related bacteria.
- Isolates: Selective for Gram-negative bacteria, particularly members of the family Enterobacteriaceae.
MacConkey Agar (MAC)
It differentiates lactose fermenters (e.g., Escherichia coli) which appear pink, from non-lactose fermenters (e.g., Salmonella, Shigella) which appear colorless.
MacConkey
- Isolates: Selective for Gram-positive bacteria, specifically Staphylococcus species.
Mannitol Salt Agar (MSA)
It differentiates Staphylococcus aureus (which ferments mannitol and turns the medium yellow) from other staphylococci which do not ferment mannitol and leave the medium red.
Mannitol Salt Agar (MSA):
- Isolates: Selective for Gram-negative enteric pathogens.
Hektoen Enteric Agar (HEA)
It differentiates Salmonella (which produces black colonies due to hydrogen sulfide production) from Shigella (which produces green colonies).
Hektoen Enteric Agar (HEA)
- Isolates: Selective for Gram-negative enteric pathogens, particularly Salmonella and Shigella.
Xylose Lysine Deoxycholate Agar (XLD)
Salmonella* appears with black centers, while Shigella appears red without black centers.
Xylose Lysine Deoxycholate Agar (XLD):
- Isolates: Selective for Neisseria gonorrhoeae and Neisseria meningitidis.
Thayer-Martin Agar:
It contains antibiotics to inhibit the growth of contaminating organisms like Gram-positive bacteria and yeast.
Thayer-Martin Agar
- Isolates: Selective for Pseudomonas aeruginosa, which produces characteristic green or blue-green colonies due to pyocyanin production.
Cetrimide Agar
- Isolates: Selective for Mycobacterium species, especially Mycobacterium tuberculosis.
Lowenstein-Jensen Medium
It contains malachite green to inhibit the growth of contaminants.
Lowenstein-Jensen Medium:
- Isolates: Selective for fungi, including yeasts and molds. The acidic pH of the medium inhibits bacterial growth, favoring fungal growth.
Sabouraud Dextrose Agar (SDA)
- Isolates: Selective for Gram-negative bacteria. It differentiates between lactose fermenters like E. coli (which produces metallic green colonies) and non-lactose fermenters (which produce colorless or pink colonies)
Eosin Methylene Blue (EMB) Agar
are those that require specific nutrients or environmental conditions to grow, often needing enriched or enrichment media.
Fastidious bacteria
Fastidious bacteria
Neisseria gonorrhoeae and Neisseria meningitidis
Haemophilus influenzae
Streptococcus pneumoniae
Legionella pneumophila
Mycobacterium tuberculosis
- Media Required: Thayer-Martin agar or Chocolate agar.
- Reason: These bacteria require enriched media with added nutrients like hemoglobin, vitamins, and coenzymes to grow.
Neisseria gonorrhoeae and Neisseria meningitidis
- Media Required: Chocolate agar or Levinthal agar.
- Reason: Requires factors X (hemin) and V (NAD) that are present in lysed red blood cells found in chocolate agar.
Haemophilus influenzae
- Media Required: Blood agar with added carbon dioxide.
- Reason: This organism is fastidious and grows better in an environment with enriched nutrients and elevated CO2.
Streptococcus pneumoniae
- Media Required: Buffered Charcoal Yeast Extract (BCYE) agar.
- Reason: Requires L-cysteine and iron salts, which are provided by BCYE agar.
Legionella pneumophila
- Media Required: Lowenstein-Jensen medium or Middlebrook agar.
- Reason: Requires enriched media with malachite green to inhibit contaminants and provide essential nutrients for growth
Mycobacterium tuberculosis
Enrichment and isolation of Salmonella spp.
Peptone-base broth; sodium selenite toxic for
most Enterobacterales
Selenite broth
Contains crystal violet, colistin, and trimethoprim-sulfamethoxazole in 5% sheep blood agar base
Selective for Streptococcus pyogenes and Streptococcus agalactiae
Streptococcal selective agar (SSA)
Selective for N. gonorrhoeae and N. meningitidis.
Supports the growth of Francisella and Brucella spp.
Blood agar base enriched with hemoglobin and supplement B; contaminating organisms inhibited by colistin, nystatin, vancomycin, and trimethoprim
Thayer Martin
Supports growth of anaerobes, aerobes, micro-aerophilic, and fastidious microorganisms
Thioglycollate broth
Selective and differential for Vibrio cholerae and Vibrio parahaemolyticus
Thiosulfate citrate-bile salts (TCBS) agar
Basal back-up broth or enrichment broth used for subculturing various bacteria from primary agar plates
All-purpose basal broth that can support the growth of many nonfastidious organisms or when supplemented with additional nutrients, it is used to cultivate fastidious microorganisms.
Trypticase soy broth
(TSB)
Cultivation of fastidious microorganisms such as Haemophilus spp., Brucella spp., and pathogenic Neisseria spp.
Chocolate agar
Isolation of Corynebacterium diphtheriae
Cystine-tellurite blood
agar
Isolation and differentiation of lactose-fermenting and non-lactose-fermenting enteric bacilli
Peptone base containing lactose; eosin Y and methylene blue as indicators
Eosin methylene blue
(EMB) agar (Levine)
Selective (enrichment) liguid medium for enteric pathogens Salmonella and Shigella spp.
Peptone-base broth with glucose and mannitol;
sodium citrate and sodium deoxycholate act as inhibitory agents
Gram-negative broth
(GN)
Differential, selective medium for the isolation and differentiation of Salmonella and Shigella spp. from other GN enteric bacilli
Peptone-base agar with bile salts, lactose, sucrose, salicin, and ferric ammonium citrate; indicators include bromothymol blue and acid fuchsin
Hektoen enteric (HE)
agar
Isolation and differentiation of lactose fermenting and non-lactose-fermenting enteric bacilli
Peptone base with lactose; gram-positive organisms inhibited by crystal violet and bile salts;
neutral red as indicator
MacConkey agar
Inverted Umbrella/Christmas Tree appearance of _______on SIM.
Listeria monocytogenes
Test Tube Brush appearance of _______on SIM.
Erysipelothrix rhusiopathiae
