Elek Medium - BioReagent

Cat. No.: E1528560

QUALITÀ & PUREZZA BioReagent

Storage

Room temperature

Shipped In

Normal

Panoramica

For toxin determination of diarrheagenic Escherichia coli

Specifiche

Specifiche e purezza

BioReagent

Condizioni di conservazione di stoccaggio

Room temperature

Spedito in

Normal

Grado

BioReagent

Product Line

Prodotti biologici

Application Protocols

The following Elek test workflow is provided as general literature guidance for research use; adapt to your SOP and regulatory requirements. Not product‑specific.

1. Materials

• Prepared Elek Medium plates (dry surface), sterile forceps, sterile filter‑paper strips, standardized diphtheria antitoxin, positive and negative control strains, sterile loops, incubator (35–37 °C).

2. Antitoxin strip preparation

• Soak sterile strips in antitoxin solution of defined potency; blot to remove excess. Alternatively, use pre‑standardized commercial strips. Place one strip centrally on each plate with aseptic technique.

3. Inoculation pattern

• Streak the test isolate as a 2–3 cm line perpendicular to the strip, ~5–10 mm away. Include a toxigenic control on one side of the strip and a non‑toxigenic control on the other. Maintain consistent spacing to avoid overlapping diffusion fronts.

4. Incubation

• Invert and incubate plates at 35–37 °C for 18–48 h. Maintain humidity to prevent drying. Observe at 24 h; extend to 48 h if necessary.

5. Interpretation

• Positive: Distinct, fine precipitin lines at ~45° angles between the growth line of the test organism and the antitoxin strip, forming lines of identity with the toxigenic control.
• Negative: No precipitin lines near the test streak; growth present.
• Indeterminate: Diffuse or ambiguous lines—repeat with adjusted inoculum or fresh reagents.

6. Controls and QA

• Document lot numbers of medium and antitoxin. Verify growth promotion and absence of inhibitory effects using reference strains per SOP.

Biological Roles

Elek Medium itself has no intrinsic biological role as a biomolecule; it is a formulated matrix that supports specific microbiological processes. The following points describe functional roles in experimental biology (general/literature):

• Growth support: Provides carbon, nitrogen, vitamins, and minerals suitable for growth of Corynebacterium spp. and related organisms under aerobic incubation.

• Toxin production and diffusion: The matrix composition and gel firmness facilitate secretion and radial diffusion of diphtheria toxin from bacterial colonies. Protein supplements (e.g., serum/albumin, when used) can stabilize toxins and enhance visible precipitin line formation during immunodiffusion against antitoxin.

• Immunodiffusion platform: Serves as a semi‑solid phase for double‑diffusion (Ouchterlony‑type) antigen–antibody interactions. The immobilized antitoxin strip establishes a linear source; equivalence zones manifest as precipitin arcs that can be compared among test and control strains.

• Selectivity considerations: Elek Medium is typically non‑selective (not strongly inhibitory), designed to allow growth of target Corynebacterium while maintaining conditions conducive to toxin expression. If background flora are present, prior isolation on selective media is recommended to ensure clean inocula.

• Research scope: Utilized in academic and industrial microbiology labs for characterization of toxigenicity phenotypes and for teaching demonstrations of antigen–antibody precipitation in gels.

Note: This product is for research use only and is not validated for clinical diagnosis unless such validation is performed by the end user under applicable regulations.

Buffer Applications

As a complex microbiological medium, Elek Medium is not a dedicated buffering agent. However, buffering capacity and pH control are important to its performance.

• General/literature guidance:

• pH setpoint: Many Elek formulations are adjusted near neutrality (circa pH 7.2–7.4) before sterilization to promote optimal growth and toxin expression. Exact pH targets and tolerances are method‑dependent; verify against your SOP.
• Buffer systems: Mild phosphate buffering (e.g., 1–10 mM) is commonly used in microbiological media to stabilize pH without excessively increasing ionic strength, which can affect diffusion patterns. Avoid high buffer molarity that may dampen precipitin line formation.
• Adjustment: Use sterile 1 N HCl/NaOH to fine‑tune pH at ~45–50 °C post‑autoclave (to account for thermal pH shifts), mixing gently to avoid bubble entrapment before pouring plates.

• Electrophoresis/cell culture: Not applicable. This medium is not intended for biochemical electrophoresis or mammalian cell culture buffering; instead, see dedicated buffers (e.g., Tris, HEPES) or cell culture media.

Item-specific buffer/pH specifications are not provided for this product; refer to the CoA/Spec Sheet and your validated method for exact targets and tolerances.

Green Alternatives

While Elek Medium is a water‑based, agar‑gel matrix and already relatively benign compared with many organic chemical processes, sustainability considerations still apply.

• Greener practice options (general):

• Right‑sizing preparations: Prepare only the volume needed to minimize discarded, expired plates and reduce autoclave energy use.
• Reusable glassware: Where biosafety policy permits, use reusable glass flasks and media bottles instead of single‑use plastics; validate cleaning/sterilization procedures.
• Energy optimization: Consolidate autoclave loads and use pre‑vacuum cycles appropriate for liquid media to reduce cycle time and energy consumption.
• Waste minimization: Segregate uninoculated (non‑biohazard) media waste from biohazardous waste to decrease volume of red‑bag/autoclave disposal.

• Alternative media/assays (context):

• Molecular assays (e.g., PCR for tox gene) avoid culture‑based incubations and agar plates; they may reduce biological waste but require plastics and enzymes—trade‑offs apply.
• Pre‑poured, ready‑to‑use plates from validated suppliers can lower in‑house energy and chemical handling but increase packaging waste and shipping footprint.

• Materials profile (general):

• Agar is a renewable marine polysaccharide; sourcing from certified sustainable suppliers can further improve environmental profile.

Note: No item‑specific environmental certifications or claims are provided for this product; consult your institutional sustainability policies for implementation.

Pharmaceutical Uses

This product is not an excipient or active ingredient and is supplied for research use only. No clinical/therapeutic claims are made.

• Relevant industrial/research contexts (general):

• Microbiology QA/QC laboratories may use Elek‑type media in non‑clinical settings for research, method development, or training related to toxin detection by immunodiffusion.
• Environmental or process microbiology groups might adapt immunodiffusion concepts for exploratory studies; however, clinical diagnostics require validated, regulated products and procedures.

• Pharmacopeial status: No pharmacopeial monograph is associated with Elek Medium. Where regulated use is contemplated, end users must qualify the medium against internal specifications and applicable standards.

• Formulation role: Not applicable as a pharmaceutical excipient, stabilizer, or processing aid.

• Documentation: For any use in a controlled environment (GLP/GMP), obtain and file the specific lot’s CoA/SDS, and perform incoming qualification (growth promotion test with defined strains, pH verification, gel firmness), as required by your quality system.

Physical Properties

• Item-specific physicochemical values: Melting point/boiling point — Not applicable (complex mixture/solid medium); not specified for this item; refer to CoA/Spec Sheet. pH (at 25 °C) — Not specified for this item; refer to CoA/Spec Sheet. Osmolality — Not specified for this item; refer to CoA/Spec Sheet. Moisture content — Not specified for this item; refer to CoA/Spec Sheet. Appearance — Not specified for this item; refer to CoA/Spec Sheet.

• General/literature properties (for context; not product specifications):

• Physical state (before use): Typically supplied as a dehydrated powder blend; after reconstitution and sterilization, forms a firm gel if agar is included.
• Solubility: Dispersible/soluble in purified water; components hydrate and dissolve upon heating. Agar solutions gel reversibly on cooling (~30–40 °C) after melting (>80–90 °C).
• Typical working pH (literature): Many Elek medium recipes target near‑neutral pH (circa 7.2–7.4) to support Corynebacterium growth; verify and adjust per method/SOP.
• Refractive index, density, logP: Not meaningful for a complex, hydrated gel system.

• Practical notes (general):

• Water quality (Type I or II) helps minimize precipitation or haze.
• Undissolved specks usually indicate incomplete hydration of agar/peptone—extend gentle boiling while stirring.
• After autoclaving, cool to 45–50 °C before adding heat‑labile supplements (e.g., serum/antitoxin) to avoid denaturation.

Quality and Grades

• Item-specific grade: BioReagent (as provided). This denotes suitability for biological research workflows. It emphasizes consistency and low background interference in typical life‑science applications but is not equivalent to clinical/diagnostic use unless specifically validated by the end user.

• What BioReagent typically implies (general):

• Compositional consistency lot‑to‑lot appropriate for research methods (e.g., microbiological cultivation, diffusion assays).
• Low bioburden in the dehydrated product; however, sterility of the final medium depends entirely on end‑user preparation/sterilization.
• Trace contaminants kept within ranges that do not inhibit target organisms under standard conditions; exact impurity/spec limits are not specified for this item; refer to CoA/Spec Sheet.

• Stabilizers/additives: Not specified for this item; refer to CoA/Spec Sheet. If supplements (e.g., serum, antitoxin) are required by your method, add them post‑sterilization under aseptic conditions.

• Documentation and release testing (expectations):

• CoA/Spec Sheet typically covers pH of a defined batch preparation, gel strength (if agar‑based), and growth promotion tests with relevant strains (literature expectation). Verify actual values on the item’s CoA.

• Suitability: For research use only (manufacturer note). Users performing regulated work (GMP/GLP/clinical diagnostics) should qualify the medium per their quality system and applicable pharmacopeial or ISO references.

Reaction and Applications

This section focuses on laboratory applications rather than chemical reactions, as Elek Medium is not a reagent for synthetic chemistry.

• Primary research application (literature):

• Elek test for toxigenicity of Corynebacterium diphtheriae and related species via immunodiffusion. The medium supports bacterial growth and allows diffusion of diphtheria toxin toward an antitoxin‑impregnated strip; precipitin lines at the zone of equivalence indicate toxin production.

• Use contexts (general):

• Microbial identification and virulence characterization in research laboratories.
• Method development/validation for immunodiffusion‑based assays involving extracellular protein toxins.

• Practical tips (general):

• Medium firmness: Aim for standard agar concentration (literature often 1.0–1.5% w/v) to balance colony growth and diffusion. Too firm reduces diffusion; too soft complicates handling.
• Surface moisture: Allow plates to dry briefly (biosafety cabinet, lids ajar) to remove excess condensation before laying antitoxin strips; minimizes run‑off and skewed diffusion fronts.
• Inoculation geometry: Streak test strains perpendicular to the antitoxin strip and include known positive and negative controls to interpret faint lines.
• Incubation: Maintain stable temperature and humidity to prevent plate desiccation, which distorts diffusion patterns.

• Result interpretation (general):

• Lines of identity forming at ~45° angles between the antitoxin strip and test streaks, converging with the positive control, support a positive call; absence of precipitin lines suggests non‑toxigenic phenotypes. Always confirm with orthogonal methods per lab policy.

• Limitations: Mixed cultures and excessive inoculum can yield ambiguous precipitin arcs. Standardize inoculum density and include controls.

Reaction Conditions

In place of chemical reaction conditions, this section summarizes typical incubation and test conditions for Elek immunodiffusion assays (general literature guidance; not product‑specific):

• Medium preparation: Autoclave agar‑containing basal medium (121 °C, ~15 min). Cool to 45–50 °C, add sterile supplements if required (e.g., serum), mix gently, and pour into sterile plates to a uniform depth of ~4 mm. Allow to solidify and surface‑dry under aseptic conditions.

• Antitoxin strip: Lay a sterile filter‑paper strip impregnated with standardized diphtheria antitoxin along the plate surface. Ensure full contact without submerging.

• Inoculation pattern: Streak test isolates perpendicular to the antitoxin strip at fixed intervals. Include a known toxigenic positive control and a non‑toxigenic negative control on the same plate for interpretive reference.

• Incubation: 35–37 °C, aerobic, typically 18–48 hours. Maintain humidity to prevent plate desiccation; inverted incubation reduces condensation.

• Readout: Examine under transmitted oblique light. Precipitin lines of identity forming between the antitoxin strip and growth lines indicate toxin production. Record at 24 h and again at 48 h if initial results are equivocal.

• Quality controls: Verify medium pH and gel uniformity prior to use. Conduct growth promotion checks with reference strains as defined in your SOP.

These conditions are general guidance only; follow your validated method and institutional biosafety requirements.

Safety and Handling

• Item-specific hazard statements/classification: Signal word — Not specified for this item; refer to SDS. H‑statements — Not specified for this item; refer to SDS. GHS classification and pictograms — Not specified for this item; refer to SDS.

• General laboratory safety (not product‑specific; follow your institutional SOPs):

• Treat dehydrated media as laboratory chemicals: avoid inhalation of dust; handle powders in a ventilated area or fume hood. Wear appropriate PPE (lab coat, safety glasses, disposable gloves).
• Microbiological risk: Once inoculated, plates/tubes contain viable organisms. Handle under appropriate biosafety level (e.g., BSL‑2 for Corynebacterium diphtheriae) within a certified biosafety cabinet. Decontaminate after use (autoclave, approved disinfectant).
• Thermal hazards: During preparation, hot agar can cause burns. Use heat‑resistant gloves; avoid boiling over.
• Incompatibilities (general): Avoid strong oxidizers contacting organic media components. Do not store prepared plates near desiccants or heat sources; dehydration cracks gels and impairs diffusion tests.
• First aid (overview; consult SDS/medical staff): If inhaled (powder dust), move to fresh air; if symptomatic, seek medical attention. Skin/eye contact: rinse with water for 15 minutes; remove contaminated clothing. If ingested, rinse mouth, do not induce vomiting; seek advice.

• Waste: Dispose of uninoculated media as chemical/solid lab waste per local regulations. Autoclave inoculated materials before disposal.

Solvent Selection

This product is a complex microbiological medium intended to be reconstituted in water rather than used as an organic solvent.

• Applicable solvent (general):

• Purified water (ASTM/CLSI Type I or II). Avoid tap water due to variable hardness, chlorine, and organics that can impair growth/diffusion.

• Water quality and preparation tips (literature guidance):

• Degas and pre‑warm water (50–60 °C) to aid dissolution and reduce bubble formation in poured plates.
• For heat‑labile supplements (e.g., antitoxin, serum), sterilize the basal medium first (autoclave 121 °C, 15 min), cool to 45–50 °C, then aseptically add sterile‑filtered supplements (0.22 μm).
• If your method specifies ionic strength or pH adjustments, use sterile phosphate or HEPES buffers (filtered) to fine‑tune after sterilization.

• Comparison with alternatives (general):

• Distilled vs deionized water: Both can work; resistivity ≥1 MΩ·cm (Type II) is a common minimum for media. Type I (≥18 MΩ·cm) may reduce haze in protein‑supplemented recipes.
• Filtration vs autoclave: Agar‑containing media require autoclaving to melt/gelate. Supplement solutions should be sterile‑filtered to preserve activity.

• Not applicable: Organic solvent selection, partitioning, and dielectric constant discussions are not relevant for this product.

Storage and Reconstitution

• Item-specific storage/shipping:

• Storage conditions: Room temperature (as provided in Product Data). Protect from moisture. Keep container tightly closed.
• Shipped: Normal (ambient) conditions.

• Reconstitution and sterilization (general literature guidance; not product‑specific):

• Weigh the specified mass of dehydrated medium per liter of purified water according to your validated recipe/SOP (exact grams per liter — Not specified for this item; refer to CoA/Spec Sheet).
• Disperse in cool water with stirring; heat to boiling to fully hydrate and dissolve components. Avoid scorching by using a hot plate with stirring.
• Adjust pH as required by method (target pH — Not specified for this item; refer to CoA/Spec Sheet).
• Sterilize by autoclaving at 121 °C for ~15 minutes. After sterilization, cool to 45–50 °C, add any sterile‑filtered heat‑labile supplements (e.g., serum, antitoxin), mix gently, and pour plates to a uniform depth.
• Allow plates to solidify and surface‑dry in a biosafety cabinet before use. Store prepared plates, inverted, in sealed sleeves at 2–8 °C if your SOP allows; typical shelf life depends on supplement and storage conditions (Not specified for this item; refer to CoA/Spec Sheet).

• Handling notes:

• Avoid repeated temperature cycling of prepared plates; condensation and dehydration impair diffusion.
• Label with preparation date, lot numbers, and any supplements added. Use on a first‑in/first‑out basis.

For authoritative safety and handling details, always consult the product’s SDS and the lot‑specific CoA/Spec Sheet.

Structure and Identity

• Item-specific identifiers: Molecular formula — Not specified for this item; refer to CoA/Spec Sheet. Molecular weight — Not specified for this item; refer to CoA/Spec Sheet. SMILES — Not applicable (complex mixture). InChIKey — Not applicable (complex mixture). CAS — Not specified for this item; refer to CoA/Spec Sheet. CID — Not specified for this item; refer to CoA/Spec Sheet.

• Product type (general/literature): Elek Medium is a complex, multi‑component microbiological growth/diffusion medium formulated to support growth of Corynebacterium species and to enable immunodiffusion of diphtheria toxin against antitoxin (Elek test). As a formulated mixture, it does not have a single, well‑defined chemical structure.

• Structural features (descriptive, literature): Typical Elek media are composed of proteinaceous/peptone nutrients, minerals/salts, and a gelling agent (agar) that yields a semi‑solid gel matrix. Some formulations incorporate serum or albumin to enhance toxin production and diffusion. No discrete stereochemical features apply because the product is a heterogeneous blend.

• 2D description in words (general): Upon preparation, the medium forms a uniform, translucent to opaque gel (when agar‑based) in which a paper strip impregnated with diphtheria antitoxin is overlaid. Toxin produced by test organisms diffuses radially; where it encounters antitoxin at equivalence, precipitin lines form in the gel (immunodiffusion).

Synthetic Utility

Not applicable. Elek Medium is a complex biological growth/diffusion matrix and is not used as a reagent or building block in chemical synthesis.

• If you are designing chemical syntheses: Refer instead to sections on organic solvents, catalysts, or building blocks relevant to your transformation. For microbiology and immunodiffusion work, see Reaction & Applications and Application Protocols in this document.

Target Specificity

Item-specific target data (antigen/epitope, isotype, clone, species reactivity) are not applicable; this product is a culture/diffusion medium, not an antibody or molecular probe.

• General application target (literature context): Elek Medium is used to assess toxigenicity of Corynebacterium diphtheriae and closely related Corynebacterium species via immunodiffusion of diphtheria toxin against a defined antitoxin source. The “specificity” arises from the antigen–antibody interaction between diphtheria toxin and its corresponding antitoxin applied to the assay strip, rather than from any selective binding property of the medium itself.