Plate Count Agar (PCA) | Standard Methods Agar for Total Aerobic Count (AS-1328)

Testing Workflow

Scientific Background

Historical Development

The formulation traces to Buchbinder et al. (1951), whose plate-counting studies established the nutrient balance later adopted into APHA Standard Methods and, subsequently, ISO 4833 and FDA-BAM. PCA is one of the longest continuously validated media in applied microbiology — its composition has remained essentially unchanged for over seven decades because it reliably satisfies the design brief of a total, non-differential count medium.

Nutritional Basis

Three complementary sources supply nutrition. Tryptone (pancreatic digest of casein) provides amino acids and short peptides supporting broad heterotrophic growth. Yeast extract contributes B-vitamins, nucleotides, and trace growth factors required by fastidious and non-fastidious organisms alike. Glucose (1.0 g/L) acts as a readily fermentable energy source at a concentration deliberately kept low enough that acid byproducts do not suppress growth or distort colony morphology. Because no selective, inhibitory, or indicator agents are present, PCA does not discriminate against Gram-positive or Gram-negative organisms — the defining property of a total, rather than differential or selective, count medium.

Growth Kinetics & Incubation Considerations

ISO 4833 permits either 30°C/72h or 35–37°C/48h incubation regimes depending on the standard being followed; results are method-specific and not directly interchangeable between temperature/time combinations. Colony counts are only considered statistically reliable within the 25–250 colonies per plate range (APHA convention) — outside this range, counts should be reported as "too numerous to count" (TNTC) or "estimated count" per the applicable method, and the dilution series repeated if necessary.

Key Applications

Formulation & Specifications

Method Comparison: Choosing the Right TVC Medium

Selection guidance based on published method scopes (ISO 4833, ISO 6222, ISO 11133) and general microbiological practice; always confirm against the specific regulatory method your laboratory operates under.

Typical Validation Performance

Representative recovery ranges for a well-performing lot of a non-selective TVC medium, expressed relative to a reference/prior lot under identical inoculum and incubation conditions (ISO 11133 productivity testing framework: acceptable productivity ratio typically ≥ 0.7). Actual batch-specific results are reported on the lot's Certificate of Analysis (COA tab).

Limitations & Technical Considerations

Cross-Reference / Equivalent Products

Ordering Information

Yield calculated at 23.5 g/L reconstitution rate. Custom pack sizes and pre-poured plate formats available on request.

Frequently Asked Questions

Common Search Queries This Product Answers

Non-selective medium for the enumeration of viable aerobic microorganisms (Total Viable Count) in food, water, environmental, and pharmaceutical samples, per ISO 4833, FDA-BAM, and APHA Standard Methods.

Tryptone and yeast extract supply amino acids, peptides, and B-vitamin growth factors that support a broad spectrum of non-fastidious heterotrophic bacteria. Glucose provides an energy source promoting rapid colony development. Because no selective, inhibitory, or indicator agents are included, essentially all viable aerobic organisms capable of growth under the incubation conditions will form countable colonies, making the medium suitable for total (non-differential) enumeration.

Final pH: 7.0 ± 0.2 at 25°C. Total: 23.5 g/L.

Suspend 23.5 g in 1 L purified water. Heat with agitation to dissolve completely. Autoclave at 121°C for 15 minutes. Cool to 45–50°C, mix, and pour or dispense.

• Buchbinder, L. et al. (1951). Studies on plate counting. Public Health Reports, 66(11), 327–329.
• ISO 4833-1:2013. Microbiology of the food chain — Horizontal method for the enumeration of microorganisms. International Organization for Standardization.
• ISO 11133:2014. Microbiology of food, animal feed and water — Preparation, production, storage and performance testing of culture media.
• U.S. Food and Drug Administration. Bacteriological Analytical Manual (BAM), Chapter 3: Aerobic Plate Count.
• American Public Health Association. Standard Methods for the Examination of Water and Wastewater (latest edition).
• United States Pharmacopeia. USP <61> Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests.

This is a summary view. The full 16-section GHS-compliant Safety Data Sheet (Australian format) is provided as a downloadable Word document alongside this page.

Not classified as a hazardous chemical or dangerous good under Safe Work Australia / GHS criteria in its dehydrated form. May cause mechanical irritation to eyes and respiratory tract as a fine powder. Prepared (autoclaved) medium presents negligible chemical hazard; standard aseptic and biological safety precautions apply once inoculated with microorganisms.

Each batch is supplied with a lot-specific Certificate of Analysis. A representative COA is provided as a downloadable Word document; the batch-specific COA accompanies your shipment.