Understand the composition, purpose, and clinical use of 40+ bacteriological culture media from blood agar to TCBS, with organism-specific selection logic.
A specimen arrives in the laboratory. Before any identification can happen, the organisms in that specimen must be grown and the medium you choose determines what grows and what does not. Select MacConkey agar and you will see lactose fermenters change color; use Thayer-Martin and you selectively support Neisseria gonorrhoeae while suppressing everything else.
Culture media are the nutrient environments prepared in the laboratory to grow, isolate, and differentiate microorganisms. Choosing the right medium is not a procedural detail, it is a diagnostic decision.
This section covers all major bacteriological and mycological culture media, organized around three questions:
Articles range from everyday laboratory workhorses like blood agar, chocolate agar, and MacConkey agar, to specialized media like Löwenstein-Jensen for mycobacteria, TCBS for Vibrio, and Sabouraud Dextrose Agar for fungi.
If you have ever wondered why the microbiology laboratory chooses three different plates for a single stool specimen, this section will make that logic clear.
Martin Lewis Agar: Principle, Composition, and Uses
Columbia CNA agar selects for gram-positive organisms by inhibiting gram-negatives with colistin and nalidixic acid. Learn when to use it, which organisms grow, and how colony appe...
Bacteriological agar is the gelling agent used in virtually all solid culture media. Learn its properties, why it's preferred over gelatin, melting and solidification temperatures,...
A complete guide to in-house culture media preparation — weighing, dissolving, autoclaving, pH verification, dispensing, drying, and storage — with a troubleshooting table for comm...
LIA differentiates enteric bacteria by lysine decarboxylation, lysine deamination, and H₂S production. Learn how to read LIA results alongside TSI and KIA to identify Salmonella, S...
Czapek Dox agar is a synthetic medium with sucrose as the sole carbon source and nitrate as the sole nitrogen source — used for identification of Aspergillus, Penicillium, and othe...
PEA agar selects for gram-positive organisms and anaerobes by inhibiting gram-negative bacteria through membrane permeability disruption. Learn when to use PEA vs Columbia CNA, and...
What is in viral transport medium and why, how it differs from universal transport medium and bacterial media like Amies, correct storage temperatures, and the freezing mistake tha...
Tinsdale agar selectively isolates and differentiates Corynebacterium diphtheriae from diphtheroids. Black colonies with brown halos after 48h incubation — learn the principle, pre...
Why a fragile gonococcus swab can die before it ever reaches the lab, the design fix that made Amies better than Stuart's medium, and when to choose the charcoal-free version inste...
A batch of agar that passes every visual check can still distort the exact reaction it's supposed to reveal. The real difference between a visual inspection and genuine quality con...
The 1919 discovery that calf brain tissue could grow bacteria ordinary broth couldn't, and why that same nutrient-rich formula is still the backbone of blood culture bottles a cent...
Deoxycholate Citrate Agar (DCA) is a selective and differential medium for isolating Salmonella and Shigella from stool. Learn its three-layer selectivity mechanism, colony morphol...
Selenite broth is the most widely used enrichment medium for isolating Salmonella from stool, urine, and food. Learn its principle, why selenite inhibits coliforms, preparation wit...
Bird seed agar selectively detects Cryptococcus neoformans by its brown-black melanin production from caffeic acid. Learn the principle, composition, colony appearance, and how it...
