---
title: "Brain Heart Infusion Broth | Microbiology"
description: "Brain Heart Infusion Broth is a rich microbiology medium for fastidious bacteria, supporting growth of pathogens and serving as a base for other media."
canonical: "https://fiveable.me/microbio/key-terms/brain-heart-infusion-broth"
type: "key-term"
subject: "Microbiology"
unit: "Unit 9"
---

# Brain Heart Infusion Broth | Microbiology

## Definition

Brain Heart Infusion Broth is a nutrient-rich liquid medium in microbiology used to grow fastidious and pathogenic bacteria. It supplies extra nutrients, so organisms that struggle on basic media can still grow.

## What It Is

Brain Heart Infusion Broth, usually shortened to BHI broth, is a complex liquid culture medium in Microbiology that gives bacteria a very rich food supply. You use it when a microorganism needs more than a basic peptone or salt mixture to grow well, especially if it is fastidious or slow-growing.

What makes BHI broth different is its composition. It contains brain and heart tissue infusions plus peptones, dextrose, sodium chloride, and buffering ingredients. That mix gives microbes amino acids, peptides, carbohydrates, and salts, so the medium supports a wide range of bacterial metabolism instead of forcing one narrow growth pattern.

In lab terms, BHI broth is not selective, so it does not block most bacteria the way a selective medium would. Instead, it is enriched, which means extra nutrients are added to help more demanding organisms grow. That is why it often shows up when the lab is trying to recover pathogens from clinical samples or maintain a culture that is sensitive to nutrient limits.

The broth is especially useful for organisms connected to infections such as meningitis, endocarditis, and septicemia, where the bacteria may be hard to grow on a simple medium. If you think about the workflow, BHI broth often comes before streaking onto a solid plate, because it can increase the number of cells and make later isolation easier.

BHI broth also matters because it can be a starting point for other media. Add blood and you can make blood agar, or process it further for chocolate agar, which helps support more demanding organisms and makes certain growth patterns easier to see. In other words, BHI broth is both a growth medium on its own and a building block for other lab media.

## Why It Matters

Brain Heart Infusion Broth matters in Microbiology because it shows the difference between ordinary growth media and media designed for hard-to-culture organisms. When a bacterium will not grow well on a basic medium, BHI broth gives you a better chance of recovering it, which is a big deal in clinical microbiology and in any lab that works with unknown samples.

It also helps you reason through media choice. If a question asks why one bacterium grew in BHI broth but not in a simpler broth, the answer is usually tied to nutritional needs, enrichment, or recovery from stress. That kind of reasoning comes up in lab reports, culture interpretation, and media comparison questions.

BHI broth connects directly to the idea of enriched media. Once you understand why this broth supports fastidious organisms, it becomes easier to understand why blood agar, chocolate agar, and other enriched media exist at all. The concept is not just memorizing a recipe, it is understanding why some microbes need a more supportive environment than others.

It also matters in clinical isolation. Fastidious pathogens can be missed if the medium is too bare, so choosing BHI broth can change whether growth is visible at all. That makes the term useful any time you are tracing the steps from sample to culture to identification.

## Connections

### [enriched media](/microbio/key-terms/enriched-media)

BHI broth is a classic example of enriched media because it has extra nutrients added to support demanding organisms. If a question asks why this medium works better than a basic broth, the answer is that enrichment supplies the growth factors some bacteria cannot make on their own.

### [Tryptic Soy Broth (TSB)](/microbio/key-terms/tryptic-soy-broth-tsb)

TSB is another common liquid medium, but BHI broth is richer and often better for more fastidious organisms. If you are comparing the two, think about nutritional depth: TSB is useful for many routine cultures, while BHI is often chosen when the organism needs more support.

### [Blood Agar](/microbio/key-terms/blood-agar)

BHI broth is often used as a base for blood agar, so the broth can be a starting point before bacteria are plated onto a solid enriched medium. Blood agar then lets you look for colony growth and hemolysis, which BHI broth by itself cannot show.

### [fastidious organisms](/microbio/key-terms/fastidious-organisms)

BHI broth is designed with fastidious organisms in mind. These microbes have more specific nutritional needs, so they may grow poorly on simple media. Seeing BHI broth in a lab context is usually a clue that the organism may be demanding or clinically significant.

## On the AP Exam

A quiz question might ask you to identify which medium would support a fastidious bacterium, and BHI broth is a strong answer when the scenario calls for an enriched liquid medium. In a lab practical, you may need to match the medium to its use, such as recovering a pathogen from a clinical sample or preparing a culture before plating.

If you are given a growth scenario, look for clues like poor growth on basic media, a suspected pathogen, or the need for a nutrient-rich broth. Then explain the choice in terms of enrichment, not just memorized names. You may also see BHI broth in questions about media preparation, especially when it is being used as the base for blood agar or chocolate agar.

## Brain Heart Infusion Broth vs Tryptic Soy Broth (TSB)

Both are general liquid media, so they can look similar at first. The difference is that BHI broth is richer and is more often used for fastidious organisms or clinical recovery, while TSB is a more routine all-purpose broth.

## Key Takeaways

- Brain Heart Infusion Broth is a rich liquid medium in Microbiology used to grow bacteria that need extra nutrients.
- It is an enriched medium, not a selective one, so it supports many organisms instead of blocking them.
- BHI broth is especially useful for fastidious and pathogenic bacteria that may not grow well on basic media.
- It can also serve as a base for other media, including blood agar and chocolate agar.
- If you see BHI broth in a lab question, think nutrient-rich recovery, clinical isolation, and support for demanding microbes.

## FAQs

### What is Brain Heart Infusion Broth in Microbiology?

Brain Heart Infusion Broth is a nutrient-rich liquid culture medium used to grow bacteria, especially fastidious organisms. It contains tissue infusions and other nutrients that help microbes grow when a basic broth is not enough.

### Is Brain Heart Infusion Broth selective or enriched?

It is enriched, not selective. That means it adds extra nutrients to support growth, but it does not contain inhibitors that block unwanted bacteria. This is why it is useful for recovering organisms with higher nutritional needs.

### Why would a lab use Brain Heart Infusion Broth instead of a simple broth?

A lab would choose BHI broth when the organism is fastidious, weak after transport, or hard to recover from a sample. The richer nutrient profile improves the chance of visible growth and can help before plating onto solid media.

### How is Brain Heart Infusion Broth different from Tryptic Soy Broth?

Both are liquid media, but BHI broth is usually richer and more supportive of demanding organisms. TSB is often fine for routine growth, while BHI is a better choice when the bacteria need extra nutritional support.

## Related Study Guides

- [9.6 Media Used for Bacterial Growth](/microbio/unit-9/6-media-bacterial-growth/study-guide/7QLOcV9AAJUXfBX5)

## About This Document

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