Bacterial Pathogenesis: Bacterial Factors that Damage the Host

I. BACTERIAL PATHOGENESIS

C. VIRULENCE FACTORS THAT DAMAGE THE HOST

2. Producing Harmful Exotoxins: An Overview

The overall purpose of this Learning Object is to list three different categories of exotoxins and introduce how the body typically defends itself against exotoxins. Each of these exotoxins will be described in greater detail in subsequent sections.

LEARNING OBJECTIVES FOR THIS SECTION

In this section on Bacterial Pathogenesis we are looking at virulence factors that damage the host. Virulence factors that damage the host include:

1. The ability to produce cell wall components (Pathogen-Associated Molecular Patterns or PAMPs) that bind to host cells causing them to synthesize and secrete inflammatory cytokines and chemokines;

2. The ability to produce harmful exotoxins.

3. The ability to induce autoimmune responses.

We will now look at the ability of bacteria to produce harmful exotoxins.

The Ability to Produce Harmful Exotoxins: An Overview

Exotoxins (def) are protein toxins usually secreted from a living bacterium but also released upon bacterial lysis and sometimes injected directly into human cells by bacteria. There are three main types of exotoxins:

1. superantigens (Type I toxins);

2. exotoxins that damage host cell membranes (Type II toxins); and

3. A-B toxins and other toxin that interfere with host cell function (Type III toxins).

The body's major defense against exotoxins is the production of antitoxin antibodies. Once the antibody binds to the exotoxin, the toxin can no longer bind to the receptors on the host cell membrane.

Flash animation showing the neutralization of exotoxins with antibodies.

We will now look at each of these three types of exotoxins.

For further information on bacterial pathogenesis, see the online Microbiology Web Textbook at the University of Wisconsin-Madison.

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