Bacterial Pathogenesis and Infections

The process by which bacteria cause disease.

The ability of a microbe to cause disease.

The degree of pathogenicity (harm caused); may vary between strains.

The initial infection by a pathogen.

A subsequent infection by the same pathogen.

New infection by a different pathogen due to weakened resistance.

The minimum amount of bacteria needed to cause infection.

The minimum amount of bacteria needed to cause death.

Microorganisms that live harmlessly in the body.

Bacteria multiplying in the blood, causing fever and toxicity.

Transmission from external sources or infected individuals, entry into the human body, overcoming host defenses, multiplication and spreading within the body, causing cell tissue damage, and spreading to others.

Many infectious diseases have symptomatic, less severe, and asymptomatic cases. Asymptomatic cases are crucial because they develop immunity and spread infection unknowingly.

The body's natural defenses against bacterial infections, including skin's high salt and fatty acids, stomach acid, mucous and cilia in the respiratory tract, peristalsis in the digestive tract, and soluble mediators.

Infections that do not show any noticeable symptoms in the infected person. They can still spread the infection to others.

The evident, symptomatic stage of an infectious disease, representing the visible tip of the disease iceberg.

A toxic component of the outer membrane of Gram-negative bacteria. It's a potent stimulator of the immune system and can lead to serious complications like septic shock.

Exposure to high levels of endotoxin (LPS) from Gram-negative bacteria. This triggers a cascade of immune responses, leading to systemic inflammation, blood clotting abnormalities, and potentially organ failure.

Endotoxin activates multiple pathways including cytokine release, clotting, and complement. This can lead to fever, inflammation, blood pressure drop (hypotension), and even death in severe cases.

Endotoxic shock is primarily associated with infections caused by certain Gram-negative bacteria, like Escherichia coli, Pseudomonas aeruginosa, and Neisseria meningitidis.

High levels of endotoxin can cause systemic effects like fever, hypotension, weakness, disseminated intravascular coagulation (DIC), inflammation, and even intestinal hemorrhage.

Short, hair-like structures on bacterial cell surfaces that mediate adhesion to surfaces, aiding infection.

The ability of bacteria to attach to surfaces, a critical step in infection.

Antigenically specific fimbriae/pili used by Enterotoxigenic Escherichia coli (ETEC) to colonize the gut.

Bacterial proteins that mediate attachment to host cells, unlike pili type adhesions

Bacterial aggregates on surfaces, providing increased resistance to host defenses and antibiotics.

Bacterial coatings that protect from phagocytosis and aid in adherence to surfaces.

The process by which white blood cells engulf and destroy bacteria.

A protective layer surrounding some bacteria, composed of polysaccharides. It contributes to the mucoid appearance of colonies and can be visualized with India ink staining. Capsules are often associated with bacterial virulence.

An enzyme produced by some bacteria that breaks down hyaluronic acid, a component of connective tissue. This allows bacteria to spread through tissues.

Enzymes that break down red blood cells. Examples include alpha and beta hemolysins produced by Staphylococci and Streptococci. Hemolysis can be observed as zones of clearing around colonies on blood agar.

An enzyme produced by Staphylococcus aureus that converts fibrinogen to fibrin, forming a fibrin barrier around the bacteria. This protects the bacteria from the immune system.

An enzyme produced by Streptococcus pyogenes that breaks down fibrin. This helps the bacteria spread through tissues.

A component of the outer membrane of Gram-negative bacteria, released when the bacteria die. Endotoxins are typically lipopolysaccharides and can trigger a strong inflammatory response in the host.

A toxic protein secreted by some bacteria. Exotoxins can have a variety of effects on the host, including damage to tissues, interference with cellular functions, and immune suppression.

Endotoxins activate various immune pathways, leading to a cascade of inflammatory and immune responses. These responses can be beneficial in clearing infections, but they can also contribute to tissue damage and organ dysfunction during severe infections.

A neurotoxin produced by the bacterium Clostridium tetani that blocks the release of inhibitory neurotransmitters, causing continuous muscle contraction and spasms.

A neurotoxin produced by Clostridium botulinum that blocks the release of acetylcholine, causing muscle paralysis and flaccid weakness.

Chemicals released by nerve cells that reduce or prevent the activity of other nerve cells, leading to muscle relaxation.

Chemicals released by nerve cells that stimulate the activity of other nerve cells, leading to muscle contraction.

Traits of bacteria that enhance their ability to cause disease, such as toxins, capsules, or enzymes.

Tetanus toxin blocks the release of inhibitory neurotransmitters, leading to continuous muscle contraction. Botulinum toxin blocks the release of acetylcholine, leading to muscle paralysis.