Pathogenicity and Virulence

Infective dosage refers to the number of organisms needed to cause disease, which is inversely proportional to their virulence.

The portal of entry is crucial as it determines the route through which pathogens enter the body, influencing their ability to cause disease.

The escape of the pathogen from its host and its entrance into a susceptible person are essential for communicability.

<p>Pathogenic microorganisms can be transmitted via contact, airborne, food and water-borne, and insect-borne methods.</p> Signup and view all the answers

<p>Natural barriers such as intact skin and mucous membranes serve as effective mechanical barriers preventing most pathogens from entering the body.</p> Signup and view all the answers

<p>Pathogenicity is the ability of a parasite to gain entrance to a host and produce physiological or anatomical changes (disease). It is significant as it determines the potential of an organism to cause an infection.</p> Signup and view all the answers

<p>Virulence refers to the degree of pathogenicity or the ability of an organism to cause infection. While pathogenicity indicates if an infection occurs, virulence measures the severity of that infection.</p> Signup and view all the answers

<p>Infestation indicates the presence of animal parasites on or in a host's body, while infection refers to the interaction between a host and pathogen, where disease results if the pathogen is successful.</p> Signup and view all the answers

<p>Toxins, such as exotoxins and endotoxins, are poisonous substances produced by microorganisms that can contribute significantly to their virulence by damaging host tissues or disrupting physiological functions.</p> Signup and view all the answers

<p>Exotoxins are heat-labile, diffusible proteins secreted into the surrounding medium, while endotoxins are heat-stable components of the gram-negative bacterial cell wall released upon cell disintegration.</p> Signup and view all the answers

<p>Hyaluronidase, known as the spreading factor, enables pathogens to penetrate host tissues by hydrolyzing hyaluronic acid, which acts as a tissue cement.</p> Signup and view all the answers

<p>Resistance is the ability of an organism to fend off infection, while susceptibility indicates a lack of resistance, affecting the outcome of the interaction between host and parasite.</p> Signup and view all the answers

<p>Differentiating between natural resistance, which is inherent in the host, and acquired immunity, which develops after exposure to pathogens, is vital for understanding how organisms protect themselves against infections.</p> Signup and view all the answers

<p>Hyaluronic acid serves as a substrate for the production of an adaptive enzyme by certain cocci and clostridia.</p> Signup and view all the answers

<p>Lecithinase functions to lyse and degrade lecithin, which is crucial for cellular membranes, and it is secreted by Clostridium perfringens.</p> Signup and view all the answers

<p>Collagenase is an enzyme that destroys collagen, which is vital for the structure of muscles, bones, and cartilage.</p> Signup and view all the answers

<p>Coagulase activates plasma to coagulate fibrinogen, forming a protective fibrin coat around bacteria, which helps evade phagocytosis.</p> Signup and view all the answers

<p>Leucocidin kills leucocytes (white blood cells), thereby impairing the host's immune response to infection.</p> Signup and view all the answers

<p>Hemolysins liberate hemoglobin from red blood cells, enhancing bacterial virulence by facilitating nutrient acquisition.</p> Signup and view all the answers

<p>Capsular materials provide a protective barrier that enhances the virulence of pathogens by preventing phagocytosis.</p> Signup and view all the answers

<p>Microorganisms often have a specific affinity for certain tissues, which can lead to injury and contribute to disease.</p> Signup and view all the answers