Virulence and Pathogenicity in Infection

Infection is the invasion of the host by microorganisms, while disease is a morbid process that does not necessarily involve infection.

Pathogenicity is the capacity of a bacterium to cause disease. An example of a primary pathogen is Salmonella spp., identified as the cause of diarrheal disease by laboratory isolation from feces.

Opportunistic pathogens are isolated from patients whose host defense mechanisms have been compromised. An example is Escherichia coli causing urinary tract infections in patients predisposed by catheterization.

<p>Some bacteria are considered nonpathogens because they rarely or never cause human disease. An example is Lactobacillus acidophilus.</p> Signup and view all the answers

<p>Pathogenesis refers to the mechanism of infection and the mechanism by which disease develops. Bacteria can be organized into three major groups based on their pathogenicity: primary pathogens, opportunistic pathogens, and nonpathogens.</p> Signup and view all the answers

<p>Virulence factors are molecules expressed on or secreted by microorganisms that enable them to colonize the host, evade or inhibit the immune responses of the host, enter into or out of a host cell, and/or obtain nutrition from the host.</p> Signup and view all the answers

<p>Adhesins enable a microbe to attach to host tissues, which is a crucial step for most microbes to infect and grow in a host.</p> Signup and view all the answers

<p>One example of a bacterial adhesin is type 1 fimbrial adhesin, which allows the fimbriae of enterotoxigenic E. coli (ETEC) cells to attach to the mannose glycans expressed on intestinal epithelial cells.</p> Signup and view all the answers

<p>Virulence can be experimentally measured by determining the number of bacteria required to cause animal death, illness, or lesions in a defined period after the bacteria are administered by a designated route.</p> Signup and view all the answers

<p>The degree of virulence is related directly to the ability of the organism to cause disease despite host resistance mechanisms.</p> Signup and view all the answers

<p>Innate immunity is antigen-independent and lacks immunologic memory, while adaptive immunity is antigen-dependent, antigen-specific, and has the capacity for memory.</p> Signup and view all the answers

<p>The hallmark of adaptive immunity is the capacity for memory, which enables the host to mount a more rapid and efficient immune response upon subsequent exposure to the antigen.</p> Signup and view all the answers

<p>Innate immunity is unable to recognize or 'memorize' the same pathogen upon subsequent exposure, while adaptive immunity can mount a more rapid and efficient immune response upon subsequent exposure to the antigen due to its capacity for memory.</p> Signup and view all the answers

<p>Immunologic memory in adaptive immunity enables the host to mount a more rapid and efficient immune response upon subsequent exposure to the antigen.</p> Signup and view all the answers

<p>The primary difference is that innate immunity is antigen-independent and lacks immunologic memory, while adaptive immunity is antigen-dependent, antigen-specific, and has the capacity for memory.</p> Signup and view all the answers

<p>Pattern Recognition Receptors (PRRs) are proteins capable of recognizing molecules frequently found in pathogens or molecules released by damaged cells (DAMPs). They recognize Pathogen-Associated Molecular Patterns (PAMPs).</p> Signup and view all the answers

<p>Cytokines are small protein-based cell signaling molecules that aid cell-to-cell communication in immune responses and stimulate the movement of cells towards sites of inflammation, infection, and trauma.</p> Signup and view all the answers

<p>The key inflammatory cytokines released during the early response to bacterial infection are: tumour necrosis factor (TNF), interleukin 1 (IL-1), and interleukin 6 (IL-6).</p> Signup and view all the answers

<p>The most current terminology used to describe cytokines is 'immunomodulating agents,' or agents that modulate or alter the immune system response.</p> Signup and view all the answers

<p>Pathogen-Associated Molecular Patterns (PAMPs) are a diverse set of microbial molecules that share a number of different general 'patterns' or structures. Examples include lipopolysaccharides (LPS) and double-stranded ribonucleic acid (RNA) produced during viral infection.</p> Signup and view all the answers