How Bacterial Pathogens Penetrate Host Defenses Flashcards
resist the host’s defenses by impairing phagocytosis,
the process by which certain cells of the body engulf and destroy microbes.
Capsules
The cell walls of certain bacteria contain chemical substances that contribute to virulence.
Cell wall components
Streptococcus pyogenes produces a heat-resistant and
acid-resistant protein called ________.
M protein
Neisseria gonorrhoeae grows inside human epithelial cells and leukocytes. These bacteria use fimbriae and an outer membrane protein called _____to attach to host cells. Following attachment by both Opa and fimbriae, the host cells take in the bacteria.
Opa
✓The waxy lipid (___________) that makes up the cell wall of Mycobacterium tuberculosis also increases virulence by resisting digestion by phagocytes, and the bacteria can even multiply inside phagocytes.
mycolic acid
Enzymes used by pathogens to penetrate the host:
Coagulases
Bacterial kinases
Hyaluronidase
Collagenase
IgA Proteases
➢refers to a specific defensive response of the body to an infection or to antigens.
➢ In the presence of antigens, the body produces proteins called antibodies, which bind to the antigens and inactivate them or target them for destruction by phagocytes.
Adaptive Immunity
➢Changes in surface antigens that occur in a microbial population.
➢ By the time the body mounts an immune response against a pathogen, the pathogen has already altered its antigens and is unaffected by the antibodies.
Antigenic Variation
Microbes Capable of Antigenic Variation:
✓Influenza virus, the causative agent of influenza (flu)
✓Neisseria gonorrhoeae, the causative agent of gonorrhea
✓Trypanosoma brucei gambiense, the causative agent of African trypanosomiasis (sleeping sickness)
How Bacterial Pathogens Damage Host
Cells Four Basic Ways:
1) By using the host’s nutrients.
2) By causing direct damage in the immediate vicinity of the invasion.
3) By producing toxins, transported by blood and lymph, that damage sites far removed from the original site of invasion.
4) By inducing hypersensitivity reactions
Iron is required for the growth of most pathogenic bacteria, to obtain iron, some pathogens secrete proteins called _______
siderophores
➢ poisonous substances that are produced by certain
microorganisms.
➢They are often the primary factor contributing to the
pathogenic properties of those microbes.
Toxins
the capacity of microorganisms to produce toxins.
Toxigenicity
Toxins transported by the _______or _______can cause serious, and sometimes fatal, effects.
blood; lymph
- refers to the presence of toxins in the blood
toxemia
Two General Types of Toxins:
Endotoxin and Exotoxin
➢produced inside some bacteria (mostly gram-negative) as part of their growth and metabolism and are secreted by the bacterium into the surrounding medium or released following lysis.
Exotoxins
Toxins are secreted to the outside of the bacterial cells that produce them.
Exotoxin
Three types of Exotoxin:
A-B Toxins
Membrane-Disrupting Toxins
Superantigens
➢they consist of two parts designated A and B, both of which are polypeptides.
A-B Toxins
In A-B toxins, the A part is the ________ component, and the B part is the ________component.
active (enzyme); binding
Most exotoxins are ________.
A-B Toxins
A type of exotoxin that cause lysis of host cells by disrupting their plasma membranes.
Membrane-Disrupting Toxins
Type of Exotoxin:
➢antigens that provoke a very intense immune response.
➢bacterial proteins that combine with a protein on macrophages; this nonspecifically stimulates the proliferation of immune cells called T cell.
Superantigens
white blood cells (lymphocytes) that act against foreign
organisms and tissues.
T cells
small protein molecules produced by various body
cells, especially T cells, that regulate immune responses and mediate cell-to-cell communication.
Cytokines
A toxin that is a part of the outer portion of the cell wall of gram-negative bacteria
Endotoxin
The lipid portion of LPS, called ________, is the endotoxin
Lipid A
Endotoxins are _________, whereas exotoxins are _________.
lipids; proteins
Microorganisms that produce endotoxin:
✓Salmonella typhi (the causative agent of typhoid fever)
✓Proteus spp. (frequently the causative agents of urinary tract infections)
✓Neisseria meningitidis (the causative agent of meningococcal meningitis).
Microbes leave the body via specific routes called __________ in secretions, excretions, discharges, or tissue that has been shed.
Portals of Exit
Portals of Exit:
Respiratory Tract
Gastrointestinal Tract
Genitourinary tract
Skin or wound infections
Arthropods and syringes
a plasma protein produced by the liver, is converted by coagulases into fibrin, the threads that form a blood clot. The fibrin clot may protect the bacterium from phagocytosis and isolate it from other defenses of the host.
Fibrinogen
One of the better-known kinases is ___________, which is produced by such streptococci as ________________.
fibrinolysin (streptokinase); Streptococcus pyogenes
Collagenase, produced by several species of ___________, facilitates the spread of gas gangrene.
Clostridium
