Tortora Microbiology Chap 15 Host-Parasite Relationships
Terms
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- Organisms that live on or in a second organism
- Parasites
- Parasites that play beneficial roles
- Normal flora
- Parasites that bring about damage or harm
- Pathogens
- OUtcome of the host-parasite relationship depends on?
- Pathogencity of parasite and resistance of host
- Growth of microorganisms in the host, does not always lead to injury
- infection
- Infections with no outward signs
- Subclinical infections
- Growth of microorganisms in the host, where host is harmed in some way
- Disease
- These are favorable environment for microbial growth due to they high amount of organic nutrients and growth factors
- Animal bodies
- When each region of the animal body differs chemically and physically from other regions
- Microenvironments
- These are almost always found on tissues exposed to outside world
- microbes
- Stages of infection
- Entry, colonization and growth, spread, Exit
- many microorganisms have surface structures that bind to receptors on animal cells this is called
- specific adherence
- Fimbriae, Glycocalyx, viral spikes and flagella are all examples of
- Microbe surface structures
- Generalized (systemic) infections are characterized by
- organisms pass through lymphatic vessels and are deposited in lymph nodes
- Prescence of bacteria in blood?
- Bacteremia
- Enzymes involved in invasion
- Hyaluronidase, Collagenase, and Streptokinase
- This enzyme is produced by streptococci and staphylococci and breaks down hyluronic acid (tissue cement)
- Hyaluronidase
- This enzyme is produced by clostridia that cause gas gangrene, it breaks down collagen network that support tissue
- Collagenase
- This enzyme is produced by streptococci and it breaks down fibrin clots formed by host in an effort to wall off microorganisms
- Streptokinase
- When organisms do not spread from site of infection this is know as a
- localized infections
- boils, carbuncles, or pimples are examples of
- localized infections
- Portals for exit of microorganisms from the body include:
- aerosols from respiratory system, fecal matter, vaginal discharge and semen, infected urine, blood, skin cells
- Proteins produced by some bacterial species and released extracellulary are
- Exotoxins
- These are highly toxic, highly specific as to "target cell" affected and can be fatal in small doses
- Exotoxins
- Neurotoxins affect
- Nervous system
- Botulinum Toxin is an example of an
- Exotoxin
- Enterotoxins affect
- Gastorintestine
- Nephrotoxins affect
- kidneys
- Two types of Hemolysins
- Phosphalipases and leukocidins
- These endotoxins attack cell membranes and cause cell lysis
- Hemolysins
- Phosphalipases ?
- attack phospholipids
- Leukocidins?
- lyze white blood cells, decrease host resistance
- These toxins are part of intergral process of cell
- endotoxins
- This toxin is contained in the LPS of outer cell wall, is released in large amounts only when cells lyse
- endotoxins
- Gas Gangrene, tetanus, botulism, diphtheria, and scarlet fever are representative diseases of
- Exotoxins
- Typhoid fever, urinary tract infections, and meningococcal meningitis are representative diseases of
- endotoxins
- Toxicity is much lower than exotoxins, but can cause death in very large doses
- Endotoxins
- The relative ability of a parasite to cause disease
- Virulence
- Determined by the invasiveness of the organism and its toxigenicity
- Virulence
- When pathogens are kept in culture for long periods, virulence is often decreased or completely lost
- Attenuation
- These strains can be used for vaccines
- Attenuated