Let’s follow the journey of a pathogen as it attacks its victim!
Salmonella : is a bacterium
What was the source of the pathogen?
Source of the pathogen: Contaminated food
What is the first defense?
Stomach acid destroys some of the bacteria
Macrophages try to destroy the Salmonella
•What does the body do next to try and get rid of the pathogen?
How does Salmonella attack the body?
•Enters the cells of the villi and destroys them
•The destroyed cells release distress chemicals
•What causes the diarrhea?
•The waves of peristalsis are so rapid that the large intestine is unable to absorb the water
•How does Salmonella cause your body to ache?
•The chemicals released from the cells leak into the blood stream and go into the muscle tissue
•Does the medicine kill the Salmonella?
How does the immune system begin to respond to the Salmonella invasion?
The immune system identifies the pathogen and produces helper cells
Helper cells “help” the macrophages to do their job – destroy the Salmonella.
Terminology
The suffix “-emia”
A suffix meaning “presence of an infectious agent”
Bacteremia = Presence of infectious bacteria
Viremia = Presence of infectious virus
Fungemia = Presence of infectious fungus
Septicemia = Presence of an infectious agent in the
bloodstream.
Terminology
The suffix “-itis”
A suffix meaning “inflammation of”
Examples:
Pharyngitis = Inflammation of the pharynx
Endocarditis = Inflammation of the heart
chambers
Gastroenteritis = Inflammation of the
gastointestinal tract.
The Normal Flora of Humans
Types of Symbiosis (cont.)
Parasitism
A symbiotic relationship in which one species
benefits, and the other species is harmed
Generally, the species that benefits (the
parasite) is much smaller than the species that
is harmed (the host).
Benefits of the normal flora
Nutrient production/processing
eg Vitamin K production by E. coli
Competition with pathogenic microbes
Normal development of the immune
system.