Transcript Ecology of Pathogenic Microbes

Ecology of Pathogenic Microbes
1. What is ¨pathogenic?”
2. “Life cycle” of pathogenic microbes
3. How do we know if microbe causes
disease? (Koch’s postulates)
4. Epidemiology—population ecology of
pathogenic micro-organisms: Tracking
disease
1. What is pathogenic?
(Plasmodium
protozoan lysing
red blood cell)
Relationship between Us (host)
and Microbe (symbiont)
• We always provide habitat and usually nutrition
for microbe
• Microbe effect on us varies:
Beneficial
Mutualism
(E. coli in gut)
Neutral
Commensalism
(Staphylococcus on skin)
Deleterious
Parasitism
(Plasmodium)
Resident Microbes (are beneficial to neutral)
(Table 14.2 from Bauman text)
Resident microbes “gone bad”
• Sometimes resident or harmless microbes can
become deleterious or harmful
• Depends on local conditions, immune health of
person, micro-habitat and strain of microbe
• For example, E. coli in gut can be pathogenic
elsewhere in body
• For example, resident fungal microbes can
become pathogenic, especially with antibiotic
treatment that kills bacteria which compete with
fungus—vaginal yeast infection, thrush in mouth.
2. “Life cycle” of pathogenic microbes
Important events in life cycle or
ecology of pathogen
(Cause Disease in host)
Exit from host
Entry into host
(INFECTION!!)
Transmission
How does microbe enter human
host—routes of infection
• Wiki Brainstorm (go to Wiki websites)
• How do microbes enter or infect our the inside or
outside of our bodies?
• Give route or mode of infection and an example if
you know one.
Portals of entry for pathogens
Exit portals for pathogens
Modes of Transmission
What is disease?
•
•
•
•
Portals of entry (check)
Portals of exit (check)
Transmission (check)
How do microbes cause disease? (coming
up in Unit IV on immunity, but…)
• How do we know microbe is cause of
disease?
3. How do we detect illness and
determine if microbe is cause?
Robert Koch (1843-1910)
Signs and Symptoms
SIGNS (can be
observed)
• Fever
• Swelling
• Rash, redness
• Vomiting, Diarrhea
• Cell counts
• Pus formation
• Change in heart rate
SYMPTOMS (felt by
patient)
• Pain
• Nausea
• Headache
• Chills
• Soreness
• Fatigue
• Malaise
• Itching
• Cramps
Syndrome: a group of signs
and symptoms that characterize
a possible diseae (usually when
disease cause is still poorly
understood)
Koch’s
postulates
Problems with Koch’s postulates
• Not always applied correctly or completely:
example Haemophilus influenzae (bacteria
originally thought to cause flu, later found in
non-victim’s lungs)
• Not always possible to apply—require
controlled laboratory conditions and usually
culturable disease-causing microbe
• When can’t use Koch’s, use epidemiological
data
4. Epidemiology
• Population dynamics of pathogens—how
does disease spread through host
population?
• Koch’s postulates—controlled laboratory
“physiological” study
• Epidemiological data—observations,
reporting, statistics from “wild” or general
population
Goal of epidemiology is to track
infection, transmission and efficacy of
treatment to determine:
•
•
•
•
•
How disease enters (mode of infection)
How virulent or damaging is it?
How does it exit?
How is it transmitted?
What is causative agent—is microbe
involved?
• Spread of disease—epidemics and
pandemics
London cholera epidemic—mapping
cases traces to one water pump site
More on epidemiology:
• Center for Disease Control Mortality and
Morbidity Weekly Report—principal
national tool for tracking diseases
• World Health Organization Weekly
Epidemiological Report—principal global
epidemiological statistical report
• Web teaching Resources
• (see course website for links)
Review
1. What is a pathogen—not all microbes that live in/on
us are pathogens (scale from mutualistic to parasitic)
2. Life cycle of pathogens includes entry or infection
and exit with transmission to new host
3. How do we determine if microbe causes disease?
Koch’s postulates are best proof, but…
4. Epidemiology is powerful tool for tracking spread of
disease in host population and can also help to
determine microbial causes.
COMING NEXT: Horror-Shop of Disease-causing
microbes and their effects!!