Download Host-Microbe Relationships

Host-Microbe Relationships
ALL PARTS of the body open to the external environment are extensively colonized
Skin, Mouth, Respiratory Tract (not to deep in health adults – cilliated epithelial cells
beating upward), GI tract Urogenital tract
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Host-Microbe Relationships
Care Free
and Germ
Free
Let colonization begin!
Colonized Alright!
Start with Lactobacillus from mom as the baby passes through the vagina
Then from the external environment – VERY RAPID COLONIZATION
Normal healthy adult == 1 x 10^13 TOTAL CELLS COMPRISE THE BODY 10
Trillion ISH
BUT Has
1 x 10^14 bacterial cells or 100 Trillion on
them
It has been calculated that the normal human houses about 10^12 bacteria on the
skin, 10^10 in the mouth, and 10^14 in the gastrointestinal tract. The latter number
is far in excess of the number of eukaryotic cells in all organs which comprise the
human host.
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In a healthy animal,
internal tissues, e.g. blood, brain, muscle, etc.,normally free of microorganisms.
Surface tissues, e.g. skin and mucous membranes, -- constantly in contact with environmental
organisms
become readily colonized by certain microbial species.
WRITE THIS ON THE BOARD ----------The mixture of organisms regularly found at any anatomical site is referred to as the normal flora
(Microbiota).
Normal flora of humans
exceedingly complex
consists of more than 200 species of bacteria.
Makeup of the normal flora depends upon various factors,
genetics, age, sex, stress, nutrition and diet of the individual.
DOWN TO HERE ---------The normal flora of humans consists of a few eukaryotic fungi and protists, and some methanogenic
Archaea that colonize the lower intestinal tract, but the Bacteria are the most numerous and
obvious microbial components of the normal flora.
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Host-Microbe Relationships
Commensalism –
One organism benefits while the other is
unaffected – many bacteria
Mutualism –
Symbiosis, both organisms benefit
Parasitism –
one organism benefits at the expense of the
other
Mutualism – GI tract E. Coli provides us with B vitamins and vitamin K
lactic acid bacteria produce certain B-vitamins
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Host-Parasite Relationships
Terms of Infectious Disease
Pathogen – Disease causing
Microorganism
Pathogenicity – Virulence
Infection – Invasion or colonization of body by a
pathogen
Disease – change from a state of health
Genus Bordetella (pertussis, parapertussis [whooping cough kills 100’s of thousands of children a
year world wide] and bronchiseptica)
PATHOGEN – Microbial parasite –
Outcome depends on
PATHOGENICITY – ability of the parasite (pathogen) to cause
damage to the host
AND the host
resistance or susceptibility to the parasite
Pathogenicity varies greatly among individual pathogens. The quantitative measure of pathogenicity
is VIRULENCE
VIRULENCE = expressed as the cell number (pathogens) that will elicit a
pathogenic response in the host within a given time period.
NEITHER Virulence nor relative resistance of the host are static. These items
change frequently. Interaction of the Host-Parasite is very dynamic..
Invasion by and multiplication of pathogenic microorganisms in a bodily part or tissue, which may
produce subsequent tissue injury and progress to overt disease through a variety of cellular or toxic
mechanisms.
the invasion of the body by pathogenic microorganisms and their multiplication which can lead to
tissue damage and disease
Disease – Also can be simply the damage or injury to the host that impairs host function caused by
pathogen
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Host-Parasite Relationships
Etiology of Infectious Disease
Koch’s Postulates –
Neisseria gonorrhoeae, the bacteria that causes gonorrhea,
Koch’s postulates – used to show association of a particular microorganism with a
particular disease
Steps –
1.) Same pathogen must be present in all cases of a disease
2.) Pathogen must be isolated, and grown in pure
culture.
3.) Pure culture put into a susceptible host must
reproduce the disease symptoms
3.) Same organism must be reisolated
Doesn’t Always work for ALL Organisms WHY???? - fastidious organisms
Won’t work if can’t grow on artificial media
Treponema pallidum (syphilis) , Mycobacterium leprae
(leprosy) Chlamydia sp. Viruses
What about must be able to isolate pure culture and re-infect susceptible host –
HIV??? Ethical considerations
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Host-Parasite Relationships
Classification of Infectious Diseases
Communicable Disease –
Spreads from one host to another
Can be directly or indirectly transferred
chickenpox, tuberculosis
Noncommunicable Disease –
Not spread from one host to another
Only causes disease when introduced into the
body
tetanus
Consider them to be contagious diseases if they are easily spread
Mycobacterium tuberculosis
Clostridium tetanii
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Host-Parasite Relationships
Classification of Infectious Diseases
Acute Disease –
Develops rapidly
Short lived
flu
Chronic Disease –
Develops slowly
Long lasting
Acute
Chronic
Chlamydia pneumoniae infection and cardiovascular disease. The bacteria cause a
common respiratory infection but Chlamydia-atherosclerosis connection exists
Helicobacter pylori gastritis and peptic ulcers
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Host-Parasite Relationships
Classification of Infectious Diseases
Emerging Infectious Disease –
New disease or Old disease which is reemergent
Causes of emergence or re-emergence
Global Warming
Global Village
Changes in animal population
Breakdown of Public Health (lack of
infrastructure)
Global Warming
Malaria and Cholera. --Vibrio cholerea
Typical of warm climates
Warm climates may enter new ranges as global
temperatures increase
Global Village
SARS
Changes in ease of rapid transportation (air specifically)
Changes in Animal Population
Increase deer population, increase deer tick population and increase
chances or rate of infection
Breakdown of Public Health diptheria increase in Russia Corynebacterium
diphtheriae
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Host-Parasite Relationships
Classification of Infectious Diseases
Nosocomial Infectious Disease –
Infection acquired as a result of a hospital stay
Main chain of infection is via hospital personnel
5-15 % of all patients acquire
20,000 deaths per year
Contributing Factors
Presence of microorganisms in hospital
Weakened patients
Primary Nosocomial Pathogens
E. coli, S. aureus, P. aerginosia
Escherischia coli
Staphylococcus aureus --Staphylococcus aureus causes a variety of suppurative
(pus-forming) infections and toxinoses in humans. It causes superficial skin lesions
such as boils, styes and furunculosis; more serious infections such as
pneumonia, mastitis, phlebitis, meningitis, and urinary tract infections; and
deep-seated infections, such as osteomyelitis and endocarditis. S. aureus is a
major cause of hospital acquired (nosocomial) infection of surgical wounds and
infections associated with indwelling medical devices. S. aureus causes food
poisoning by releasing enterotoxins into food, and toxic shock syndrome by
release of superantigens into the blood stream.
Pseudomonas aeruginosa --Pseudomonas aeruginosa is an opportunistic
pathogen, meaning that it exploits some break in the host defenses to initiate an
infection. It causes urinary tract infections, respiratory system infections,
dermatitis, soft tissue infections, bacteremia, bone and joint infections,
gastrointestinal infections and a variety of systemic infections, particularly in
patients with severe burns and in cancer and AIDS patients who are
immunosuppressed. Pseudomonas aeruginosa infection is a serious problem in
patients hospitalized with cancer, cystic fibrosis, and burns. The case fatality rate in
these patients is 50 percent.
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Host-Parasite Relationships
Reservoirs of Infection
Human Reservoirs –
Principle reservoir for many pathogens
Some people are carriers
Animal Reservoirs –
zoonoses
Nonliving Reservoirs –
Soil – fungi, C. tetanii
H2O – Vibrio cholera
Food -- Salmonella
AIDS, diptheria, gonorrhea, streptococcal infections
Carriers carry the organism without themselves showing any disease symptoms –
Typhoid
Zo – ON – o- Seas
RABIES – Lyme Disease – West Nile
Non-Living
Clostridium tetanii
H20 and Food often involve fecal contamination –
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Host-Parasite Relationships
Transmission of Diseases
Contact Transmission –
Person to Person
patient Ùmedical personel
Indirect Contact Transmission –
Infected person Î fomite Îuninfected person
Droplet Transmission –
Infected person Îdroplet nuclei Î uninfected
person
Contact
physical contact between infected and unifected host
touching, kissing, sexual intercourse (STD’s)
Nosocomial – gloves and hand washing can prevent – Staph
infections most common
Indirect Contact
Fomite – inanimate object or substance which can transmit infections
disease towel, toy syringe
Droplet Transmission
coughing sneezing formation of an aerosol carrying infectious
microorganisms
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Host-Parasite Relationships
Transmission of Diseases
Vehicle Transmission –
Usually food, water and air
Vector Transmission –
Insects and arthropods as vectors
Malaria -- Plasmodium a protozoan
mosquito Î human
Plague – Yersinia pestis
rat flea Î human
Food – foodborne infections and intoxications
E. coli and Salmonella
Contaminations from improper cooking, or
improper microbial control procedures
Water - Fecal contamination
Pathogens the transmitted to new host
cholera, dysentery
Airborne – small droplets which remain airborne
can remain airborne for > 1m from the host
– Tuberculosis can be spread this way
VECTOR
Malaria - mosquitoes – Plasmodium (a protozoan)
Plaque - Rat Flea – Yersinia pestis (bacterium)
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