Microbiology Chapter 7 Infection and Disease (Part 3)
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How does a successful pathogen establish itself ? (8 steps)
Reservoir > transmission >penetration /entry portal > colonization /attachment > persistence > reproduction > invasion /toxigenicity >dissemination; portals of exit
1. Maintain a reservoir
2. Leave the reservoir and be transported to the host (transmission)
3. Enter the host (penetration; portals of entry)
4. Establish a site of reproduction and growth within the host (colonization)Adhere to the surface of the host (attachment) invade the body of the host
5. Evade the host defenses (persistence)
6. Multiply within the host (reproduction)
7. Damage the host (invasion and toxigenicity)
8. Leave the host and return to the reservoir or find a new host (dissemination; portals of exit)
What is a reservoir ?
What are the three types of reservoirs ?
Reservoir: a place to live before and after infecting a host.
- -Three types of reservoirs
- 1. Animal (non-human)
- 2. Human
- 3. Environmental
What is Zoonosis ?
Zoonosis: a disease spread from animals to humans
What are symptomatic carriers and asymptomatic carries ?
Symptomatic -those who are sick
Asymptomatic carriers-those who are infected but not sick
Explain these Asymptomatic types ?
Incubatory carriers: people who are infected with a pathogen but appear healthy; will get sick soon.
chronic carriers: people who are infected with a pathogen but do not become sick for months or years.
Latent/Dormant carriers: people who are infected with a pathogen that undergoes latency.
What are some typical reservoirs ?
Arthropods - insects , Arachnids
Fomites - (objects) & Surfaces
Soil, Water , Food , Air , House ,Dust
What are the two possible ways transmission can be seen as ?
-The spread of a pathogen from one organism to another
-The transfer of disease from one organism to another
What is the difference between lateral and vertical transmission ?
Vertical: mother to child; parent to off-spring-
Lateral: person to person, environment to person, etc.
what do the following words indicate about a disease ? Infectious, contagious or communicable (are used interchangeably)
If a disease is transmissible (capable of being spread from one organism to another) then the disease can be termed
In terms of transmission , what is Direct transmission and Indirect transmission ?
Direct contact -Physical touch between individuals,handshake,kissing,sexual intercourse
Indirect contact-Individuals contract pathogen via fomites , inanimate objects involved in the spread of a pathogen e.g. fork, doorknob, stair rails, etc.
What are vectors ?
Name some of the most common vectors ?
Why are vectors important in Zoonotic diseases ?
- Vectors -Living organisms that transmit diseases to humans
- -Most common vectors are arthropods Ticks ,Fleas,Mites,Flies,Lice,Mosquitoes
They are important because most of this vectors involve animals.
What are mechanical vectors and biological vectors ?
Mechanical Vectors-The pathogen is on the external surfaces of the vector-Organism is not involved in the life cycle of the pathogen
Biological Vectors-Pathogen lives within the body of the vector; often serves as the definitive host-Vector transmits the pathogen by biting, sucking, aerosol formation
What are some types of Mechanical vectors and Biological vectors ?
Types of Mechanical Vectors :common housefly, cockroach
Types of Biological Vectors :biting and blood sucking vectors,Flies (sand flies, tsetse flies), mosquitoes, lice, tick, mites, fleas
Match these biting vectors with thier proper transmission ?
Mosquito , fleas, tsetse fly
Penetrate the skin and inject saliva infected with the pathogen directly into the blood.
Penetrate the skin and defecate around the wound, thereby introducing pathogen into the host.
Penetrate the skin and regurgitate infected blood into the wound.
Mosquito -Penetrate the skin and inject saliva infected with the pathogen directly into the blood.
Fleas-Penetrate the skin and defecate around the wound, thereby introducing pathogen into the host.
Tsetse Fly -Penetrate the skin and regurgitate infected blood into the wound.
What is a parenteral mode of transmission ?
the pathogen is deposited directly into the blood stream, into tissue below the skin or into mucous membranes
What type of bacteria are the most frequent to be involved in the transmission via ingestion?
What are two ways these organisms can be ingested ?
Water (water-borne) -Consuming contaminated drinking water; bathing or swimming in contaminated water.
Food (Food-borne) -Consumption of contaminated food products.
What is the fecal-oral mode of transmission ?
Infected feces of one host enters a new host via ingestion
Direct contact with feces
Indirect contact with fomites contaminated with fecal matter.
Contaminated food and contaminated water.
Animal to human and human to human transmission
What is an infection cycle ?
What is a simple and complex infection cycle ?
Infection cycle: the route an organism takes to pass from one person (or animal or plant) to another.
-Simple infection cycle:Pathogen is spread directly from person to person
-Complex infection cycle : Vector
Name some Bodily fluids involved in transmission ?
Blood: usually sterile; contains most pathogens; microbes use the circulatory system for dissemination.
Urine: usually sterile
Saliva: often via spit
Respiratory secretions: sneezing, coughing (sputum)
What are the F's of transmission ?
- Fomites (e.g., fields, floors etc.)
- Fornication (STI)
Are mucosal surfaces of the body , portals of entry ?
conjunctiva (mucosal lining of the eye)
Name some bacteria that utilize the Alimentary tract ?
- Alimentary Tract
- Mouth: enter via ingestion of contaminated food, drink, etc.Ingested pathogens can survive stomach pH and enzyme activity
e.g., Salmonella, poliovirus, hepatitis A virus
Name some pathogens that utilize the Respiratory tract ?
Respiratory TractNose: pathogen enters the body through inhaled droplets or aerosols inhaled particles can be deeply inhaled bacteria: sore throat (strep throat)
- E.g.(streptococci), meningitis, diphtheria, pneumonia .
- viruses: measles, mumps, chickenpox, cold
Name some pathogens that use the Genitourinary tract ?
- Genitourinary (also Urogenital) Tract
- Vagina, urethra ,sexually transmitted diseases (STDs)
e.g., syphilis, gonorrhea, chlamydia, herpes, AIDS, yeast infection
Names some pathogens involved in Trans-Placental and Birth Canal infections ?
Trans-Placental and Birth Canal Infections.Pathogens can cross the placenta.Fetus can become infected during pregnancy and parturition (the act of giving birth)
What types of pathogens usually use breaks in skin to transmit themselves ?
Clostridium tetani and tetanus, Herpes simplex type 1 and cold sores/fever blisters
What is colonization of a pathogen ?
The establishment of the pathogen at the appropriate portal of entry.
The establishment of a site of microbial reproduction on or within a host.
The presence of microorganisms in a site of the body that may lead to tissue damage and signs of disease.
What stage is colonization ?
what type of tissues do they usually attack ?
What are virulence factors ?
The first stage
Surfaces external to the environment
Structures involved in colonization are considered virulence factors
What type of structures are used for pathogens to adhere to the host site ?
Structures used in attachment
- -Adhesive slimes layers or capsules
- -Specialized receptors on viral surfaces (glycoprotein spikes)
- -Suckers, hooks, barbs (important for parasitic worms)
Explain Active mechanisms and Passive mechanisms for pathogens to penetrate defenses ?
Produce lytic enzymes that alter the host tissue.Destroy the extra cellular matrix or basement membranes.Degrade carbohydrate-protein complexes between cells.Disrupt cell surface molecules and their function
Passive mechanisms:Pre-existing tissue damage; e.g burns, ulcerations.Existing internalization methods; e.g endocytosis, phagocytosis
Are the following enzymes use for dissemination ?
have pathogens developed way to avoid the host defenses , why ?
- -To hide from the immune system.
- -To avoid destruction by immune cells.
- -To persist and multiply within the host.
- -The immune response becomes stronger as the microbial population increases
how do pathogens like diphtheria and botulism cause damage ?
What is cytopathic , Oncogenic , and Tetrogenic ?
- Cytopathic: resulting in cell death.
- Apoptosis/programmed cell death
- Oncogenic: cancer causing
- Teratogenic: damage to the fetus
Name some portals of exit ?
Respiratory and salivary: sneezing, coughing and spitting
- Skin: sweating
- Fecal: defecation
- Urogenital: urination
- Blood and bleeding
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