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41 Cards in this Set
- Front
- Back
What is normal microbiota?
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• Normal Microbiota- microorganisms colonizing the human body without harming it
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What are • Transient microbes?
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• Transient microbes- rapidly lost
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WHat are Pathogenic microbes?
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• Pathogenic microbes- invade and damage the cells and tissue
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How do we acquire resident biota?
As fetus-newborn. |
• The uterus is germ-free
• First exposure to microbes during the passage through the birth canal • Feeding • Contact with the environment and family members |
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How does an infection start and on what does it depend for success?
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• Infection starts with an invasion of a pathogen
• How successful this invasion will be depends on: o Pathogenicity- the ability of a microbe to cause disease in another organism - Virulence- the degree of pathogenicity; relative ability of a microbe to cause disease - Virulence factors (enzymes, toxins, capsule…) |
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How is an infection established?
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“Establishing the Infection”
• The microbes enter the body through- portal of entry • Attaching to the host • Surviving host defenses • Causing disease |
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What is the portal of entry of microorganisms into the body?
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“How Microorganisms enter a Host”
Portals of entry: • Mucous membrane (lines the body cavities that are open to the environment) • Skin (openings or cuts) |
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Describe agents that enter through the skin.
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“Infectious agents that enter the skin”
• Skin is a tough barrier • Broken skin enables penetration of microbes • The common infectious agents: o Staphylococcus o Streptococcus o Clostridium |
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What are ways of penetrating the skin?
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• Other ways of penetrating the skin
o Digestive enzyme of microbes o Insect bites o Hypodermic needles |
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what are the mucus membranes?
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• Mucus membranes (respiratory, gastrointestinal, genitourinary tract)
o Respiratory tract is the most common portal of entry. Inhalation (common cold, influenza, pneumonia, tuberculosis…) • Gastrointestinal tract- through food, water and contaminated hands • Genitourinary tract- through sexual contact (STD’s) |
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Is the number of invading microbes important?
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• A certain (minimal) number of microbes have to enter the body in order to cause an infection- infectious dose
• Infectious dose for: o Q fever- 1 cell o Tuberculosis- 10 cells o Gonorrhea- 1,000 cells o Cholera- 1,000,000,000 |
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True or false.
• Pathogens have preferred portal of entry |
True.
• Pathogens have preferred portal of entry o Ex: streptococcus that is : inhaled can cause pneumonia, when swallowed it does not show symptoms |
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How does a microorganism attach to the host?
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• Microorganisms attach themselves to the host cell through:
o Fimbriae (Bacteria) o Capsules (bacteria) o Spikes (viruses) |
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Describe the adherence in infections.
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“Adherence”
• Attachment is based on binding of specific molecules on both host and pathogen • Surface molecules of the pathogens bind to the specific molecules of host tissue cells • Ligands are located on Glycocalyx or on Fimbriae |
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How do microorganisms survive host defense?
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“Surviving Host Defense”
• Pathogenic microbes are recognized by white blood cells o Phagocytes • Phagocytes engulf and destroy the pathogen • Some microbes know how to evade Phagocytosis o Produce toxins that kill phagocytes o Produce capsule o Can survive inside the phagocyte |
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How Virulence Factors Contribute to Tissue Damage?
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“Causing Disease”
How Virulence Factors Contribute to Tissue Damage? • Virulence factors: o Exoenzymes and o Toxins directly affect the host tissue o Capsules |
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What are exoenzymes?
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“Exoenzymes”
• Some pathogens produce Exoenzymes that can dissolve structural chemicals in the body o Hyaluronidase- hydrolysis of hyaluronic acid, a substance that cements animal cells together o Kinases- digest the blood clots- formed to isolate the infection o Coagulases- coagulate (clot) the fibrinogen (protection against phagocytes) |
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What are the two types of bacterial toxins?
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• Exotoxins
o Actively excreted by a living bacterial cell • Endotoxins o Part of the cell wall of Gr- bacteria |
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Describe exotoxins.
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“Exotoxins”
• Are released from bacterial cells (Gr+ or Gr-) • They are proteins, some are enzymes Naming Exotoxins: • Hepatotoxins • Cytotoxins • Neurotoxins • Entertoxins • Botulinum toxin |
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What effects do Botulinum toxin- Clostridium Botulinum cause?
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• Botulinum toxin- Clostridium Botulinum
o Nuerotoxin that prevents the transmission of impulses from the nerve cell to the muscle o Flaccid paralysis |
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What effects do Tetanus toxin- Clostridium Tetani cause?
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• Tetanus toxin- Clostridium Tetani
o Blocks the relaxation pathway of muscles; uncontrollable muscle contraction |
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Describe endotoxins.
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“Endotoxins”
• Is part of the outer layer of the cell wall of Gr- bacteria • Endotoxins are Lipopolysaccharides • Endotoxin has to be released from the cell wall in order to cause the symptoms • The symptoms are: chills, fever, weakness aches, shock and even death |
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How is the potency of a toxin expressed?
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“Potency of Toxin”
• Expressed as lethal Dose- LD50 - Botulinum toxin- 0.03 ng/kg (mice) - Shiga toxin- 250 ng/kg |
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FIll in the blanks.
• Microbial toxins can cause: |
• Microbial toxins can cause:
- Fever, diarrhea, cardiovascular disturbance, shock , inhibition of protein synthesis, disrupt the nervous system |
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What are the three types (patterns) of infection?
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“The Patterns of Infection”
• Localized infection- infection that is limited to a small area of body (abscesses) • Systemic infection- microbes are spread throughout the body (measles) • Focal infection- infectious agent migrates from a local infection to other tissues • Mixed (polymicrobial) infection- more than one infectious agent is involved • Primary infection- infection that causes the initial illness • Secondary infection- infection by opportunistic pathogen • Acute infection- develops rapidly but lasts a short time (influenza) • Chronic infection- develops slowly but lasts for long period of time |
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What are the stages of clinical infections?
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“Stages of Clinical Infections”
• Incubation period- time period between initial infection and first symptoms of disease (several hours in pneumonic plague; several years leprosy) • Prodromal stage- feeling of discomfort (1-2 days) • Period of invasion- expression of all symptoms • Convalescent period- decline of symptoms- recovery |
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What are the symptoms and signs of an infection?
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• Inflammation- swelling of the tissue
o Edema- accumulation of fluid o Granulomas and abscesses- walled-off cells of damaged cells and microbes o Rashes, skin eruption • Signs of infection in the blood o Leukocyotsis- increased level of blood cells o Bacteremia- bacteria present in the blood; do not multiply o Septicemia- microorganisms multiply in the blood • Unnoticed infections o Asymptomatic, subclinical |
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What are the portals of exit of an infectious microorganism?
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“The Portal of Exit”
The discharged microorganisms are the source of a new infection • Respiratory or salivary portals • Skin • Fecal exit • Urogenital tract • Blood • Respiratory or salivary portals o Moist secretion-coughing, sneezing, laughing and talking • Fecal o Intestinal infection causes rapid peristalsis- diarrhea • Urogenital tract o Vaginal discharge, semen, urine • Blood o When removed for testing purposes or when released during tissue injury |
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What are the two reservoirs from which a microbe can start an infection?
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• Microbes start an infection from the reservoirs
• Reservoir: o Living reservoir - Human body - Animal body o Non-living reservoir - Soil - Water - Plants |
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What is the source of infection of a living reservoir?
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“Living Reservoirs”
Source of infection: • Diseased person or animal • Carrier- people that harbor pathogens without any signs of illness o Incubation carriers- spreads the disease during the incubation period o Convalescent carriers- recuperating patients o Chronic carries- carry the agent for long period of time o Passive carriers- medical personnel |
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How do animals act as reservoirs?
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“Animals as Reservoirs”
• Animals are vectors- they transmit the infectious agent from one organism to another • Biological vectors o The agent multiplies within the vector • Mechanical vectors o Mechanically transmits the agent to food or directly to humans |
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What are Communicable diseases?
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• Communicable diseases- infected host transmits the agent to another host
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What are Non-communicable diseases?
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• Non-communicable diseases- infection acquired through:
o Contact with an agent from its own body o From nonliving reservoir |
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Describe contact transmission of infection.
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• Contact transmission- microbes directly transferred
o STDs o Droplet contact- sneezing |
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Describe indirect transmission of infection.
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• Indirect transmission
o Contaminated materials - Vehicle: food water, biological products and fomites o Air as vehicle - Droplet nuclei- dried material (mucus) generated by sneezing |
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what is a nosocomial infection?
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“Nosocomial Infectious- hospital acquired”
• 5-15% of hospital patients acquire nosocomial infection • Factors responsible for nosocomial infections: o The characteristics of microbes in the Hospital o Weakened status of the hosts • Patients are compromised by: o Broken skin or mucous membranes o Suppressed immune system • Chain of transmission o Transmission from hospital staff to patient o From patient to patient o From fomites to patients o Through ventilation system |
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What is epidemiology?
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“Epidemiology”
Study of frequency and distribution of disease in human population • Frequency of cases: o Incidence of a disease- number of new cases of a disease during a given time interval, usually one year • Prevalence of a disease- total number of current cases in the entire population regardless of when it first appeared |
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What is an endemic disease?
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• Endemic disease- constantly present in a population
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What is a Sporadic disease?
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• Sporadic disease- occurs occasionally
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What is an Epidemic disease?
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• Epidemic disease- many people in a given area acquire a disease in a short period of time
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What is a Pandemic disease?
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• Pandemic disease- epidemic disease but occurs in a large geographic region
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