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Chapter 6:Microbe-Human
Interactions:
Infection and Disease
Lecturer: Eng. Mohamed Ali, B.s.c & M. Eng.
College of Agricul...
Chapter 6 Contents:
1. Normal Microflora
2. Progress of Infection
a) Pathogenicity
b) Portals of entry
c) Mode of Transmis...
1- NORMAL MCIR0FLORA
3
Human Host (normal flora)
- Human body constant contact with
microbe, some invade & multiply in body
- wide range of micro...
Normal Flora
• microbes that are normally found on or in the
human body without causing disease.
• internal organs & tissu...
6
7
Resident Flora
• Bacterial flora benefit host by preventing
overgrowth of harmful microbes –
microbial antagonism
• Endoge...
normal flora
• Beneficial outcome
– Removed by immune system
– Microbial antagonism
• Adverse effects
– Escape immune syst...
The benefits and adverse effects of microbial contact.
Association between microbes and humans.
10
2-Progress of infection: Major Factors in the
Development of an Infection
11
Progress of an Infection:
a) Pathogenicity
b) Portals of entry
c) Mode of Transmission
d) Process of infections and diseas...
a) Pathogenicity
Pathogenicity: Ability of microbes to cause
infection
Virulence : degree to which microbe can
invade and ...
True or opportunistic pathogen
• True pathogen: Cause disease in healthy
individuals
• Associated with a specific and
reco...
Factors that predispose a person to infections.
Factors that weaken host defenses and increase susceptibility to infection...
b) Portals of entry
• Microbes enter in body
by various transmission
methods
• Most pathogens have
specific portals on ent...
Skin
• example:
mosquito bite
skin and
cause Malaria
• enters body
through bite
skin
17
Gastrointestinal tract
• Salmonella, Shigella, Vibrio
• Viruses – polio, hepatitis A
• Protozoan – Giardia lamblia
• Enter...
Respiratory tract
• Streptococcus pneumoniae
– Sore throat, meningitis
• Fungi – Cryptococcus
– pneumonia
19
Urogenital
• Numerous sexual transmitted diseases (STDs)
• Virus – human papillomavirus
– Genital warts
• Protozoan – Tric...
Common STDs which include viruses, protozoan, fungi,
and bacteria.
21
Placenta
• Some bacteria can penetrate the placenta
barrier
– Syphilis spirochete
• Birth canal
– Herpes simplex virus
22
A fetus can acquire an infection from the mother via transplacental
infections.
Transplacental infection of the fetus.
23
1) Contact Transmission
a) Direct Contact Transmission
 Person to person transmission. No intermediate
object is involved...
25
2) Vehicle Transmission:
 Transmission of disease via
medium such as water, food, air,
blood, body fluids, and
intravenou...
3) Vector Transmission
 Animals that carry disease from one host to another,
Arthropods (insects) are most important anim...
A mosquito is a biological vector and the common
house fly is a mechanical vector.
Two types of vectors.
28
D) The Process of Infection &
Disease
• 4 distinct stages of clinical infections:
– Incubation period – time from initial ...
30
Process of infections and
disease
1- Establishment:
Patterns of infection
2-Signs and symptoms:
Earliest symptoms of disea...
Infection are classified by
a. Whether they remain at the site of
inoculation (localized infection, systemic
infection, fo...
A) Patterns of infection:
• Localized infection – microbes enter the body and
remains confined to a specific tissue e-g bo...
34
Establishment of infections vary depending on location,
type of microbe, and length of time.
The occurrence of infections ...
• Sign of infection refer to the objective evidence of
infection
• Symptom of the infection refer to subjective evidence
–...
Some commons signs and symptoms associated with
infectious diseases.
Common signs and symptoms of infectious diseases
37
E) Portal of exit
• Enables pathogen to spread to other hosts
– Respiratory
– Salivary
– Skin
– Fecal
– Urogenital
– Blood...
Site at which microbes leave body. Most commonSite at which microbes leave body. Most common
exit portals are respiratory ...
c) Urogenital Tract
– Exit in secretions of urine
c) Skin and Wound infections
– Spread through direct contact or through ...
Representation of the different portals of exit.
Major portals of exit of infectious diseases.
41
• Hygiene refers to conditions and practices that help to maintain health
and prevent the spread of diseases. Medical hygi...
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Chapter 6 microbe human interaction

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Chapter 6 microbe human interaction

  1. 1. Chapter 6:Microbe-Human Interactions: Infection and Disease Lecturer: Eng. Mohamed Ali, B.s.c & M. Eng. College of Agriculture, University of Hargeisa. Course: Microbiology 1
  2. 2. Chapter 6 Contents: 1. Normal Microflora 2. Progress of Infection a) Pathogenicity b) Portals of entry c) Mode of Transmission d) Process of infections and disease e) Portals of exit 3. Disease Prevention: Hygiene 2
  3. 3. 1- NORMAL MCIR0FLORA 3
  4. 4. Human Host (normal flora) - Human body constant contact with microbe, some invade & multiply in body - wide range of microbe can inhabit our body - What is normal flora? - Microbes that inhabit in our body but do not harm the host 4
  5. 5. Normal Flora • microbes that are normally found on or in the human body without causing disease. • internal organs & tissues & fluids are microbe-free (no flora microbes available in our sterile part of our the body- eig internal organs). • Normal Flora is harmful if they reached the sterile part of our body e-g internal organs • Bacterial flora benefit host by preventing overgrowth of harmful microbes 5
  6. 6. 6
  7. 7. 7
  8. 8. Resident Flora • Bacterial flora benefit host by preventing overgrowth of harmful microbes – microbial antagonism • Endogenous infections – occur when normal flora is introduced to a site that was previously sterile, and it cause disease. • Pathogen: Microorganism capable cause a disease. 8
  9. 9. normal flora • Beneficial outcome – Removed by immune system – Microbial antagonism • Adverse effects – Escape immune system – Multiply and disrupt sterile tissue – Cause a disease to internal organs 9
  10. 10. The benefits and adverse effects of microbial contact. Association between microbes and humans. 10
  11. 11. 2-Progress of infection: Major Factors in the Development of an Infection 11
  12. 12. Progress of an Infection: a) Pathogenicity b) Portals of entry c) Mode of Transmission d) Process of infections and disease e) Portals of exit 12
  13. 13. a) Pathogenicity Pathogenicity: Ability of microbes to cause infection Virulence : degree to which microbe can invade and damage host tissue Two types of virulence: • True pathogens • Opportunistic pathogens 13
  14. 14. True or opportunistic pathogen • True pathogen: Cause disease in healthy individuals • Associated with a specific and recognizable disease. E-g – Influenza virus, plague bacillus, malarial protozoan • Opportunistic Pathogen: • Cause disease in immune compromised host • Gain access (injury) to sterile regions 14
  15. 15. Factors that predispose a person to infections. Factors that weaken host defenses and increase susceptibility to infections15
  16. 16. b) Portals of entry • Microbes enter in body by various transmission methods • Most pathogens have specific portals on entry 1) Skin 2) Gastrointestinal tract 3) Respiratory tract 4) Urogenital 5) Placenta 16
  17. 17. Skin • example: mosquito bite skin and cause Malaria • enters body through bite skin 17
  18. 18. Gastrointestinal tract • Salmonella, Shigella, Vibrio • Viruses – polio, hepatitis A • Protozoan – Giardia lamblia • Enter via ingestion or the anal route 18
  19. 19. Respiratory tract • Streptococcus pneumoniae – Sore throat, meningitis • Fungi – Cryptococcus – pneumonia 19
  20. 20. Urogenital • Numerous sexual transmitted diseases (STDs) • Virus – human papillomavirus – Genital warts • Protozoan – Trichomonas – trichomoniasis • Bacteria – Neisseriagonorrhoeae – Gonorrhea • Acquire by intercourse or intimate contact 20
  21. 21. Common STDs which include viruses, protozoan, fungi, and bacteria. 21
  22. 22. Placenta • Some bacteria can penetrate the placenta barrier – Syphilis spirochete • Birth canal – Herpes simplex virus 22
  23. 23. A fetus can acquire an infection from the mother via transplacental infections. Transplacental infection of the fetus. 23
  24. 24. 1) Contact Transmission a) Direct Contact Transmission  Person to person transmission. No intermediate object is involved.  Examples: Touching, kissing. a) Indirect Contact Transmission  Agent is transferred via a nonliving object.  Examples: towels, eating utensils, thermometers, stethoscopes, bedding, clothes, money, and syringes. a) Droplet Transmission  Microbes are spread in mucus droplets that travel short distance (less than 1 meter).  Examples: sneezing, coughing, talking and laughing. C) Mode of Transmission 24
  25. 25. 25
  26. 26. 2) Vehicle Transmission:  Transmission of disease via medium such as water, food, air, blood, body fluids, and intravenous fluids. a) Waterborne Transmission  Usually caused by water contaminated with sewage. a) Airborne Transmission  Spread of agents by droplets in dust that travel more than 1m to host Mode of Transmission 26
  27. 27. 3) Vector Transmission  Animals that carry disease from one host to another, Arthropods (insects) are most important animal vectors. a) Mechanical Transmission  Passive transport of pathogens on insect’s body. For example, Bee a) Biological Transmission  Pathogen spends part of its life cycle in the vector. For example, Mosquito Mode of Transmission 27
  28. 28. A mosquito is a biological vector and the common house fly is a mechanical vector. Two types of vectors. 28
  29. 29. D) The Process of Infection & Disease • 4 distinct stages of clinical infections: – Incubation period – time from initial contact with the infectious agent to the appearance of first symptoms; agent is multiplying but damage is insufficient to cause symptoms; several hours to several years – Prodromal stage – vague feelings of discomfort; nonspecific complaints – Period of invasion – multiplies at high levels, becomes well-established; more specific signs and symptoms – Convalescent period – as person begins to respond to the infection, symptoms decline 29
  30. 30. 30
  31. 31. Process of infections and disease 1- Establishment: Patterns of infection 2-Signs and symptoms: Earliest symptoms of disease as a result of the activation of the body defenses 31
  32. 32. Infection are classified by a. Whether they remain at the site of inoculation (localized infection, systemic infection, focal infection) b. Number of microbes involved in infection and the order in which they infect the body (mixed infection, primary infection, secondary infection) c. Persistence of the infection (acute infection, chronic infection, subacute infection) 32
  33. 33. A) Patterns of infection: • Localized infection – microbes enter the body and remains confined to a specific tissue e-g boil • Systemic infection – infection spreads to several sites and tissue fluids usually in the bloodstream e- g influenza • Focal infection – when infectious agent breaks loose from a local infection and is carried to other tissues B) Number of microbes involved: • Mixed microbe: several microbes grow simultaneously at the infection site • Primary and secondary: initial and another infection Establishment 33
  34. 34. 34
  35. 35. Establishment of infections vary depending on location, type of microbe, and length of time. The occurrence of infections with regard to location, type of microbe and length of time. 35
  36. 36. • Sign of infection refer to the objective evidence of infection • Symptom of the infection refer to subjective evidence – Inflammation – fever, pain, soreness, swelling • Syndrome is a disease that manifests as a predictable complex of symptom • After the initial infection pathogens may remain in the body in a latent state and may later cause recurrent infections • Microbes are release from the body through a specific portal of exit that allows them access to another host Signs and symptoms 36
  37. 37. Some commons signs and symptoms associated with infectious diseases. Common signs and symptoms of infectious diseases 37
  38. 38. E) Portal of exit • Enables pathogen to spread to other hosts – Respiratory – Salivary – Skin – Fecal – Urogenital – Blood 38
  39. 39. Site at which microbes leave body. Most commonSite at which microbes leave body. Most common exit portals are respiratory and gastrointestinal tracts.exit portals are respiratory and gastrointestinal tracts. a) Respiratory Tract (Saliva): – Exit in discharges (mucus droplets) from nose and mouth. Transmission by coughing, sneezing, spitting, etc. – Examples: Tuberculosis, influenza etc. a) Gastrointestinal Tract (fecal): – Exit in feces or sliva. – Feces: Cholera, typhoid fever, salmonella. – Saliva: Rabies virus, herpes simplex 1. Portal of Exit 39
  40. 40. c) Urogenital Tract – Exit in secretions of urine c) Skin and Wound infections – Spread through direct contact or through fomites. c) Blood – Transmission through insects, needles, and syringes. • Insects: Malaria, yellow fever etc. • Needles: AIDS and Hepatitis B. Portal of Exit 40
  41. 41. Representation of the different portals of exit. Major portals of exit of infectious diseases. 41
  42. 42. • Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases. Medical hygiene therefore includes a specific set of practices associated with this preservation of health, for example environmental cleaning, sterilization of equipment, hand hygiene, water and sanitation and safe disposal of medical waste. Disease Prevention - Hygiene UseUse antimicrobialantimicrobial agentsagents 42

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