MICROBIOLOGY INFECTION AND DISEASE

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MICROBIOLOGYINFECTION AND DISEASE
Edward Jenner

• Instructor
• Terry Wiseth
• Northland Community Technical College

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POPULATIONS OF MICROORGANISMS

•  The number of organisms at a site is determined
  by
• The amount of oxygen
• pH
• Other organisms
• Nutrients
• Immune response of thehost
• Availability of receptors for organisms

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SYMBIOSIS

• Interaction between 2 organisms
• Mutualism - Both benefit
• Commensalism - One benefits while the other,
  neither benefits nor is harmed

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SYMBIOSIS

• Synergism - Together both can accomplish what
  neither can achieve alone
• Parasitism - One benefits and causes harm to the
  other

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PATHOGENICITY

• Colonizer
• Organism that live with a host without causing an
  immune or allergic response
• Pathogenic
• Organisms that cause disease

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VIRULENCE

• a quantitative measure of pathogenicity
• measured in
• Infectious dose (ID50)
• the number of organisms that will cause disease
  in 50 of test animals
• Lethal dose (LD50)
• the number of organisms that will cause death in
  50 of test animals

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ATTENUATION

• Loss or reduction of virulence
• Organisms can be treated with agents to achieve
  attenuation in order to be used as vaccines

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CARRIERS

• Some individuals can be infected by a pathogen,
  but show no symptoms

Typhoid carrier Rosina Bryans was held in an
insane asylum for 60 years even though never
insane
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SYSTEMIC

• Organisms spreading through the body

Systemic Staph Infection
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TYPES OF DISEASES

• Chronic disease
• microbial persistence in the host
• with symptoms over a long period

TINEA PEDIS ATHLETES FOOT
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TYPES OF DISEASES

• Acute disease
• Symptoms appear quickly
• become intense and subside when the host's immune
  system disposes of the pathogen and toxic products

MORBILLIVIRUS causative agents of measles
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STAGES OF ACUTE DISEASE

• 1) Incubation
• From the time organisms enter the hosts until the
  first symptoms appear

Open Wound not currently infected
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STAGES OF ACUTE DISEASE

• 2) Prodromal
• Symptoms indicate the onset of disease
• e.g. Malaise, headache, fever, etc..

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STAGES OF ACUTE DISEASE

• 3) Acme (Acute)
• Symptoms are at their peak and there is an immune
  response by the host

Acute stage of Small pox infection
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STAGES OF ACUTE DISEASE

• 4) Period of decline
• A recovery period with the decline of symptoms
  and, their is maximum antibody levels in the host

Chicken Pox Scar
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STAGES OF ACUTE DISEASE

• 5) Convalescence
• The body returns to normal

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SOURCE OF DISEASE

• For organisms to be pathogenic they require
• a site to maintain their ability to infect and
  replicate
• Such a place is called a Reservoir
• The object, place or person from which organisms
  pass to the host is called the Source
• Sometimes reservoir and source are the same

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HUMAN SOURCE

• Convalescent carriers
• are recovering from a disease
• Healthy carriers
• do not show symptoms of the disease but harbor
  the organisms

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ANIMAL SOURCE

• Zoonosis
• e.g. Rabies, Plague

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INSECT SOURCE

• Mechanical vectors
• Organisms are carried on the appendages of the
  insect

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INSECT SOURCE

• Biological vectors
• Insects are the reservoir of the organisms and
  transmit them to humans or animals
• Insects are required for at least part of the
  developmental cycle of the organism

Malaria is dependent on part of its development
in the gut of the mosquito
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INANMIMATE RESERVOIR

• Soil, water and food
• Spores can be inhaled, then germinate, multiply
  and produce disease

Anthrax is inhaled to the alveoli where they
germinate and cause disease
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INANMIMATE RESERVOIR

• Some bacteria that produce harmful toxins are
  indigenous to the soil
• e.g. Clostridium
• Pathogens can be passed into water and live in
  fish and shell fish
• Food is a reservoir for agents infectious to man

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TRANSMISSION OF INFECTIOUS ORGANISMS

• contact
• water
• food
• fomites
• air

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CONTACT

• Direct
• From person to person by close association
• e.g. kissing, sexual contact, sneezing etc..

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CONTACT

• Indirect
• From one person to another through intermediates
  such as food, dust, water or fomites

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WATER

• can be fecally contaminated
• Besides drinking, water borne pathogens can also
  enter the body through sweat glands, abraded skin
  etc..

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FOOD

• Analysis must confirm the food as the source of
  the disease
• Factors that contribute to food infections are
• Improper storage temperatures
• poor hygiene
• contaminated equipment
• inadequate cooking

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FOMITES

• Inanimate objects, other than food and water
• e.g. Catheters, needles etc..

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AIR

• not a reservoir but is a means of transmission
• e.g. coughing and sneezing

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PATTERNS OF DISEASE

• Endemic
• A continuous subepidemic level of disease in a
  specified community
• Outbreak
• A slight increase in the level of disease over
  endemic level

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PATTERNS OF DISEASE

• Epidemic
• A large number of new cases of a disease, in a
  defined time, above the endemic level

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PATTERNS OF DISEASE

• Pandemic
• World Wide epidemics
• Sporadic
• Disease occurs in an irregular pattern therefore
  no frequency can be calculated

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ENDINFECTION AND DISEASE