Nature of Disease

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Nature of Disease

• Introduction - Definitions
• Normal Bacteria Host
• Kochs Postulates
• Patterns of Disease
• Spread of Infection
• Nosocomial Infections

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Disease - Introduction

• Pathogens - disease causing with special
  properties that permit host invasion
• Disease - when microorganism overcomes host
  defenses an abnormal physiological state
• Pathology - the study of disease

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Disease - Introduction

• Infection - invasion growth of pathogen in
  host systemic vs. localized
• Pathogenesis the study of the development of
  disease
• Etiology the study of the cause of disease

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Disease - Normal Bacteria

• Animals - germ free in utero but are colonized
  almost immediately after birth
• Different bacteria are normally associated with
  different parts of body
• Transients - microorganisms that may occasionally
  be found associated with the host

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Disease - Normal Bacteria

• Skin
• S. epidermidis/S. aureus
• Gastrointestinal Tract
• Gram negative bacteria (large intestine)
• Streptococcus. mutans (mouth)
• Genito-Urinary Tract
• Lactobacillus

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Disease - Normal Bacteria

• Antagonism - normal bacteria prevent growth of
  others
• Bacteria and host have symbiotic relationship
  (living together)
• Three types of symbiosis
• Commensalism (one benefits)
• Mutalism (both benefit)
• Parasitism (one benefits other harmed)
• Opportunistic - do not cause disease normally

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Disease - Kochs Postulates

• Etiology or cause established using Kochs
  postulates
• same pathogen present in every instance of
  disease
• pathogen isolated in pure culture
• isolated pathogen causes disease when
  reintroduced into a healthy host
• pathogen re-isolated from the now diseased host

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Disease - Patterns

• Predisposing factors make hosts more susceptible
  include
• age
• gender
• climate
• level of fatigue
• nutrition

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Disease - Patterns - Development

• Incubation period - time between infection
  first signs
• Prodromal period - first mild signs
• Illness period - period when all symptoms are
  present
• Decline period
• Convalescence period

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Disease - Spread of Infection

• Reservoirs of Infection
• a continuing source of infection
• Reservoirs include
• Human - people who have disease or are carriers
  (infected but no symptoms)
• Zoonoses - wild or domestic animals that transmit
  disease to humans
• Nonliving - soil water

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Disease - Spread of Infection

• Transmission
• Direct contact
• Fomites - inanimate objects
• Droplet - saliva, mucus coughing or sneezing
• Medium - food, water air
• Airborne - carried gt 1 meter
• Arthropod - insect vectors

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Disease - Nosocomial Infection

• Acquired during hospitalization or a stay in
  other health care facilities
• Occurs at 5-15
• Can be normal organisms introduced into wrong
  part of body during invasive procedures
• Opportunitic drug resistant G-, e.g. Pseudomonas

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Disease - Nosocomial Infection

• Compromised host
• burns
• wounds
• immune suppressed (disease or drugs)
• Chain of Transmission
• Direct contact
• Fomites

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Disease - Nosocomial Infection

• Control
• Aseptic techniques
• Proper cleaning storage
• Maintenance
• Properly trained staff
• Problems
• Multiple drug resistance
• Nonuse of effective cleaning agents
• Training of staff

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