nature of disease introduction - definitions normal bacteria & host koch’s postulates patterns...
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Nature of DiseaseNature of DiseaseIntroduction - DefinitionsNormal Bacteria & Host
Koch’s PostulatesPatterns of DiseaseSpread of Infection
Nosocomial Infections
Disease - IntroductionDisease - 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
Disease - IntroductionDisease - 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
Disease - Normal BacteriaDisease - 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
Disease - Normal BacteriaDisease - Normal Bacteria
Skin– S. epidermidis/S. aureus
Gastrointestinal Tract– Gram negative bacteria (large
intestine)– Streptococcus. mutans (mouth)
Genito-Urinary Tract– Lactobacillus
Disease - Normal BacteriaDisease - 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
Disease - Koch’s Disease - Koch’s PostulatesPostulates Etiology or cause established using
Koch’s 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
Disease - PatternsDisease - Patterns
Predisposing factors make hosts more susceptible & include:– age– gender– climate– level of fatigue– nutrition
Disease - Patterns - Disease - Patterns - DevelopmentDevelopment Incubation period - time between
infection & first signs Prodromal period - first mild signs Illness period - period when all
symptoms are present Decline period Convalescence period
Disease - Spread of Disease - Spread of InfectionInfection 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
Disease - Spread of Disease - Spread of InfectionInfection Transmission
– Direct contact– Fomites - inanimate objects– Droplet - saliva, mucus coughing or
sneezing– Medium - food, water air– Airborne - carried > 1 meter– Arthropod - insect vectors
Disease - Nosocomial Disease - Nosocomial InfectionInfection 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
Disease - Nosocomial Disease - Nosocomial InfectionInfection Compromised host
– burns– wounds– immune suppressed (disease or
drugs) Chain of Transmission
– Direct contact– Fomites
Disease - Nosocomial Disease - Nosocomial InfectionInfection Control
– Aseptic techniques– Proper cleaning storage– Maintenance– Properly trained staff
Problems– Multiple drug resistance– Nonuse of effective cleaning agents– Training of staff