Chpt 14 Principles of Disease and Epidemiology

Principles of Disease and Epidemiology
Chapter 14

I Pathology, Infection, and Disease
A. Pathology: the scientific study of disease
1. etiology: the cause of disease
2. pathogenesis: the manner in which a disease develops
B. Infection: invasion or colonization of the body (host) by potentially pathogenic microorganisms.
C. Disease: any change from a state of health. An abnormal state in which the body is not properly adjusted or capable of performing its normal functions.
II Normal Microbiota (flora): the microorganisms that establish permanent residence (colonize) but that do not produce disease under normal conditions.
A. Protect the host by:
1. occupying niches that pathogens might occupy.
2. producing acids
3. Microbial antagonism (competitive exclusion): A phenomenon in which normal microbiota can benefit the host by preventing the overgrowth of harmful microorganisms.
a. Example: bacteriocins by E. coli dells in the large intestine, which inhibits pathogens such as Salmonella and Shigella.
b. symbiosis: the relationship between normal microbiota of a healthy person and the person.
i. commensalism: one organism benefiting, the other unaffected.
ii. mutualism: both parties benefiting
iii. parasitism: one organism benefited a the expense of the other.
B. Types:
1. gram + (aerobe)
a. Staphylococcus
b. Streptococcus
c. Candida
2. gram – (facultative anaerobe)
a. E. coli
b. Klebsiella
c. Proteus
d. Lactobacillus
e. Candida (listed under positive and negative)
C. Opportunistic Microorganisms (pathogens): They ordinarily do not cause disease in the normal habitat of a healthy person, but may do so in a different environment.
1. in the immunocompromised cell
2. as a result of a reduction in microbial microflora (as in broad spectrum antibiotics)
3. when introduced into an abnormal area of the body
4. Types:
a. E. coli.
D. Synergism: two microbes acting together have a greater effect than either acting alone.
1. probiotics: live bacterial cultures administered for beneficial effects.
2. prebiotics: chemicals administered to promote their growth.
III Etiology of Infectious Disease (did not cover this)
IV Classifying Infectious Diseases
A. Symptoms (did not cover)
B. Communicable Disease: spread directly or indirectly from one host to another.
1. contagious disease: easily spread
C. Noncommunicable diseases: not spread between hosts
D. Occurrence of a disease:
1. Endemic: disease constantly present in a population
2. Epidemic: Disease acquired by many hosts in a given area in a short time
3. Pandemic: worldwide epidemic
4. Sporadic: occurs only occasionally
E. Severity or duration (did not cover)
F. Extent of Host Involvement
1. Local infection: one in which the invading microorganisms are limited to a relatively small area of the body. (boil)
2. Systemic infection (generalized): spread throughout the body by the blood or lymphatic system.
3. Sepsis: toxic, inflammatory condition arising from the spread of bacteria or bacterial toxins from a focus of infection.
a. Septicemia: pathogens in the blood stream
i. bacteremia: bacteria pathogens in the blood
b. Toxemia: presence of toxins in the blood
V Patterns of Disease (did not cover)
VI Spread of Infection
A. Resevoirs of infection: a continual source of the pathogen
1. Human (carriers) AIDS
2. Animal (zoonoses) Rabies
3. Nonliving: soil, water. Botulism
B. Transmission of disease
1. Contact
a. direct: kissing, intercourse. Requires close association between carrier and host.
b. droplet: less than a meter (airborne)
c. indirect: involves a nonliving object such as a cup. (fomite) Syringe
2. Vehicle: inanimate reservoirs such as food, water or blood.
a. Oral-fecal
b. foodborn
c. airborne: when droplets or dust travel distance of more than a meter.
d. waterborne
3. Vectors: animals that carry pathogens from one host to another.
a. mechanical transmission: vectors carry pathogens on their bodies to food that is later swallowed by the host.
b. biological transmission: passed in a bite, or feces which later enter the wound caused by the vector.
VII Nococomial (hospital acquired) infections: one not evident or present at admission to a hospital but acquired as a result of a hospital stay.
A. 5 – 15% of all hospital patients acquire nosocomial infections.
B. Reasons:
1. Microorganisms in hospital environment
2. Compromised host
a. poor immunity
b. antibiotic resisitant drugs
3. Chain of transmission
VIII Emerging Infectious Diseases: new or changing diseases showing an increase of incidence in the recent past or a potential for increase in the near future.
A. Contributing factors:
1. evolution of new strains
2. changes in weather patterns
a. Malaria
3. Modern transportation
a. West Nile Virus
4. Ecological disaster
5. Animal control measures
a. Lyme disease
6. Public health failure
IX Epidemiology: the science that deals with the transmission of diseases in the human population, and where and when they occur. (did not cover different kinds)