Principles of Disease and Epidemiology |
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21. Define reservoir. 22. List the five types of reservoirs. 23. List the seven mechanisms of disease transmission. 24. 25. Define nosocomial infections. 26. List the three major determinants of nosocomial infections. 27. List the sources of microorganisms involved in nosocomial infections. 28. List the common bacterial causes of nosocomial infections. 29. Describe the role of the compromised host in nosocomial infections. 30. Describe the chain of transmission in nosocomial infections. 31. Describe the control of nosocomial infections. 32. Define predisposing factors.
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A continual source of infection is called a reservoir of infection.
Living Reservoirs
Human reservoirs of infection:
- People who have a disease.
- People who are carriers of pathogenic microorganisms.
Zoonoses are diseases that affect wild and domestic animals and can be transmitted to humans.
Nonliving Reservoirs
Soil (fungi, C. botulinum, C. tetani)
Water (V. cholerae, S. typhi, protozoans, algae)
Improperly prepared or stored foods (trichinosis and salmonellosis)
Contact Transmission
Direct contact (person-to-person) involves close physical contact between the source of the disease and a susceptible host (sexual contact falls into this category, n’est-ce pas?).
Indirect contact involves transmission by fomites (inanimate objects).
Droplet transmission is transmission via droplet nuclei (mucus droplets) in coughing or sneezing, laughing or talking.
Vehicle Transmission
Common vehicle transmission is transmission by a medium such as water, food or air.
- Waterborne
- Foodborne
- Airborne - pathogens are carried on droplet nuclei in dust for a distance greater than 1 meter.
Vector Transmission
Arthropod vectors carry pathogens from one host to another by both mechanical and biological transmission.
- Mechanical transmission is the passive transport of a pathogen on a vector 's feet or other body parts.
- Biological transmission involves reproduction of the pathogen in the vector and transmission in saliva or feces.
Contact Transmission | |||
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a) direct contact |
b) prevention of contact transmission |
c) indirect contact |
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d) droplet |
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Vehicle Transmission |
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a) water |
b) food |
c) air |
Vectors of Disease |
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Mechanical Transmission |
A nosocomial infection is any infection that is acquired during the course of stay in a hospital, nursing home, or other health care facility.
About 5-15% or all hospitalized patients acquire nosocomial infections.
Three factors contribute to nosocomial infections:
Certain normal microbiota are often responsible for nosocomial infection when they are introduced into the body through such medical procedures as surgery and catheterization.
Opportunistic, drug-resistant gram-negative bacteria are the most frequent causes of nosocomial infections.
Patients with burns, surgical wounds, and suppressed immune systems are the most susceptible to nosocomial infections.
Nosocomial infections are transmitted by direct contact between staff members and patients and between patients.
Fomites such as catheters, syringes, and respiratory devices can transmit nosocomial infections.
Aseptic techniques can prevent nosocomial infections.
Hospital infection control staff members are responsible for overseeing the proper cleaning, storage, and handling of equipment and supplies.
New diseases and diseases with increasing incidences are called emerging infectious diseases (EIDs).
EIDs can result from the use of antibiotics and pesticides, climatic changes, travel, the lack of vaccination, and insufficient case reporting.
The CDC, NIH, and WHO are responsible for surveillance and responses to emerging infectious diseases.
