Principles of Disease and Epidemiology

Host and Microbe A delicate relationship exists between pathogenic microorganisms and body defenses. When the defenses resist the pathogens, the body remains healthy. But when the pathogens overcome the defenses, the result is disease. Once disease has been established, the infected individual may suffer temporary or permanent damage or may experience death. The outcome depends upon many factors attending the episode of disease.

Relationships The normal flora is the population of microorganisms found where the body tissues interface with the environment. Much of the normal flora is permanent, but some portions are transient. The transient flora is present for a time and then disappears.

Relationships Symbiosis, a term that means living together. In some cases, the symbiosis is further identified as a commensalism, when one organism benefits and the other remains unaffected. A type of symbiosis called mutualism exists when both organisms benefit one another. A symbiosis called parasitism develops when one organism damages the other

Relationships Opportunistic organisms are potentially pathogenic organisms that normally do not cause disease. However, in a compromised host, the organisms may see “opportunity” to invade the tissues. An example occurs in individuals who have AIDS. Opportunistic organisms such as Pneumocystis carinii invade the lung tissues and cause a lethal pneumonia.

How Infection Travels

Epidemiology and Public Health Epidemiology: The branch of medicine that deals with the incidence, distribution, and control of diseases. Public health is "the science and art of preventing disease, prolonging life and... or infirmity", as defined by the United Nations' World Health Organization. Webster-The art and science dealing with the protection and improvement of community health by organized community effort and including preventive medicine and sanitary and social science he study of factors influencing, distribution, prevention and control of disease in a defined population

The World Clock and NKY ck/ ck/ ation/show.aspx?loc=19 ation/show.aspx?loc=19

Nosocomial or Hospital Acquired nos·o·co·mi·al (ns-km-l) adj. 1. Of or relating to a hospital. 2. Of or being a secondary disorder associated with being treated in a hospital but unrelated to the patient's primary condition. TYPES OF NOSOCOMIAL INFECTIONS.ppt TYPES OF NOSOCOMIAL INFECTIONS.ppt xa.yimg.com/kq/.../TYPES+OF+NOSOCOMIAL+IN FECTIONS.ppt

Four most common types of Nosocomial infections: 1.UTI 2.SSI 3.Nosocomial Pneumonia 4.Nosocomial Bacteremia

Urinary Tract Infection 80% associated with the use of indwelling catheters Associated with less morbidity – Gram-negative enterics, 50% – Fungi, 25% – Enterococci, 10%

Surgical Site Infection Are also frequent – 15% Presence of purulent discharge around the wound or the insertion site of a drain or – Presence of cellulites which is emanating from the wound Patients acquire infection either endogenously or exogenously Contamination varies with the length of the procedure and the health condition of the patient – Staphylococcus aureus, 20% – Pseudomonads, 16%

Nosocomial Pneumonia About 3% of patients on ventilators acquire pneumonia The source is often endogenous but may also be exogenous with transfer of an organism from the respiratory equipment

Risks Risk Factors – mechanical ventilation (high risk), – elderly, – neonates, – severe underlying disease, – immunodeficiency, – depressed sensorium, – cardiopulmonary disease, – recent thoraco-abdominal surgery Pathogens infecting the Respiratory tract Bacterial pneumonia Legionnaires' disease Pulmonary aspergillosis Mycobacterium tuberculosis Viral pneumonias - Respiratory Syncytial Virus(RSV) - influenza

Prevention Hand washing Standard precautions Limit catheter use