MP MT

• Infection - Is the invasion and multiplication of microbes in or on body tissues, resulting in signs and symptoms as well as an immunologic response
• Communicable Disease

  Transmitted from one person to another
• Contagious Disease

  A communicable disease that is easily

  transmitted from one person to another
• Epidemiology:

  The study of the factors that influence

  the occurrence and distribution of disease
• Sporadic Diseases

  If investigators find cases occurring occasionally and irregularly with no specific pattern
• Epidemic Diseases

  If a greater-than-expected number of cases of a given disease arises

  suddenly in a specific area over a specific period
• Pandemic

  An epidemic that affects several several countries or continents
• Endemic Diseases

  Are those that are present in a population or community at all times

  They usually involve relatively fewpeople during a specified time.
• Herd Immunity

  When a high proportion of a population has developed immunity to a specific infectious agent
• Endogenous Microbes

  Found on microbes and in such body substances as saliva, feces, and sputum. They can cause disease in a susceptible individual
• Exogenous Microbes

  Originate from sources outside the body

  Usually, humans and exogenous microbes live together in harmony

  However, if something disrupts this harmonious relationship, the

  microbes may cause infection
• Causative Agents

  A causative agent for infection is any microbe capable of producing disease
• Reservoir

  Is the environment or object in or on which a microbe can survive and, in some cases, multiply.
• Case

  A patient with an acute clinical infection such as chickenpox
• Carrier

  A person colonized by a specific

  microbe but showing no signs or

  symptoms of infection

  Or may have a subclinical or

  asymptomatic infection (hepatitis)
• Incubatory Carrier

  • One who is incubating the illness
  • Has acquired the illness but does not yet show symptomsIncubation periods vary from one

  infectious organism to the next
• Convalescent Carrier

  Is in the recovery of an illness but

  continues to shed the pathogenic organism
• Intermittent Carrier

  Occasionally sheds the pathogenic

  organism

  Some people are intermittent carriers of S. aureus
• Chronic Carrier

  Always has the infectious organism in

  his system

  Some people are chronic carrier o f

  hepatitis B, their blood harbors the

  hepatitis B surface antigen for years
• Portal of Exit

  Is the path by which an infectious agent leaves its reservoir

  Usually, this portal is the site where the organism grows
• Mode of Transmission

  The means by which the infectious

  agent passes from the portal of exit in

  the reservoir to the susceptible host
• Direct Contact

  Refers to person-to-person spread of

  organisms through actual physical contact
• Indirect Contract

  Occurs when a susceptible person

  comes in contact with a contaminated object
• Droplet Transmission

  Results from contact with contaminated respiratory secretions
• Airborne Transmission

  Occurs when fine microbial particles containing pathogens remain suspended in the air for a prolonged period, and then are spread widely by air currents and inhaled
• Vehicle

  A substance that maintains the life of the microbe until it is ingested or

  inoculated into the susceptible host
• Vector-borne Transmission

  When an intermediate carrier, or vector such as flea or a mosquito, transfer a microbe to another living organism
• Portal of Entry

  Refers to the path by which an infectious agent invades a susceptible host
• Susceptible Host

  Required for the transmission of

  infection

  The human body has many defense

  mechanism for resisting the entry and

  multiplication of pathogens
• Pathogenicity

  Refers to a microbe's ability to cause

  pathogenic changes, or disease
• Virulence

  Refers to the degree of a microbe's

  pathogenicity

  It can vary with the condition of the

  body's defense
• Dose

  A microbe must be present in a

  sufficient dose to cause human disease
• Invasiveness (Infectivity)

  Refers to the ability of a microbe to

  invade tissues
• Toxigenicity

  Refers to a microbe's potential to damage host tissue by producing and releasing toxins
• Specificity

  Refers to the attraction of a microbe to a specific host or range of hosts
• Viability

  Refers to the ability of a microbe to survive outside the body
• Antigenicity

  The degree to which a microbe can

  induce a specific immune response,

  varies among microorganisms
• Nosocomial Infections

  Infections acquired during

  hospitalization (hospital-acquired)

  Have been a problem since hospital began
• Enterococcus

  A part of the normal intestinal flora

  Common cause of urinary tract

  infections as well as wound and blood

  infection
• Pseudomonas species

  They grow readily in many moist,

  nutrient-poor environments such as the

  water humidifier of a mechanical ventilator