Where do pathogens usually colonize?
In host tissues that aren't in contact with the external environment
Definition: Organisms that regularly inhabit the human body; may or may not be capable of causing disease
Definition: Organisms that only occasionally come into contact with the human body; the most frequent cause of disease
Definition: An organism that usually does not require a parasitic relationship, but will establish one when the opportunity arises
Main categories of disease
Infectious, nutritional deficiency, congenital, inherited, metabolic, degenerative, neoplastic, immunologic
Definition: A condition that makes the body more susceptible to a disease or alters the course of the disease
List the predisposing factors
Gender, genetic background, climate, age, nutritional habits, unhealthy environment
Definition: Includes individuals who currently have the disease or are carriers from previous infections
Definition: Diseases carried by animals, but can be transmitted to humans called "zoonoses"
Type of disease transmission: directly from one host to another through intercourse, handshaking, kissing, etc OR some time of close association between the hosts such as droplet infection from mouth or nose
Most diseases spread by indirect contact enter the body by the _____, and can survive ________ the body for extended periods of time.
Definition: A very important group of disease vectors that carry pathogens from one host to another. Two general methods are used.
Type of vector method: Carrying organism on body parts, especially feet that contaminate food
Type of vector method: Insect bites infected person and ingests blood. Typically, the organism multiplies, the is spread when vector bites an uninfected person
A disease caused by members of the normal flora or by organisms introduced directly into the body
The fraction of a population that contracts the disease during a particular length of time
A disease that develops more slowly, but is continuous or reoccurs for long periods of time
A disease acquired by an unusually large number of people in a given area with a short period of time
Type of Infection: Caused by an opportunistic pathogen after a primary infection has weakened the immune system
Type of Infection: Infection that does not cause any signs or symptoms
Inapparent orsubclinical infection
Any negative change that is not visible or measurable (such as pain, nausea, weakness, etc)
Any negative change that is visible or measurable (such as diarrhea, fever, inflammation, edema, etc)
The science that deals with when and where the disease occurred and how it is transmitted
The main premise of epidemiology
Disease does not occur at random, but rather in patterns that reflect the operation of underlying factors.
The primary goal of epidemiology
To measure the relationships between "exposures" and health outcomes which may provide a basis for public health initiatives and policies
The study of the distribution and determinants of disease frequency in human populations
The study of the distribution and determinants of health-related states or events in specific populations, and the application of this study is to control health problems
Epidemiology: Methodology steps
Defining a health problem, determine the extent of diseases in the community, study the natural history of the disease, identify associations and potential etiology (causes) of a disease and risk factors for disease, and evaluate new preventative and therapeutic measures and new modes of health care delivery
Epidemiology: Steps to the science of public health
Identify risk factors associated with the problem, develop and test community level interventions to control or prevent the causes of the problem, Implement interventions to improve the health of the population, monitor those interventions to assess their effectiveness
Conditions for a disease outbreak
Agent and susceptible hosts are present in sufficient number and the agent can be effectively conveyed from a source to susceptible hosts
Causes of disease outbreaks
1. Increase in amount or virulence of agent
2. Recent introduction of the agent into a new setting
3. Enhanced mode of transmission, exposing more susceptible individuals
4. Factors that increase host exposure or involve introduction through new portals of entry
Which portal of entry: Easiest and most frequently traveled route; inhalation of moisture droplets and other air-borne particles
Portal of entry: Most microbes cannot penetrate this when it is unbroken. Infection through hair follicles and sweat glands. Infection through mucous membranes is much easier.
Skin and mucous membranes
Portal of entry: Deposited directly under the skin and mucous membranes by injury (bites, cuts, surgery, injection)
What is the most dangerous portal of entry and why?
The parenteral route because it provides direct input into the bloodstream
Pathogenic Properties of bacteria
Invasiveness, mechanisms of colonization (adherence and initial multiplication), ability to bypass or overcome host defense mechanisms, and the production of extra cellular substances which facilitate invasion
Pathogenic bacteria cause disease by two basic functions: _______ & __________
Invasiveness and Physiological processes by toxins
Colonies due to invasiveness are evidence of
The ability to establish residence in host and cause structural damage through metabolic activities
Invasiveness and tissue damage is facilitated by
glycocalyx, toxins, and components of the cell wall
Function in invasiveness: Components of cell wall
M-protein is a heat-resistant and acid-resistant protein, A-protein contributes antiphygocytotic abilities
Function of Coagulases
Coagulate fibrinogens in blood to form clot around bacteria to help prevent phagocytosis (not good in healthy cells)
A slimy layer external to the cell wall; will greatly decrease the ability of macrophages to engulf the bacterium
What does the "physiological processes by toxins" refer to?
Toxins transported by blood and lymph that can cause damage far from the site of infection
True of false: Toxins only cause damage at the site of infection
FALSE. Toxins can cause damage far from the site of infection
Metabolic by-products or structural components that happen to have a negative impact on other organisms. Not produced intentionally for the purpose of damaging other cells
What is the difference between toxins and venoms?
Toxins are by-products that are not created to harm other cells (excretion); Venoms are intentionally created for damaging and killing (secretion)
Toxins that are a structural part in the cell wall of gram negative bacteria. The bacterium must be consumed to be affected by the toxin. All produce same signs and symptoms (fever, weakness, generalized aches, possibly shocka and death, etc)
Two key characteristics about Endotoxins
Only gram negative and bacterium must be consumed in order to cause harm
True or false: Bacterium must be consumed and broken down for endotoxins to cause signs and symptoms
Toxins that are excreted by mostly gram positive bacteria into the environment. You do not have to inject the bacterium to ingest the toxin.
Two key characteristics about exotoxins
Mostly gram positive and the bacterium does not have to be ingested in order to ingest the toxin
Toxins that affect the gastrointestinal system (food poisoning, etc)
Entertoxins (think of Entercocci to remember this!)
Neurotoxin, most deadly toxin known to man, paralyzes muscles in skin, found in dirt and so improperly canned foods, inactivated by normal heat, most common in a home environment than an industrial environment
Do exotoxins require a high concentration to cause severe damage?
No, a low concentration will cause severe damage.
Patterns of Disease:Time interval between the infection and the first appearance of signs or symptoms
Period of Incubation
Patterns of Disease:Time that the disease is most severe (The time that you are noticeably sick)
Period of illness
Patterns of Disease: Time in which there is a decrease of signs and symptoms (when you begin to feel better, but still have signs and symptoms and can still infect others)
Period of decline
Patterns of Disease: Return to predisease state (almost better, some recovery related weakness may be present, time of rapid recovery)
Period of Convalescence
Which portal of exit contributes to the following diseases: Tuberculosis, whooping cough, pneumonia, meningitis, measles, mumps, and influenza
The respiratory tract
Which portal of exit contributes to the following diseases:Cholera, typhoid fever, bacillary dysentery, poliomyelitis
Name 3 portals of EXIT, besides the most common 2
Urogenital tract, drainage from wounds, and insect bites