Lecture 1 Flashcards
Definition of Disease
Infection with subsequent symptoms
Definition of Asymptomatic Carrier
Reservoir of pathogenic organisms
What is the spectrum of infection
Sum of species that can be infected by a pathogenic organism.
How many species can serve as a host for a pathogen.
Infectious dose
minimal number of microorganisms required to cause an infection in a host
Puerperal sepsis definition
defined as an infection of the genital tract occuring at any time between rupture of membrane or labour or postpartum.
infection
colonization of a host by a pathogenic organism
pathogenic organisms
microorganism and small, biological active units that under certain conditions can infect a higher organism and cause disease
Pathogenicity
Ability of a whole species to cause an infection or disease
Opportunistic pathogen
Do not cause disease in normal habitat and a healthy person
Virulence
Degree of pathogenicity of members of a species; strain-specific trait; host-dependent
incidence of disease
Number of people developing a disease during a particular period of time
Prevalence of Disease
Number of people suffering from a disease during a given time period (no matter when they first developed symptoms)
Acute Disease
Rapid Development, usually short duration (eg. influenza)
Chronic Development
Slow development, may continue for a long time (eg. tuberculosis, leprosy, hepatitis B)
Latent disease
Causative agent remains inactive for sometime but may become active at any time and may cause symptoms (eg. shingles caused by varicella virus)
Local Infection
Small area in the body invaded by pathogens.(eg. pimples by Staphylococcus aureus)
Systemic Infection
Pathogens and their products spread throughout the body by blood or lymph (eg. measles)
Focal infection
pathogen from local infection enter blood or lymph and spread to the other confined body parts (eg. endocarditis by oral streptococci)
Bacteremia
Presence of pathogens in the blood
Septicemia
Pathogens able to multiply in the blood
Sepsis
Toxic inflammatory condition by spread of pathogens or their toxic products
Primary infection
Acute infection with symptoms
Secondary Infection
Caused by opportunistic pathogen after primary infection
Measuring Virulence (lethal dose 50)
number of pathogens that will kill 50% of an experimental group of hosts
Measuring Virulence (infectious dose 50)
number of pathogens that will infect 50% of an experimental group of hosts
Epidemiology
Science concerned with the distribution and prevalence of communicable diseases in populations. World travel offers pathogens many opportunities for transmission
Epidemic Disease
A disease that occurs in a unusually high number of individuals in a population at the same time
Pandemic
A worldwide epidemic
Descriptive epidemiology
Collecting data about affected individuals, place and period in which disease occured.
Often Retrospective
Analytical Epidemiology
Looking for factors that preceded the disease: age, sex, nutrition, risk factors, socioeconomic status, location, genetic background etc.
Anthrax
Anthrax is an infectious disease caused by gram positive, rod shaped bacteria known as bacillus anthracis
How was anthrax detected?
Detedtion of aerobic rods in the spleen of cattle that died of anthrax
Koch’s postulates
- Presence of pathogenic organism in all persons with the respective disease in the respective body region.
- Isolation of pathogenic organism from infected person and propagation as pure culture in the laboratory.
- Infection of human/animal by pure culture results in the same symptoms of disease.
- Repeated isolation of pathogenic organism and propagation as pure culture.
Pathogenic Organisms identified by Robert Koch
Bacillus Anthracis: Anthrax
Mycobacterium Tuberculosis: Tuberculosis
Vibrio Cholerae: Cholera
Yersinia Pestis: Plague
Salmonella Typhi: Typhoid fever
Pseudomonas aeruginosa
Major threat to patients with cystic fibrosis.
common encapsulated, gram-negative, aerobic facultative anaerobic, rod-shaped bacterium that can cause disease in plants and animals including humans.
Streptococcus Pyogenes
Can cause different kinds of disease.
species of gram positive, aerotolerant(can survive despite presence of oxygen) bacteria.
3 infections only to humans
Streptococcus Pyogenes, Treponema pallidum, Mycobacterium leprae
Mycobacterium leprae
cannot be grown on artificial media.
Rickettsia
Require host cells for multiplication.
Escherichia Choli
Non-pathogenic, enteropathogenic and uropathogenic strains present.
Salmonella Typhimurium(mice)
causes typhoid fever in mice but relatively mild diarrhea in humans
Salmonella typhi
causes typhoid fever in humans
Meningitis
Can be caused by different pathogens.
infection of meninges that line our brain
Limitations of Koch’s Postulates
Host is not taken into account.(opportunistic pathogens)
Non-culturable pathogens not taken into account.
Not all strains of one species are equally virulent.
Results of animal experiments connot be directly transferred to humans.
One disease can be caused by different pathogens.
One pathogen can cause different diseases.
Microbiota
The types of organisms present in a specific environment (organ system or entire organ).
Microbiome
Functional collection of microbes (the microbes, their genes and metabolites) in a specific environment.
Commensal Flora
Act on the host’s immune system to induce protective responses that prevent colonization and invasion by opportunistic pathogens.
Human Microbiota now called
Normal flora or resident flora
