MicroLecE3Ch14 Flashcards
Pathology
The study of disease
Etiology
The study of the cause of a disease
Pathogenesis
The development of disease
Infection
Colonization of the body by pathogens
Disease
Abnormal state when the body is not functioning normally. Disease does not always mean caused by an infection (i.e. Cancer)
Transient Microbiota
Present for days, wks, mnths. Normal microbiota that body comes in contact w/on daily basis but does not stay on the body for very long
Normal Microbiota
Permanently colonize the host. Bacteria, fungus, protozoa that naturally live on the body, typically not removed by washing/handwashing
Symbiosis
1) Commensalism: 1 organism benefits, other is unaffected
2) Mutualism: both organisms benefit (Ex: E. coli in the gut)
3) Parasitism: 1 organism benefits at the expense of the other
Opportunistic Pathogens
Some normal microbiota are opportunistic pathogens. Humans live w/them commensally or mutually but they can turn pathogenic and parasitic under certain circumstances
- Ex: MSRA on healthcare workers
Normal Microbiota Functions
Protect host by –
- Occupying niches that pathogens might occupy
- Producing acids
- Producing bacteriocins (specific toxins that can kill off other bacteria)
- Microbial antagonism: competition btwn microbes, helps keep each other in check (Ex: yeast infection if woman goes on certain antibiotics)
- Probiotics: taking pill full of bacteria to re-colonize the body, intended to replenish and restore balance of normal microbiota in body
Koch’s Postulates
Used to prove cause of an infectious disease. Some pathogens can cause several diseases. Some pathogens only cause disease in humans
- Same pathogen must be present in every case of the disease
- Isolation Step: Pathogen must be isolated from the diseased host and grown in pure culture
- Match Signs and Symptoms: Pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible lab animal
- 2nd Isolation Step: Pathogen must be isolated from the inoculated animal and must be shown to be the same pathogen that was in the original diseased animal
Koch’s Postulates Limitations
- Some microorganisms cannot be grown in cell culture which messes up steps 2 and 4
- Some diseases produce different signs and symptoms in different people (inconsistent disease conditions)
- Some pathogens cause disease only in humans and cannot test them on humans
Symptom
Change in body fxn that is felt by a patient as result of disease, cannot be measure
- headaches, fatigue, stomach ache
Sign
Change in body that can be measured or observed as result of disease
- rash, fever, elevated white blood cell count
Syndrome
Signs + Symptoms
Communicable disease
Disease spread from one host to another
- flu
Contagious disease
Disease easily spread from one host to another
- chicken pox
Noncommunicable disease
Disease not transmitted from one host to another
- cancer
Incidence
Fraction of a population that contracts a disease during a specific time
Prevalence
Fraction of a population having a specific disease at a given time
- If a rapidly-cured disease, incidence and prevalence rates usually the same, but if not then prevalence rate usually higher
Sporadic disease
Disease that occurs occasionally in a population
- chicken pox
Endemic disease
Disease constantly present in a population
- head cold
Epidemic disease
Disease acquired by many hosts in a given area in a short time
- Ebola in Africa
Pandemic disease
Worldwide epidemic, reached more than 1 continent
- Zika virus
Herd Immunity
Immunity in most of a population. If some people have immunity then it protects those who do not, but if that amount of people w/immunity drops below certain level, herd immunity becomes ineffective
- vaccinated kids protect unvaccinated kids
Acute disease
Symptoms develop rapidly
Chronic disease
Disease develops slowly
Subacute disease
Symptoms btwn acute and chronic
Latent disease
Disease w/a period of no symptoms when the causative agent is inactive
Local infection
Pathogens limited to small area of body
- cutaneous anthrax
Systemic infection
Infection throughout the body
Focal infection
Systemic infection that began as a local infection
- if cutaneous anthrax got into bloodstream and started circulating through body
Sepsis
Toxic inflammatory condition from the spread of microbes, especially bacteria or their toxins, from a focus of infection
Bacteremia
Bacteria in the blood
Septicemia
Growth of bacteria in the blood
Toxemia
Toxins in the blood
Virema
Viruses in the blood
Primary infection
Acute infection that causes the initial illness
- HIV
Secondary infection
Opportunistic infection after a primary (predisposing) infection
- pneumonia in someone who has HIV
Subclinical disease
No noticeable signs or symptoms (unapparent infection)
- HPV in men
Predisposing Factors for Disease
- Short urethra in females, higher chance of UTIs and STDs
- Inherited traits (i.e., sickle cell gene)
- Climate and weather
- Fatigue
- Age
- Lifestyle
- Chemotherapy
Stages of Disease
1) Incubation period: no signs or symptoms. Can vary a lot in terms of length of time
2) Prodromal period: mild/early signs or symptoms
3) Period of Illness: most severe signs and symptoms
4) Period of Decline: signs and symptoms
5) Period of Convalescence: signs and symptoms gone, body going through tissue repair of anything damaged during disease
Reservoirs of Infection
Continual sources of infection –
- Human: AIDS, gonorrhea. Carriers may have unapparent infections or latent diseases
- Animal: rabies, Lyme disease. Some zoonoses may be transmitted to humans
- Nonliving: Botulism, tetanus. Soil
Transmission
1) Direct Contact: requires close association btwn infected and susceptible host
- STDs
2) Indirect Contact: spread by fomites (inanimate object like a cup)
- Vehicle Transmission: transmission by food, water, air
- Vectors: arthropods (fleas, ticks, mosquitoes). Transmit by Mechanical transmission where arthropod carries pathogen on its feet, or Biological transmission where the pathogen reproduces inside the vector
3) Droplet: transmission by airborne droplets. Not close up like direct contact
Nosocomial Infections
- Get it as result of hospital stay
- # 4 killer worldwide
- Caused by microorganisms in hospital environment, compromised host, and chain of transmission (direct route of transmission from healthcare workers touching both sick and healthy people)
- Most common is UTIs from unsterile catheters
Emerging Infectious Diseases
- Diseases that are new, increasing in incidence, or showing potential to increase in near future
Emerging Infectious Diseases Contributing Factors
1) Genetic Recombination
2) Evolution of new strains
3) Inappropriate use of antibiotics and pesticides
4) Changes in weather patterns
5) Modern Transportation
6) Ecological disaster, war, and expanding human settlement
7) Animal Control Measures
8) Public Health Failure
Crossing the Species Barrier
Ex: Flu virus
- Has multiple reservoirs like birds, pigs, goats, chickens, humans
- Bird gets flue and builds immunity, pig gets different flu virus and builds immunity, and human gets flu and builds immunity but they do not have cross-immunity. This is why there are always new strains of flu b/c of all different reservoirs and constant mutation, and there are always new flu vaccines every year
Epidemiology
Study of where and when diseases occur
Centers for Disease Control and Prevention (CDC)
- Collects and analyzes epidemiological info in the U.S. (World Health Organization - WHO - internationally does this)
- Publishes Morbidity and Mortality Weekly Report (MMWR)
Morbidity
Incidence of a specific notifiable (pathogenic) disease
Mortality
Deaths from notifiable diseases
Morbidity Rate
Number of people affected in relation to the total population in a given time period
Mortality Rate
Number of deaths from a disease in relation to the population in a given time
