Module 1 Flashcards
Homeostasis
all mechanisms by which an organism responds to normal and abonormal conditions in a way that preserves a stable internal environmnet
Symptoms
subjective, experienced, and desriable characteristics reported by an individual
Signs
objective, observable, physical characteristics detected by a physician and technological aids
Disease
can range from health to morbidity and from acute to chronic
can be sub-clinical
- an individual may be infected and develop immunity to the infectious agent without been symptomatically ill; still a reservoir
Defence Mechanisms against Infection
1) Host surface defences (non-immunologic)
2) Inflammatory reaction (non-specific response)
3) Immunologic defence (specific)
Host Surface defences
Are a primary barrier to the vast majority of microbes in our environment
Include:
- mucus (traps organism)
- coughing/peristalsis/micturition (eliminates organisms)
- high rate of epithelial cell turnover (sloughing off of skin cells eliminates skin organisms)
- local disinfectants (tears, gastric acid, fatty acids in skin)
- normal microbial flora
Inflammatory response
Once a infectious agent bypasses the surface defence, a non-specific response is set in motion
In a pyogenic (pus producing) response, polymorphonuclear white blood cells (PMNs) attach the infectious agent and attract more PMNs and monocyte-macrophages
Rise in temperature is due to cytokines, tumor necrosis factor and interferon produced by the interacting, responding phagocytic cells as well as vasodilation. This is termed as pyrogenic (fever)
Immunologic defences
Specific towards invading pathogen due to immunoglobins and T-lymphocytes
Immune repsonse usually requires interaction with non-specific defence components (ie. complement and phagocytic cells)
Recognizing self from non-self
During embrogenesis, T cells undergo an education process in which antigens of the major histocompatibility classes (MHC) within the human leukocyte antigen complex (HLA) come to recognize self; programmed to respond to non-self antigens
If self-antigens are seen as non-self, the harmful response is auto-immune
Cells of the immune system
Lymphocytes (B, T, and natural killers), mononuclear phagocytes (monocytes/macrophages-antigen processing/presenting cells) and granulocytes (including neutrophils)
Lymphocytes
- activated by macrophages
- differentiate into T cells with specific activities (cytotoxic, memory)
- activate B ells (proliferate into memory B cells or differentiate into plasma cells which produce antiibodies against foreign antigens)
Through interaction and secretion of soluable substances, these cells regulate the immune system, inflammation and functions in other tissues and organs
Antigen Elimination
Toxin neutralization: antibodies produced against toxins (ie. anti-toxin)
Virus neurtalization
Bacterial opsonization: Bacteria become coated with opsonins (primarily antibodies and complement) and are cleared by macrophages
Complement
Functions:
-lysis of cells, bacteria, and enveloped viruses
opsonization process mediattion to increase particle clearance
generation of peptide fragements that regulate feautures of the inflammatory and immune response (vasoldilation, phagocytic adherence and egress) to clear infections
Mutualism
Host and parasite benefit
Ex: E.coli in gastrointestinal tract; GIT produces vitamin K
Parasitism
One benefits and other is harmed
ex: roundworms
Commensalism
One benefits and the other is unaffected
Germ theory
regarded microorganisms as foes (parasitism) that caused disease
One microbe-one disease
In 1890, investigators went on a quest to ID infectious disease microorganisms but discovred a whole array that grew in culture; realized that they should be preset and their absence would be as significance as the presence of a known pathogen
The human microbiome
comprised of 100 trillion microbes that live on and in us, and the genes they contain
we aquire them through contact with people and food and environment, starting at brith with mom and her milk (continueing in a process of mutual selection during first 2 years)
Why is antibiotic resistance such a problem
If one bacterium evolves resistance to antibiottics, the responsible gene can be transffered to other bacteria, rendering them resistant too.
Because the microbiome can change more quickly than the human genome, the microbiome provides a much more rapid means for humans to adapt and thrive when environmental conditions change
Colonization
Occurs when microoganisms persis on the body surface
Transient colonization
At birth, transient colization occurs due to flora from the birth canal or in the mothers skin flora (c-section)
These survive but do not multiply
Normal Flora
Exist on all surfaces of the body exposed to the environment
- unique to enviornment in which it grows
- gut microbiome fluctuates in response to diet
- is protective: imbalances in the relative amounts of these micoorganisms or a decrease in the absolute amount often preceds infection
Nosocomial Colonizaton
refers to transient colonization with hospital or institution (long term care facility)
- usually resistant to antibiotics
- virulent
Carriers
Are those individuals colonized with organisms that are not considered normal flora but are not presently causing the host carrier any damage
considered potential reservoir for inection of others and may occur following a resolved systomatic infection and/or a sub-clinical infection
Commensals
Normal flora organisms - may be opportunistic pathogens causing endogenous infection
usually when introduction of commensals into sites that should be sterile
-virulent
Patterns of infectious disease (timeline)
1) exposure
2) incubation
3) prodromal
4) acute
5) decline
6) convalescene
Exposure
disease can be contagious through all five phases of disease
Incubation
- no visible symptoms but communicable
- incubation times varies
carriers - individuals can remain asymptomatic but do not clear the pathogen; others become carriers post-illness
Prodromal
genetic malaise, symptoms are non-specific
Acute
Specific symptoms reach peak
Decline
infection declines and disease resolves
Convalescence
Patient regains strength
Sources of infection
1) congenital
2) Exogenous
3) Endogenous
Congenital
present at birth (often before)
- Treponema pallidum (causes syphilis); example of transplacental infection; can cause birth defects or death
- Group B streptococci, listeria monocytogenes are examples of bacterial agents that may be vertically transmitted to baby
Exogenous
Source of infection is external to the host
- organisms are aquired from a variety of reservoirs
- person to person, animals, soil, water, food, hospital
- organisms are transmitted: directly (communicable or zoonotic), indirectly (vectors, inhalation, ingestion
Endogenous
the source of infection form within the host
- normal flora may cause disease if: its virulence increases, hosts immunocompetence ecreases, enviornment is altered, or introduced to new habitat where it doesnt belong
Barriers to infection
- physical: keratin, mucous, flushing
- chemical: interferon, lysozymes, stomach acid
- cellular: cilia, phagocytes, pyogenic-response
- humoral: antibodies
- biological: normal flora
Virulence Factors
- adaptation to specific sites
- chemical signal molecules used in communication with other bacterial species
- adherence factors
- enzymes
- capsules
- toxins: endo (cell wall component of gram negative organisms released on bacterial lysis and death) and exo (released by organism into environment)
- adaptation
Endemic
Endemic disease is either cyclic (expected) or continuous but confined to a defined geographic location and affects small numbers of population
ex. california flu
Epidemic
attacks many people at the same time in the same location or the same population for a period of time
ex. cholera
Pandemic
are epidemics that have spread over a very wide are
they attack the majority of the population in a large area
The Micro-ologies
1) Bacteriology
2) Mycology
3) Parasitology
4) Virology
Mycoplasmas
Bacteria
- no cell wall but have cell membrane
- cant gram stain
- smallest free-living forms
- fastidious: culture is possible but difficult
- cultured by special media
Rickettsiaceae
obligate intracellular parasites that cannot be cultured
risk group 3; highly infectious
do not gram stain
spread by arthropods (ticks, fleas)
Chlamydiales
infective form (elementary body)
reproductive
non-infectious growth from reticulate body &
inert
do not stain
cannot be cultured; have an unusual life cycle
obligate intraceullular parasites
Mycology
- study of fungi
- candida albicans
- reproduce by budding
Parasitology
- study of parasites
- Giardia lamblia
Virology
Study of viruses
- non-cellular
- require host to reproduce
Taxonomy
study of systems by which living organisms are placed in a group
1) Classification (arranges bacteria into groups)
2) Nomenclature (labelling of organisms); binomial system
3) ID
Bacterial Genetics
- have a singular, circular, double-stranded DNA chromosome that is not associated with histones
- plasmids can replicate independently of the chromosome (autonomous replication)
- plasmids may contain trasnposable elements and plasmids may insert into the chromosome
- genes can be chromosomal (more stable) or extr-chromosomal (plasmids and transposable elements)
Replication (bacteria)
Reproduction by asexual binary fission
- single cell elongates, DNA replicates, cross wall forms, and 2 identical daughter cells are formed
- rate at which cells double will determine size of the colony we observe ; colony size is primarily an expression of generation time (ie. rate of replication)
DNA replication
- supercoiled DNA relaxes, strands seperate at point of origin, parent strand acts as template and DNA polymerase builds, replication terminates at fork
rate is proportional to available nutrients and inversely proportional to build up of toxic waste
Regulation of gene expression
- gene expression may be constituitive (metabollically essential process)
- inducible (in response to a stimulus in the enivornment, either the presence of a substrate or the depletion of a substance which when present, acts as a gene repressor)
or
- consituitive-inducible (always present but accelerates with the appropriate stimulus)
Chronic Ilnnes
refers to persistence, not severity of symptoms
Prokaryotes
- cell envelope: complex cell wall with peptoidoglycan; plasma membrane no CHO or sterols (exception-sterols in myoplasmas)
- gemone: no nucleus; single, circular chromosome & usually addition genetic material extrachromosomal (plasmids)
- ribosomes 70s= 50S/30s
Extrachomosomal elements
- is in plasmids, insertion sequences, transposons, and integrons
- importance: ability for transfer of antibiotic resistance between bacteria
Insertion Sequence
code for movement of genes
Transposons
have functional genes
must be inserted into plasmid to replicate but can be transferred
Integrons
to provide a convient insertion site for antibiotic-resistance genes from foreign DNA sources
- cannot replicate autonomously
- capture gene cassettes
- code for ABX resistance
- cassettes shuffled in response to stimulus (exposure to ABX)
- require transposition proteins for transfer
