Microbiome, colonization, pathogenicity Flashcards
When does colonization begin?
Colonization begins at birth.
Probiotics
group of organisms we can benefit from when ingested
Cause and effect relationships microbiome?
Not only is a person affected by his or her microbiota, but a person’s microbiota also responds to his or her activities, health, and diet.
The sites of the human body inhabited by microorganisms include
the mouth,
nasal cavities,
throat, stomach,
intestines,
urogenital tracts,
Skin
Host–microbiome superorganism
together, the human body as the host and its associated microbes
- genetic information from human and genetic information from microbes
Gut microbial community in the healthy human consist of commensal microbes, that are critical to
development of the immune system
overall health later in life
predisposition to disease
What does the host-microbiome superorganism do?
Connections between the microbial composition of a body site and the health status of the person.
Most predominant microorganism on the skin
Propionibacterium
Most predominant microorganism in the GI tract
Bacteroidetes
Most predominant microorganism in the urogenital tract
Lactobacillis
Most predominant microorganism in the saliva
Streptococcus
To induce pathogenesis, pathogenic microbes must:
- adhere to host tissues
- overcome immune defenses
Definition of infection
The ability to filtrate into an area, multiply and colonize
Infection vs disease
Infection will begin colonizing however is not necessarily harmful. If presence becomes harmful to the host is disease
Pathogen
Microbes that are able to cause disease
Disease
When microorganisms enter the body and their presence causes harm/damage to the host.
Does adherence always cause disease?
Adherence is required to initiate disease; it is not sufficient to initiate disease.
How does infection become disease?
First adheres to those tissues, multiplies to yield many cells or viral particles,
proceeds to damage tissues by
1. the release of toxic or
2. invasive substances
What makes a microbe a pathogen?
Virulent factors: make a microorganism able to cause disease
What does the infection process entail?
- Exposure to pathogens
- Microorganism adheres
- Microorganism invades the tissue
- Multiplication- growth and production of virulent factors and toxins
What does the disease process entail?
- Toxicity- toxin effects are local or systemic
or - invasiveness- further growth at originical and distant sites
- tissue or systemic damage
When are symptoms present?
The disease process not the infection
adherence
the enhanced ability of a microorganism to attach to a cell or a surface.
Pathogens adhere to:
epithelial cells
surfaces
each other, forming biofilms
The biofilm itself adheres to specific tissues
Where do you prevent infection?
Stop at exposure or adherence
Portal of entry:
mucous membranes
the skin surface
under mucous membranes or the skin e.g. during injury
How does someone catch streptococcus pneumoniae
Resp tract:
If swallowed, they will be killed by the strong acidity of the stomach
If reach the respiratory tract, they could trigger a fatal case of pneumonia.
Why is the portal of entry important?
The portal of entry is critical for establishing an infection because a pathogen that gains access to incompatible tissues is typically ineffective.
Adhesin
the molecules in which the microorganisms adheres and attaches to the host
What are adhesins made of>
composed of glycoprotein or lipoprotein covalently bound to the outer layer of the cell
How have receptors on pathogens evolved to bind?
evolved to bind specifically to complementary molecules in the host
What are Adherence Structures?
Some adhesins form part of an outer cell surface structure that may or may not be covalently linked to components of the cell wall.
Capsules
Fimbriae
Pili
Flagella
Anthrax
skin lesion that turns black that can turn into respiratory disease.
Caused by bacillus anthracis.
Has a capsule
how does a anthrax capsule surface assist the attachment process?
- Contains specific receptors that facilitate adherence to host tissues
- Has inherently a sticky nature
How is the bacillus anthracis capsule different to regular?
Covered in polypeptide containing only amino acid d-glutamate and becomes sticky when wet
Outside of adherence, what do capsules do?
protecting pathogenic bacteria from host defenses
Virulence factor
What causes symptoms of disease?
Protective factors of the capsule
What other factors help adherence?
Opa (opacity associated protein): a cell surface protein
Hemagglutinin is present on the virus surface
How does gonorrhea adhere to the cell?
Capsule + Opa (opacity associated protein): a cell surface protein
Fimbriae
How does influenza attach to its host cell?
Hemagglutinin is present on the virus surface
What is Pilli?
Short structures that stick out of the capsule
typically longer and fewer in number than fimbriae
attachment
the bacterial genetic transfer process
What is a Flagella?
Long Tail from capsule
may facilitate adherence of bacterial cells to host cells.
What event is required but not sufficient to cause an infectious disease?
adherence
Plasmids
DNA in bacteria that is extracellular genetic information that is not apart of the genome and can transfer from one microorganism to another through pilli
What is sexual pilli?
The exchange of plasmid from one microorganism to another one via a pilli
Infectious Disease
Onset of the disease depends on infectious organisms. The same microorganism can cause the same symptoms if it is transferred from one person to another
Non-infectious disease
Disease that does not necessarily cause the same symptoms from one person when transferred to the next
What is the difference between pilli and fimbrae?
Both are technically pilli but pilli is sexual pilli which transfers plasmid from one microorganism to another. Alternatively, frimbrae are structures which help the bacteria adhere to host structure.
The human body is favorable for the growth of microorganisms- why?
rich in organic nutrients
controlled pH
osmotic pressure
temperature
Colonization
growth of a microorganism after it has gained access to host tissues
Where does colonization typically begin?
mucous membranes
Why does attachment happen in the mucous membranes?
Because they are mucusy and mucus is sticky
Nonpathogenic microbes
Nonpathogenic microbes that penetrate mucous membranes include large numbers—potentially that contribute to what has been called the
intrabody phageome;
intrabody phageome
many billions—of innocuous bacteriophages
What happens if attached microbes are pathogens
If attached microbes are pathogens, it sets the stage for infection, invasion, and disease.
What do Oral streptococci do?
breaks down carbohydrates into different acids which contribute to our oral health
The S. sobrinus capsule contains adhesins specific for host salivary glycoproteins
The S. mutans resides in crevices and small fissures where it relies on dextran—a strongly adhesive exopolysaccharide—that it produces to secure cells to the tooth and gum surface.
What are lactic acid bacteria?
S. sobrinus and S. mutans
What causes dental cavities?
The trigger for decay activities is sucrose
sucrose allows these species to produce the dextran exopolysaccharide and capsules necessary for attachment and colonization.
The microbiota secrete locally high concentrations of lactic acid that decalcifies tooth enamel, resulting in dental caries.
What is dental plaque?
Extensive bacterial growth of these oral streptococci results in a thick biofilm
What is present in dental plaque?
Streptococci, + many other gram-positive and gram-negative Bacteria are present in plaque, including species of Corynebacterium, Porphyromonas, Leptotrichia, Neisseria, the filamentous anaerobe Fusobacterium, and many others.
What causes oral disease
Oral pathologies, including gingivitis and periodontitis, bacterial diseases that erode the tooth-supporting gum and bone tissues.
Invasion
the ability of a pathogen to enter into host cells or tissues, spread, and cause disease.
Localised invasion
Some pathogens remain localized after initial entry, multiplying and invading at a single focus of infection, such as the boil that may arise from Staphylococcus skin infections.
Virulence:
A pathogen that causes disease in a given host can trigger mild or severe outcomes depending on its inherent capacity to elicit disease.
Bacteremia:
The mere presence of bacteria in the blood typically self-limiting and asymptomatic, as the bacterial cells do not grow in the bloodstream, and the immune system quickly removes them
Septicemia
bacteria multiply in the bloodstream, and the organism spreads systemically from an initial focus and produces toxins or other poisonous substances.
Viremia:
viruses present in the bloodstream e.g. measles
At what body sites do pathogens typically attach and colonize?
Mucous membranes- GI, urogenitary and respiratory tract
How does the capsule of Streptococcus mutans assist in the formation of dental caries?
Streptococcus mutans, which causes dental caries, splits the sucrose in food and uses one of the sugars to build its capsule, which sticks tightly to the tooth. The bacteria that are trapped in the capsule use the other sugar to fuel their metabolism and produce lactic acid which causes further decay
Which is the more serious condition, bacteremia or septicemia, and why?
Septicemia- produce toxins which are lethal
Pathogenicity:
Unique properties of each pathogen, the overall ability to cause disease.
Virulence:
The measure of pathogenicity/ the relative ability of a pathogen to cause disease.
The virulence of a given pathogen depends on:
Abilities to adhere
Colonize
Invade
Arsenal of virulence factors
are some microorganisms more virulent then others?
Virulence is a quantifiable entity, especially if a pathogen is lethal and an experimental animal model is available.
LD50
(“lethal dose”): the number of cells of a pathogen (or virions, for a viral pathogen) that kills 50% of the population of the host organism in a test group.
Sporatic
Randomly people catch disease. Not put to a specific population
Endemic
Constantly occurring- goes away and comes back. Always exists in a population
Epidemic
an unexpected increase in the number of disease cases in a specific geographical area.
Pandemic
Worldwide incidence of a pathogen.
