Module 10: Microbe-Host Interactions Flashcards
What is a microbiome?
a functional collection of different microbes in a particular environmental system.
What is a microbiota?
all the microbes in a microhabitat
How many microbes are in the human microbiome?
1013
What are the benefits of knowing the human microbiome?
- development of biomarkers for predicting predisposition to diseases
- designing targeted therapies
- personalized drug therapies and probiotics
What are the six microbial habits of the human body?
- skin
- airways
- oral
- skin
- gut
- vagina
List the bacterial group that predominates at each of the following body sites:
- Skin
- Saliva
- Urogenital tract
- Gastrointestinal tract
- Propionibacterium (Gram +)
- Streptococcus (Gram +)
- Lactobacillus (Gram +)
- Bacteroidetes (Gram +)
What is disbiosis?
an imbalance in the quantity and type of microorganisms in the human microbiome (ex. cause: taking antibiotics)
What are the objectives of the Canadian Human Microbiome Initiative?
- characterize the microorganisms colonizing the human body
- evaluate their relationship to health
- examine compositional changes associated with chronic disease
Microbes in the gut affect:
- early development
- health
- predisposition to disease
The bacterial numbers in the gut increase from 102 to 1012 as pH increases or decreases?
Increases
Firmicutes, Bacteroides and Actinobacteria are common in:
gastric fluid
Firmicutes and Proteobacteria are common in:
the mucus layer of the stomach
This acid-resistant bacteria causes chronic and acute gastritis and leads to the formation of peptic ulcers.
Helicobacter pylori
98% of all human gut phylotypes fall into one of thre major bacterial phyla:
- firmicutes
- bacteroidetes
- proteobacteria
Peptide antibiotics that contain unusual amino acids; synthesized by Gram + bacteria.
lantibiotics
What are bacteriocins?
antibacterial products
These two small bioactive molecules produced by bacteria in the large intestine, help bacteria to maintain a niche in the body or inhibit the growth of transient bacteria.
- lantibiotics
- bacteriocins
The three prominent phyla in the oral cavity:
- firmicutes
- proteobacteria
- bacteroidetes
What are the defense mechanisms of the oral cavity?
- lysozyme in saliva, which cleaves glycosydic linkages in the cell wall
- mucous membranes promote the growth of normal bacteria and can inhibit pathogens
- secretes mucin which helps mucous layer retain moisture and inhibits attachment of bacteria to epithelial cells
Which microbe is the first to colonize on the tooth surface?
streptococcus
_________ is a major contributor to the biofilm called dental plaque. It generates lactic acid that wears down tooth enamel.
Streptococcus mutans
Altered pH conditions can cause potential pathogens in the urethra to multiply and cause disease. These two pathogens frequently cause UTIs.
- Escherichia coli
- Proteus mirabilis
___________, is a resident organism of the vagina that ferments glycogen producing lactic acid. The lactic acid maintains a local acidic environment.
Lactobacillus acidophilus
The four predominant phyla of the skin are:
- actinobacteria
- firmicutes
- proteobacteria
- bacteroidetes
The most abundant viruses in all body sites are not animal viruses by instead are ____________.
bacteriophages
What are Koch’s postulates?
- the suspected causative agent must be absent from all healthy organisms but present in all diseased organisms.
- the causative agent must be isolated from the diseased organism and grown in pure culture
- the cultured agent must cause the same disease when inoculated into a health susceptible organism.
- the same causative agent must then be reisolated from the inoculated diseased organism.
Microbial parasites that cause disease or tissue damage in a host.
Pathogens
The ability of a parasite to inflict damage on the host.
Pathogenicity
Relative ability of a pathogen to cause disease (measure of pathogenicity)
Virulence
Causes disease only in the absence of normal host resistance.
Opportunistic Pathogen
Situation in which a microorganism is established and growing in a host, whether or not the host is harmed.
Infection
Damage or injury to the host that impairs host function.
Disease
After to exposure to pathogens, that are the steps of the infection process that follow?
- Adherence - to skin or mucous
- Invasion - through epithelium
- Multiplication - growth and production of virulence factors and toxins.
The enhanced ability of microbes to attach to host tissues.
Adherence
Bacteria and viruses that initiate infection often adhere specifically to _____________ through macromolecular interactions on the surfaces of the pathogen and the host cell.
Epithelial cells
Glycoproteins or lipoproteins found on the pathogen’s surface that enable it to bind to host cells.
Adhesins
N. gonorrhoeae adheres to mucosal epithelial cells using the __________ and ________.
- opa protein
- pili
Influenza virus binds cells via it’s ___________.
haemagglutinin
What is SdrG (serine-aspartate dipeptide repeats)
an adhesin protein found in Gram + pathogens that binds fibrinogen.
The bacterial capsule forms a thick coating outside the plasma membrane and cell wall and serves two important functions in bacterial pathogenicity:
- the capsule is both stick and contains specific receptors to facilitate attachment on host tissues
- capsules protect the bacteria from ingestion by white blood cells
Three bacterial cell surface protein structures that function in attachment:
- fimbriae
- flagella
- pili
The ability of a pathogen to spread and cause disease.
Invasion
Pathogens produce various virulence factors that enhance invasiveness:
- enzymes that enhance virulence by breaking down or altering host tissue to provide access to nutrients (ex. hyaluronidase, collagenase, protease, nuclease, lipase, etc)
- protect the pathogen by interfering with normal host defense mechanisms such as clotting (ex. coagulase)
Toxic or destructive substances produced by the pathogen that directly or indirectly enhance invasiveness and host damage by facilitating and promoting infection.
Virulence factors
Highly virulent pathogens show little/large difference in the number of cells required to kill 100% of the population as compared to 50% of the population.
little
Name the pathogen property:
Organism produces a toxin that inhibits host cell function or kills host cells.
Toxicity
Name the pathogen property:
Ability of a pathogen to grow in host tissue at densities that inhibit host function.
Invasiveness
Name the pathogen property:
Decrease or loss of virulence.
Attenuation
________ strains of various pathogens are valuable to clinical medicine because they are often used for the production of viral vaccines.
Attenuated
Name four examples of attenuated vaccines.
- measles
- mumps
- rubella
- rabies
A virus is _________ in hosts that are increasingly dissimilar to the original host.
attenuated
Genes that direct invasion are clustered together on the chromosomes as _____________ .
pathogenicity islands
Invasiveness requires a pathogen to break down host tissues. This is often done with _______ that attack host cells.
enzymes
Name three tissue destroying enzymes:
- hyaluronidase
- coagulase
- stretokinase
This enzyme breaks down host tissue.
hyaluronidase
This enzyme forms clots.
coagulase
This enzyme breaks down clots.
streptokinase
The function of this exoenzyme is to:
Degrade hyaluronic acid that cements cells together to promote spreading through tissues.
Glycohydrolases
(Hyaluronidase S in Staphylococcus aureusI)
The function of this exoenzyme is to:
Degrade DNA released by dying cells (bacteria and host cells) that can trap the bacteria, thus promoting spread.
Nucleases
(DNAse produced by S. aureus)
The function of this exoenzyme is to:
Degrade phospholipid bilayer of host cells, causing cellular lysis, and degrade membrane phagosomes to enable escape into the cytoplasm.
Phopholipases
(Phopholipase C of Bacillus anthracis)
The function of this exoenzyme is to:
Degrade collagen in connective tissue to promote spread.
Proteases
(Collagenase in Clostridium perfringens)
Toxic proteins released from the pathogen as it grows.
Exotoxins
Three categories of exotoxins.
- cytolytic toxins
- AB toxins
- superantigen toxins
Ability of microorganism to cause disease as a result of preformed toxin that inhibits host function or kills host cells.
Toxicity
