Block 2 - Host-Microbe Relationships Flashcards
Describe the term “symbiosis”.
the close associate and interaction of two dissimilar organisms living together
Those microorganisms which are normally and consistently found in or on the body in the absence of disease.
Describe “resident” flora and “transient” flora.
normal flora
resident: generally live in a specific place
transient: “non-pathogens” that are passing through the area
True or False:
Normal flora found in one area may cause an infection in another region of the body.
True
What is the term for each definition below?
Association between organisms in which one is benefitted and the other is neither benefitted nor harmed.
Both the microbe and host derive benefits from the relationship
Commensalism
Mutualism
What is the term for this definition?
Disease traits of the resident flora are demonstrated only when normal host-microbe relationship is altered.
What are some ways this can occur?
opportunism
a. Prolonged antibiotic therapy alters flora
b. Traumatic injury, surgery
c. Immunological compromise
d. Hormonal or chemical changes
What term(s) are described below?
Symbiotic relationship in which a microorganism lives in or on a host at the expense of the host.
- *A carrier of microbes from one host to another**
- (i.e: a. Insects and other animals b. Inanimate articles (fomite) e.g. personal items, eating utensils, tools, hospital instruments, food water, body discharges, bandages, etc)*
Parasitism
Vector
The growth and spread of a pathogen in or on a host resulting in injury to the host tissue.
Define the term “pathogen”.
Infectious Disease
A microbe capable of causing diease by invading tissues, providing toxins, or both
Virulence is the degree of what?
What are two things that effect virulence?
Describe each.
pathogenicity
Infectivity: how easily the microbe survives the normal host defenses and establishes infection
Severity: degree of the damage it causes the infection host
What are the four modes of transmission regarding pathogens?
Direct contact with the skin or mucous membranes of a diseased person (or carrier) with or without active penetration of the microbe through the skin or mucous membranes
Inhalation - droplets or particles in the air
Ingestion - of food and water (or other items we put into our mouths) that is contaminated with fecal material, insects, dead or live animals, soil, and other sources
Parenteral – direct contamination of blood, body fluids, or tissues by arthropod and other animal vectors and by nonsterile syringes and needles
What are the four “attachment and establishment factors” of the microbe?
Portal of Entry
Attachment
Quantity of microbe needed to establish infection
Quorum-sensing Regulators
What are the various chemicals that:
(1) restrain the disease-causing actions of the microbe until sufficient quantity of microbes are present
* then*,
(2) switch on the disease-causing actions all at once.
Quorum-sensing regulators
Within microbe attachment,
what is the features that the microbe may use to gain attachment to the host?
What type of “chemical” and “molecule” is used by the microbe to facilitate attachment?
Fimbrae: attach to specific receptor site on specific tissue
Surface chemicals: dissolve covering of cells and aid chemical attachment
Adhesive Matrix Molecules: produces biofilm thus providing “protection” for bacteria within harsh human environments
What are 4 examples of antiphagocytic factors of microbes?
Capsule: most notable - “slippery/slimey” nature assists bacteria from being completely engulfed by the phagocyte
Leukocidin: causes destruction of WBCs
“leuko = white / cidin = kill”
Coagulase: causes blood fibrin clot to form around the microbes (coagulase = enzyme that coagulates)
Survival of phagocytosis: resistance to killing within a phagocyte (e.g. mycobacteria, gonococcus, Listeria)
What are factors that promote the invasion and spread of a pathogen in/on the tissue?
“invasive” enzymes
What are the 8 “invasive enzymes”?
(1) Collagenase – breaks down collagen fibers thus destroying tissue integrity
(2) Lecithinase – destructive to cell membranes of red blood cells and other tissue cells
(3) Hyaluronidase (Staphylococcus, Streptococcus, Clostridium perfringens) – breaks down hyaluronic acid in cell membranes
(4) Fibrinolysin & Streptokinase – lyses fibrin in blood clots thus preventing isolation of the infection
(5) Hemolysins (Staphylococcus, Streptococcus, C. perfringens) – dissolve red blood cell membranes
(6) Lipase – digest lipids allowing bacteria to enter
(7) Proteases – digest proteins (e.g. IgA, certain other protective chemicals) thus permitting bacteria to evade entrapment, digestion, etc.
(8) Super Antigens – cause exacerbated immune or inflammatory response
What the 5 examples of exotoxins?
tetanus neurotoxin
staphylococcal enterotoxin
cholera toxin
diptheria toxin
streptococcal erythrogenic toxin
The characteristics below describe what type of proteins?
- Cytolytic and receptor-binding proteins (usually)
- Many are dimeric: A&B subunits; facilitates entry into tissue cells
- Tissues affected are very defined and limited
- Superantigens are special group of toxins
- Often coded on plasmid or lysogenic phage
exotoxins
What type of substance has the following characteristics:
- “LIPID A” (Lipopolysaccharide LPS) component of gram-negative cell walls
(released upon disintegration of the cell) - Binds to CD14/TLR4 (toll-like receptor 4) on macrophages, B cells, and other cells
- Not extremely potent
- Stimulates production and release of acute-phase cytokines
endotoxins
Gram-negative bacillus cell wall sloughs off or disintegrates in __________.
endotoxins
What are the extrachromosomal DNA in bacteria?
Transmitted to daughter cells through what process?
How is this structure passed to other bacteria?
the plasmid
cell division
through conjugation
In short, describe lysogeny.
What can lysogenic bacteria DNA code for?
Viral DNA incorporated into bacterial DNA.
Can code for some exotoxins and invasive enzymes.
The recombination of genes result in what?
- different (new types) of antigens are produced which the current immunity response is not effective
- causes increased resistance to antibiotics
What are the 3 ways many bacteria gain antibiotic resistance?
- mutated genes
- plasmid encoded genes
- lysogenic virus
Beta-lactamase is what?
What is the version of this enzyme that affects a larger groupof antimicrobics?
a bacterial enzyme that inactivates many beta-lactam antibiotics
Extended Spectrum Beta-Lactamase (ESBL)
What is the beta-lactam resistant bacteria that encodes a low-affinity penicillin bind protein and has a mutated mecA gene?
What is the beta-lactam resistant bacteria that possess mutated genes for outer membrane porins and PBP transpeptides; they are also carried by plasmids?
Methicillin-Resistant Staphylococcus aureus (MRSA)
Carbapenem-Resistant Enterobacteriaceae (CRE)-
Carbapenemase-producing Enterobacteriaceae (CPE)
In host resistance factors, what are the two types?
non-specific
specific
Within non-specific factors, what are the physical/mechanical barriers?
skin
mucous membranes
cilia of the respiratory tract
peristaltic action of the gut
normal flora
What are chemical barriers that are included in host resistance factors?
acidic pH (stomach, skin, vagina, urine)
bile salts
lysozyme (tears, saliva)
antimicrobial chemical from normal flora
interferon (a type of lymphokine)
During inflammation, what is formed to enclose the pus (phagocytes, dead microbes, dead tissue cells, plasma)?
the fibrin clot/wall
In cell-mediated immunity, the antigen stimulates the release of biologically active substances called ___________.
What do these substances do?
lymphokines
enhance phagocytosis
What is the term for the antibody that combines with bacterial cells and makes them more suceptible to phagocytosis?
opsonin
What type of substance is not very potent per unit weight but in high levels in the bloodstream can trigger very large effects including shock and death?
Endotoxins
