Exam 1 - (1) Introduction to bacterial infection Flashcards
A 2001 WHO report showed that bacterial infections caused ___% deaths worldwide.
26.3
What is the most common reason individuals seek treatment for an infectious disease?
Oral infections
What is an infection?
Invasion of the body by a microbe:
-bacterium, fungus, parasite
that causes damage either directly or indirectly
Describe the six steps in the disease process.
- Encounter
- Entry
- Colonization and Invasion
- Multiplication and/or spread
- Damage
- Outcome
There is a natural reservoir of infectious microbes, however encounter =/=
infection
An endogenous infection is one which:
is caused by the body’s own innate infectious agents that have previously been dormant or inapparent
Pathogens must _____ the body to establish an infection
enter
We are a ____ tube with _____ cavities.
hollow
Pathogens must _____ a surface before causing a disease. This is done by pathogen _____ to a host tissue.
- colonize
- adherence
The two types of adherence are:
Nonspecific and specific
Two types of Nonspecific adherence are R_____ and D_____. Examples of D____ are:
- Reversible
- Docking
- Brownian movement (random interactions), electrostatic interactions, interactions with glycocalyx or extracellular matrices.
Two types of specific adherence:
Irreversible and Anchoring
______ are substances on the surface of microbes that are involved with adherence to host tissue. Where can they be found topographically on microbes?
- Adhesins
- On fibrae/pilli, capsules, cell surface
Adhesins interact specifically with what? An example of this is S. mutans binding to tooth pellicle via:
- Adhesin receptors
- Glucosyl transferase which binds to a salivary protein that is involved in pellicle formation
Some pathogens only colonize, but most must ______.
Invade
What does a pathogen require for successful colonization?
adaptation for growth in a given niche (e.g. skin pathogens withstanding the skin environment/garnering nutrients on the skin)
Name three ways bacteria take up nutrients
1-Carrier-mediated diffusion (facilitated)
2-Phosphorylation-linked transport (group translocation)
3-Active transport (energy dependent)
What specifically must a pathogen have to invade?
virulence factors that allow them to invade the host: Invasins (Hyaluronidase, streptokinase (blood clot), and specific proteins that induce endocytocis/phagocytosis)
Spread of microbes is important for disease progression and often occurs through:
multiplication
Spread occurs through 2 different mechanisms:
1- Lateral propagation to contiguous tissues (multiply then spread
2- Dissemination to distant sites (spread then multiply)
Disease symptoms are often dependent on ______ also known as pathogen _____.
- pathogen density
- pathogen load
Damage to host tissue as a result of an infection can be caused by either ______ or ______.
- Host response
- Infectious organism
Damage via host response can be caused by:
- Phagocytes
- Cytotoxic T cell activity
Damage via infectious organism can be caused by
- Lytic viral infections
- Invasins damaging host tissue
- Toxin producing microbes
What are the two types of toxins?
-Endotoxins and Exotoxins
What is an endotoxin typically and what is the term generally reserved for?
- Component of the cell wall
- lipopolysaccharide
What typically is an exotoxin?
a soluble substance secreted into host tissues
Describe/define three examples of exotoxins
- Cytotoxins: lyse cells (Hemolysis ->RBC’s, Leukocidins -> WBC’s)
- Enterotoxins: affect intestinal cells
- Neurotoxins: affect neurons
Describe the chronological stages of an infection and the courses it can take:
,-Death
,- Disease–I-Recurent Illnesses
-Incubation period —I ‘-Recovery and cure
‘
‘- No disease- Asymptomatic Infection
How many microbes does the body normally contain compared to host cells?
10X
Normal microflora/microbiota are found on all body _____. They can have _____ effects on the host. They coexist with the host without causing ______.
- surfaces
- beneficial
- harm
Name two places in the body that can safely harbor bacteria:
1-Gastrointestinal tract (10^2 bacteria per gram)
2-mouth (estimated 500 different species)
What makes a microbe a pathogen?
- Ability to adhere to a host
- Ability to colonize a host
- Ability to replicate within a given niche
- Ability to cause damage (Invasion, production of toxin, activation of the immune system)
Although there are differences between commensals and pathogens:
No microorganism is intrinsically benign or pathogenic!
Fungal cells are
Eukaryotic duhhh!
Bacteria can have varied responses to oxygen depending on their type. What are three responses/types of bacteria in terms of oxygen presence.
1- Strict aerobes
2- Obligate anaerobes
3- Facultative anaerobes
Describe Strict aerobes:
must have oxygen to grow
Describe Obligate anaerobes:
cannot tolerate oxygen
Describe Facultative anaerobes:
can grow with or without oxygen (most medically important bacteria)
Describe Oligotrophs:
Can grow with limited nutrients
Describe Microaerophiles:
require some oxygen, but lower levels of oxygen
Describe Mesophiles:
they grow well in mild temperatures
What is fundamentally different between Gram + and Gram - bacteria?
the structure of their cell membranes
Describe the makeup of Gram + cell surface:
has a cell membrane covered by a large cell wall which is composed of murein (peptidoglycan). on the surface of the cell wall are teichoic acid and lipoteichoic acid.
Describe the makeup of a Gram - cell surface
has an inner cell membrane and a thin cell wall (murein) separated by a space called the periplasm. The cell wall is superficially attached to another “outer” cell membrane by lipoproteins. On the surface of the outer membrane are lipopolysaccharides, and embedded within the cell membrane are porins.
The structure of the peptidoglycan, murein is composed of chains of alternating ______ and ______ , cross-linked by ______.
- N-acetylmuramic acid (NAM)
- N-acetylglucosamine (NAG)
- peptides
Murein wihtin Gram + and Gram - differ in structure. How?
-Gram +: L-lys-gly-D-ala
-Gram -: DAP-D-ala
(DAP = diaminopimelic acid)
Certain antibiotics operate by ______ murien biosynthesis
interrupting/disrupting
