Lecture 3 Flashcards
- Almost all pathogens belong to what classification of nutrient organisms? What does this mean?
- What is the optimal pH of MOST bacteria?
- Heterotrophs. They require reduced organic molecules (sugar, AA, FA, or nucleic acids) as sources of energy and carbon for growth
- Around 7.0
T or F
Many bacteria may grow on simple media. However, some bacteria require rather complex media
True!
Most bacteria are not picky where they get their food but some may require blood augar with specific nutrients to satisfy their nutritional needs.
In regards to oxygen, what are the two highly toxic forms talked about in class and enzymes do bacteria use to detoxify them?
The two highly toxic oxygen forms are:
•Superoxide radical 2O2-
•Hydrogen peroxide H2O2
Enzymes which are used by bacteria to detoxify these are:
•Superoxide dismutase (2O2 breakdown)
•Catalase and Peroxidase (H2O2 breakdown)
Define these types of microbes:
- Strict aerobes
- Strict or obligate anaerobes
- Facultative anaerobes
- Microaerophiles
- *Strict aerobes-** An organism which needs oxygen for growth because they cannot ferment or respire anaerobically.
- *Strict or obligate anaerobes-** Organisms that grow in the absence of free oxygen.
- *Facultative anaerobes-** An organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentationor anaerobic respiration if oxygen is absent.
- *Microaerophiles-** Organisms which need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen.
- Name three areas where you would find normal flora on an animal?
- Define these terms: Incubation period and shedding
- Literally anywhere you can think of. ( Skin, Mouth, Small intestine, Large intestine, Etc.)
- Incubation period- Period from the time of infection until time where clinical signs appear
Shedding- Period when infected individual is spreading the disease
Define the different types of carriers:
- Convalescent carrier
- Subclinical carrier
- Contact carrier
Convalescent carrier- An individual who is clinically recovered from an infectious disease but is still capable of transmitting the infectious agent to others.
Subclinical carrier- An infected individual who is nearly or completely asymptomatic.
Contact carrier- Individual just has contact with the organism and transmit it through their hands or other way.
What are some possible sources of infection?
- Droplet- Sneeze on someone…
- Dust- Generally infection through the respiratory tract
- Ingestion- Food poisoning!
- Contact- Touching auger with disease and touching your face
- Wounds- Open cuts provide the perfect environment
- Injection- Injection site abscesses
- Via the genital tract (STD’s) -…
- Transplacental- Mother to baby
- Umbilical- Born in dirty environment
- Nosocomial- Hospital acquired
- What are Saprophytes?
- How common are they among pathogenic bacteria?
- Can we grow them in the lab?
Saprophytes- heterotrophs which live on dead or decaying organic matter.
Most pathogenic bacteria belong to this class.
Yes, the use of blood auger plates!!!
Name the four aspects of Koch’s Postulates
Koch’s Postulates:
- The organism must be regularly isolated from cases of the disease
- It must be grown in vitro in pure culture
- Such a culture should produce the typical disease when inoculated into a susceptible animal
- The same organism must be isolated from the experimentally induced disease
Name the three components of colonization of mucosal surfaces
Association
Adhesion
Invasion
What roles do mucus (or exudates) and chemotactants have on the association of a bacterial colony to mucosal surfaces in the infection process?
Bacteria can be harbored within the mucus on the surface of mucosal tissues protecting it from normal clearance mechanisms.
Bacteria are often drawn towards epithelial surfaces by chemotaxis.
- Bacteria however are required to: have necessary mechanisms to move toward source, have the specific taxin receptors on their surface
T or F
Association component of the colonization of a bacteria is classified as a stable, irreversible attachment to the mucosal surface
False
The association component of bacterial colonization is classified as a loose and reversible process allowing for bacteria to respond to chemotactic factors.
- Attachment is usually usually between what areas of the bacteria and what type of molecules on the eukaryotic cell surface?
- What else also may function as adhesins?
- The attachment is usually between specific surface proteins (adhesins) of the bacterium and carbohydrate-containing molecules on the eucaryotic cell surface or glycocalyx x.
- Hemagglutinins!
Name the type of charge which is commonly seen on the surface of both the capsule of bacteria and the glycocalyx of eukaryotic cell? Why is this significant?
Both have a negative charge.
Like-charged surfaces repel one another!
What is the Derjaguin-Landau and Verwey-Overbeek (DLVO) theory?
The DLVO theory states:
As two rigid bodies of like charge approach each other they are affected by attractive and repulsive forces, which vary independently with the distance between the bodies.
What distances according to the DLVO theory will have a net force attraction and a net force repulsion?
Over distances of > 10nm there is a net force attraction
Over distances of 1nm to 10nm there is a net repulsive force
Over distances of less than 1 nm there is a strong attractive force
List the key features bacteria utilize to their advantage of overcoming these intermediate zones of repulsion
- Bacterial surfaces covered w/ fimbriae or capsular material
- Fe3+ and Ca2+
- Epithelial cell cilia
- Decreased radius of curvature
- “Think of ice pick to the head scenario. You will penetrate easier using the pointy end…” -Dr. Griffith
List the types of bacterial adhesins
Proteins
Polysaccharides
Lipoteichoic acids
- List the types of morpholically distinct fimbrin patterns
- List the ways fimbrial adhesins can be arranged
- Type 1 fimbriae and F4 (K88) fimbriae
- Polar or peritrichous (see below)
List two key features for each type of fimbrin
- *Type 1-** Fimbria can recognize mannose on RBC’s and bind. Ridged structure which is uniform cross-sectional diameter w/ an axial hole.
- *F4 (K88)-** Mannose resistant. More flexible structure
Mannose binding is significant because you can add mannose to suspension to block mucous adherence
What are nonfimbrial proteinaceous adhesions
Adhesins which lack a definite structure and often take the form of secreted proteins or proteins associated with the outer membrane.
Give two examples Dr. Griffith talked about when explaining nonfimbrial proteinaceous adhesins
- Streptococcus equi- M-Protein
- Staphylococcus aureus - Surface protein which has a specific affinity for fibronectin
- Neisseria gonorrhoeae- Group of outer membrane proteins (OMP’s) that aggregate the organism
- Bordetella pertussis- Two secreted proteins which function in adhesion: Filamentous hemagglutinin (not filamentous), Pertussis toxin- contains both toxic and adhesive properties
- Mucoid exopolysaccharide capsules are important for the formation of what? Which may help them resist being phagocytosed by neutrophils.
- T or F many bacteria can use their capsules as a mean of specific or nonspecific attachment
- Microcolonies
- True
List the carbohydrate and lipid type of adhesins talked about in class
Mucoid exopolysaccharide capsules
Lipoteichoic Acids
What are the two locations of where lipoteichoic acids adhere two we talked about in class
Fibronectin receptors (Streptococci and staphylococci)
Hydroxyapatite of the tooth enamel (S. mutans)
- Why might bacteria switch off the production of some adhesin proteins?
- How does this switch occur?
- It takes a lot of cell energy to make fimbria and other adhesins, fimbria may act as a disadvantage once an organism is bound/invades.
- The fimbrial phase to the non-fimbrial phase is under transcriptional control (at least with type 1 fimbriae) and the shift from one phase to the other occurs with a frequency of 10-3 per bacterium per generation.
List the media/growth conditions which may effect the production of adhesins
Temperature- Ex. lowering temperature on Bordetella
Nutrients- Ex. blood constituents required by Bordetella
Presence of antibiotics
Why is there a great diversity in host tissue receptors for bacterial adhesins ?
This is because the receptors on the mucosal cells are normally for hormones, nutrients, and a variety of other molecules used by the cells. Bacterial adhesins have mimiced these receptors over evolution.
Define:
•Extracellular pathogens
•Obligate intracellular pathogens
•Facultative intracellular pathogens
•Extracellular pathogens- Bacteria which reside outside of eukaryotic cells
•Obligate intracellular pathogens- Bacteria which can grow only within cells
•Facultative intracellular pathogens- Bacteria which have the capacity to grow and survive both inside and outside of eukaryotic cells
List the possible mechanisms for invasion
- Trauma or puncture (Clostridium tetani)
- not true invasion
- Endocytosis (Salmonella typhimurium)
- Receptor-mediated endocytosis (Chlamydophila psittaci)
- Uptake by antigen sampling sites (Salmonella sp.)
- Disruption by cytotoxins (Salmonella sp.)
- Direct penetration (Leptospira)
- What is the most common method which facultative and obligate intacellular parasites use to gain entry into the cell?
- List the two ways bacteria spread after replicating intracellularly?
- Endocytosis
- Destruction of the eukaryotic cell membrane; exocytosis
What are the two molecular basis of invasion that are though to be genetic?
Stimulation of uptake- ability of a bacterium to stimulate its uptake
Resistance to being killed- ability to survive and multiply once inside a cell.
