Microbiology-Biofilms/Lab Test 2 Study Guide
Describe how microbes spread from a biofilm to another part of the wound bed or to other wounds.
Fully mature biofilms shed planktonic bacteria, micro colonies, and fragments of biofilm that disperse and attach to other parts of the wound.
What chronic diseases are associated with biofilms?
Periodontal disease, cystic fibrosis, chronic acne, and osteomyelitis.
What is the term for bacterial communication that develops in Stage Two?
Quorum Sensing
Relate the importance of contrast to the need to stain microbes for microscopy.
Some cells are not naturally pigmented so it is important to stain them to get the full view of them through the microscope.
Describe the source, location, and texture of the extracellular polymeric substance (EPS) that develops in Stage Three?
Source: Bacteria, Location: Outside of the cell, Texture: consists of polysaccharides, proteins, glycolipids, and bacterial DNA.
Describe what is meant by "hibernation" in biofilms and its significance.
Subpopulations of biofilms become metabolically quiescent.
What does the microbial term "sessile" mean?
firmly attached
Define the term aseptic
free from contamination cause by harmful microorganisms
Name the negative stain used in lab.
Nigrosin
Do all chronic skin wounds show overt signs of infection?
No
In Stage One of biofilm formation, are the microbes sessile? Explain.
No because they most often begin in a planktonic stage.
Under natural conditions, do most microbes remain planktonic? Explain.
No because they tend to attach to surfaces and eventually form biofilms.
Describe how reactive oxygen species (ROS) and proteases naturally secreted during an inflammatory response to a biofilm can result in impaired wound healing.
They damage normal/healing tissues, proteins, and cells.
In terms of electrical charge of the chromogen, explain why a basic stain colorizes the bacterial cell and not the background.
Through ionic or covalent bonds between the chromogen and the cell.
Name a biofilm that forms each day in our mouth and is visible to the naked eye.
Tooth plaque
T or F: Conditions which impair the immune system can make a patient more likely to develop biofilms in wounds.
True
T or F: Tissue ischemia (reduced blood supply), tissue necrosis (destruction), and poor nutrition are factors which increase the risk of developing biofilms.
True
What medical devices are biofilms found on the surface of?
Urinary catheters, endotracheal/tympanostomy tubes, orthopaedic/breast implants, contact lenses, intrauterine devices, and sutures.
Describe three ways in which mature biofilms offer "mutual protection" to the microbes.
1. Secrete protective enzymes 2. Transfer genes into another substance 3. Attach/incorporate into an existing biofilm
List two reasons why negative staining is used.
1. To determine morphology and cellular arrangement on bacteria that are too delicate to withstand heat-fixing. 2. Produces minimal cell shrinkage
What is the order of planktonic bacteria activity?
1. Attach to a surface 2. Form strongly attached micro colonies 3. Develop the initial EPS and become increasingly tolerant to biocides 4. Evolve into mature biofilms with extreme resistance to biocides 5. Reform mature biofilms after mechanical disruption
Describe the general principles of wound biofilm management (biofilm-based wound care).
1. Chronic wound found 2. Suspected biofilm 3. Reduce biofilm burden (debridement/vigorous cleansing) 4. Prevent recontamination w/ microoganisms 5. Barrier dressing 6. Suppress biofilm reformation 7. Sequential topical antimicrobials 8. Reassess healing 9. Healed
List three common basic stains.
1. Crystal Violet 2. Safranin 3. Methylene blue
List the three purposes of heat-fixing a bacterial smear.
1. Kills the bacteria 2. Makes bacteria adhere to slide 3. Coagulates cytoplasmic proteins to make them more visible
What does the microbial term "planktonic" mean?
Free-floating and solitary microorganisms
What two categories of microbes are found in biofilms?
Bacteria and Fungi
How can the presence of a biofilm cause the production of wound slough (fibrin slough)?
Biofilms stimulate inflammation which increases vascular permeability and production of wound exudate and the build up of fibrin slough.
Are biofilms more frequent in acute wounds or in chronic wounds?
Chronic wounds
Define the term bacterial pleomorphism
Have an inconsistent, variable shape
Summarize the research on the lowest concentration of antibiotics required to kill biofilms compared to prescription levels of the same antibiotics. What is the clinical significance of these results?
It exceeds the maximum prescription levels for antibiotics. Standard oral doses may have no affect.
Define the term simple stain
It has a single base
List 3 molecules that the EPS of a mature biofilm resists by "blocking".
Large molecules, antibodies, and inflammatory cells (WBC).
Describe the characteristics of Stage Two that are different from Stage One?
The bacteria in stage two multiply and differentiate, whereas the bacteria in stage one are free-floating and solitary at first and then attach themselves to surfaces.
Describe how an acidic (negative) stain colorizes the background and not the cells.
The chromogen is acidic and carries a negative charge. The negative charge on the bacterial surface repels the negative charge on the chromogen, staining the background without staining the cell.
Are most biofilms made of one species or many (polymicrobial)?
They can be both. The may have a single bacterial or fungal species or they could be polymicrobial.
How does a biofilm benefit from the wound exudate?
When the chronic inflammatory response is not successful.
Do chronic skin wounds usually involve biofilms?
Yes
Identify shapes/arrangements of bacilli, vibrios, coccobacilli, diplobacilli, streptobacilli:
bacilli: rods vibrios: slightly curved rods coccobacilli: short rods diplobacilli: two daughter cells (2) streptobacilli: remain attached (form a chain)
Identify shapes/arrangements of cocci, diplococci, streptococcus, staphylococcus, tetrads, sarcinae:
cocci: spheres diplococci: two daughter cells remain attached after coccus divide (2) streptococcus: cells that remain attached to form a chain (chain) staphylococcus: cluster tetrads: second division thats perpendicular to the first sarcinae: cube-shaped arrangement of 8 cells
Define the term chromogen.
colored molecule
Identify the shapes/arrangements of spirals and spirochetes:
spirals: spirals spirochetes: flexible spirals
How quickly can a wound biofilm reform after debridement?
within 24 hours
