Lecture 33: Control of microorganisms II Flashcards
Give 4 reasons why antimicrobial control can fail.
- Suboptimal method of microbial control
- High bacterial load
- Highly virulent pathogens
- Resistant microorganisms
Give 2 possible ways that microoganisms can resist microbial control
Resistance to antiseptics or biofilm formation
Explain how microorganisms can become resistant to antiseptics.
Some bacteria that are good at sensing their environment and resisting the conditions can detoxify it for the rest of the population.
Describe the composition of biofilms.
They are highly organized bacterial communities with cells aggregated within an extracellular matrix that can adhere to the surface. It contains microbial cells as well as sugars, free DNA, and communication molecules between microbial cells.
The communication between bacterial cells in a biofilm is called […]
Quorum sensing
Where can biofilms form?
They can form either on surfaces or on other cells.
What is the purpose of quorum sensing in a biofilm?
This allows them to sense how many other bacteria are around them. This determines whether the biofilm should keep growing or if the surface is saturated and growth should be limited.
Where are biofilms typically found? Name 4 places.
They are found in natural environments, water pipes, in the mouth (i.e. plaque on the teeth), and on medical devices.
What are the two major proteins in biofilms?
Adhesins and elastins
What is the purpose of adhesins in biofilms?
It makes the cells sticky, allowing them to adhere to surfaces
What is the purpose of elastins in biofilms?
They allow the biofilm to take on a slimy structure, minimizing penetration in the case of environmental change.
What part of the biofilm is most resistant to antibiotics?
The cells towards the inside of the biofilm, as they have many layers of protection above them such as other cells and the polysaccharides + proteins
Explain how antibiotics behave in the presence of a biofilm.
If you want to apply an antimicrobial compound to a biofilm, there is poor penetration. Antibiotics, for example, won’t make it deep into the biofilm.
Explain how specialization of cells varies throughout biofilms.
Cells on the outside might be more specialized to detoxify incoming materials, while cells on the inside might be specialized to provide inside cells with enough nutrients.
Name 3 advantages of biofilms for bacteria.
- Poor penetration of antibiotics
- Trapping or inactivation of toxic molecules in the biofilm matrix
- Physiological state (slow growth) which makes bacteria become tolerant
What are the 4 levels of biohazard control in a lab? Explain which type of bacteria each one addresses.
- Non-pathogens
- Opportunistic pathogens that are not infectious through aerosol
- Pathogens that are infectious through aerosol
- Deadly pathogens that are transferred through aerosol
What are the typical safety precautions taken in a level 1 lab?
Decontamination of all biological materials
What are the typical safety precautions taken in a level 2 lab?
Restricted access, use of biological safety cabinets, extreme care with sharps
What are the typical safety precautions taken in a level 3 lab?
All air in lab is controlled and filtered, and everything is decontaminated
What are the typical safety precautions taken in a level 4 lab?
Entrance and exit to lab involves showers, vacuum room, UV, hazmat suit required
What lab safety level is Ebola?
4
What lab safety level is E. Coli?
1
What lab safety level is S. aureus?
2
What lab safety level is M. tuberculosis?
3
What lab safety level is P. aeruginosa?
2
Rank the following modes in transmission in order of easiest to hardest to control: droplets, contact, airborne.
Contact, airborne, droplets
Give 5 examples of typical PPE.
Protective gloves, vented googles, ear-loop masks, N-95 masks, lab coats/gowns
How is the ebola virus transmitted?
Through blood, urine, semen, saliva, and droplets (to some extent)
Is the infectious dose of ebola high or low?
Low
Can ebola be transmitted on surfaces?
It is possible but the risk of indirect transmission is low.
Give 3 reasons why ebola is so hard to control.
The infectious dose is low, it travels via contact and droplets, and there is no real treatment aside from using PPE (which is hard to put in place at a large scale)
What is the vector/reservoir for ebola?
Animals
Does ebola affect immunocompetent hosts or just immunocompromised hosts?
It affects immunocompetent hosts as well.
How is SARS-CoV2 transmitted?
Droplets, contact, aerosols
Can covid be transmitted on surfaces?
Possible but relatively low risk of indirect transmission.
Name 3 challenges involved in the infectious control of SARS CoV2
- Evolving science and knowledge about transmission route, infectivity, and strain variants
- Highly heterogeneous mortality and morbidity
- Very large but heterogeneous susceptible population
