Biofilms + Lab Diagnosis Flashcards
What is a Biofilm
cell community enclosed in slime
- main component : extracellular polymeric substance matrix that is mostly made of polysaccharides that improve adhesion of bacteria
Steps to Biofilm Formation
1) adhesion of planktonic bacteria: some just sticks
2) line up to form monolayer: EPS is made
3) Multilayer forms: micro-colony because more friends join
4) Mature biofilm forms; proliferation and pulls in more friends; form mushroom shape and some leave
What Variables impact bacteria attachment
1) Texture and hydrophobicity of substratum: rougher and more hydrophobic (plastic) == more likely to stick
2) Conditioning film: various polymers make it easier to stick
3) Media/Fluid velocity
4)pH
5) Temperature
6) Cations
What is Quorum sensing
communication in biofilm that is dependent on autoinducers (AI)
- AI are species dependent + self-regulated
**once extracell >intracell —- stop proliferation and AI production
Impact of flow velocity on bacteria attachment
hydrodynamic boundary: layer that forms with no movement over substratum
- as increase speed of bacteria flowing over - hydrodynamic layer gets smaller —- easier for bacteria to stick
If go too fast — no hydrodynamic boundary + bacteria will flow right off
Benefit of biofilms
share nutrients and DNA; shelter each other from harmful stuff
- can share plasmids and Ab R genes
- mutual benefit
Prevention of Biofilm Formation
- prevent adhesion: add coating to substratum
- destruction of EPS matrix: mechanical, laser, heat
- target persister cells: normally stick around and have low levels of activity
Specimen collection
need to reflect the disease process and be collected in high enough amount
- always risk of contaminating bacteria
How to limit sample contamination
collect prior to antibiotic treatment
- sample as directly as possible
- use aseptic technique and PPE
- containers must be sterile and run tests right away
Direct Specimens
collected from normally sterile body fluids (blood, CSF)
- positive finding: diagnostic
Indirect Specimen
specimens of inflammatory exudates (voided urine) that have passed through sites known to be colonized with normal flora
- site of origin is sterile but likely to get contaminated when collecting
Samples from normal flora sites
primary site of infection is area already known to be colonized with other bacteria
- need to make selective examinations of what is normal vs what is causing infection
Why is transport media used
to provide stable conditions and prevent drying out
Enzyme linked immunosorbent assay
use antibodies linked to enzyme to detect Ag/bacteria
1) Direct primary antibody conjugated with detection molecule; primary detects Ag
2) Indirect: use primary antibody specific for Ag, 2nd specific for primary antibody and is conjugated with detection molecule
3) Sandwich: use capture antibody to detect bacteria + capture it , binds to different Ag; then use primary and secondary antibody to detect
—- helps capture specific bacteria with 2 Ag etc
Latex Agglutination
helps screen for specific Ag in sample
1) Positive control: sample that know has Ag
2) negative control: sample known without Ag
3) Sample
** add antibody conjugated with latex and if clump —- Ag present**
