Persistent Infections Flashcards
(42 cards)
If antibiotics and the immune system were a 100% effective
All infections would be cleared
What is a persister?
A phenotypic variant that constitutes about 1% of cells in stationary phase and biofilms
What is a persister cell?
Dormant variants of regular cells that form stochastically (randomly) in microbial populations and are highly tolerant to antibiotics
The presence of persister cells
Might be important in the aetiology of many recalcitrant infectious diseases
The formation of persisters rapidly increases during
Mid- exponential phase in several species, but the mechanism that underlies this remains unknown
Bacterial growth
Log phase, stationary phase, death phase
Unlike resistant cells, persisters are
genetically identical to susceptible bacteria, constituting phenotypic variants of the wild type
Persister cells are isolated by
Applying a lethal dose of antibiotics to a growing culture
A biphasic killing curve is
The 1st slope of the initial phase of killing represents the rapid death of the sensitive population
The 2nd slope of the second phase represents the much slower death of persisters
After removal of antibiotic persisters can
regrow and give rise to antibiotic-sensitive cells that are genetically identical to the original population
The persister state is
An altruistic behaviour benefiting the kin
Most cells do not become persisters
Averaged data sets
Do not show single cell variation within a population
Single cell analysis can be done by
Microscopy, flow cell cytometry or microfluidics
Persister cells are formed by
A stochastic process
Two processes control persister formation
- Stochastic fluctuation in the level of persister proteins
2. Controlled, regulated mean level of expression of these proteins
Regulation of persister proteins
Is dependent on the density of the population, and probably on several other factors as well
What ultimately controls stochastic persister fluctuation
The environment
How do we identify persisters?
- Treat a culture with ABs (cells left alive are persisters)
- Microfluidics
- FACS (fluorescent activated cell sorting)
- FD (fluorescence dilution)
FACS
Fluorescent activated cell sorting
A form of flow cytometry using degradable GFP
FD
Fluorescence dilution
Bacterial cells are loaded with a fluorescent protein
After the induction is switched off dilution of the pre- formed pool of fluorescent protein will report the extent of bacterial replication
The lack of FD is a marker for the absence of replication
Microfluidics
The science of manipulating and controlling fluids, usually in the range of microliters (10-6) to picoliters (10-12), in networks of channels with dimensions from tens to hundreds of micrometers
Flow cytometry
A technique used to detect and measure physical and chemical characteristics of a population of cells or particles.
A sample containing cells or particles is suspended in a fluid and injected into the flow cytometer instrument. The sample is focused to ideally flow one cell at a time through a laser beam and the light scattered is characteristic to the cells and their components. Cells are often labeled with fluorescent markers so that light is first absorbed and then emitted in a band of wavelengths
Persister cells are formed by
An overproduction of proteins that are toxic to the cell and inhibit growth - toxins
Persister toxin expression is
under regulatory control
