The
evolution of more severe infections is not necessarily driven by bacteria
multiplying faster, new research shows. Humans and animals can develop resistance
to harmful bacteria (pathogens) over time or with antibiotics or vaccines, and
it is usually assumed that pathogens respond by multiplying faster.
The
new study shows pathogen virulence and replication rates can evolve separately.
The researchers believe that, once
resistance spreads in host species, virulence may be driven by other means such
as by manipulating host immune systems.
The
research examined the spread of bacteria called Mycoplasma gallisepticum among house finches -- a rare example of a
well-studied host-bacteria evolution where humans have not intervened with
antibiotics or vaccines.
For
example, if trying to kill the pathogen inevitably leads to more virulent
infections, it might be worth trying to slow down pathogen evolution by
combining treatments that both eliminate the pathogen and prevent it
manipulating host immune systems.
Some
populations of house finches have been exposed to Mycoplasma gallisepticum for more than 20 years, while others have
not -- and have therefore not developed resistance.
In the study, carried out in
Arizona and supported by Arizona State University and Auburn University, 57
finches from previously unexposed populations were exposed to the pathogen.
The
findings show virulence has increased consistently over more than 150,000 bacterial
generations since outbreak (1994 to 2015).
By
contrast, while replication rates increased from outbreak to the initial spread
of resistance (1994 to 2004), no further increases have occurred subsequently
(2007 to 2015).
See:
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology
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