Bjarnsholt T
APMIS. Supplementum. Date of publication 2013 May 1;volume (136):1-51.
1. APMIS Suppl. 2013 May;(136):1-51. doi: 10.1111/apm.12099.
The role of bacterial biofilms in chronic infections.
Bjarnsholt T(1).
Author information:
(1)Københavns Universitet, København N, Denmark. tbjarnsholt@sund.ku.dk
Acute infections caused by pathogenic bacteria have been studied extensively for
well over 100 years. These infections killed millions of people in previous
centuries, but they have been combated effectively by the development of modern
vaccines, antibiotics and infection control measures. Most research into
bacterial pathogenesis has focused on acute infections, but these diseases have
now been supplemented by a new category of chronic infections caused by bacteria
growing in slime-enclosed aggregates known as biofilms. Biofilm infections, such
as pneumonia in cystic fibrosis patients, chronic wounds, chronic otitis media
and implant- and catheter-associated infections, affect millions of people in the
developed world each year and many deaths occur as a consequence. In general,
bacteria have two life forms during growth and proliferation. In one form, the
bacteria exist as single, independent cells (planktonic) whereas in the other
form, bacteria are organized into sessile aggregates. The latter form is commonly
referred to as the biofilm growth phenotype. Acute infections are assumed to
involve planktonic bacteria, which are generally treatable with antibiotics,
although successful treatment depends on accurate and fast diagnosis. However, in
cases where the bacteria succeed in forming a biofilm within the human host, the
infection often turns out to be untreatable and will develop into a chronic
state. The important hallmarks of chronic biofilm-based infections are extreme
resistance to antibiotics and many other conventional antimicrobial agents, and
an extreme capacity for evading the host defences. In this thesis, I will
assemble the current knowledge on biofilms with an emphasis on chronic
infections, guidelines for diagnosis and treatment of these infections, before
relating this to my previous research into the area of biofilms. I will present
evidence to support a view that the biofilm lifestyle dominates chronic bacterial
infections, where bacterial aggregation is the default mode, and that subsequent
biofilm development progresses by adaptation to nutritional and environmental
conditions. I will make a series of correlations to highlight the most important
aspects of biofilms from my perspective, and to determine what can be deduced
from the past decades of biofilm research. I will try to bridge in vitro and in
vivo research and propose methods for studying biofilms based on this knowledge.
I will compare how bacterial biofilms exist in stable ecological habitats and
opportunistically in unstable ecological habitats, such as infections. Bacteria
have a similar lifestyle (the biofilm) in both habitats, but the fight for
survival and supremacy is different. On the basis of this comparison, I will
hypothesize how chronic biofilm infections are initiated and how bacteria live
together in these infections. Finally, I will discuss different aspects of
biofilm infection diagnosis. Hopefully, this survey of current knowledge and my
proposed guidelines will provide the basis and inspiration for more research,
improved diagnostics, and treatments for well-known biofilm infections and any
that may be identified in the future.
© 2013 APMIS Published by Blackwell Publishing Ltd.
DOI: 10.1111/apm.12099
PMID: 23635385 [Indexed for MEDLINE]
