Biofilms in Disease - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 3

bacterial pathogens. In addition, bacteria cause a wide array of nonfatal but
nevertheless severe infections, such as infections of the skin and soft tissues, the
lung, the intestine, and the urinary tract, to name but a few.
Many bacterial infections occur in the hospital in patients with a weakened
immune system, which is due to underlying genetic or infection-related immune
deficiencies, or the generally weakened status of the patient. Widespread antibiotic
resistance often makes these infections extremely difficult to treat.
Another important reason for the problems associated with treating bacterial
infections is the formation of biofilms. The National Institutes of Health estimated
that more than 60 % of microbial infections proceed with the involvement of
biofilms. Biofilms are sticky agglomerations of bacteria or other microorganisms.
They significantly decrease the efficacy of antibiotics and the patient's immune
defenses.
In nature, bacteria commonly form biofilms. However, for more than a century,
microbiological research was limited to growing bacteria under artificial conditions
which we now know barely reflect their natural biofilm mode of growth. William
J. Costerton, a pioneer of biofilm research, introduced the biofilm concept and the
term “biofilms” to microbiology in the 1970s (Costerton et al. 1978 ). Initially
focused on in vitro research and “environmental” bacteria, biofilm research over
time increasingly included the investigation of “medical” biofilms formed by
bacterial pathogens during infection.
Medical biofilm research comes with significant challenges that biofilm
researchers are still struggling to cope with. This is due to the fact that in vitro
biofilmmodels, despite the fact that they revealed many molecular determinants and
principles of biofilm formation, barely reflect the situation that the bacteria encoun-
ter in the human host. The more recent focus on establishing animal models of
biofilm infection and the capacity to directly investigate infectious isolates by
modern genetic methods has taken biofilm research to a new level. Notably, con-
cepts developed based on in vitro biofilm research often were not confirmed on the
in vivo level, demonstrating the necessity to complement in vitro biofilm research by
appropriate methods to ascertain their in vivo relevance (Joo and Otto 2012 ).
2 Biofilm Infections
Among the many types of infection in which biofilms are involved, a few have
gained particular attention from researchers, owing to their frequency, severity, or
potential model character for other biofilm-associated infections. Infections on
indwelling medical devices, such as catheters or joint prostheses, are virtually
always biofilm related. Owing to the high number of surgical interventions being
performed nowadays, they are very common. By far the most important pathogens
causing infections of indwelling medical devices are Staphylococcus aureus and
coagulase-negative staphylococci, such as Staphylococcus epidermidis (Otto 2008 ).
As these bacteria are commensals on the human skin and mucosal surfaces,