Biomedical Engineering Reference
In-Depth Information
and coordinating their activities as a group. Thus, multicellularity is distin-
guishable from the unicellular behavior by cell-cell cooperation resulting, in
some cases, in individual cells “sacrificing” their capability to reproduce for
communal benefit (Velicer 2003).
4.1.2 Biofilms in Medicine
Biofilm-based infections can occur on abiotic or biotic surfaces (Pace et al.
2006). Infections involving biofilm formation are most frequently associated
with microbial colonization of the abiotic surfaces of indwelling medical
devices (IMDs) and are commonly referred to as foreign body infections (FBIs)
(Lynch and Robertson 2008; Romeo 2008; Shirtliff and Leid 2009). Although
clinical biofilms are typically of lower cell densities when compared to biofilms
grown in vitro , their overall architecture, as revealed by electron microscopy
methods, is similar. In the United States, device infections associated with
low-attributable mortality have been estimated to have initial rates of infec-
tion that vary from 1% to 3% for mammary implants, penile implants, and
joint prosthesis and 10% to 30% for urinary catheters (Donlan and Coster-
ton 2002; Thomas et al. 2006). Recent studies have also provided evidence on
interactions of infectious biofilms and their host tissues: although most biofilm-
related infections are associated with colonization of abiotic surfaces, there is
a growing number of reports on biofilm colonization of natural surfaces, for
example, urinary tract infections caused by uropathogenic Escherichia coli
(Anderson et al. 2003).
Biofilm infections affect a wide spectrum of tissues and structures, includ-
ing ear, nose, throat, mouth, eye, lung, heart, kidney, gall bladder, pancreas,
nervous system, skin, bone, in addition to contamination of the surfaces of
implanted medical devices (Donlan and Costerton 2002). The Centers for
Disease Control and Prevention estimate that more than 80% of infections
in humans are caused by bacteria growing as biofilms (National Institutes of
Health 1999). Should biofilm infections be considered as a single disease cat-
egory, the prevalence of this disease and the mortality associated with it is
substantial.
A typical biofilm infection is mostly treated first with antibiotics. As this
medication is ineffective in many of these cases a broader spectrum of antibi-
otics, sometimes combined with steroids, is used. Should the combined treat-
ment fail, a decision often is made to remove the infected tissue or biomaterial
by surgical intervention.
An early-stage diagnostic method that would allow for detection of the
early stages of tissue (Mansson et al. 2007; Dowd et al. 2008; Nett and
Andes 2008; Trampuz and Zimmerli 2008) or biomedical implant infection
(Bauer et al. 2006; Selan et al. 2008) is now emerging. Xiong and colleagues
(Xiong et al. 2005) report a rapid, continuous method for real-time moni-
toring of biofilm development, both in vitro and in a mouse infection model,
through noninvasive imaging of bioluminescent bacteria. An alternative to this
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