Biomedical Engineering Reference
In-Depth Information
information by analysis of cell extracts, supernatants, biological fluids, and
live biological samples. 1 H and 1 H-detected 13 C NMR provide direct, time-
resolved monitoring of metabolite concentrations. The disadvantage of NMR
is its inherent low sensitivity due to the low energies involved, requiring
careful optimization to reduce measurement times and lower concentration
detection thresholds. NMR has been used to measure flow and diffusion in
biofilm systems (Van As and Lens 2001; Seymour et al. 2004; Hornemann et al.
2008).
Recently, the capability of a combined CLSM and NMR microscope com-
bination was demonstrated to measure time and depth-resolved metabolite
concentrations under flow in viable biofilms (Majors et al. 2005). Unlike the
traditional flow-tube geometry used for biofilm imaging and diffusion studies,
this application employs a growth media perfusable sample chamber of planar
geometry that supports a sample grown on a thin surface. Using this system,
one can apply a series of combined techniques to perform magnetic resonance
imaging (MRI), magnetic resonance spectroscopy (MRS), and also diffusion
in a novel way on a single biofilm sample. McLean and colleagues (McLean
et al. 2007) studied, with the help of this system, biomass volume and dis-
tributions as well as time- and depth-resolved metabolite concentrations in
active Shewanella oneidensis and S. mutans biofilms.
4.4 Infectious Microbial Biofilms—Treatment
Modalities and Resistance
Commonly employed antimicrobial agents were not specifically designed
to target bacterial biofilms. As described earlier, bacterial biofilms may
have more than one antimicrobial resistance mechanism, and that these
diverse mechanisms may act concurrently, and in some cases, synergistically
(Drenkard 2003). Antibiofilm strategies must address and target a range of
potential resistance mechanisms and take into account the substantial het-
erogeneity inside biofilms. It was shown, for example, that the dynamics and
spatial distribution of
-lactamase induction in P. aeruginosa cells growing
in biofilms is highly heterogeneous (De Kievit et al. 2001). In addition, as
bacterial cells growth rate within biofilms is not synchronized, a nonuniform
susceptibility pattern to antimicrobial agents should be anticipated.
β
4.4.1 Antibacterial and Antifungal Treatment Modalities
of Infectious Biofilms
Prophylactic use of antibiotics and biocides can reduce the incidence of
biofilm-associated infections of medical devices. Strategies for prophylaxis
include device coatings, device immersion, surgical site irrigation, antibiotic-
loaded cements, and antibiotic lock therapy. Although the use of antibiotic
 
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