Biomedical Engineering Reference
In-Depth Information
compared to static conditions, especially when pure cultures were tested. The presence of
Streptococci
reduced material invasion by the yeast, thereby revealing the importance of
testing materials in a biological environment (Rodger et al., 2010).
A continuous flow culture (CFC) aims at cultivating microorganisms in a continuous flow of
fresh medium to mimic physiological conditions and to avoid the decline of the culture by
nutrient depletion. Such instrumentation is easy to assemble in a microbiology laboratory
equipped with an incubator, peristaltic pump, fresh medium flask, tubing, and chamber(s)
where the material of interest, on which biofilm was already initialized, is inserted
(Uppulari et al., 2009). Serial chambers allow independent samples to be produced under
similar conditions (nutrients, flow rate, temperature, and incubation time).
Candida albicans
biofilms have been reported to grow more rapidly under continuous flow than in static
culture (Uppulari et al., 2009).
Specific devices have been developed for continuous flow studies. The Modified Robbins
Device (MRD) is a small channel-shaped chamber with different openings in which
biomaterial discs could be inserted when the instrument is mounted to form the channel
wall. These devices are provided with a liquid circulator for low-pressure applications.
Microorganisms introduced into the fluid stream can adhere to the plugs and generate a
biofilm that is easy to remove for analysis. This instrumentation was used to evaluate some
maintenance protocols for oral devices (Coenye et al., 2008), as well as for other purposes.
The constant depth film fermenter (CDFF) is an instrument that is able to generate
standardized biofilms on any materials that can thereafter be removed for subsequent
investigations; the advantages of such a device includes controlled experimental conditions
for growth that mimic the oral environment. Some authors (Lamfon et al., 2003) used the
CDFF to produce
Candida
biofilms in the presence of artificial saliva on enamel, dentine, and
denture acrylic disks. Their data demonstrated that the roughness of the material influences
formation and development of
Candida
biofilms.
3.2.
In vivo
models
The rat catheter biofilm infection model (Andes et al., 2004; Lazzell et al., 2009; Ricicová et
al., 2010) allows evaluation
in vivo
of the comportment of one microorganism that is exposed
to host proteins and immune factors. Other animal models have been utilized to monitor
materials and devices that are placed in the bathing conditions of the oral cavity and to
mimic denture stomatitis with fungal invasion and neutrophil infiltration of the adjacent
mucosa. The rodent acrylic denture model was developed for such purposes (Nett et al.,
2010). In humans, abrased pieces of self-adhesive (Budtz-Jörgensen et al., 1981) or acrylic
resin disk (Avon et al., 2007) were fixed on dentures to gain some information
in vivo
concerning biofilm formation in the oral cavity.
4. Surface treatment to control
Candida
biofilms
Candida
in biofilms on prosthetic materials is difficult to remove. If it is absurd to eradicate a
commensal of the oral environment, it is important to consider the prosthesis and the
patient simultaneously because the prosthesis is a nest for
Candida
growth and a possible
source of infection for the oral mucosa. Daily brushing should be encouraged in all denture-
wearers; in denture stomatitis, decontamination of the denture becomes a mandatory part of
treatment. Often, the family or professional caregivers must compensate for the difficulties
that the elderly face due to loss of independence, dexterity, or memory. Thus, antifungals
