Observations of binary population biofilms

Siebel, Maarten A.; Characklis, William G.

doi:10.1002/bit.260370813

Cited by 78 publications

(36 citation statements)

References 19 publications

(2 reference statements)

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“…Biofilm thicknesses and biofilm areal cell densities were converted by using an average biofilm cell density (s,p,) of 4,700 g of carbon per mi3, obtained by review of extensive measurements on Pseudomonas aeruginosa biofilms (6,17,20). To compare experiment and theory, the data described by Anwar et al (1) were converted from CFU per centimeter of tubing to CFU per square centimeter by using the surface area of the tubing pieces, which was calculated to be 3.47 cm2/cm.…”

Section: Materuils and Methodsmentioning

confidence: 99%

Biofilm accumulation model that predicts antibiotic resistance of Pseudomonas aeruginosa biofilms

Stewart

1994

Antimicrob Agents Chemother

122

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A computer model of biofilm dynamics was adapted to incorporate the activity of an antimicrobial agent on bacterial biofilm. The model was used to evaluate the plausibility of two mechanisms of biofilm antibiotic resistance by qualitative comparison with data from a well-characterized experimental system (H. Anwar, J. L. Strap, and J. We l2osterton, Antimicrob. Agents Chemother. 36:1208Chemother. 36: -1214Chemother. 36: , 1992. The two mechanisms involved either depletion of the antibiotic by reaction with biomass or physiological resistance due to reduced bacterial growth rates in the biofilm. Both mechanisms predicted the experimentally observed resistance of 7-day-old Pseudomonas aeruginosa biofilms compared with that of 2-day-old ones. A version of the model that incorporated growth rate-dependent killing predicted reduced susceptibility of thicker biofilms because oxygen was exhausted within these biofilms, leading to very slow growth in part of the biofilm. A version of the model that incorporated a destructive reaction of the antibiotic with biomass likewise accounted for the relative resistance of thicker biofilms. Resistance in this latter case was due to depletion of the antibiotic in the bulk fluid rather than development of a gradient in the antibiotic concentration within the biofilm. The modeling results predicted differences between the two cases, such as in the survival profiles within the biofilm, that could permit these resistance mechanisms to be experimentally distinguished.It is widely recognized that bacteria colonizing a surface as a biofilm can be much more resistant to antimicrobial chemotherapy than are their planktonic counterparts (4,14). The reduced susceptibility of attached bacteria becomes crucial in the treatment of infections such as those associated with medical implants or cystic fibrosis (4). Two leading hypotheses have be.en advanced to explain the persistence of biofilm infections. The first hypothesis relates to antibiotic transport. According to this hypothesis, antimicrobial agents fail to fully penetrate the biofilm, so that in some regions of the biofilm, bacteria simply are not exposed to effective concentrations of an antibiotic (4, 10). The second explanation postulates that physiological differences of sessile cells, for example, low growth rates, reduce the susceptibility of microorganisms in the biofilm mode of growth (3,8 994-6098. to incorporate either of the two resistance mechanisms, with data from a well-characterized experimental system (1). The purpose of this investigation was to assess whether either mechanism, when analyzed quantitatively in terms of its constituent phenomena, could capture the qualitative behavior of the experimental data. A second objective was to discover differences between the predicted behaviors of the two mechanisms that might allow them to be experimentally discriminated. MATERUILS AND METHODSAn existing computer model of biofilm dynamics (9) was adapted to describe the activity of an antimicrobial agent on biofilm. This mod...

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Section: Materuils and Methodsmentioning

confidence: 99%

Biofilm accumulation model that predicts antibiotic resistance of Pseudomonas aeruginosa biofilms

Stewart

1994

Antimicrob Agents Chemother

122

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“…ml 21 for K. pneumoniae and P. aeruginosa, respectively, formed stable mixed-species biofilm over a period of 7 days. Siebel & Characklis (1991) have reported appearance of putative 'towers' of K. pneumoniae protruding above the base biofilm of P. aeruginosa. A similar structural heterogeneity was observed in our study: when dual-species biofilm was formed on the polycarbonate disc, a top pink film of K. pneumoniae blanketed the colourless basal biofilm of P. aeruginosa.…”

Section: Discussionmentioning

confidence: 99%

Disrupting the mixed-species biofilm of Klebsiella pneumoniae B5055 and Pseudomonas aeruginosa PAO using bacteriophages alone or in combination with xylitol

2015

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We investigated the potential of bacteriophages alone as well as in combination with xylitol for tackling mixed-species biofilm of Pseudomonas aeruginosa and Klebsiella pneumoniae. When mixed-species biofilm was established on polycarbonate discs, P. aeruginosa formed the base layer which was physically shielded on the top by K. pneumoniae. Thereafter, mixed-species biofilm was treated with bacteriophages. K. pneumoniae-specific depolymerase-producing phage KPO1K2 caused significant reduction in the count of Klebsiella. In contrast, P. aeruginosaspecific non-depolymerase-producing phage Pa29 failed to cause any reduction in the count of Pseudomonas. However, application of both phages together resulted in significant reduction in the count of both organisms. This suggests that depolymerase produced by phage KPO1K2 hydrolysed the top layer of K. pneumoniae and guided the entry of Pa29 to reach P. aeruginosa lying underneath. This phenomenon was confirmed when K. pneumoniae-specific nondepolymerase-producing phage NDP was used along with Pa29. Pa29 could not penetrate and reach its host bacterium. Xylitol worked synergistically along with the phage, resulting in a significant decrease in counts of both organisms. Disruption of mixed species biofilm by phage and xylitol was confirmed on the basis of the amount of protein and DNA released. This phagebased approach to altering the structural pattern and disrupting the mixed species biofilm is the first of its kind. It can be used as a topical application, a coating for foreign bodies or for aerosol delivery to tackle infections where both pathogens coexist in a biofilm mode.

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“…Indeed electron microscopy and specific staining of polysaccharides with ruthenium identify the nature of the extracellular fibers as biofilms and their association with cells [19,20]. However, the solvents necessary for the gradual dehydration of the sample, is responsible for generating images of biofilms with artifacts.…”

Section: Introductionmentioning

confidence: 99%

Nasal cytology: the “infectious spot”, an expression of a morphological-chromatic biofilm

Gelardi

Passalacqua

Fiorella

et al. 2011

Eur J Clin Microbiol Infect Dis

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The purpose of study was to describe some "morphological-chromatic" patterns (i.e.spots of cyan colour) identified during the study of nasal cytology in patients with both bacterial and fungal infectious rhinological disorders. These peculiar aspects strongly suggest the presence of a microscopic biofilm. We retrospectively examined 1,410 nasal cytology specimens from subjects who underwent clinical-instrumental investigations (history, ENT visit, nasal endoscopy and nasal cytology) from January to August 2010. The control samples were represented by 30 subjects not suffering from infectious rhinological diseases. The presence of particular spots of "Cyan", was found in colour in 107/1,410 rhinocytograms (7.6 %) within which bacterial colonies and/or fungal spores were found.We called these colored spot formations "Infectious Spots" (IS). 2The positivity to PAS staining confirmed the polysaccharide nature of the colored spots and allowed us to relate them to biofilms. This study demonstrates, for the first time, that nasal cytology performed by optical microscope can play an important role in detecting biofilms.

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Observations of binary population biofilms

Cited by 78 publications

References 19 publications

Biofilm accumulation model that predicts antibiotic resistance of Pseudomonas aeruginosa biofilms

Biofilm accumulation model that predicts antibiotic resistance of Pseudomonas aeruginosa biofilms

Disrupting the mixed-species biofilm of Klebsiella pneumoniae B5055 and Pseudomonas aeruginosa PAO using bacteriophages alone or in combination with xylitol

Nasal cytology: the “infectious spot”, an expression of a morphological-chromatic biofilm

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