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Biofilm

About: Biofilm is a research topic. Over the lifetime, 23010 publications have been published within this topic receiving 906812 citations. The topic is also known as: biofilms.


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Journal ArticleDOI
TL;DR: The high resistance of S. aureus biofilms to multiple unrelated antibiotics is largely dependent on the presence of persister cells, and the intrinsic resistance of these variants may in turn contribute to the enhanced antibiotic resistance of the biofilm-forming capacity.
Abstract: The presence of persister cells and small-colony variants (SCVs) has been associated with enhanced antibiotic resistance of many organisms in biofilms. This study investigated whether persisters and/or SCVs contribute to the antibiotic resistance of Staphylococcus aureus biofilms. A detailed dose-dependent killing of biofilms and planktonic cells with five antibiotics (oxacillin, cefotaxime, amikacin, ciprofloxacin and vancomycin) was analysed by treating them with each antibiotic at a concentration of 0-100 microg ml(-1) at 37 degrees C for 48 h. The killing of biofilm cells by all of the antibiotics showed the presence of persister cells - most cells in the population died, leaving a fraction that persisted, even at higher concentrations of the antibiotics. These persisters represented a transient resistant phenotype and reverted to a killing curve resembling that of the wild-type parent upon re-exposure to the antibiotics. SCVs were observed in biofilms only after treatment with ciprofloxacin, and these SCVs were of a transient nature. The treatment of planktonic cells with oxacillin, cefotaxime, ciprofloxacin and vancomycin killed the entire population and no persisters were detected. Transient SCVs, observed in planktonic cells following exposure to these antibiotics, were killed at higher antibiotic concentrations. The treatment of planktonic cells with amikacin yielded a small subpopulation of survivors that included persisters (at numbers significantly lower than for the biofilms) and highly resistant, stable SCVs with an increased biofilm-forming capacity in comparison with the wild-type parent. Thus the high resistance of S. aureus biofilms to multiple unrelated antibiotics is largely dependent on the presence of persister cells. Biofilms harbour a large number of persisters in comparison with planktonic cultures, which either do not harbour persisters or harbour only a small number. SCVs, although not specifically associated with S. aureus biofilms, have an increased biofilm-forming capacity and this may explain the frequent isolation of SCVs from biofilm-associated infections. The intrinsic resistance of these variants may in turn contribute to the enhanced antibiotic resistance of the biofilms thus formed.

240 citations

Journal ArticleDOI
TL;DR: It is demonstrated that S. mutans produces eDNA by multiple avenues, including lysis-independent membrane vesicles, and deficiency of protein secretion and membrane protein insertion machinery components caused significant reductions in eDNA.
Abstract: Streptococcus mutans, a major etiological agent of human dental caries, lives primarily on the tooth surface in biofilms. Limited information is available concerning the extracellular DNA (eDNA) as a scaffolding matrix in S. mutans biofilms. This study demonstrates that S. mutans produces eDNA by multiple avenues, including lysis-independent membrane vesicles. Unlike eDNAs from cell lysis that were abundant and mainly concentrated around broken cells or cell debris with floating open ends, eDNAs produced via the lysis-independent pathway appeared scattered but in a structured network under scanning electron microscopy. Compared to eDNA production of planktonic cultures, eDNA production in 5- and 24-h biofilms was increased by >3- and >1.6-fold, respectively. The addition of DNase I to growth medium significantly reduced biofilm formation. In an in vitro adherence assay, added chromosomal DNA alone had a limited effect on S. mutans adherence to saliva-coated hydroxylapatite beads, but in conjunction with glucans synthesized using purified glucosyltransferase B, the adherence was significantly enhanced. Deletion of sortase A, the transpeptidase that covalently couples multiple surface-associated proteins to the cell wall peptidoglycan, significantly reduced eDNA in both planktonic and biofilm cultures. Sortase A deficiency did not have a significant effect on membrane vesicle production; however, the protein profile of the mutant membrane vesicles was significantly altered, including reduction of adhesin P1 and glucan-binding proteins B and C. Relative to the wild type, deficiency of protein secretion and membrane protein insertion machinery components, including Ffh, YidC1, and YidC2, also caused significant reductions in eDNA.

240 citations

Journal ArticleDOI
TL;DR: It is shown that the cell density-dependent synthesis of stewartan EPS, governed by the EsaI/EsaR QS system, is required for proper bacterial adhesion and development of spatially defined, 3D biofilms, and epifluorescence microscopic imaging of infected leaf tissue and excised xylem vessels reveals that the bacteria colonize thexylem with unexpected specificity.
Abstract: The phytopathogenic bacterium Pantoea stewartii subsp. stewartii synthesizes stewartan exo/capsular polysaccharide (EPS) in a cell density-dependent manner governed by the EsaI/EsaR quorum-sensing (QS) system. This study analyzes biofilm development and host colonization of the WT and QS regulatory mutant strains of P. stewartii. First, we show that the cell density-dependent synthesis of stewartan EPS, governed by the EsaI/EsaR QS system, is required for proper bacterial adhesion and development of spatially defined, 3D biofilms. Second, a nonvirulent mutant lacking the esaI gene adheres strongly to surfaces and develops densely packed, less structurally defined biofilms in vitro. This strain appears to be arrested in a low cell density developmental mode. Exposure of this strain to exogenous N-acyl-homoserine lactone counteracts this adhesion phenotype. Third, QS mutants lacking the EsaR repressor attach poorly to surfaces and form amorphous biofilms heavily enmeshed in excess EPS. Fourth, the WT strain disseminates efficiently within the xylem, primarily in a basipetal direction. In contrast, the two QS mutant strains remain largely localized at the site of infection. Fifth, and most significantly, epifluorescence microscopic imaging of infected leaf tissue and excised xylem vessels reveals that the bacteria colonize the xylem with unexpected specificity, particularly toward the annular rings and spiral secondary wall thickenings of protoxylem, as opposed to indiscriminate growth to fill the xylem lumen. These observations are significant to bacterial plant pathogenesis in general and may reveal targets for disease control.

239 citations

Journal ArticleDOI
TL;DR: Transmission electron microscopy revealed that cells at the inner biofilm layers tend to remain intact after antibiotic treatment and that TSB-grown biofilms favoured a uniformity of cell distribution and increased cell density in comparison with milk-grownBiofilm aged revealed a reduced matrix distribution and enhanced cell density were observed as the biofilm aged.
Abstract: Four slime-producing isolates of Staphylococcus aureus were used in an antibiotic susceptibility assay for biofilms developed on 96-well polystyrene tissue culture plates. The study involved 11 antibiotics, two biofilm ages (6 and 48 h), two biofilm growth media (tryptone soy broth (TSB) and delipidated milk) and three antibiotic concentrations (4 x MBC, 100 mg/L and 500 mg/L). ATP-bioluminescence was used for automated bacterial viability determination after a 24 h exposure to antibiotics, to avoid biofilm handling. Under the conditions applied, viability in untreated biofilms (controls) was lower when biofilm growth was attempted in milk rather than in TSB. Various antibiotics had a greater effect on viability when used at higher (> or =100 mg/L) antibiotic concentrations and on younger (6 h) biofilms. Increased antibiotic effect was observed in milk-grown rather than TSB-grown biofilms. Phosphomycin and cefuroxime, followed by rifampicin, cefazolin, novobiocin, vancomycin, penicillin, ciprofloxacin and tobramycin significantly affected biofilm cell viability at least under some of the conditions tested. Gentamicin and erythromycin had a non-significant effect on cell viability. Transmission electron microscopy revealed that cells at the inner biofilm layers tend to remain intact after antibiotic treatment and that TSB-grown biofilms favoured a uniformity of cell distribution and increased cell density in comparison with milk-grown biofilms. A reduced matrix distribution and enhanced cell density were observed as the biofilm aged. The S. aureus biofilm test discriminated antibiotics requiring shorter (3 h or 6 h) from those requiring longer (24 h) exposure and yielded results which may be complementary to those obtained by conventional tests.

239 citations

Journal ArticleDOI
TL;DR: All pneumococcal strains developed biofilms that exhibited extracellular dsDNA in the biofilm matrix, however strains with a high BFI correlated with greater carbohydrate-associated structural complexity and antibiotic resistance, however all strains of S. pneumoniae showed downregulation of the cpsA gene during biofilm growth compared to planktonic culture, regardless of BFI ranking.
Abstract: Streptococcus pneumoniae is a common respiratory pathogen and a major causative agent of respiratory infections, including otitis media (OM). Pneumococcal biofilms have been demonstrated on biopsies of the middle ear mucosa in children receiving tympanostomy tubes, supporting the hypothesis that chronic OM may involve biofilm development by pathogenic bacteria as part of the infectious process. To better understand pneumococcal biofilm formation six low-passage encapsulated nasopharyngeal isolates of S. pneumoniae were assessed over a six-eight day period in vitro. Multiparametric analysis divided the strains into two groups. Those with a high biofilm forming index (BFI) were structurally complex, exhibited greater lectin colocalization and were more resistant to azithromycin. Those with a low BFI developed less extensive biofilms and were more susceptible to azithromycin. dsDNA was present in the S. pneumoniae biofilm matrix in all strains and treatment with DNase I significantly reduced biofilm biomass. Since capsule expression has been hypothesized to be associated with decreased biofilm development, we also examined expression of cpsA, the first gene in the pneumococcal capsule operon. Interestingly, cpsA was downregulated in biofilms in both high and low BFI strains. All pneumococcal strains developed biofilms that exhibited extracellular dsDNA in the biofilm matrix, however strains with a high BFI correlated with greater carbohydrate-associated structural complexity and antibiotic resistance. Furthermore, all strains of S. pneumoniae showed downregulation of the cpsA gene during biofilm growth compared to planktonic culture, regardless of BFI ranking, suggesting downregulation of capsule expression occurs generally during adherent growth.

239 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
20233,430
20226,827
20212,025
20202,079
20191,885