Multifunctionality and Diversity in Bacterial Biofilms

Bacteria are highly diverse and drive a bulk of ecosystem processes. Analysis of relationships between diversity and single specific ecosystem processes neglects the possibility that different species perform multiple functions at the same time. The degradation of dissolved organic carbon (DOC) followed by respiration is a key bacterial function that is modulated by the availability of DOC and the capability to produce extracellular enzymes. In freshwater ecosystems, biofilms are metabolic hotspots and major sites of DOC degradation. We manipulated the diversity of biofilm forming communities which were fed with DOC differing in availability. We characterized community composition using molecular fingerprinting (T-RFLP) and measured functioning as oxygen consumption rates, the conversion of DOC in the medium, bacterial abundance and the activities of five specific enzymes. Based on assays of the extracellular enzyme activity, we calculated how the likelihood of sustaining multiple functions was affected by reduced diversity. Carbon source and biofilm age were strong drivers of community functioning, and we demonstrate how the likelihood of sustaining multifunctionality decreases with decreasing diversity

Bacterial biofilms and capsular contracture in patients with breast implants.

BACKGROUND: It has been hypothesized that bacterial biofilms on breast implants may cause chronic inflammation leading to capsular contracture. The association between bacterial biofilms of removed implants and capsular contracture was investigated. METHODS: Breast implants explanted between 2006 and 2010 at five participating centres for plastic and reconstructive surgery were investigated by sonication. Bacterial cultures derived from sonication were correlated with patient, surgical and implant characteristics, and the degree of capsular contracture. RESULTS: The study included 121 breast implants from 84 patients, of which 119 originated from women and two from men undergoing gender reassignment. Some 50 breast prostheses were implanted for reconstruction, 48 for aesthetic reasons and 23 implants were used as temporary expander devices. The median indwelling time was 4·0 (range 0·1-32) years for permanent implants and 3 (range 1-6) months for temporary devices. Excluding nine implants with clinical signs of infection, sonication cultures were positive in 40 (45 per cent) of 89 permanent implants and in 12 (52 per cent) of 23 temporary devices. Analysis of permanent implants showed that a positive bacterial culture after sonication correlated with the degree of capsular contracture: Baker I, two of 11 implants; Baker II, two of ten; Baker III, nine of 23; and Baker IV, 27 of 45 (P < 0·001). The most frequent organisms were Propionibacterium acnes (25 implants) and coagulase-negative staphylococci (21). CONCLUSION: Sonication cultures correlated with the degree of capsular contracture, indicating the potential causative role of bacterial biofilms in the pathogenesis of capsular contracture. Registration number: NCT01138891 (http://www.clinicaltrials.gov).

Persistence of porcine reproductive and respiratory syndrome virus and porcine circovirus type 2 in bacterial biofilms.

The aim of this pilot project was to investigate association of viruses with bacterial biofilms. Our preliminary data indicate that important viral pathogens of swine, namely, porcine reproductive and respiratory syndrome virus and porcine circovirus type 2, can associate with and persist within bacterial biofilms for several days.

Bacterial biofilms in cholesteatomas of Mongolian gerbils

This paper studies cholesteatomas of Mongolian gerbils and the presence of bacterial biofilms.

Bacterial biofilms in the human gastrointestinal tract

Microbial biofilms were first described in 1936 and subsequent research has unveiled their ubiquity and physiological distinction from free-living (planktonic) microorganisms. In light of their emerging significance this review examines the bacterial biofilms within the human gastrointestinal tract. Attention is paid to the nature of these mucosally- associated populations, focusing on the protected environment afforded by the continual secretion of mucus by host epithelial cells. It also examines the attributes possessed by various bacterial species that facilitate habitation of this microenvironment. Additionally, contrasts are drawn between planktonic bacteria of the lumen and sessile (biofilm) bacteria growing in close association with host cells and food particles. In particular the different fermentation profiles exhibited by these two fractions are discussed. The potential role of these communities in host health and disease, as well as the stabilisation of the lumenal population, is also considered. Reference is made to the state of mutualism that exists between these little understood populations and the host epithelia, thus highlighting their ecological significance in terms of gastrointestinal health.

Bacterial biofilms with emphasis on coagulase-negative staphylococci

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Bacterial biofilms, antibiotic resistance and healthcare-associated infections: a dangerous connection

In 2012, were estimated 6.7 million cases of healthcare-associated infections (HAI) either in long-term care facilities or acute-care hospitals from which result 37,000 deaths configuring a serious public health problem. The etiological agents are diverse and often resistant to antimicrobial drugs. One of the mechanisms responsible for the emergence of drug resistance is biofilm assembly. Biofilms are defined as thin layers of microorganisms adhering to the surface of a structure, which may be organic or inorganic, together with the polymers that they secrete. They are dynamic structures which experience different stages of organization with the ageing and are linked to an increase in bacterial resistance to host defense mechanisms, antibiotics, sterilization procedures other than autoclaving, persistence in water distribution systems and other surfaces. The understanding of bacteria organization within the biofilm and the identification of differences between planktonic and sessile forms of bacteria will be a step forward to fight HAIs.

INTEGRATED THRESHOLD-ACTIVATED FEEDBACK MICROSYSTEM FOR REAL-TIME CHARACTERIZATION, SENSING AND TREATMENT OF BACTERIAL BIOFILMS

Biofilms are the primary cause of clinical bacterial infections and are impervious to typical amounts of antibiotics, necessitating very high doses for treatment. Therefore, it is highly desirable to develop new alternate methods of treatment that can complement or replace existing approaches using significantly lower doses of antibiotics. Current standards for studying biofilms are based on end-point studies that are invasive and destroy the biofilm during characterization. This dissertation presents the development of a novel real-time sensing and treatment technology to aid in the non-invasive characterization, monitoring and treatment of bacterial biofilms. The technology is demonstrated through the use of a high-throughput bifurcation based microfluidic reactor that enables simulation of flow conditions similar to indwelling medical devices. The integrated microsystem developed in this work incorporates the advantages of previous in vitro platforms while attempting to overcome some of their limitations. Biofilm formation is extremely sensitive to various growth parameters that cause large variability in biofilms between repeated experiments. In this work we investigate the use of microfluidic bifurcations for the reduction in biofilm growth variance. The microfluidic flow cell designed here spatially sections a single biofilm into multiple channels using microfluidic flow bifurcation. Biofilms grown in the bifurcated device were evaluated and verified for reduced biofilm growth variance using standard techniques like confocal microscopy. This uniformity in biofilm growth allows for reliable comparison and evaluation of new treatments with integrated controls on a single device. Biofilm partitioning was demonstrated using the bifurcation device by exposing three of the four channels to various treatments. We studied a novel bacterial biofilm treatment independent of traditional antibiotics using only small molecule inhibitors of bacterial quorum sensing (analogs) in combination with low electric fields. Studies using the bifurcation-based microfluidic flow cell integrated with real-time transduction methods and macro-scale end-point testing of the combination treatment showed a significant decrease in biomass compared to the untreated controls and well-known treatments such as antibiotics. To understand the possible mechanism of action of electric field-based treatments, fundamental treatment efficacy studies focusing on the effect of the energy of the applied electrical signal were performed. It was shown that the total energy and not the type of the applied electrical signal affects the effectiveness of the treatment. The linear dependence of the treatment efficacy on the applied electrical energy was also demonstrated. The integrated bifurcation-based microfluidic platform is the first microsystem that enables biofilm growth with reduced variance, as well as continuous real-time threshold-activated feedback monitoring and treatment using low electric fields. The sensors detect biofilm growth by monitoring the change in impedance across the interdigitated electrodes. Using the measured impedance change and user inputs provided through a convenient and simple graphical interface, a custom-built MATLAB control module intelligently switches the system into and out of treatment mode. Using this self-governing microsystem, in situ biofilm treatment based on the principles of the bioelectric effect was demonstrated by exposing two of the channels of the integrated bifurcation device to low doses of antibiotics.

New weapons to fight old enemies: novel strategies for the (bio)control of bacterial biofilms in the food industry

Biofilms are microbial communities characterized by their adhesion to solid surfaces and the production of a matrix of exopolymeric substances, consisting of polysaccharides, proteins, DNA and lipids, which surround the microorganisms lending structural integrity and a unique biochemical profile to the biofilm. Biofilm formation enhances the ability of the producer/s to persist in a given environment. Pathogenic and spoilage bacterial species capable of forming biofilms are a significant problem for the healthcare and food industries, as their biofilm-forming ability protects them from common cleaning processes and allows them to remain in the environment post-sanitation. In the food industry, persistent bacteria colonize the inside of mixing tanks, vats and tubing, compromising food safety and quality. Strategies to overcome bacterial persistence through inhibition of biofilm formation or removal of mature biofilms are therefore necessary. Current biofilm control strategies employed in the food industry (cleaning and disinfection, material selection and surface preconditioning, plasma treatment, ultrasonication, etc.), although effective to a certain point, fall short of biofilm control. Efforts have been explored, mainly with a view to their application in pharmaceutical and healthcare settings, which focus on targeting molecular determinants regulating biofilm formation. Their application to the food industry would greatly aid efforts to eradicate undesirable bacteria from food processing environments and, ultimately, from food products. These approaches, in contrast to bactericidal approaches, exert less selective pressure which in turn would reduce the likelihood of resistance development. A particularly interesting strategy targets quorum sensing systems, which regulate gene expression in response to fluctuations in cell-population density governing essential cellular processes including biofilm formation. This review article discusses the problems associated with bacterial biofilms in the food industry and summarizes the recent strategies explored to inhibit biofilm formation, with special focus on those targeting quorum sensing.

Viewing biofilms within the larger context of bacterial aggregations

The ‘Microbial Cities’ vision of bacterial biofilms has dominated our understanding of the development and functioning of bacterial aggregations for the past 20 years, during which active sludge, clumps, colonies, flocs, mats, pellicles, rafts, slimes, zooglea, etc. have been largely forgotten or ignored. Although the medically inspired developmental model of human pathogen biofilms has merits including providing a rationale for the development of anti-biofilm therapeutics, it fails to provide links to other types of bacterial aggregation that are commonly found in a wide range of natural and man-made environments. Possibly as a result, applied and environmental microbiologists tend to avoid the term ‘biofilm’ and use others such as ‘microbial mats’ instead. Here we challenge the simplistic planktonic (independent and free-swimming bacteria)-biofilm (sessile and co-operative bacteria) dichotomy, and consider biofilms within the larger context of bacterial aggregations. By placing biofilms into context, which we see as a continuum of aggregations or communities with varying abiotic and biotic properties, fundamental physical, biological, and evolutionary ecological processes that effect community development and function can no longer be considered unique to biofilms, but may also be important in other aggregations that develop over time and change in nature depending on prevailing conditions. By doing this, we will be better able to distinguish those processes which govern bacterial colonisation and ecological success in a wider sense from those that are unique to particular environments and specialised strategies.

Culturable Bacterial Diversity From A Feed Water Of A Reverse Osmosis System, Evaluation Of Biofilm Formation And Biocontrol Using Phages.

Biofilm formation on reverse osmosis (RO) systems represents a drawback in the application of this technology by different industries, including oil refineries. In RO systems the feed water maybe a source of microbial contamination and thus contributes for the formation of biofilm and consequent biofouling. In this study the planktonic culturable bacterial community was characterized from a feed water of a RO system and their capacities were evaluated to form biofilm in vitro. Bacterial motility and biofilm control were also analysed using phages. As results, diverse Protobacteria, Actinobacteria and Bacteroidetes were identified. Alphaproteobacteria was the predominant group and Brevundimonas, Pseudomonas and Mycobacterium the most abundant genera. Among the 30 isolates, 11 showed at least one type of motility and 11 were classified as good biofilm formers. Additionally, the influence of non-specific bacteriophage in the bacterial biofilms formed in vitro was investigated by action of phages enzymes or phage infection. The vB_AspP-UFV1 (Podoviridae) interfered in biofilm formation of most tested bacteria and may represent a good alternative in biofilm control. These findings provide important information about the bacterial community from the feed water of a RO system that may be used for the development of strategies for biofilm prevention and control in such systems.

Biofilms in Chronic Rhinosinusitis with Nasal Polyps

Objective. (1) Evaluate the presence of biofilms in patients with chronic sinusitis with nasal polyps (CRSwNP) and (2) investigate the association of biofilm presence and CRSwNP. Study Design. Cross-sectional study. Setting. University-based tertiary care center. Subjects and Methods. The study group consisted of 33 consecutive patients undergoing functional endoscopic sinus surgery for CRSwNP. The control group consisted of 27 control patients undergoing septoplasty for nasal obstruction without diagnosis of chronic sinusitis. Mucosal samples were harvested intraoperatively for scanning electron microscopic examination to determine biofilm presence. Statistical analysis was performed. For all statistical tests, P = .05 was considered significant. Results. Biofilms were found in 24 (72.7%) of the 33 patients with CRSwNP and in 13 (48.1%) of the 27 septoplasty patients (odds ratio = 2.87; 95% confidence interval, 0.98-8.42; P = .051). Conclusion. (1) Biofilms were present in patients undergoing functional endoscopic sinus surgery for CRSwNP and also in controls without chronic sinusitis. This suggests that biofilms may not be sufficient to cause chronic sinusitis without other cofactors. Host factors could be the responsible for the pathogenesis of biofilms. (2) Although the prevalence of biofilms in patients with CRSwNP was not significantly different from that in the controls, the extremely wide 95% confidence interval, which is just below unity, suggests that a meaningful clinical difference may have been missed because of low statistical power. Further studies are necessary.

Biofilms, Infection, and Parenteral Nutrition Therapy

Parenteral nutrition therapy is used in patients with a contraindication to the use of the gastrointestinal tract, and infection is one of its Frequent and severe complications. The objective of the present study was to detect the presence of biofilms and microorganisms adhering to the central venous. catheters used for parenteral nutrition therapy by scanning electron microscopy. Thirty-nine central venous catheters belonging to patients with clinical signs of infection (G I) and asymptomatic patients (G2) and patients receiving central venous catheters for clinical monitoring (G3) were analyzed by semi-quantitative culture and scanning electron microscopy. The central venous catheters of G1 presented more positive cultures than those of G2 and G3 (81% vs 50% and 0%, respectively). However, biofilms were observed in all catheters used and 55% of them showed structures that suggested central venous catheters colonization by microorganisms. Approximately 53% of the catheter infections evolved with systemic infection confirmed by blood Culture. The authors conclude that the presence of a biofilm is frequent and is all indicator of predisposition to infection, which may even occur in patients who are still asymptomatic. (JPEN J Parenter Enteral Nutr. 2009;33:397-403)

High vancomycin resistance among biofilms produced by Staphylococcus species isolated from central venous catheters

Biofilm production is an important mechanism that allows microbes to escape host defences and antimicrobial therapy. Vancomycin has been used largely for the treatment of methicillin-resistant staphylococcal infections. Here, we determined the minimal inhibitory concentration (MIC) and minimal biofilm eradication concentration (MBEC) for 82 Staphylococcus species isolated from central venous catheters (CVC). Our results showed that the 41 strong and moderate-biofilm-producing isolates presented a higher MBEC/MIC ratio for vancomycin than the 24 weak-biofilm-producing isolates, illustrating the importance of biofilm production ability and the difficulty in treating biofilm-related infections. The MBEC was significantly higher in moderate-biofilm-producing isolates than in weak-biofilm-producing isolates (p < 0.001) and in strong-biofilm-producing isolates than in weak-biofilm-producing isolates (p = 0.001). The correlation between the MIC and the MBEC was poor. Based on our results, we recommend that bacterial biofilms be suspected in all cases of CVC infection.