Removal of biofilms by impinging water droplets

The process of impinging water droplets on Streptococcus mutans biofilms was studied experimentally and numerically. Droplets were experimentally produced by natural breakup of a cylindrical liquid jet. Droplet diameter and velocity were varied between 20 and 200¿µm and between 20 and 100 m/s, respectively. The resulting erosion process of the biofilm was determined experimentally with high-speed recording techniques and a quantitative relationship between the removal rate, droplet size, and velocity was determined. The shear stress and the pressure on the surface during droplet impact were determined by numerical simulations, and a qualitative agreement between the experiment and the simulation was obtained. Furthermore, it was shown that the stresses on the surface are strongly reduced when a water film is present

High-velocity microsprays enhance antimicrobial activity in S. mutans biofilms

Streptococcus mutans in dental plaque biofilms play a role in caries development. The biofilm’s complex structure enhances the resistance to antimicrobial agents by limiting the transport of active agents inside the biofilm. We assessed the ability of high-velocity water microsprays to enhance delivery of antimicrobials into 3-days old S. mutans biofilms. Biofilms were exposed to a 90° or 30° impact, firstly using a 1-?m tracer beads solution (109 beads/mL) and secondly, a 0.2% Chlorhexidine (CHX) or 0.085% Cetylpyridinium chloride (CPC) solution. For comparison, a 30-sec diffusive transport and simulated mouthwash were also performed. Confocal microscopy was used to determine number and relative bead penetration depth (RD) into the biofilm. Assessment of antimicrobial penetration was determined by calculating the killing depth (KD) detected by live/dead viability staining. We firstly demonstrated that the microspray was able to deliver significantly more microbeads deeper in the biofilm compared to diffusion and mouthwashing exposures. Next our experiments revealed that the microspray yielded better antimicrobial penetration evidenced by deeper killing inside the biofilm and a wider killing zone around the zone of clearance than a diffusion transport with the same antimicrobials. Interestingly the 30° impact in the distal position delivered approximately 16 times more microbeads and yielded approximately 20% more bacteria killing (for both CHX and CPC) than the 90o impact. These data suggest that high-velocity water microsprays can be used as an effective mechanism to deliver micro-particles and antimicrobials inside S. mutans biofilms. High shear stresses generated at the biofilm/burst interface might have enhanced beads and antimicrobials delivery inside the remaining biofilm by combining forced advection into the biofilm matrix and physical restructuring of the biofilm itself. Further, the impact angle has potential to be optimized both for biofilm removal and active agents’ delivery inside biofilm in those protected areas where some biofilm might remai

Polydopamine-mediated immobilization of alginate lyase to prevent P. aeruginosa adhesion

Given alginate’s contribution to Pseudomonas aeruginosa virulence, it has long been considered a promising target for interventional therapies, which have been performed by using the enzyme alginate lyase. In this work, instead of treating pre-established mucoid biofi lms, alginate lyase is immobilized onto a surface as a preventive measure against P. aeruginosa adhesion. A polydopamine dip-coating strategy is employed for functionalization of polycarbonate surfaces. Enzyme immobilization is confi rmed by surface characterization. Surfaces functionalized with alginate lyase exhibit anti-adhesive properties, inhibiting the attachment of the mucoid strain. Moreover, surfaces modifi ed with this enzyme also inhibit the adhesion of the tested non-mucoid strain. Unexpectedly, treatment with heat-inactivated enzyme also inhibits the attachment of mucoid and non-mucoid P. aeruginosa strains. These fi ndings suggest that the antibacterial performance of alginate lyase functional coatings is catalysis-independent, highlighting the importance of further studies to better understand its mechanism of action against P. aeruginosa strains.T he authors acknowledge the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684). This study was also supported by FCT and the European Community fund FEDER, through Program COMPETE, under the scope of the Projects “PTDC/SAU-SAP/113196/2009” (FCOMP-01-0124-FEDER-016012) and “RECI/BBB-EBI/0179/2012” (FCOMP-01-0124-FEDER-027462). The authors also acknowledge Dr. Margarida Martins from 3B’s Research Group – Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine (AvePark, 4806-909 Taipas/Guimarãe s, Portugal) for kindly providing the isolated strains which were obtained under the scope of the project “Insights into peritoneal dialysis catheter associated biofi lms” funded by the Portuguese Society of Nephrology to Dr. Anabela Rodrigues. The authors also acknowledge the Ph.D. Grant of Diana Alves (SFRH/BD/78063/2011). T.S.S. was funded by a National Science Foundation graduate fellowship (Grant No. GRFP 2011124091), the Ryan Fellowship of Northwestern University, and NIH grant R37 DE014193 to P.B.M

Abundance and Distribution of Enteric Bacteria and Viruses in Coastal and Estuarine Sediments—a Review

The long term survival of fecal indicator organisms (FIOs) and human pathogenic microorganisms in sediments is important from a water quality, human health and ecological perspective. Typically, both bacteria and viruses strongly associate with particulate matter present in freshwater, estuarine and marine environments. This association tends to be stronger in finer textured sediments and is strongly influenced by the type and quantity of clay minerals and organic matter present. Binding to particle surfaces promotes the persistence of bacteria in the environment by offering physical and chemical protection from biotic and abiotic stresses. How bacterial and viral viability and pathogenicity is influenced by surface attachment requires further study. Typically, long-term association with surfaces including sediments induces bacteria to enter a viable-but-non-culturable (VBNC) state. Inherent methodological challenges of quantifying VBNC bacteria may lead to the frequent under-reporting of their abundance in sediments. The implications of this in a quantitative risk assessment context remain unclear. Similarly, sediments can harbor significant amounts of enteric viruses, however, the factors regulating their persistence remains poorly understood. Quantification of viruses in sediment remains problematic due to our poor ability to recover intact viral particles from sediment surfaces (typically <10%), our inability to distinguish between infective and damaged (non-infective) viral particles, aggregation of viral particles, and inhibition during qPCR. This suggests that the true viral titre in sediments may be being vastly underestimated. In turn, this is limiting our ability to understand the fate and transport of viruses in sediments. Model systems (e.g., human cell culture) are also lacking for some key viruses, preventing our ability to evaluate the infectivity of viruses recovered from sediments (e.g., norovirus). The release of particle-bound bacteria and viruses into the water column during sediment resuspension also represents a risk to water quality. In conclusion, our poor process level understanding of viral/bacterial-sediment interactions combined with methodological challenges is limiting the accurate source apportionment and quantitative microbial risk assessment for pathogenic organisms associated with sediments in aquatic environments

How Do Bacteria Know They Are on a Surface and Regulate Their Response to an Adhering State?

Bacteria adhere to virtually all natural and synthetic surfaces [1,2]. Although there are a number of different reasons as to why bacteria adhere to a surface, the summarizing answer is brief: ‘‘Adhesion to a surface is a survival mechanism for bacteria’’. Nutrients in aqueous environments have the tendency to accumulate at surfaces [1,3], giving adhering bacteria a benefit over free floating, so-called planktonic ones. This is why mountain creeks may contain crystal clear, drinkable water, while stepping stones underneath the water may be covered with a slippery film of adhering microbes. In the oral cavity, adhesion to dental hard and soft tissues is life-saving to the organisms, because microbes that do not manage to adhere and remain planktonic in saliva are swallowed with an almost certain death in the gastrointestinal tract. Bacterial adhesion is generally recognized as the first step in biofilm formation, and for the human host, the ability of

Advances in Microbial Biofilm Prevention on Indwelling Medical Devices with Emphasis on Usage of Acoustic Energy

Microbial biofilms are a major impediment to the use of indwelling medical devices, generating device-related infections with high morbidity and mortality. Major efforts directed towards preventing and eradicating the biofilm problem face difficulties because biofilms protect themselves very effectively by producing a polysaccharide coating, reducing biofilm sensitivity to antimicrobial agents. Techniques applied to combating biofilms have been primarily chemical. These have met with partial and limited success rates, leading to current trends of eradicating biofilms through physico-mechanical strategies. Here we review the different approaches that have been developed to control biofilm formation and removal, focusing on the utilization of acoustic energy to achieve these objectives

Anti-Biofilm Compounds Derived from Marine Sponges

Bacterial biofilms are surface-attached communities of microorganisms that are protected by an extracellular matrix of biomolecules. In the biofilm state, bacteria are significantly more resistant to external assault, including attack by antibiotics. In their native environment, bacterial biofilms underpin costly biofouling that wreaks havoc on shipping, utilities, and offshore industry. Within a host environment, they are insensitive to antiseptics and basic host immune responses. It is estimated that up to 80% of all microbial infections are biofilm-based. Biofilm infections of indwelling medical devices are of particular concern, since once the device is colonized, infection is almost impossible to eliminate. Given the prominence of biofilms in infectious diseases, there is a notable effort towards developing small, synthetically available molecules that will modulate bacterial biofilm development and maintenance. Here, we highlight the development of small molecules that inhibit and/or disperse bacterial biofilms specifically through non-microbicidal mechanisms. Importantly, we discuss several sets of compounds derived from marine sponges that we are developing in our labs to address the persistent biofilm problem. We will discuss: discovery/synthesis of natural products and their analogues—including our marine sponge-derived compounds and initial adjuvant activity and toxicological screening of our novel anti-biofilm compounds

Unveiling the fate of adhering bacteria to antimicrobial surfaces: expression of resistance-associated genes and macrophage-mediated phagocytosis

Since most antibacterial coatings reported to fight biomaterial-associated infections (BAI) fail in completely preventing bacterial colonization, it is crucial to know the impact of that small fraction of adhered bacteria in BAI recrudescence. This study aims to understand the fate of Staphylococcus aureus able to adhere to an antimicrobial coating previously developed, in terms of potential development of bacterial resistance and their macrophage-mediated phagocytosis. Antimicrobial coating comprised the co-immobilization of Palm peptide and DNase I onto polydimethylsiloxane. Expression of genes associated to resistance and virulence mechanisms showed that cells in contact with antimicrobial surfaces for a long period of 30 days, exhibit genes equally or less expressed, as compared to cells recovered from control surfaces. Recovered cells also exhibit the same susceptibility patterns, which strengthens the evidence of no resistance development. Remarkably, cells adhered to modified surfaces shows a reduced metabolic activity upon vancomycin treatment unlike the cells found on control surfaces, which can be identified as a clinical opportunity for prophylactically administration after implant surgery. Furthermore, results highlight that functionalization of PDMS with Palm and DNase I should not compromise the action of host immune cells. The overall results reinforce the potential of this antimicrobial strategy to fight BAI.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01 0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 – Programa Operacional Regional do Norte. The authors also acknowledge the support by FCT and the European Community fund FEDER, through Program COMPETE, under the scope of the Project AntiPep PTDC/SAUSAP/113196/2009 (FCOMP-01-0124-FEDER-016012) and the PhD Grant of Diana Alves (SFRH/BD/78063/2011) and Andreia Magalhães (SFRH/BD/132165/2017). A special thanks to Doctor Agostinho Carvalho and Doctor Cristina Amorim from Life and Health Sciences Research Institute (ICVS), University of Minho for kindly providing the monocyte cell line used in this study. Doctor Nuno Cerca, from CEB, Centre of Biological Engineering, University of Minho, is also acknowledged for his important contribution on the interpretation of gene expression results.info:eu-repo/semantics/publishedVersio