Beta toxin catalyzes formation of nucleoprotein matrix in staphylococcal biofilms

Biofilms are surface-associated communities of microbes encompassed by an extracellular matrix. It is estimated that 80% of all bacterial infections involve biofilm formation, but the structure and regulation of biofilms are incompletely understood. Extracellular DNA (eDNA) is a major structural component in many biofilms of the pathogenic bacterium Staphylococcus aureus, but its role is enigmatic. Here, we demonstrate that beta toxin, a neutral sphingomyelinase and a virulence factor of S. aureus, forms covalent cross-links to itself in the presence of DNA (we refer to this as biofilm ligase activity, independent of sphingomyelinase activity) producing an insoluble nucleoprotein matrix in vitro. Furthermore, we show that beta toxin strongly stimulates biofilm formation in vivo as demonstrated by a role in causation of infectious endocarditis in a rabbit model. Together, these results suggest that beta toxin cross-linking in the presence of eDNA assists in forming the skeletal framework upon which staphylococcal biofilms are established.     

In vitro biofilm formation by uropathogenic Escherichia coli and their antimicrobial susceptibility pattern

ObjectiveTo detect in vitro biofilm formation of uropathogenic Escherichia coli (E. coli) (UPEC) strains isolated from urine specimens and also to determine their antimicrobial susceptibility pattern using 13 commonly used antibiotics.MethodsThe present study comprised of 166 urine specimens collected from tertiary care hospitals in and around Coimbatore, South India. All the specimens were subjected to gram staining, bacterial culture and the E. coli strains were screened for biofilm formation using Tube Method (TM), Congo Red Agar (CRA) and Tissue Culture Plate method (TCP) respectively. Subsequently, the antimicrobial susceptibility test was performed by Kirby Bauer-disk diffusion method for the biofilm and non-biofilm producing E. coli strains.ResultsOf the 100 (60.2 %) E. coli strains, 72 strains displayed a biofilm positive phenotype under the optimized conditions in the Tube Method and the strains were classified as highly positive (17, 23.6%), moderate positive (19, 26.3 %) and weakly positive (36, 50.0 %), similarly under the optimized conditions on Congo Red agar medium, biofilm positive phenotype strains were classified as highly positive (23, 23 %), moderate positive (37, 37 %) and weakly positive (40, 40%). While in TCP method, the biofilm positive phenotype strains were also classified as highly positive (6, 6 %), moderate positive (80, 80 %) and weakly positive (14, 14 %), it didn't not correlate well with the tube method for detecting biofilm formation in E. coli. The rates of antibiotic resistance of biofilm producing E. coli were found to be 100 % for chloramphenicol and amoxyclav (amoxicillin and clavulanic acid), 86% for gentamicin and cefotaxime, 84% for ceftazidime, 83% for cotrimoxazole and piperacillin/tazobactam, 75% for tetracycline and 70% for amikacin.ConclusionsThis study reveals the prevalence and antimicrobial susceptibility pattern of biofilm and non-biofilm producing uropathogenic E. coli strains.     

Recent Advances in the Surface Functionalization of Nanomaterials for Antimicrobial Applications

Innovations in nanotechnology have had an immense impact on medicine, such as in drug delivery, tissue engineering, and medical devices that combat different pathogens. The pathogens that may cause biofilm-associated nosocomial diseases are multidrug-resistant (MDR) bacteria, such as Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), including both Gram-positive and Gram-negative bacterial species. About 65–80% of infections are caused by biofilm-associated pathogens creating a move in the international community toward developing antimicrobial therapies to eliminate such pathogenic infections. Several nanomaterials (NMs) have been discovered and significantly employed in various antipathogenic therapies. These NMs have unique properties of singlet oxygen production, high absorption of near-infrared irradiation, and reasonable conversion of light to heat. In this review, functionalized NPs that combat different pathogenic infections are introduced. This review highlights NMs that combat infections caused by multidrug-resistant (MDR) and other pathogenic microorganisms. It also highlights the biomedical application of NPs with regard to antipathogenic activities.     

Effect of Bacteriophage Infection in Combination with Tobramycin on the Emergence of Resistance in Escherichia coli and Pseudomonas aeruginosa Biofilms

Bacteriophage infection and antibiotics used individually to reduce biofilm mass often result in the emergence of significant levels of phage and antibiotic resistant cells. In contrast, combination therapy in Escherichia coli biofilms employing T4 phage and tobramycin resulted in greater than 99% and 39% reduction in antibiotic and phage resistant cells, respectively. In P. aeruginosa biofilms, combination therapy resulted in a 60% and 99% reduction in antibiotic and PB-1 phage resistant cells, respectively. Although the combined treatment resulted in greater reduction of E. coli CFUs compared to the use of antibiotic alone, infection of P. aeruginosa biofilms with PB-1 in the presence of tobramycin was only as effective in the reduction of CFUs as the use of antibiotic alone. The study demonstrated phage infection in combination with tobramycin can significantly reduce the emergence of antibiotic and phage resistant cells in both E. coli and P. aeruginosa biofilms, however, a reduction in biomass was dependent on the phage-host system.     

Disinfection efficacy of ozone on ESKAPE bacteria biofilms: Potential use in difficult-to-access medical devices

BackgroundMedical devices can be reservoirs of multidrug-resistant bacteria that may be involved in the acquisition of infections since bacteria with the ability to form biofilms that are difficult to eradicate, mainly in mechanical ventilators. The aim of this work was to evaluate the efficacy of O₃ against biofilms of bacteria ESKAPE group through disinfection studies.MethodsThe formation of biofilms of ESKAPE group bacteria was induced in vitro. O₃ was injected at different exposure times at a constant dose of 600 mg/h. The recovery of surviving bacteria after O₃ treatment was assessed by bacterial counts and biofilm disruption was analyzed. Finally, the viability and integrity of biofilms after O₃ treatment was determined by confocal laser scanning microscopy (CLSM).ResultsO₃ showed bactericidal activity on biofilms from 12 min/7.68 ppm for A. baumannii and C. freundii. P. aeruginosa, K. pneumoniae and S. aureus were killed after 15 min/9.60 ppm. Correlation analyses showed inversely proportional relationships between the variables "disruption versus O₃". CLSM revealed that death was time-dependent of biofilms upon O₃ exposure. Orthogonal plane analysis showed that bacteria located in the outer region of the biofilms were the ones that initially suffered damage from O₃ exposure.ConclusionsOur findings suggest that this method could be an alternative for the disinfection in mechanical ventilators colonized by bacteria biofilm forming.     

Evaluation of S. aureus ID, a Chromogenic Agar Medium for the Detection of Staphylococcus aureus

Abstract Background: Screening for staphylococci among various patient populations has become important for appropriate therapeutic management and for control of nosocomial infections. The purpose of this study is to evaluate the in vitro sensitivity and specificity of a chromogenic agar medium, S. aureus ID (bioMérieux, France), for the identification of Staphylococcus aureus. Materials and Methods: A well-defined collection of S. aureus and coagulase-negative staphylococci (CNS) was used. The methicillin-resistant S. aureus (MRSA) isolates were collected in The Netherlands and all had a unique typing pattern. The methicillin-susceptible S. aureus (MSSA) and CNS were isolated from cultures of blood. The isolates were inoculated on Columbia agar plates with 5% sheep blood and incubated for 24 h at 35 °C. From the resulting cultures, a suspension of 0.5 McFarland was made and subsequently 10 μl was streaked on a S. aureus ID plate using a sterile loop. The results were read after 24 h and 48 h of incubation at 35 °C. Growth of colonies showing green coloration was considered to be positive (indicating S. aureus). Results: A total of 519 S. aureus strains were tested (249 MSSA, 270 MRSA). The sensitivity to detect S. aureus was 96.5% (501/519) after 24 h and 97.5% (506/519) after 48 h. A total of 478 CNS were tested. The specificity was 98.5% (471/478) after 24 h and 98.3% (470/478) after 48 h. The differences between 24 h and 48 h incubation were not statistically significant. Conclusion: S. aureus ID is highly sensitive and specific to differentiate between S. aureus and CNS in vitro. Since the performance does not significantly differ between 24 h or 48 h of incubation, samples need only 1 day of incubation before optimal results can be obtained.     

A pH-Gated Functionalized Hollow Mesoporous Silica Delivery System for Photodynamic Sterilization in Staphylococcus aureus Biofilm

Multidrug-resistant bacteria are increasing, particularly those embedded in microbial biofilm. These bacteria account for most microbial infections in humans. Traditional antibiotic treatment has low efficiency in sterilization of biofilm-associated pathogens, and thus the development of new approaches is highly desired. In this study, amino-modified hollow mesoporous silica nanoparticles (AHMSN) were synthesized and used as the carrier to load natural photosensitizer curcumin (Cur). Then glutaraldehyde (GA) and polyethyleneimine (PEI) were used to seal the porous structure of AHMSN by the Schiff base reaction, forming positively charged AHMSN@GA@PEI@Cur. The Cur delivery system can smoothly diffuse into the negatively charged biofilm of Staphylococcus aureus (S. aureus). Then Cur can be released to the biofilm after the pH-gated cleavage of the Schiff base bond in the slightly acidic environment of the biofilm. After the release of the photosensitizer, the biofilm was irradiated by the blue LED light at a wavelength of 450 nm and a power of 37.4 mV/cm² for 5 min. Compared with the control group, the number of viable bacteria in the biofilm was reduced by 98.20%. Therefore, the constructed pH-gated photosensitizer delivery system can efficiently target biofilm-associated pathogens and be used for photodynamic sterilization, without the production of antibiotic resistance.     

A zinc-dependent adhesion module is responsible for intercellular adhesion in staphylococcal biofilms

Hospital-acquired bacterial infections are an increasingly important cause of morbidity and mortality worldwide. Staphylococcal species are responsible for the majority of hospital-acquired infections, which are often complicated by the ability of staphylococci to grow as biofilms. Biofilm formation by Staphylococcus epidermidis and Staphylococcus aureus requires cell-surface proteins (Aap and SasG) containing sequence repeats known as G5 domains; however, the precise role of these proteins in biofilm formation is unclear. We show here, using analytical ultracentrifugation (AUC) and circular dichroism (CD), that G5 domains from Aap are zinc (Zn²⁺)-dependent adhesion modules analogous to mammalian cadherin domains. The G5 domain dimerizes in the presence of Zn²⁺, incorporating 2–3 Zn²⁺ ions in the dimer interface. Tandem G5 domains associate in a modular fashion, suggesting a “zinc zipper” mechanism for G5 domain-based intercellular adhesion in staphylococcal biofilms. We demonstrate, using a biofilm plate assay, that Zn²⁺ chelation specifically prevents biofilm formation by S. epidermidis and methicillin-resistant S. aureus (MRSA). Furthermore, individual soluble G5 domains inhibit biofilm formation in a dose-dependent manner. Thus, the complex three-dimensional architecture of staphylococcal biofilms results from the self-association of a single type of protein domain. Surface proteins with tandem G5 domains are also found in other bacterial species, suggesting that this mechanism for intercellular adhesion in biofilms may be conserved among staphylococci and other Gram-positive bacteria. Zn²⁺ chelation represents a potential therapeutic approach for combating biofilm growth in a wide range of bacterial biofilm-related infections.     

Exposure to bile influences biofilm formation by Listeria monocytogenes

In the present study we demonstrate that the initial attachment of Listeria monocytogenes cells to plastic surfaces was significantly increased by growth in the presence of bile. Improved biofilm formation was confirmed by crystal violet staining, microscopy and bioluminescence detection of a luciferase-tagged strain. Enhanced biofilm formation in response to bile may influence the ability of L. monocytogenes to form biofilms in vivo during infection and may contribute to survival of this important pathogen in the human gastrointestinal tract and gallbladder.     

Detection of meningoencephalitis caused by Listeria monocytogenes with ischemic stroke-like onset using metagenomics next-generation sequencing: A case report

Rationale:Listeria monocytogenes (L. monocytogenes) is a compatible intracellular bacterial pathogen that can invade different mammalian cells and reach the central nervous system (CNS), leading to meningoencephalitis and brain abscesses. In the diagnosis of L. monocytogenes meningoencephalitis (LMM), conventional tests are often reported as negative due to antibiotic therapy or low bacterial content in cerebrospinal fluid. To date, prompt diagnosis and accurate treatment remain a challenge for patients with Listeria infections.Patient concerns:Here, we report a case of a 64-year-old male diagnosed with LMM by using metagenomics next-generation sequencing (mNGS).Diagnosis:LMM was confirmed by mNGS analysis of cerebrospinal fluid.Interventions:The patient was treated with piperacillin and sensitive antibiotics.Outcomes:The patient could walk independently about 1 month after admission and was discharged from the hospital.Lessons:This case highlights the value of mNGS in the diagnosis of LMM and emphasizes the inadequate sensitivity of conventional diagnostic methods for Listeria infection.     

Antibacterial and antibiofilm activities of polysaccharides,essential oil,and fatty oil extracted from Laurus nobilis growing in Lebanon

ObjectiveTo evaluate the antibacterial activity of the extracts of Laurus nobilis against three Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212 and Staphylococcus epidermidis CIP 444) and two Gram-negative bacteria (Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 27853). Also, the antibiofilm activity has been investigated against the biofilm produced by Staphylococcus epidermidis CIP 444.MaterialsThe polysaccharides, essential oil, and fatty oils extracted from the plant were used in broth microdilution methods to study the minimal inhibitory concentration, and then the minimal bactericidal concentration was determined.ResultsThe results showed that alginate, fucoidan, fatty oils and essential oil have good antibacterial activities against the 5 bacterial strains, and a negligible biofilm eradication activity of fucoidan, laminaran, fatty oil, and essential oil was observed, but a promising biofilm eradication activity was obtained with alginate, which showed a reduced biofilm mass even at low concentration.ConclusionsThe extracts obtained have promising antibacterial capacities which need further investigation for them to be incorporated in medical or nutritional applications.     

Incidence of Listeria species in bovine,ovine, caprine,camel and water buffalo milk using cultural method and the PCR assay

ObjectiveTo determine the prevalence rate of Listeria species in bovine, ovine, caprine, camel and water buffalo milk in Iran.MethodsFrom September 2010 to December 2011 a total of 260 bulk milk samples including 85 bovine, 37 camel, 34 water buffalo, 56 ovine and 48 caprine bulk milk samples were collected from commercial dairy herds, in Fars and Khuzestan provinces, Iran and were evaluated for the presence of Listeria species using cultural method and the PCR assay.ResultsUsing cultural method, 19 samples (7.3%) were positive for Listeria spp. The highest prevalence of Listeria was found in raw water buffalo milk (11.8%), followed by raw bovine milk (10.6%), raw ovine milk (7.1%), and raw caprine milk (4.2%) samples. All 37 camel milk samples from 20 camel breeding farms were negative for Listeria spp. The overall prevalence of Listeria was 7.3%, in which Listeria innocua was the most recovered species (4.2%); the remaining isolates were Listeria monocytogenes (1.9%), Listeria ivanovii (0.08%) and Listeria seeligari (0.04%). The PCR assay could identify 8 Listeria-contaminated milk samples that were negative using the cultural method.ConclusionsThe results presented in this study indicate the potential risk of infection with Listeria in people consuming raw and unpasteurized milk.     

Evaluation of antimicrobial peptide LL-37 for treatment of Staphylococcus aureus biofilm on titanium plate

The antimicrobial peptide LL-37 belongs to the cathelicidin family and is one of the few human bactericidal peptides with potent antistaphylococcal activity. Staphylococcus aureus is one of the main infection bacteria in orthopedic implant therapy. Biofilm formation after bacterial infection brings more and more severe test for clinical antiinfection treatment.However, there are few studies on LL-37 in S. aureus infection of prosthesis. In this work, addition to research the antibacterial activity and the inhibitory effect on bacterial adhesion of LL-37, an in vitro model of S. aureus biofilm formation on titanium alloy surface was established to observe the inhibitory effect of LL-37.The results showed that LL-37 has a strong antibacterial effect on S. aureus in vitro, and the minimum inhibitory concentration (MIC) is about 0.62 μΜ. Moreover, LL-37 has significant impact on the adhesion of S. aureus when the concentration ≥0.16 μM and significant anti-staphylococcal biofilm effects on static biofilm models at the concentration of 0.31 to 10 μM. Additionally, LL-37 at 5 μM had a significant destructive effect on S. aureus biofilm (P < .05) that formed on the titanium alloy surface.This study further confirmed the role of LL-37 in the process of S. aureus infection, including antimicrobial activities, inhibition of bacterial adhesion, and inhibition of mature biofilm. LL-37 can significantly destroy the stable biofilm structure on the titanium alloy surface in vitro, which may provide a new way for refractory infection caused by S. aureus in titanium alloy prosthesis infection.     

Effect of Surface Tooling Techniques of Medical Titanium Implants on Bacterial Biofilm Formation In Vitro

The aim of this study was to assess the biofilm formation of Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli on titanium implants with CAD-CAM tooling techniques. Twenty specimens of titanium were studied: Titanium grade 2 tooled with a Planmeca CAD-CAM milling device (TiGrade 2), Ti₆Al₄V grade 5 as it comes from CAD-DMLS device (computer aided design-direct metal laser sintering device) (TiGrade 5), Ti₆Al₄V grade 23 as it comes from a CAD-CAM milling device (TiGrade 23), and CAD-DMLS TiGrade 5 polished with an abrasive disc (TiGrade 5 polished). Bacterial adhesion on the implants was completed with and without saliva treatment to mimic both extraoral and intraoral surgical methods of implant placement. Five specimens/implant types were used in the bacterial adhesion experiments. Autoclaved implant specimens were placed in petri plates and immersed in saliva solution for 30 min at room temperature and then washed 3× with 1× PBS. Bacterial suspensions of each strain were made and added to the specimens after saliva treatment. Biofilm was allowed to form for 24 h at 37 °C and the adhered bacteria was calculated. Tooling techniques had an insignificant effect on the bacterial adhesion by all the bacterial strains studied. However, there was a significant difference in biofilm formation between the saliva-treated and non-saliva-treated implants. Saliva contamination enhanced S. mutans, S. aureus, and E. faecalis adhesion in all material types studied. S. aureus was found to be the most adherent strain in the saliva-treated group, whereas E. coli was the most adherent strain in the non-saliva-treated group. In conclusion, CAD-CAM tooling techniques have little effect on bacterial adhesion. Saliva coating enhances the biofilm formation; therefore, saliva contamination of the implant must be minimized during implant placement. Further extensive studies are needed to evaluate the effects of surface treatments of the titanium implant on soft tissue response and to prevent the factors causing implant infection and failure.     

Chloroquine sensitizes biofilms of Candida albicans to antifungal azoles

Biofilms formed by Candida albicans, a human pathogen, are known to be resistant to different antifungal agents. Novel strategies to combat the biofilm associated Candida infections like multiple drug therapy are being explored. In this study, potential of chloroquine to be a partner drug in combination with four antifungal agents, namely fluconazole, voriconazole, amphotericin B, and caspofungin, was explored against biofilms of C. albicans. Activity of various concentrations of chloroquine in combination with a particular antifungal drug was analyzed in a checkerboard format. Growth of biofilm in presence of drugs was analyzed by XTT-assay, in terms of relative metabolic activity compared to that of drug free control. Results obtained by XTT-metabolic assay were confirmed by scanning electron microscopy. The interactions between chloroquine and four antifungal drugs were determined by calculating fractional inhibitory concentration indices. Azole resistance in biofilms was reverted significantly (p < 0.05) in presence of 250 μg/mL of chloroquine, which resulted in inhibition of biofilms at very low concentrations of antifungal drugs. No significant alteration in the sensitivity of biofilms to caspofungin and amphotericin B was evident in combination with chloroquine. This study for the first time indicates that chloroquine potentiates anti-biofilm activity of fluconazole and voriconazole.     

Production of biofilm by Staphylococcus aureus: Association with infective endocarditis?

ObjectivesStaphylococcus aureus is a well-known biofilm-producing pathogen that is capable of causing chronic infections owing to its ability to resist antibiotic treatment and obstruct the immune response. However, the possible association between high biofilm production and infective endocarditis (IE) has not been assessed. Our objective was to compare production of biofilm by S. aureus strains isolated from patients with bacteremia and IE, catheter-related bloodstream infection (C-RBSI), or non-device associated bacteremia.MethodsWe isolated 260 S. aureus strains from the blood of patients with bacteremia who were diagnosed during hospital admission between 2012 and 2015. Patients were divided into 3 groups according to whether they had IE, C-RBSI, or non-device associated bacteremia. Biofilm production was measured in terms of biomass and metabolic activity using the crystal violet and XTT assays, respectively. High biomass and metabolic activity rates (based on tertile ranks classification) were compared between the 3 groups.ResultsThe high biomass and metabolic activity rates of each group were 41.9% and 37.2% for IE, 32.5% and 35.0%, for C-RBSI, and 29.0% and 33.3% for non-device associated bacteremia (p = 0.325 and p = 0.885, respectively).ConclusionsHigh biomass and metabolic activity levels for S. aureus isolates from IE were similar to those of S. aureus isolates from C-RBSI or non-device associated bacteremia.     

Combined effect of linezolid and N-acetylcysteine against Staphylococcus epidermidis biofilms

Introduction

Staphylococcus epidermidis is an organism commonly associated with infections caused by biofilms. Biofilms are less sensible to antibiotics and therefore are more difficult to eradicate. Linezolid and N-acetylcysteine (NAC), have demonstrated to be active against gram-positive microorganisms. Therefore and since linezolid and NAC have different modes of action, the main objective of this work was to investigate the single and synergistic effect of linezolid and NAC against S. epidermidis biofilms.

Methods

This work reports the in vitro effect of linezolid and NAC against S. epidermidis biofilms, treated with MIC (4 mg ml⁻¹) and 10×MIC of NAC, and MIC (1 μg ml⁻¹) and peak serum concentration (PS = 18 μg ml⁻¹) of linezolid alone and in combination. After exposure of S. epidermidis biofilms to linezolid and/or NAC for 24 h, several biofilm parameters were evaluated, namely the number of cultivable cells [colony forming unit (CFU) enumeration], total biofilm biomass and cellular activity.

Results

When tested alone, NAC at 10×MIC was the most effective agent against S. epidermidis biofilms. However, the combination linezolid (MIC) + NAC (10×MIC) showed a synergistic effect and was the most biocidal treatment tested, promoting a 5 log reduction in the number of biofilm viable cells.

Conclusion

This combination seems to be a potential candidate to combat infections caused by S. epidermidis biofilms, namely as a catheter lock solution therapy.     

Antibacterial activity of selected ethnomedicinal plants from South India

ObjectiveTo screen the antimicrobial potential of three ethnomedicinal plants Chassalia curviflora Thw. (C. curviflora), Cyclea peltata Hook. F. &; Thomson (C. peltata) and Euphorbia hirta L (E. hirta) used in folk medicines in Aarukani hills Kani tribe, Tamil Nadu, India against human bacterial pathogens.MethodsAntibacterial efficacy was performed by disc diffusion method against the pathogens viz., Escherichia coli (E. coli) (ATCC 35218), Staphylococcus aureus (S. aureus) (ATCC 6538), Salmonella typhi (S. typhi) (MTCC 733), Proteus vulgaris (P. vulgaris), Proteus mirabilis (P. mirabilis) and Streptococcus pyogenes (S. pyogenes) and incubated for 24 h at 37 °C.ResultsThe maximum degree of antibacterial activity was observed in C. peltata followed by C. curviflora. While E. hirta showed comparatively low degree of antibacterial activity. The methanolic extract of C. peltata showed the antibacterial activity against three pathogens viz., S. pyogenes, P. vulgaris and E. coli with the inhibition zones 12 mm, 10 mm and 9 mm, respectively. hexane extracts of C. peltata also showed the antibacterial activity against two selected pathogens viz., P. vulgaris and P. mirabilis with 15 mm and 12 mm of inhibition zones. All the three different concentrations (0.25, 0.50 &; 0.75 mg/mL) of methanolic extract of C. peltata show the inhibitory effect on the three susceptible bacteria S. pyogenes, P. vulgaris and E. coli with the maximum inhibition in the highest concentration (0.75 mg/mL). The methanolic and hexane extracts of C. curviflora exhibited the antibacterial activity against only one bacterium each i.e. P. vulgaris and S. typhi with the maximum zone of inhibition 13 and 11 mm respectively. The methanolic and hexane extracts of E. hirta exhibited the antibacterial activity against only one bacterium i.e. S. pyogenes with the maximum zone of inhibition 13 and 11 mm respectively.ConclusionsThe present investigation revealed that the C. curviflora, C. peltata and E. hirta are potentially good source of antibacterial agents and demonstrates the importance of such plants in traditional medicines.     

Liquid-infused structured surfaces with exceptional anti-biofouling performance

Bacteria primarily exist in robust, surface-associated communities known as biofilms, ubiquitous in both natural and anthropogenic environments. Mature biofilms resist a wide range of antimicrobial treatments and pose persistent pathogenic threats. Treatment of adherent biofilm is difficult, costly, and, in medical systems such as catheters or implants, frequently impossible. At the same time, strategies for biofilm prevention based on surface chemistry treatments or surface microstructure have been found to only transiently affect initial attachment. Here we report that Slippery Liquid-Infused Porous Surfaces (SLIPS) prevent 99.6% of Pseudomonas aeruginosa biofilm attachment over a 7-d period, as well as Staphylococcus aureus (97.2%) and Escherichia coli (96%), under both static and physiologically realistic flow conditions. In contrast, both polytetrafluoroethylene and a range of nanostructured superhydrophobic surfaces accumulate biofilm within hours. SLIPS show approximately 35 times the reduction of attached biofilm versus best case scenario, state-of-the-art PEGylated surface, and over a far longer timeframe. We screen for and exclude as a factor cytotoxicity of the SLIPS liquid, a fluorinated oil immobilized on a structured substrate. The inability of biofilm to firmly attach to the surface and its effective removal under mild flow conditions (about 1 cm/s) are a result of the unique, nonadhesive, “slippery” character of the smooth liquid interface, which does not degrade over the experimental timeframe. We show that SLIPS-based antibiofilm surfaces are stable in submerged, extreme pH, salinity, and UV environments. They are low-cost, passive, simple to manufacture, and can be formed on arbitrary surfaces. We anticipate that our findings will enable a broad range of antibiofilm solutions in the clinical, industrial, and consumer spaces.