Effectiveness of phages in the decontamination of Listeria monocytogenes adhered to clean stainless steel, stainless steel coated with fish protein, and as a biofilm

Listeria monocytogenes is a food-borne pathogen which causes listeriosis and is difficult to eradicate from seafood processing environments; therefore, more effective control methods need to be developed. This study investigated the effectiveness of three bacteriophages (LiMN4L, LiMN4p and LiMN17), individually or as a three-phage cocktail at ≈9 log₁₀ PFU/ml, in the lysis of three seafood-borne L. monocytogenes strains (19CO9, 19DO3 and 19EO3) adhered to a fish broth layer on stainless steel coupon (FBSSC) and clean stainless steel coupon (SSC), in 7-day biofilm, and dislodged biofilm cells at 15 ± 1 °C. Single phage treatments (LiMN4L, LiMN4p or LiMN17) decreased bacterial cells adhered to FBSSC and SSC by ≈3–4.5 log units. Phage cocktail reduced the cells on both surfaces (≈3.8–4.5 and 4.6–5.4 log₁₀ CFU/cm², respectively), to less than detectable levels after ≈75 min (detection limit = 0.9 log₁₀ CFU/cm²). The phage cocktail at ≈5.8, 6.5 and 7.5 log₁₀ PFU/cm² eliminated Listeria contamination (≈1.5–1.7 log₁₀ CFU/cm²) on SSC in ≈15 min. One-hour phage treatments (LiMN4p, LiMN4L and cocktail) in three consecutive applications resulted in a decrease of 7-day L. monocytogenes biofilms (≈4 log₁₀ CFU/cm²) by ≈2–3 log units. Single phage treatments reduced dislodged biofilm cells of each L. monocytogenes strain by ≈5 log₁₀ CFU/ml in 1 h. The three phages were effective in controlling L. monocytogenes on stainless steel either clean or soiled with fish proteins which is likely to occur in seafood processing environments. Phages were more effective on biofilm cells dislodged from the surface compared with undisturbed biofilm cells. Therefore, for short-term phage treatments of biofilm it should be considered that some disruption of the biofilm cells from the surface prior to phage application will be required.     

Comparison of in vivo infectivity of tissue-cultured nonoccluded virus and alkali-liberated occluded virus of Baculovirus heliothis

Feeding and intrahemocelic injection studies using tissue-culture-derived-nonoccluded virus (TCNOV) and occluded virus liberated by alkaline solution (ALOV) from polyhedral inclusion bodies were conducted with the single-embedded Heliothis nuclear polyhedrosis virus, Baculo-virus heliothis (H_zSEV). Comparisons of infectivity between ALOV and NOV were based upon the number of adminstered plaque-forming-units (PFU). There was little, if any, difference in infectivity between ALOV and TCNOV of H_zSEV when injected into 4th-instar larvae of Heliothis virescens. The LD₅₀, from the multiple dose injection studies, for ALOV and TCNOV was 6.5 ± 1.2 PFU per larva and 3.4 ± 0.9 PFU per larva, respectively. Injection of a single dose (5 PFU per larva) resulted in a larval mortality of 83.2 ± 3.4 and 62.6 ± 5.7% for ALOV and TCNOV of the H_zSEV, respectively. The LC₅₀ of ALOV and TCNOV, from the multiple-dose feeding tests, was 3.1 ± 0.4 PFU/cm² and 4.5 ± 0.9 PFU/cm², respectively. Feeding 24-hr-old larvae on virus-treated diets at a single dose (50.0 PFU/cm²) resulted in a 1.5-fold difference in percentage larval mortality between ALOV (91.0 ± 4.0%) and TCNOV (61.2 ± 3.0%). Counts of viral particles (VP), based upon electron microscopy, were 14.3 ± 2.6 × 10¹⁰ and 5.2 ± 1.1 × 10⁷ VP/ml for the ALOV and TCNOV, respectively. Thus, each larva ingesting or injected with one PFU received ca. 3500 × more VP of ALOV than in did of TCNOV.     

Diffusion properties of bacteriophages through agarose gel membrane

A simple two‐chamber diffusion method was developed to study the diffusion properties of bacteriophages (phages). The apparent diffusion coefficients (D_app) of Myoviridae phage T4 and filamentous phage fNEL were investigated, and the diffusion of the phages was found to be much slower than the diffusion of three antibiotics, ciprofloxacin, penicillin G, and tetracycline. D_app of T4 and fNEL in water through filter paper were calculated to be 2.8 × 10^?11 m²/s and 6.8 × 10^?12 m²/s, respectively, and D_app of fNEL through agarose gel membrane, an artificial biofilm, was also calculated to be smaller than that of T4. In addition, D_app of phages through agarose gel was dependent on agarose concentration due to the similar size of phage and agarose gel mesh. We concluded that D_app of phages through an artificial biofilm is dependent on both phage morphology and biofilm density, and suggest the use of this method to study diffusion properties through real biofilms. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

On-demand release of Candida albicans biofilms from urinary catheters by mechanical surface deformation

Abstract

Candida albicans is a leading cause of catheter-associated urinary tract infections and elimination of these biofilm-based infections without antifungal agents would constitute a significant medical advance. A novel urinary catheter prototype that utilizes on-demand surface deformation is effective at eliminating bacterial biofilms and here the broader applicability of this prototype to remove fungal biofilms has been demonstrated. C. albicans biofilms were debonded from prototypes by selectively inflating four additional intralumens surrounding the main lumen of the catheters to provide the necessary surface strain to remove the adhered biofilm. Deformable catheters eliminated significantly more biofilm than the controls (>90% eliminated vs 10% control; p < 0.001). Mechanical testing revealed that fungal biofilms have an elastic modulus of 45 ± 6.7 kPa with a fracture energy of 0.4–2 J m^?2. This study underscores the potential of mechanical disruption as a materials design strategy to combat fungal device-associated infections.     

Rapid detection of bacteriophages in starter culture using water-in-oil-in-water emulsion microdroplets

Bacteriophage contamination of starter culture and raw material poses a major problem in the fermentation industry. In this study, a rapid detection of lytic phage contamination in starter culture using water-in-oil-in-water (W/O/W) emulsion microdroplets was described. A model bacteria with varying concentrations of lytic phages were encapsulated in W/O/W emulsion microdroplets using a simple needle-in-tube setup. The detection of lytic phage contamination was accomplished in 1 h using the propidium iodide labeling of the phage-infected bacteria inside the W/O/W emulsion microdroplets. Using this approach, a detection limit of 10² PFU/mL of phages was achieved quantitatively, while 10⁴ PFU/mL of phages could be detected qualitatively based on visual comparison of the fluorescence images. Given the simplicity and sensitivity of this approach, it is anticipated that this method can be adapted to any strains of bacteria and lytic phages that are commonly used for fermentation, and has potential for a rapid detection of lytic phage contamination in the fermentation industry.     

Inhibition and eradication of Salmonella Typhimurium biofilm using P22 bacteriophage,EDTA and nisin

Abstract

P22 phage >10⁵ PFU ml^?1 could be used to inhibit Salmonella Typhimurium biofilm formation by 55–80%. Concentrations of EDTA >1.25?mM and concentrations of nisin >1,200?µg ml^?1 were also highly effective in reducing S. Typhimurium biofilm formation (≥96% and ≥95% reductions were observed, respectively). A synergistic effect was observed when EDTA and nisin were combined whereas P22 phage in combination with nisin had no synergistic impact on biofilm formation. Triple combination of P22 phage, EDTA and nisin could be also used to inhibit biofilm formation (≥93.2%) at a low phage titer (10² PFU ml^?1), and low EDTA (1.25?mM) and nisin (9.375?µg ml^?1) concentrations. A reduction of 70% in the mature biofilm was possible when 10⁷ PFU ml^?1 of P22 phage, 20?mM of EDTA and 150?μg ml^?1 of nisin were used in combination. This study revealed that it could be possible to reduce biofilm formation by S. Typhimurium by the use of P22 phage, EDTA and nisin, either alone or in combination. Although, removal of the mature biofilm was more difficult, the triple combination could be successfully used for mature biofilm of S. Typhimurium.     

A flow cytometric protocol for titering recombinant adenoviral vectors containing the green fluorescent protein

As the use of adenoviral vectors in gene therapy protocols increases, there is a corresponding need for rapid, accurate, and reproducible titer methods. Multiple methods currently exist for determining titers of recombinant adenoviral vector, including optical absorbence, electron microscopy, fluorescent focus assay, and the “gold standard” plaque assay. This paper introduces a novel flow cytometric method for direct titer determination that relies on the expression of the green fluorescent protein (GFP), a tracking marker incorporated into several adenoviral vectors. This approach was compared to the plaque assay using 10⁻⁴-to 10⁻⁶-fold dilutions of a cesium-chloride-purified, GFP expressing adenovirus (AdEasy+GFP+GAL). The two approaches yielded similar titers: 3.25±1.85×10⁹ PFU/mL versus 3.46±0.76×10⁹ green fluorescent units/(gfu/mL). The flow cytometric method is complete within 24 h in contrast to the 7×10 days required by the plaque assay. These results indicate that the GFU/mL is an alternative functional titer method for fluorescent-tagged adenoviral vectors.     

A novel approach combining the Calgary Biofilm Device and Phenotype MicroArray for the characterization of the chemical sensitivity of bacterial biofilms

A rapid method for screening the metabolic susceptibility of biofilms to toxic compounds was developed by combining the Calgary Biofilm Device (MBEC device) and Phenotype MicroArray (PM) technology. The method was developed using Pseudomonas alcaliphila 34, a Cr(VI)-hyper-resistant bacterium, as the test organism. P. alcaliphila produced a robust biofilm after incubation for 16 h, reaching the maximum value after incubation for 24 h (9.4 × 10⁶ ± 3.3 × 10⁶ CFU peg^?1). In order to detect the metabolic activity of cells in the biofilm, dye E (5×) and menadione sodium bisulphate (100 μM) were selected for redox detection chemistry, because they produced a high colorimetric yield in response to bacterial metabolism (340.4 ± 6.9 Omnilog Arbitrary Units). This combined approach, which avoids the limitations of traditional plate counts, was validated by testing the susceptibility of P. alcaliphila biofilm to 22 toxic compounds. For each compound the concentration level that significantly lowered the metabolic activity of the biofilm was identified. Chemical sensitivity analysis of the planktonic culture was also performed, allowing comparison of the metabolic susceptibility patterns of biofilm and planktonic cultures.     

Multi-species biofilms defined from drinking water microorganisms provide increased protection against chlorine disinfection

A model biofilm, formed of multiple species from environmental drinking water, including opportunistic pathogens, was created to explore the tolerance of multi-species biofilms to chlorine levels typical of water-distribution systems. All species, when grown planktonically, were killed by concentrations of chlorine within the World Health Organization guidelines (0.2–5.0?mg?l^?1). Higher concentrations (1.6–40-fold) of chlorine were required to eradicate biofilm populations of these strains, ～70% of biofilms tested were not eradicated by 5.0?mg?l^?1 chlorine. Pathogenic bacteria within the model multi-species biofilms had an even more substantial increase in chlorine tolerance; on average ～700–1100?mg?l^?1 chlorine was required to eliminate pathogens from the biofilm, 50–300-fold higher than for biofilms comprising single species. Confocal laser scanning microscopy of biofilms showed distinct 3D structures and multiple cell morphologies and arrangements. Overall, this study showed a substantial increase in the chlorine tolerance of individual species with co-colonization in a multi-species biofilm that was far beyond that expected as a result of biofilm growth on its own.     

Distribution of viruses in the water column of the ice-covered Rybinsk Reservoir and their contribution to heterotrophic bacteria mortality

Virioplankton and bacterioplankton abundance has been determined in the pelagic and littoral zones of the Rybinsk Reservoir during the ice-covered period. The role of viruses in heterotrophic bacterioplankton infection and mortality is assessed. At water temperatures between 0.3 and 0.9°C, the number of planktonic virus particles and planktonic bacteria varies from 37.1 × 10⁶ to 84.1 × 10⁶ particles/mL, (57.3 ± 2.1) × 10⁶ particles/mL on average and from 2.50 × 10⁶ to 6.11 × 10⁶ cells/mL, (3.66 ± 0.16) × 10⁶ cells/mL on average, respectively. The ratio of the virus number to the bacteria number varies from 8.8 to 27.9, being 16.5 ± 0.7 on average. Visually infected cells comprise 0.3–0.5% (1.5 ± 0.2% on average) of the total number of bacterioplankton. Infected bacterial cells contain from 5 to 107 (17 ± 4 on average) mature virus particles. The average virus-induced mortality of bacteria accounts for 13.0 ± 1.9% (variations range from 2 to 55%) of the daily bacterial production, indicating that viruses play an important role in the regulation of bacterioplankton production and abundance in the Rybinsk Reservoir during the ice-covered period.     

Genetic engineering biofilms in situ using ultrasound-mediated DNA delivery

The ability to directly modify native and established biofilms has enormous potential in understanding microbial ecology and application of biofilm in 'real-world' systems. However, efficient genetic transformation of established biofilms at any scale remains challenging. In this study, we applied an ultrasound-mediated DNA delivery (UDD) technique to introduce plasmid to established non-competent biofilms in situ. Two different plasmids containing genes coding for superfolder green fluorescent protein (sfGFP) and the flavin synthesis pathway were introduced into established bacterial biofilms in microfluidic flow (transformation efficiency of 3.9 ± 0.3 × 10^-7 cells in biofilm) and microbial fuel cells (MFCs), respectively, both employing UDD. Gene expression and functional effects of genetically modified bacterial biofilms were observed, where some cells in UDD-treated Pseudomonas putida UWC1 biofilms expressed sfGFP in flow cells and UDD-treated Shewanella oneidensis MR-1 biofilms generated significantly (P < 0.05) greater (61%) bioelectricity production (21.9 ± 1.2 µA cm⁻²) in MFC than a wild-type control group (~ 13.6 ± 1.6 µA cm⁻²). The effects of UDD were amplified in subsequent growth under selection pressure due to antibiotic resistance and metabolism enhancement. UDD-induced gene transfer on biofilms grown in both microbial flow cells and MFC systems was successfully demonstrated, with working volumes of 0.16 cm³ and 300 cm³, respectively, demonstrating a significant scale-up in operating volume. This is the first study to report on a potentially scalable direct genetic engineering method for established non-competent biofilms, which can be exploited in enhancing their capability towards environmental, industrial and medical applications.     

Effect of host plant on susceptibility of whitefly Bemisia tabaci (Homoptera: Aleyrodidae) to the entomopathogenic fungus Beauveria bassiana (Ascomycota: Hypocreales)

We determined host plant effect on susceptibility of whitefly Bemisia tabaci to the entomopathogenic fungus Beauveria bassiana under controlled conditions. Insects were reared on cucumber, eggplant, tomato or cabbage. Fungal suspensions of 1×10⁴, 10⁵, 10⁶, 10⁷ and 10⁸ conidia/mL were applied on second-instar nymphs. Nymphal survival significantly differed among different host plant species on which the nymphs were reared. Ten days after inoculation with 1×10⁸ conidia/mL, percent survival was 4.2±0.7, 9.6±0.4, 13.4±0.8, and 24.3±0.9% on cucumber, eggplant, tomato and cabbage, respectively. Average survival times of nymphs were also significantly influenced by host plant species. After inoculation with 1×10⁸ conidia/mL, survival times were 4.8±0.15, 6.0±0.11, 5.7±0.13, and 6.2±0.08 days for nymphs reared on cucumber, eggplant, tomato, and cabbage, respectively. Virulence also differed depending on host plant species; 10 days after inoculation, LC₅₀ values were 4.6×10⁴, 1.6×10⁵, 4.2×10⁵ and 2.1×10⁶ conidia/mL on cucumber, eggplant, tomato and cabbage, respectively. Nymphs on cucumber showed highest susceptibility.     

Influence of surface copper content on Stenotrophomonas maltophilia biofilm control using chlorine and mechanical stress

Abstract

This work aimed to evaluate the action of materials with different copper content (0, 57, 96 and 100%) on biofilm formation and control by chlorination and mechanical stress. Stenotrophomonas maltophilia isolated from drinking water was used as a model microorganism and biofilms were developed in a rotating cylinder reactor using realism-based shear stress conditions. Biofilms were characterized phenotypically and exposed to three control strategies: 10?mg l^?1 of free chlorine for 10?min, an increased shear stress (a fluid velocity of 1.5?m s^?1 for 30s), and a combination of both treatments. These shock treatments were not effective in biofilm control. The benefits from the use of copper surfaces was found essentially in reducing the numbers of non-damaged cells. Copper materials demonstrated better performance in biofilm prevention than chlorine. In general, copper alloys may have a positive public health impact by reducing the number of non-damaged cells in the water delivered after chlorine exposure.     

Quantification of water and biomass in small colony variant PAO1 biofilms by confocal Raman microspectroscopy

The Raman spectra, water content, and biomass density of wild-type (WT) Pseudomonas aeruginosa PAO1, small colony variant (SCV) PAO1, and Pseudoalteromonas sp. NCIMB 2021 biofilms were compared in order to determine their variation with strain and species. Living, fully submerged biofilms were analyzed in situ by confocal Raman microspectroscopy for up to 2 weeks. Water to biomass ratios (W/BRs), which are the ratios of the O–H stretching vibration of water at 3,450 cm⁻¹ to the C–H stretching band characteristic of biomass at 2,950 cm⁻¹, were used to estimate the biomass density and cell density by comparison with W/BRs of protein solutions and bacterial suspensions, respectively, on calibration curves. The hydration within SCV biofilm colonies was extremely heterogeneous whereas W/BRs were generally constant in young WT biofilm colonies. The mean biomass in biofilm colonies of WT or colony cores of SCV was typically equivalent to 16% to 27% protein (w/v), but was 10% or less for NCIMB 2021. The corresponding cell densities were 7.5 to >10 × 10¹⁰ cfu mL⁻¹ for SCV, while the maximum cell density for NCIMB biofilms was 2.8 × 10¹⁰ cfu mL⁻¹.     

Inhibition and destruction of Pseudomonas aeruginosa biofilms by antibiotics and antimicrobial peptides

Pseudomonas aeruginosa is one of the major nosocomial pathogen that can causes a wide variety of acute and chronic infections P. aeruginosa is a dreaded bacteria not just because of the high intrinsic and acquired antibiotic resistance rates but also the biofilm formation and production of multiple virulence factors. We investigated the in vitro activities of antibiotics (ceftazidime, tobramycin, ciprofloxacin, doripenem, piperacillin and colistin) and antimicrobial cationic peptides (AMPs; LL-37, CAMA: cecropin(1–7)-melittin A(2–9) amide, melittin, defensin and magainin-II) alone or in combination against biofilms of laboratory strain ATCC 27853 and 4 clinical strains of P. aeruginosa. The minimum inhibitory concentrations (MIC), minimum bactericidal concentration (MBC) and minimum biofilm eradication concentrations (MBEC) were determined by microbroth dilution technique. The MBEC values of antibiotics and AMPs were 80–>5120 and 640–>640 mg/L, respectively. When combined with the LL-37 or CAMA at 1/10× MBEC, the MBEC values of antibiotics that active against biofilms, were decreased up to 8-fold. All of the antibiotics, and AMPs were able to inhibit the attachment of bacteria at the 1/10× MIC and biofilm formation at 1× or 1/10× MIC concentrations. Time killing curve studies showed 3-log₁₀ killing against biofilms in 24 h with almost all studied antibiotics and AMPs. Synergism were seen in most of the studied combinations especially CAMA/LL-37 + ciprofloxacin against at least one or two strains’ biofilms. Since biofilms are not affected the antibiotics at therapeutic concentrations, using a combination of antimicrobial agents including AMPs, or inhibition of biofilm formation by blocking the attachment of bacteria to surfaces might be alternative methods to fight with biofilm associated infections.     

一株溶藻细菌对海洋原甲藻的溶藻效应

从深圳大鹏湾南澳赤潮爆发海域的表层海水中分离得到1株对海洋原甲藻(Prorocentrum micans)具有溶藻活性的海洋细菌,菌株编号为N10。利用液相感染法研究了该溶藻细菌的溶藻效果和溶藻作用方式。结果表明,菌株N10能使藻细胞失去运动活性,并膨胀变形,细胞膜内物质聚集于一端,藻细胞最终破裂死亡。菌悬液接种到藻液中的量越大,初始细菌密度越高,其溶藻效果越强。菌悬液以1∶10的体积比接种到藻液中时,藻细胞在24 h的死亡率为83%,至72 h全部溶解死亡;体积比为1∶20的藻细胞在24 h的死亡率为71%,之后藻细胞密度略有波动,120 h时死亡率达77%;而体积比为1∶100的藻细胞密度在前24 h有所下降,死亡率达39%,之后藻细胞密度又开始明显上升;对照组的藻细胞密度均呈明显上升趋势。菌悬液过滤液和高温加热处理后的菌悬液过滤液对海洋原甲藻均无溶藻活性,表明菌株N10的溶藻方式为直接溶藻。通过16S rRNA序列分析并与GenBank数据进行同源性检索,并结合细菌形态及生理生化特征,菌株N10隶属于黄杆菌科(Flavobacteriaceae)中的Muricauda sp.。     

Linking biofilm spatial structure to real-time microscopic oxygen decay imaging

Two non-destructive techniques, confocal laser scanning microscopy (CLSM) and planar optode (VisiSens imaging), were combined to relate the fine-scale spatial structure of biofilm components to real-time images of oxygen decay in aquatic biofilms. Both techniques were applied to biofilms grown for seven days at contrasting light and temperature (10/20°C) conditions. The geo-statistical analyses of CLSM images indicated that biofilm structures consisted of small (~10⁰ μm) and middle sized (~10¹ μm) irregular aggregates. Cyanobacteria and EPS (extracellular polymeric substances) showed larger aggregate sizes in dark grown biofilms while, for algae, aggregates were larger in light-20°C conditions. Light-20°C biofilms were most dense while 10°C biofilms showed a sparser structure and lower respiration rates. There was a positive relationship between the number of pixels occupied and the oxygen decay rate. The combination of optodes and CLMS, taking advantage of geo-statistics, is a promising way to relate biofilm architecture and metabolism at the micrometric scale.     

Novel phage-based bio-processing of pathogenic Escherichia coli and its biofilms

To explore new approaches of phage-based bio-process of specifically pathogenic Escherichia coli bacteria in food products within a short period. One hundred and forty highly lytic designed coliphages were used. Escherichia coli naturally contaminated and Enterohemorrhagic Escherichia coli experimentally inoculated samples of lettuce, cabbage, meat, and egg were used. In addition, experimentally produced biofilms of E. coli were tested. A phage concentration of 10³ PFU/ml was used for food products immersion, and for spraying of food products, 10⁵ PFU/ml of a phage cocktail was used by applying a 20-s optimal dipping time in a phage cocktail. Food samples were cut into pieces and were either sprayed with or held in a bag immersed in lambda buffer containing a cocktail of 140 phages. Phage bio-processing was successful in eliminating completely E. coli in all processed samples after 48 h storage at 4°C. Partial elimination of E. coli was observed in earlier storage periods (7 and 18 h) at 24° and 37°C. Moreover, E. coli biofilms were reduced >3 log cycles upon using the current phage bio-processing. The use of a phage cocktail of 140 highly lytic designed phages proved highly effective in suppressing E. coli contaminating food products. Proper decontamination/prevention methods of pathogenic E. coli achieved in this study can replace the current chemically less effective decontamination methods.     

Repeated lipopolysaccharide exposure causes corticosteroid insensitive airway inflammation via activation of phosphoinositide-3-kinase δ pathway

Corticosteroid resistance is one of major barriers to effective management of chronic inflammatory respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and severe asthma. These patients often experience exacerbations with viral and/or bacterial infection, which may cause continuous corticosteroid insensitive inflammation. In this study, we observed that repeated exposure of lipopolysaccharide (LPS) intranasally attenuated the anti-inflammatory effects of the corticosteroid fluticasone propionate (FP) on neutrophils and CXCL1 levels in bronchoalveolar lavage (BAL) fluid in an in vivo murine model. Histone deacetylase-2 (HDAC2) and NF-E2 related factor 2 (Nrf2) levels in lungs after LPS administration for 3 consecutive days were significantly decreased to 38.9±6.3% (mean±SEM) and 77.5±2.7% of the levels seen after only one day of LPS exposure, respectively. In addition, 3 days LPS exposure resulted in an increase of Akt phosphorylation, indicating activation of the phosphoinositide-3-kinase (PI3K) pathway by 4-fold in lungs compared with 1 day of exposure. Furthermore, combination treatment with theophylline and FP significantly decreased the neutrophil accumulation and CXCL1 concentrations in BAL fluid from 22.5±1.8×10⁴ cells/mL and 214.6±20.6 pg/mL to 7.9±0.5×10⁴ cells/mL and 61.9±13.3 pg/mL, respectively. Combination treatment with IC87114, a selective PI3Kδ inhibitor, and FP also significantly decreased neutrophils and CXCL1 levels from 16.8±0.7×10⁴ cells/mL and 182.4±4.6 pg/mL to 5.9±0.3×10⁴ cells/mL and 71.4±2.7 pg/mL, respectively. Taken together, repeated exposure of LPS causes corticosteroid-insensitive airway inflammation in vivo, and the corticosteroid-resistance induced by LPS is at least partly mediated through the activation of PI3Kδ, resulting in decreased levels of HDAC2 and Nrf2. These findings provide a potentially new therapeutic approach to COPD and severe asthma.     

Roughness effects of diatomaceous slime fouling on turbulent boundary layer hydrodynamics

Abstract

Biofilm fouling significantly impacts ship performance. Here, the impact of biofilm on boundary layer structure at a ship-relevant, low Reynolds number was investigated. Boundary layer measurements were performed over slime-fouled plates using high resolution particle image velocimetry (PIV). The velocity profile over the biofilm showed a downward shift in the log-law region (ΔU⁺), resulting in an effective roughness height (k_s) of 8.8?mm, significantly larger than the physical thickness of the biofilm (1.7?±?0.5?mm) and generating more than three times as much frictional drag as the smooth-wall. The skin-friction coefficient, C_f, of the biofilm was 9.0?×?10^?3 compared with 2.9?×?10^?3 for the smooth wall. The biofilm also enhances turbulent kinetic energy (tke) and Reynolds shear stress, which are more heterogeneous in the streamwise direction than smooth-wall flows. This suggests that biofilms increase drag due to high levels of momentum transport, likely resulting from protruding streamers and surface compliance.