Reduction Of Antibacterial Activity Research Articles

Evaluation of Aging Effect on the Durability of Antibacterial Treatments Applied on Textile Materials for the Automotive Industry.

The automotive industry is always seeking novel solutions to improve the durability and the performance of textile materials used in vehicles. Indeed, especially after the coronavirus pandemic, antibacterial treatments have gained interest for their potential of ensuring cleanliness and safety toward microbial contamination within vehicles. This study gives a panoramic view of the durability of antibacterial treatments applied on textile materials in the automotive industry, focusing on their performance after experiencing accelerated aging processes. Two different textile materials, a fabric and a synthetic leather, both treated with antibacterial agents, were tested according to ISO 22196 and ISO 20743 standards, respectively, using two model microorganisms, Escherichia coli and Staphylococcus aureus. The impact of mechanical, thermal, and solar aging on the antibacterial properties has been evaluated. In addition, scanning electron microscope (SEM) analysis was performed to investigate the surface morphology of the materials before and after aging. Furthermore, contact angle measurements were conducted. The results suggest that neither mechanical nor thermal aging processes determined diminished antibacterial action. It was determined, instead, that the most damaging stressor for both textile materials was UV aging, causing severe surface alterations and a reduction in antibacterial activity.

Robust design of starch composite nanofibrous films for active food packaging: Towards improved mechanical, antioxidant, and antibacterial properties

Developing efficient and biodegradable packaging films is of paramount significance owing to the scarcity of petroleum based resources. However, their applications in food packaging are limited due to their poor mechanical properties and inadequate biological activities. This study proposes a novel approach to develop the starch composite nanofibrous films (SNFs/TA/Fe3+) consisting of starch, tannic acid, and Fe3+ using the temperature-assisted electrospinning method. The addition of TA resulted in a decrease in the rate of thermal degradation, indicating an improvement in the thermal stability of SNFs. However, the incorporation of TA or TA/Fe3+ showed only a slight impact on the internal structure of SNFs. SNFs/TA/Fe3+ loaded with 0.1 wt% of Fe3+ demonstrated a significantly higher tensile strength compared to SNFs and those loaded with TA alone. The presence of TA enhances the antioxidant activity of SNFs, and the robust SNFs/TA/Fe3+ exhibited comparable antioxidant activity to SNFs/TA. However, the SNFs/TA/Fe3+ showed a reduction in antibacterial activity, possibly due to the high valence state of the metal ions. Overall, these findings highlighted that a simple electrospinning method was used to produce SNFs/TA/Fe3+ resulted in improved mechanical properties and antioxidant activity, offering a new strategy for the development of active food packaging using SNFs.

The growth rate and antibacterial activity of lactic acid bacteria GMH2 and GMH3 in various salt concentration

Lactic acid bacteria (LAB) can be naturally found in fermented fish products that contain various salt concentrations. LAB is reported to produce proteinogenic antibacterial compounds named bacteriocin that can inhibit the growth of pathogenic and spoilage bacteria. In order to evaluate the performance of previously isolated LABs, namely GMH2 and GMH3, to inhibit the growth of these bacteria in fermented food systems, it is necessary to examine the effect of salt concentration on the growth rate and antibacterial activity. LAB GMH2 and GMH3 were inoculated on de man rogosa and sharp broth (MRSB) at various salt concentrations, including 0%, 7.5%, and 15%, followed by incubation at 37°C for 30 hours with observation every 6 hours. Bacterial growth was tested using the Total Plate Count (TPC) method, which was then further processed using the DMFit program to obtain growth rates, while antibacterial activity was tested using the macrodilution method against histamine-producing bacteria (HPB) Klebsiella pneumoniae (CK2). Both strains showed the highest growth rate at 0% NaCl, with 0.171 and 1.681 log CFU/hour for GMH2 and GMH3, respectively and remained steady until 7.5% salt concentration at 0,153 log CFU/hour for GMH2 and 0.044 log CFU/hour for GMH3. Antibacterial activity for both isolates showed the highest inhibitory value of 39.87±2.25% for GMH2 and 79.55±1.08 for GMH3. The addition of 7.5% and 15% interestingly did not show a significant reduction in antibacterial activity. The results of this study concluded that LAB GMH2 and GMH3 have the potency to be used as starters in fish fermented products, which possess up to 7.5% salt content.

Enhanced visible light-driven photodegradation of tetracycline by salicylic acid-modified graphitic carbon nitride and toxicity assessment.

The tetracycline (TC) in water has led to serious concern. Graphitic carbon nitride (g-C3N4) photocatalysts were produced via copolymerization of mono-benzene ring-mediated precursors (urea, melamine, and dicyandiamide) involving salicylic acid (SA) for TC degradation. The SA-modified g-C3N4 samples showed improved visible light absorbance, transfer and separation of photogenerated electrons, and prospective photocatalytic application in TC degradation. As a result, the optimal SA-modified g-C3N4 (2 wt% of SA) using urea (CNU-SA-2) showed 2 times higher TC degradation than that of pristine g-C3N4. The process of TC degradation was evaluated by the reduction of antibacterial activity and extensively studied by varying the types of TC, initial pH values, co-existing anions, and natural organic materials. In addition, the catalyst could be reused for at least four cycles, indicating good reusability. The main active species were revealed to be h+ and ·O2- by scavenging experiments and electron spin resonance. The CNU-SA-2 photocatalyst and TC intermediates during degradation had no adverse impact on zebrafish embryos. This work could provide a design strategy and a perspective on the practical application of g-C3N4-based photocatalysts for the treatment of wastewater containing antibiotics.

Antimicrobial effects of bacterial binding to a dialkylcarbamoyl chloride-coated wound dressing: an in vitro study.

Wound dressings that inactivate or sequestrate microorganisms, such as those with a hydrophobic, bacteria-binding dialkylcarbamoyl chloride (DACC) surface, can reduce the risk of clinical infections. This 'passive' bioburden control, avoiding bacterial cell wall disruption with associated release of bacterial endotoxins aggravating inflammation, is advantageous in hard-to-heal wounds. Hence, the full scope of DACC dressings, including the potential impact of higher inoculum densities, increased protein load and different pH on antibacterial activity, needs to be evaluated. The Japanese Industrial Standard (JIS) L 1902 challenge test was used to evaluate the antimicrobial activity of the DACC-coated dressing against several World Health Organization (WHO)-prioritised wound pathogens (e.g., meticillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, microorganisms with extended-spectrum beta-lactamases and Acinetobacter baumannii), the effect of repeated bacterial challenge in an adverse wound environment, and antimicrobial performance at wound-related pH. High antibacterial activity of the DACC-coated dressing against the WHO-prioritised bacteria strains by its irreversible binding and inhibition of growth of bound bacteria was confirmed using JIS L 1902. At increased inoculation densities, compared to standard conditions, the DACC-coated dressing still achieved strong-to-significant antibacterial effects. Augmenting the media protein content also affected antibacterial performance; a 0.5-1 log reduction in antibacterial activity was observed upon addition of 10% fetal calf serum. The pH did not influence antibacterial performance. The DACC-coated dressing also sustained antibacterial activity over subsequent reinfection steps. It can be assumed that the DACC-coated dressing exerts beneficial effects in controlling the wound bioburden, reducing the overall demand placed on antibiotics, without using antimicrobial substances.

Changes in microbial community composition affect bioactivities of mucus isolated from coral acropora millepora

Antibiotic resistance is increasingly popular together with emerging diseases presents an urgent requirement for more and more discovery of novel marine bioactive compounds. Paired-end reads of 16S rRNA sequence of bacteria living in the coral Acropora millepora obtained by the Illumina next-generation sequencing technology to be processed by DADA2 pipeline, phyloseq and ggplot2 packages showed that bleached coral mucus had an alpha diversity to be higher than healthy coral mucus. The coral surface mucus layer (SML) of healthy coral exhibited higher growth inhibition activity to Vibrio parahaemolyticus test strain than that of bleached coral in any amount (10 – 30 µL). The cytotoxicity against the colon cancer cell line HCT 116 was also clearly observed when treated with healthy SML and was 1.5 times higher than mucus was taken from bleached coral. The composition of the microbial community was shifted when corals changed from a healthy state to a bleached one, resulting in the reduction of antibacterial activity and cytotoxicity.

Antibacterial Profile of a Microbicidal Agent Targeting Tyrosine Phosphatases and Redox Thiols, Novel Drug Targets.

The activity profile of a protein tyrosine phosphatase (PTP) inhibitor and redox thiol oxidant, nitropropenyl benzodioxole (NPBD), was investigated across a broad range of bacterial species. In vitro assays assessed inhibitory and lethal activity patterns, the induction of drug variants on long term exposure, the inhibitory interactions of NPBD with antibiotics, and the effect of plasma proteins and redox thiols on activity. A literature review indicates the complexity of PTP and redox signaling and suggests likely metabolic targets. NPBD was broadly bactericidal to pathogens of the skin, respiratory, urogenital and intestinal tracts. It was effective against antibiotic resistant strains and slowly replicating and dormant cells. NPBD did not induce resistant or drug-tolerant phenotypes and showed low cross reactivity with antibiotics in synergy assays. Binding to plasma proteins indicated lowered in-vitro bioavailability and reduction of bactericidal activity in the presence of thiols confirmed the contribution of thiol oxidation and oxidative stress to lethality. This report presents a broad evaluation of the antibacterial effect of PTP inhibition and redox thiol oxidation, illustrates the functional diversity of bacterial PTPs and redox thiols, and supports their consideration as novel targets for antimicrobial drug development. NPBD is a dual mechanism agent with an activity profile which supports consideration of tyrosine phosphatases and bacterial antioxidant systems as promising targets for drug development.

Enhancing the expression of recombinant small laccase in Pichia pastoris by a double promoter system and application in antibiotics degradation.

Low-expression levels remain a challenge in the quest to use the small laccase (rSLAC) as a viable catalyst. In this study, a recombinant Pichia pastoris strain (rSLAC-GAP-AOX) producing rSLAC under both AOX and GAP promoters (located in two different plasmids) was generated and cultivated in the presence of methanol and mixed feed (methanol:glycerol). Induction with methanol resulted in a maximum laccase activity of 1200 U/L for rSLAC-GAP-AOX which was approximately 2.4-fold higher than rSLAC-AOX and 5.1-fold higher than rSLAC-GAP. The addition of methanol:glycerol in a stoichiometric ratio of 9:1 consistently improved biomass and led to a 1.5-fold increase in rSLAC production as compared to induction with methanol alone. The rSLAC removed 95% of 5mg/L ciprofloxacin (CIP) and 99% of 100mg/L tetracycline (TC) in the presence of a mediator. Removal of TC resulted in complete elimination of antibacterial activity while up to 48% reduction in antibacterial activity was observed when CIP was removed. Overall, the present study highlights the effectiveness of a double promoter system in enhancing SLAC production.

The impact of serum protein binding on bacterial killing of minocycline

ObjectivesMinocycline is increasingly used clinically for treating infections due to multidrug resistant bacteria. We previously reported that the serum protein binding of minocycline atypically correlated with total concentration using microdialysis, but the therapeutic implications of this finding remained unclear. The objective of this study was to ascertain the functional impact of serum protein binding on bacterial killing. MethodsTime-kill experiments using 4 strains of Acinetobacter baumannii were conducted comparing the activity of minocycline in mouse serum (50 mg/L) and 50% cation-adjusted Mueller-Hinton broth (CA-MHB) (4 mg/L). As a control, similar experiments were also conducted for a clinically achievable levofloxacin concentration (4 mg/L) in serum and 50% CA-MHB (2 mg/L). Serial samples were collected in duplicate over 6 hours, and bacterial burden was determined by quantitative culture. ResultsMinocycline exhibited concentration-dependent bactericidal activity against the reference strain in mouse and human serum. Despite using approximately 10× the peak concentration associated with clinical dosing, only moderate bacterial killing was observed. All the minocycline killing profiles in serum were inferior to those observed in CA-MHB. In contrast, the reduction in bactericidal activity seen with levofloxacin was less dramatic. ConclusionAntimicrobial activity of minocycline was dramatically reduced in the presence of serum, which corroborated with our atypical serum protein binding findings. If validated, these results implied dose escalation might not the best approach to improve the clinical efficacy of minocycline for bacteremia. Future investigations will focus on the specificity and mechanism(s) of minocycline protein binding.

Energy-saving photo-degradation of three fluoroquinolone antibiotics under VUV/UV irradiation: Kinetics, mechanism, and antibacterial activity reduction

Due to the inefficient treatment by the biotic and UV-disinfection processes in wastewater treatment plants, the broad-spectrum Fluoroquinolone antibiotics (FQs) are frequently detected in water environment around the world. In this work, the photo-degradation of three FQs (norfloxacin-NOR, ciprofloxacin-CIP, levofloxacin-LEV) by VUV/UV irradiation was investigated. The results showed that the degradation of FQs in VUV/UV irradiation system were more effective than that in UV irradiation system by enhanced the defluorination and decarboxylation. FQs could be degraded more efficiently with high temperature and low initial concentration, and the effect of flow rate was small. Initial pH played a key role in degradation of NOR and CIP. Most anions could slightly affect the FQs removal in water, except the carbonate and phosphate species. 1O2 and ·OH played the primary role in FQs degradation in VUV/UV system. Defluorination, decarboxylation, and piperazine ring oxidation were the main degradation pathways for three FQs degradation, but demethylation was a particular degradation pathway of LEV. Antibacterial activities of FQs aqueous sample were reduced in both VUV/UV and UV system, while the removal of antibacterial activities in the VUV/UV process were more efficient than UV process for NOR and LEV. VUV/UV system was more energy-saving for removing FQs. These results suggested that VUV/UV system is potential alternative in replacing or enhancing UV system in wastewater treatment plants for FQs removal in the future.

Detection and determination of stability of the antibiotic residues in cow's milk.

In the present study, antibiotic residues were detected in milk samples collected from the dairy herds located in Karnataka, India, by microbiological assay. Subsequently, the detected antibiotics were identified as azithromycin and tetracycline, by high-performance liquid chromatography, further both the antibiotics detected in the cow milk samples were found to be at high concentration (9708.7 and 5460 μg kg-1, respectively). We then investigated the effects of temperature and pH on the stabilities of azithromycin and tetracycline to determine the degradation rate constant k using first-order kinetic equation. Results indicated that significant reduction in stability and antibacterial activity of azithromycin solution when subjected to 70 and 100°C for 24 h. While stability of tetracycline was significantly reduced when subjected to 70 and 100°C for 24 h. However no significant reduction in antibacterial activity of tetracycline was observed at respective temperatures when compared with that of control. In addition, the stabilities of azithromycin and tetracycline were found to be decreased in acidic pH 4–5. The results of the present study revealed the high risk of contamination of milk sample with veterinary antibiotics and also demonstrated the effect of temperature and pH on stability of antibiotics. Therefore the study suggest that the qualitative and quantitative screening of milk for the presence of antibiotics need to be strictly performed to ensure safe drinking milk for consumers.

High dose of vancomycin plus gentamicin incorporated acrylic bone cement decreased the elution of vancomycin.

PurposeLow doses of vancomycin and gentamicin were commonly incorporated into acrylic bone cement (antibiotic-impregnated bone cement, AIBC) during revision arthroplasty. Previous studies showed that only a very small amount of antibiotics could be eluted from AIBC. Given the fact that a high dose of antibiotic would elute high concentration of antibiotic, this study investigated the influence of a high dose of dual-antibiotic loading on the properties of cement.MethodsA total of 8 groups of AIBC containing either gentamicin or vancomycin or both with different amounts of antibiotics (1 g, 2 g and 4 g) were tested on material properties, elution profiles, antibacterial activity and cytological toxicity.ResultsA high dose of gentamicin and vancomycin AIBC (with 2 g gentamicin and 2 g vancomycin loaded) regiment showed acceptable compressive strength of 74.25±0.72 MPa. No cytotoxicity or antibacterial activity reduction was observed in any group tested in this study. The elution profiles indicated that incorporating 2 g vancomycin resulted in 4.77% (1049.57±3.74 μg) released after 28 days. However, after 2 g gentamicin was added, the vancomycin released was significantly reduced to 2.42% (532.24±1.77 μg) (p<0.001), approximately 50% reduction. No significant influence of vancomycin on gentamicin was observed.ConclusionThese findings suggest that the addition of 2 g vancomycin and 2 g gentamicin into acrylic bone cement was preferred while considering this dual-antibiotic AIBC regiment with acceptably material properties and effective antibacterial activity. However, special attention should be drawn to the reduction of vancomycin elution when incorporated with gentamicin.

Glibenclamide Reduces Primary Human Monocyte Functions Against Tuberculosis Infection by Enhancing M2 Polarization.

Tuberculosis (TB) is a global public health problem, which is caused by Mycobacterium tuberculosis (Mtb). Type 2 diabetes mellitus (T2DM) is one of the leading predisposing factors for development of TB after HIV/AIDS. Glibenclamide is a widely used anti-diabetic drug in low and middle-income countries where the incidence of TB is very high. In a human macrophage cell line, glibenclamide, a K+ATP-channel blocker, promoted alternative activation of macrophages by enhancing expression of the M2 marker CD206 during M2 polarization. M2 macrophages are considered poorly microbicidal and associated with TB susceptibility. Here, we investigated the effect of glibenclamide on M1 and M2 phenotypes of primary human monocytes and further determined whether specific drug treatment for T2DM individuals influences the antibacterial function of monocytes in response to mycobacterial infection. We found that glibenclamide significantly reduced M1 (HLA-DR+ and CD86+) surface markers and TNF-α production on primary human monocytes against mycobacterial infection. In contrast, M2 (CD163+ and CD206+) surface markers and IL-10 production were enhanced by pretreatment with glibenclamide. Additionally, reduction of bactericidal activity also occurred when primary human monocytes from T2DM individuals who were being treated with glibenclamide were infected with Mtb in vitro, consistent with the cytokine responses. We conclude that glibenclamide reduces M1 and promotes M2 polarization leading to impaired bactericidal ability of primary human monocytes of T2DM individuals in response to Mtb and may lead to increased susceptibility of T2DM individuals to TB and other bacterial infectious diseases.

Bioactivity-Guided Metabolite Profiling of Feijoa ( Acca sellowiana) Cultivars Identifies 4-Cyclopentene-1,3-dione as a Potent Antifungal Inhibitor of Chitin Synthesis.

Pathogenic fungi continue to develop resistance against current antifungal drugs. To explore the potential of agricultural waste products as a source of novel antifungal compounds, we obtained an unbiased GC-MS profile of 151 compounds from 16 commercial and experimental cultivars of feijoa peels. Multivariate analysis correlated 93% of the compound profiles with antifungal bioactivities. Of the 18 compounds that significantly correlated with antifungal activity, 5 had not previously been described from feijoa. Two novel cultivars were the most bioactive, and the compound 4-cyclopentene-1,3-dione, detected in these cultivars, was potently antifungal (IC50 = 1-2 μM) against human-pathogenic Candida species. Haploinsufficiency and fluorescencemicroscopy analyses determined that the synthesis of chitin, a fungal-cell-wall polysaccharide, was the target of 4-cyclopentene-1,3-dione. This fungal-specific mechanism was consistent with a 22-70-fold reduction in antibacterial activity. Overall, we identified the agricultural waste product of specific cultivars of feijoa peels as a source of potential high-value antifungal compounds.

Enhanced antibacterial activity of silver-ruthenium coated hollow microparticles.

The oxidation based antimicrobial activity of silver is long known. Microparticles with a particular silver-ruthenium coating and specific physical properties were developed. The coating showed a considerably increased silver ion release rate in comparison to a plain silver coating. Accordingly, an exposure of Escherichia coli and Staphylococcus aureus to these silver-ruthenium coated microparticles resulted in a time and concentration dependent cell killing. Even though contact killing may contribute to this efficacy, rather a release associated diffusion gradient dependent killing was observed. Moreover, cell killing did not involve lysis. The coated microparticles manifested no reduction in antibacterial activity for months. Due to their specific size and density, they sedimented slowly in aqueous solution, showed a low aggregation tendency, and could be recycled easily. Hence, these silver-ruthenium coated microparticles lend themselves to a wide range of antibacterial applications as they combine long-term stability and high efficacy with ease of use.

Isolation and screening of Lactobacillus species from dogs for probiotic action

The present study aimed at the detection of suitable Lactobacillus species from dogs for usage as probiotic. A total of 67 rectal swabs from healthy pups were analyzed and 49 (73.1%) Lactobacillus isolates were identified based on morphological, biochemical characteristics and confirmed by genus specific PCR targeting 16S rRNA gene. A total of 20 isolates that showed strong aggregation, high cell surface hydrophobicity, acid and bile tolerance were screened for in-vitro antibacterial activity by agar well diffusion assay, where prominent inhibitory zones were observed against majority of the test pathogens. Reduction in antibacterial activity was noticed after neutralization, proteinase K and heat treatment of supernatants. Partial 16S rRNA nucleotide sequence analysis of seven Lactobacillus isolates that showed prominent in-vitro antibacterial activity revealed maximum sequence homology with Lactobacillus fermentum (for six isolates) and Lactobacillus agilis (for one isolate). The in-vitro antibacterial activity results highlighted the need for in-vivo studies in India to establish probiotic potential of canine faecal Lactobacillus species in the near future.

Antimicrobial and Immunomodulatory Activity of PMAP-23 Derived Peptides

The Porcine Myeloid Antibacterial Peptide (PMAP)-23 is a porcine host defence peptide with strong antibacterial activity against Gram-positive and Gram-negative bacteria, and fungi. PMAP-23 and truncated/mutated derivatives were tested for antibacterial and immunomodulatory activities to determine core elements of the peptide required for functionality. PMAP-23 and truncated and/or mutated derivatives were synthesized. Antibacterial activity against Gram positive and negative bacteria was determined using colony counting assays. Cytotoxicity was measured against red blood cells and epithelial cells. Peptide induced cytokine production of epithelial cells was determined by ELISA. LPS neutralization was measured using isothermal titration calorimetry and inhibition of LPS induced cytokine production by macrophages. The effect of peptides on phagocytosis was performed by measuring uptake of fluorescently labelled beads by porcine macrophages. Truncation of the peptide did not lead to a strong reduction in antibacterial activity, but interestingly, all C-terminal truncated forms were strongly inhibited by salt addition, unlike the full length peptide or the two N-terminally truncated peptides. None of the peptides were hemolytic or toxic in concentrations up to 40 μM. Full length PMAP-23 induced IL-8 production in porcine epithelial cells, however, this activity was lost in all truncated peptides. None of the peptides bound LPS and subsequently did not inhibit LPS-induced cytokine production of monocytes. Finally, all PMAP-23 derived peptides reduced the uptake of beads by freshly isolated monocytes. PMAP-23 is mainly antibacterial with only limited immunomodulating capacity; the full length peptide is required for the full spectrum of activities.

IL-1α-induced microvascular endothelial cells promote neutrophil killing by increasing MMP-9 concentration and lysozyme activity.

The recruitment of neutrophils by endothelial cells during infection has been extensively studied, but little is known about the regulation of neutrophils activity by endothelial cells. To examine the role of microvascular endothelial cells in neutrophil killing, we established a transmigration model using rat intestinal microvascular endothelial cells (RIMVECs) and measured the extracellular and intracellular killing of Escherichia coli, Lactobacillus acidophilus, and Staphylococcus aureus by transendothelial neutrophils. We observed that blood neutrophils engulfed bacteria but did not kill them, and lipopolysaccharide- or hemolysin-injured RIMVECs inhibited the extracellular and intracellular bactericidal activity of transendothelial neutrophils. In comparison, interleukin-1α-induced RIMVECs promoted the extracellular and intracellular killing activity of transendothelial neutrophils and significantly increased MMP-9 concentration and lysozyme activity in transendothelial neutrophils (p < 0.01 and p < 0.001, respectively). Our results demonstrated that activation of endothelial cells enhanced bactericidal activity of transendothelial neutrophils and bacterial toxin damage of endothelial cells led to reduction in bactericidal activity of transendothelial neutrophils. These findings offered new insight into the role of endothelial cells in the bactericidal activity of neutrophils.

Effect of surface treatments on the surface morphology, corrosion property, and antibacterial property of Ti–10Cu sintered alloy

Ti–10Cu sintered alloy has shown strong antibacterial properties against S. aureus and E. coli and good cell biocompatibility in vitro and in vivo, displaying potential application as an implant material. Surface treatments are always applied to implants to improve the surface biocompatibility. In this paper, several typically used surface treatments, including sandblasting (SB), sandblasted and large-grits acid etching (SLA), and alkaline heat treatment (AH) were chosen to modify the Ti–10Cu. A cp-Ti (commercially pure titanium) sample was used as control sample. The effect of surface treatments on the corrosion properties and antibacterial properties of the Ti–10Cu sintered alloy was investigated. After SB and SLA treatments, a rough surface with a TiO2 layer was formed on the surface, which reduced the corrosion resistance and enhanced the Ti and Cu ion release. After AH treatment, a smooth but microporous surface with a TiO2/titanate layer was formed, which improved slightly the corrosion resistance. However, the Cu ion and Ti ion release from the Ti–10Cu sample was promoted by AH treatment due to the fact that more Ti2Cu phases were exposed on the AH-treated Ti–10Cu sample. It was demonstrated that the Ti–10Cu samples after surface treatments still exhibited good antibacterial properties against S. aureus, which indicated that the surface treatment did not reduce the antibacterial activity. The control mechanism was thought to be related to the high Cu ion release even after surface treatments. It was expected that the surface treatments provided Ti–10Cu sintered alloy with good surface bioactivity without reduction in antibacterial activity.

Pathogenic challenge reveals immune trade-off in mussels exposed to reduced seawater pH and increased temperature

Ocean acidification (OA) and warming pose a considerable threat to marine ecosystems. Previous studies show that these environmental co-stressors significantly impact upon a number of key physiological functions, including calcification, metabolism and growth, in many marine organisms. Yet despite the importance of the immune system, to date only a handful of studies have investigated the impact of reduced seawater pH on an organism's immune response. Furthermore, whilst temperature has received far greater attention with respect to host defence, there is a dearth of information concerning the possible synergism of these two stressors on immune defence. Here we show that a 90day exposure to reduced seawater pH led to a reduction in the antibacterial activity of cell-free haemolymph in the blue mussel Mytilus edulis, whilst temperature led to an increase in this immune parameter. However in contrast to previous research, following this initial 90day exposure, mussels in the current study were then exposed to the pathogenic bacterium, Vibrio tubiashii. Crucially, whilst reduced seawater pH initially appeared to impair immunological functioning, as has been interpreted previously, mussels demonstrated the ability to restore haemolymph bactericidal activity when required. This indicated that the initial reduction in antibacterial activity was in fact a reversible physiological trade-off, rather than an irreversible impairment of immune function. By demonstrating this plasticity, the current study illustrates the need to measure organism responses within a realistic natural context (i.e. measuring the immune response of an organism in the presence of a pathogen). Failure to do so may result in a misleading interpretation of the ecological relevance of experimental data, and thus the sensitivity of different species in a rapidly changing environment.