Impacts of metal and metal oxide nanoparticles on marine organisms

Increasing use of metal and metal oxide nanoparticles [Me(O)NPs] in products means many will inevitably find their way into marine systems. Their likely fate here is sedimentation following hetero-aggregation with natural organic matter and/or free anions, putting benthic, sediment-dwelling and filter feeding organisms most at risk. In marine systems, Me(O)NPs can absorb to micro-organisms with potential for trophic transfer following consumption. Filter feeders, especially bivalves, accumulate Me(O)NPs through trapping them in mucus prior to ingestion. Benthic in-fauna may directly ingest sedimented Me(O)NPs. In fish, uptake is principally via the gut following drinking, whilst Me(O)NPs caught in gill mucus may affect respiratory processes and ion transport. Currently, environmentally-realistic Me(O)NP concentrations are unlikely to cause significant adverse acute health problems, however sub-lethal effects e.g. oxidative stresses have been noted in many organisms, often deriving from dissolution of Ag, Cu or Zn ions, and this could result in chronic health impacts.

Simultaneous removal of di-(2-ethylhexyl) phthalate and nitrogen in a laboratory-scale pre-denitrification biofilter system

This study demonstrated the excellent di-(2-ethylhexyl) phthalate (DEHP) removal performance of a pre-denitrification biofilter system. Experimental results showed that DEHP removal efficiency remained stable while total nitrogen removal efficiency fluctuated with the nitrate recycle ratio changes when the hydraulic loading rate at 1.1m(3)/m(2)h. DEHP removal efficiency increased from 48% to 82% while the hydraulic loading rate increased from 1.1 to 2.2m(3)/m(2)h. DEHP concentration decreased gradually along the wastewater flow direction in the denitrification biofilter and a plug flow model with the reaction order of 5 and the rate constant of 0.54 was obtained. Both the denitrification biofilter and the nitrification biofilter showed similar DEHP removal performance. The overall DEHP removal efficiency of the system was 83.8%, in which biodegradation contributed 72.3%. Biodegradation plays a key role in DEHP removal in the pre-denitrification biofilter system.

Investigation on the iron-uptake by natural biofilms

Biofilms are natural communities of microorganisms living in aquatic ecosystems which play an important role in the biogeochemistry of many inorganic elements, including iron. The present work aimed to study the uptake of iron by natural river biofilms (produced in the laboratory) and to examine the relationships between biofilms and iron in water. For that, biofilms were formed from natural water samples collected at different times of the year. Total content and global localization of iron were determined by a combination of chemical analyses and microscopy, which indicated that iron was systematically distributed throughout the biofilm matrix. Depending on the level of iron uptake, iron was diffuse or present as hot spots, was primarily localized to the fraction ascribed to OM compounds (45-60%) or the residual fraction (∼14-40%). Additional experiments were conducted using iron-organic complexes with different affinities (log K) to study iron uptake according to the speciation. These experiments suggested the association between iron and organic ligands (i.e. depending on the affinity constant) influenced the uptake of iron, but did not control the biofilm affinity for iron, which appeared to be controlled by chemical-kinetic laws.

Direct measurement and characterization of active photosynthesis zones inside wastewater remediating and biofuel producing microalgal biofilms

Microalgal biofilm based technologies are of keen interest due to their high biomass concentrations and ability to utilize light and CO2. While photoautotrophic biofilms have long been used for wastewater remediation, biofuel production represents a relatively new and under-represented focus area. However, the direct measurement and characterization of fundamental parameters required for industrial control are challenging due to biofilm heterogeneity. This study evaluated oxygenic photosynthesis and respiration on two distinct microalgal biofilms cultured using a novel rotating algal biofilm reactor operated at field- and laboratory-scales. Clear differences in oxygenic photosynthesis and respiration were observed based on different culturing conditions, microalgal composition, light intensity and nitrogen availability. The cultures were also evaluated as potential biofuel synthesis strategies. Nitrogen depletion was not found to have the same effect on lipid accumulation compared to traditional planktonic microalgal studies. Physiological characterizations of these microalgal biofilms identify fundamental parameters needed to understand and control process optimization.

Photodynamic therapy versus ultrasonic irrigation: interaction with endodontic microbial biofilm, an ex vivo study

INTRODUCTION

Photodynamic therapy was introduced as an adjuvant to conventional chemo-mechanical debridement during endodontic treatment to overcome the persistence of biofilms. The aim of this study was to evaluate the ability of photodynamic therapy (PDT) to disrupt an experimental microbial biofilm inside the root canal in a clinically applicable working time.

MATERIALS AND METHODS

Thirty extracted teeth were prepared and then divided in three groups. All samples were infected with an artificially formed biofilm made of Enterococcus faecalis, Streptococcus salivarius, Porphyromonas gingivalis and Prevotella intermedia bacteria. First group was treated with Aseptim Plus® photo-activated (LED) disinfection system, second group by a 650 nm Diode Laser and Toluidine blue as photosensitizer, and the third group, as control group, by ultrasonic irrigation (PUI) using EDTA 17% and NaOCl 2.6% solutions. The working time for all three groups was fixed at 3 min. Presence or absence of biofilm was assessed by aerobic and anaerobic cultures.

RESULTS

There was no statistically significant difference between results obtained from groups treated by Aseptim Plus® and Diode Laser (P<0.6267). In cultures of both groups there was a maximal bacterial growth. The group that was treated by ultrasonic irrigation and NaOCl and EDTA solutions had the best results (P<0.0001): there was a statistically significant reduction of bacterial load and destruction of microbial biofilm.

CONCLUSION

Under the condition of this study, Photodynamic therapy could not disrupt endodontic artificial microbial biofilm and could not inhibit bacterial growth in a clinically favorable working time.

An assessment of the effectiveness of mechanical and chemical cleaning of Essix orthodontic retainer

OBJECTIVES

To determine the effectiveness of mechanical and chemical cleaning on the removal of microorganisms from Essix orthodontic retainers.

DESIGN

In vitro laboratory study.

SETTING

Department of Orthodontics and Microbiology, Eastman Dental Institute, University College London, UK.

METHODS

Study 1: 120 Essix retainers were divided into four cleaning groups. The effectiveness of each cleaning method to remove a single species biofilm of Streptococcus mutans from the retainer was assessed. Study 2: 140 Essix retainers were divided into four study groups (brushing with fluoride toothpaste, chlorhexidine gel, immersion in chlorhexidine solution only and a control) to investigate the chemical and mechanical cleaning of the multispecies biolfilm of (Streptococcus sanguis, Actinomyces naeslundii, methicillin-resistant Staphylococcus aureus and Candida albicans).

RELEVANT RESULTS

In study 1, brushing with toothpaste resulted in 99% reduction of Streptococcus mutans. In study 2, all three cleaning methods recorded similarly statistically significant reductions in colony forming units per millilitre compared to the control. There were no statistically significant differences between any of the cleaning groups for any of the microorganisms except MRSA-16. For MRSA-16, chlorhexidine mouthwash and gel were significantly more potent in eliminating the microorganism than the fluoride toothpaste.

CONCLUSIONS

All three cleaning methods effectively removed 99% of microorganisms from the Essix retainers. Brushing with fluoride toothpaste can therefore be confirmed as an effective method for cleaning retainers in most circumstances. The use of chlorhexidine gel or mouthwash is recommended in patients where bacterial infection has to be avoided due to immunosuppression or other reasons.

Simulation of batch-operated experimental wetland mesocosms in AQUASIM biofilm reactor compartment

In this study, a mathematical biofilm reactor model based on the structure of the Constructed Wetland Model No.1 (CWM1) coupled to AQUASIM's biofilm reactor compartment has been used to reproduce the sequence of transformation and degradation of organic matter, nitrogen and sulphur observed in a set of constructed wetland mesocosms and to elucidate the development over time of microbial species as well as the biofilm thickness of a multispecies bacterial biofilm in a subsurface constructed wetland. Experimental data from 16 wetland mesocosms operated under greenhouse conditions, planted with three different plant species (Typha latifolia, Carex rostrata, Schoenoplectus acutus) and an unplanted control were used in the calibration of this mechanistic model. Within the mesocosms, a thin (predominantly anaerobic) biofilm was simulated with an initial thickness of 49 μm (average) and in which no concentration gradients developed. The biofilm density and area, and the distribution of the microbial species within the biofilm were evaluated to be the most sensitive biofilm properties; while the substrate diffusion limitations were not significantly sensitive to influence the bulk volume concentrations. The simulated biofilm density ranging between 105,000 and 153,000 gCOD/m(3) in the mesocosms was observed to vary with temperature, the presence as well as the species of macrophyte. The biofilm modeling was found to be a better tool than the suspended bacterial modeling approach to show the influence of the rhizosphere configuration on the performance of the constructed wetlands.

Evidence of arsenic release promoted by disinfection by-products within drinking-water distribution systems

Changes in disinfectant type could trigger a cascade of reactions releasing pipe-anchored metals/metalloids into finished water. However, the effect of pre-formed disinfection by-products on the release of sorbed contaminants (arsenic-As in particular) from drinking water distribution system pipe scales remains unexplored. A bench-scale study using a factorial experimental design was performed to evaluate the independent and interaction effects of trihalomethanes (TTHM) and haloacetic acids (HAA) on arsenic (As) release from either scales-only or scale-biofilm conglomerates (SBC) both anchored on asbestos/cement pipe coupons. A model biofilm (Pseudomonas aeruginosa) was allowed to grow on select pipe coupons prior experimentation. Either TTHM or HAA individual dosing did not promote As release from either scales only or SBC, detecting <6 μg AsL(-1) in finished water. In the case of scales-only coupons, the combination of the highest spike level of TTHM and HAA significantly (p<0.001) increased dissolved and total As concentrations to levels up to 16 and 95 μg L(-1), respectively. Similar treatments in the presence of biofilm (SBC) resulted in significant (p<0.001) increase in dissolved and total recoverable As up to 20 and 47 μg L(-1), respectively, exceeding the regulatory As limit. Whether or not, our laboratory-based results truly represent mechanisms operating in disinfected finished water in pipe networks remains to be investigated in the field.

Bacterial community of biofilms developed under different water supply conditions in a distribution system

In order to understand the bacterial community characteristics of biofilms developed under different finished water supply histories in drinking water distribution systems (DWDS), biofilm samples on different type of iron corrosion scales in a real DWDS were collected and systematically investigated using 454 pyrosequencing of 16S rRNA gene. The richness and diversity estimators showed that biofilms formed in DWDS transporting finished groundwater (GW) had the lowest level of bacterial diversity. From phylum to genus level, the dominant bacterial groups found in the biofilms under finished surface water (SW) and GW conditions were distinct. Proteobacteria was the dominant group in all biofilm samples (in the range of 40%-97%), but was relatively higher in biofilms with GW. The relative abundance of Firmicutes in biofilms with SW (28%-35%) was significantly higher (p<0.01) than that in biofilms with GW (0.5%-2.88%). Statistical analysis (Spearman's rank) revealed that alkalinity and chemical oxygen demand (CODMn) positively correlated with the relative abundance of Proteobacteria and Firmicutes, respectively. The abundance of sequences affiliated to iron-reducing bacteria (mainly Bacillus) and iron-oxidizing bacteria (mainly Acidovorax) were relatively higher in biofilms with SW, which might contribute to the formation of much thicker or tubercle-formed corrosion scales under SW supply condition. Several potential opportunistic pathogens, such as Burkholderia fungorum, Mycobacterium neoaurum, Mycobacterium frederiksbergense were detected in the biofilms.

Clinical characteristics of biofilms in patients with chronic rhinosinusitis: a prospective case-control study

Recent studies have indicated that biofilms are involved in the pathogenesis of recurrent and recalcitrant chronic rhinosinusitis (CRS). The present study was performed to evaluate the presence of biofilms and to evaluate the relationships between the presence of biofilms and clinical features of CRS. A total of 33 patients were included in this study. Maxillary sinus mucosa from 26 CRS patients and the ethmoid mucosa from 7 patients undergoing septoplasty were collected. Biofilms were evaluated by scanning electron microscopy. Preoperative symptom scores, preoperative and intraoperative nasoendoscopic findings, and postoperative healing period were compared between the groups. Biofilms were detected in 14 (42.4 %) of the 33 patients. Biofilms were present in 13 (50 %) of the 26 patients in the CRS group, but in only one (14.3 %) of the seven patients in the control group. There were no significant differences in preoperative symptom scores or preoperative nasal Lund-Kennedy endoscopic scores between the groups. However, the average Lund-Mackay and intraoperative sinus Lund-Kennedy endoscopic scores were significantly higher in biofilm-positive than biofilm-negative patients (P < 0.05). In the follow-up period, the healing time was significantly longer in biofilm-positive than biofilm-negative patients (P < 0.05). This study suggested that the presence of bacterial biofilms may contribute to the pathogenesis of CRS and the clinical characteristics of CRS patients after endoscopic sinus surgery.

Listeria Monocytogenes Persistence in Ready-to-Eat Sausages and in Processing Plants

Listeria monocytogenes is of major concern in the fermented meat products and is able to persist in their processing environments. The aim of the present work was to evaluate the virulence profile and the persistence capacity of L. monocytogenes strains isolated in Sardinian fermented sausages processing plants. Food (ground meat, sausages at the end of acidification and ripening stage) and environmental samples (a total of n. 385), collected from 4 meat processing plants located in Sardinia (Italy), were examined to detect L. monocytogenes presence. All the L. monocytogenes isolates were identified by polymerase chain reaction (PCR) method. A subset of strains was also characterised by multiplex PCR-based serogrouping, using the lmo0737, lmo1118, ORF2819 and ORF2110 genes. Three different multiplex PCRs were used to obtain the virulence profiles by the rrn, hlyA, actA, prfA, inlA, inlB, iap, plcA, plcB and mpl marker genes. Furthermore, in vitro biofilm forming ability and resistance to disinfectants were carried out on microtiter plate. The overall prevalence was 31.5% in food, and 68.5% in environmental samples. The prevalent serotype resulted 1/2c (43%), followed by 1/2a (40%), 4b (8.6%), and 1/2b (8.6%). The amplification products of the virulence genes were found in all the isolates with the following prevalence: 77.1% hlyA; 100% rrn; 100% prfA; 97.1% iap; 65.7% inlB; 88.6% inlA; 100% plcA; 100% plcB and 74.3% mpl. As for biofilm forming ability, 37.1% of the strains were positive and resulted weak producer, but all the isolates were sensible to disinfectants showing a reduction of L. monocytogenes growth after each incubation time. More appropriate technologies and application of measures of hygienic control should be implemented to prevent the L. monocytogenes growth and cross-contamination in salsiccia sarda processing plants.

Characterization of N-Acyl-homoserine Lactones (AHLs)-Deficient Clinical Isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen causing severe respiratory infections. Acylated homoserine lactones (AHLs) are self-generated diffusible signal molecules that mediate population density dependent gene expression (quorum sensing, QS) in a variety of Gram-negative bacteria, and several virulence genes of bacterial pathogens are known to be controlled by QS. Hence, fitness mutant of virulent factors is beneficial for natural selection. In this study, strains of P. aeruginosa isolated from chronic lung infection of cystic fibrosis patients, were screened for AHLs production by using indicator strains of Chromobacterium violaceum CV026 and Agrobacterium tumefaciens strain At136. Four AHLs defective strains were selected from fifty-three clinical isolates. PCR analysis revealed that only one isolate was negative for lasR gene. These four AHLs defective isolates produced less virulence factors and forming less biofilm than PAO1. Only isolate PA41 produce little more pyocyanin than PAO1. The results indicate that, despite the pivotal role of QS in the pathogenesis of P. aeruginosa infections, AHLs-deficient strains are still capable of causing infections in human.

Application of a prototype-scale Twin-Layer photobioreactor for effective N and P removal from different process stages of municipal wastewater by immobilized microalgae

In the view of limited phosphorous resources and tightened discharge regulations, the recovery of phosphate and nitrate from wastewater is of great interest. Here, the integration of microalgae into wastewater treatment processes is a promising approach. A prototype-scale Twin-Layer photobioreactor immobilizing the green alga Halochlorella rubescens on vertical sheet-like surfaces was constructed and operated using primary and secondary municipal wastewater. The process was not impaired by suspended solids, bacteria or loss of algal biomass by leaching. The average areal microalgal growth was 6.3 gm(-2) d(-1). After treatment, P and N concentrations in the effluents could efficiently be reduced by 70-99%, depending on element and type of wastewater. Mean effluent values of ⩽ 1.0mg L(-1)P and 1.3 mg L(-1)N met the legal discharge limits of the European Water Framework Directive and show a potential to comply with upcoming, more stringent legislation.

Eradication of Pseudomonas aeruginosa Biofilms Using the Combination of n-butanolic Cyclamen coum Extract and Ciprofloxacin

Background:

Biofilm formation is a major pathogenic factor in different bacteria such as Pseudomonas aeruginosa. A number of studies have reported that bacterial biofilms show different levels of antibiotic resistance. In order to re-sensitize the bacterial biofilms to antibiotics, biofilms should be dispersed.

Objectives:

In this study, the effect of n-butanolic Cyclamen coum extract in combination with ciprofloxacin was examined on one, three and five day old P. aeruginosa biofilms. The synergistic effect of n-butanolic C. coum extract and ciprofloxacin towards dispersing pre-established P. aeruginosa biofilms was also studied.

Materials and Methods:

The ability of biofilm formation by six different P. aeruginosa strains was confirmed by microtiter plate method and PCR assay for the cupA gene. The extraction of C. coum tubers was achieved by fractionation method using different solvents. The minimum inhibitory concentration (MIC) of n-butanolic C. coum extract and ciprofloxacin against planktonic cells was evaluated using agar well diffusion and microdilution methods. The microdilution chequerboard method was used to determine the fractional biofilm eradication concentration index (FBCI), when the combination of n-butanolic C. coum extract and ciprofloxacin were used against P. aeruginosa biofilms.

Results:

The ability of biofilm formation by P. aeruginosa strains was quantitatively confirmed. The PCR method confirmed the existence of cup A gene (172 bp) in all studied strains. Saponin content of the n-butanolic C. coum extract was 156 µg/mL. The extract revealed antibacterial activity against planktonic cells of P. aeruginosa strains. The results showed that one and three day old biofilms are affected by either ciprofloxacin or n-butanolic C. coum extract. However, n-butanolic C. coum extract in combination with ciprofloxacin was significantly more effective against P. aeruginosa biofilms.

Conclusions:

Using n-butanolic C. coum extract in combination with ciprofloxacin offers a novel strategy to control biofilm-based infections caused by P. aeruginosa.

The Capacity of Listeria Monocytogenes Mutants with In-Frame Deletions in Putative ATP-Binding Cassette Transporters to form Biofilms and Comparison with the Wild Type

Listeria monocytogenes (Lm) is a food-borne pathogen responsible for human listeriosis, an invasive infection with high mortality rates. Lm has developed efficient strategies for survival under stress conditions such as starvation and wide variations in temperature, pH, and osmolarity. Therefore, Lm can survive in food under multiple stress conditions. Detailed studies to determine the mode of action of this pathogen for survival under stress conditions are important to control Lm in food. It has been shown that genes encoding for ATP-binding cassette (ABC) transporters are induced in Lm in food, in particular under stress conditions. Previous studies showed that these genes are involved in sensitivity to nisin, acids, and salt. The aim of this study was to determine the involvement of some ABC transporters in biofilm formation. Therefore, deletion mutants of ABC transporter genes (LMOf2365_1875 and LMOf2365_1877) were created in Lm F2365, and then were compared to the wild type for their capacity to form biofilms. Lm strain F2365 was chosen as reference since the genome is fully sequenced and furthermore this strain is particularly involved in food-borne outbreaks of listeriosis. Our results showed that ΔLMOf2365_1875 had an increased capacity to form biofilms compared to the wild type, indicating that LMOf2365_1875 negatively regulates biofilm formation. A deeper knowledge on the ability to form biofilms in these mutants may help in the development of intervention strategies to control Lm in food and in the environment.

Structure of the Proteus vulgaris HigB-(HigA)2-HigB toxin-antitoxin complex

Bacterial toxin-antitoxin (TA) systems regulate key cellular processes to promote cell survival during periods of stress. During steady-state cell growth, antitoxins typically interact with their cognate toxins to inhibit activity presumably by preventing substrate recognition. We solved two x-ray crystal structures of the Proteus vulgaris tetrameric HigB-(HigA)2-HigB TA complex and found that, unlike most other TA systems, the antitoxin HigA makes minimal interactions with toxin HigB. HigB adopts a RelE family tertiary fold containing a highly conserved concave surface where we predict its active site is located. HigA does not cover the solvent-exposed HigB active site, suggesting that, in general, toxin inhibition is not solely mediated by active site hindrance by its antitoxin. Each HigA monomer contains a helix-turn-helix motif that binds to its own DNA operator to repress transcription during normal cellular growth. This is distinct from antitoxins belonging to other superfamilies that typically only form DNA-binding motifs upon dimerization. We further show that disruption of the HigB-(HigA)2-HigB tetramer to a HigBA heterodimer ablates operator binding. Taken together, our biochemical and structural studies elucidate the novel molecular details of the HigBA TA system.

Catalytic mechanism and mode of action of the periplasmic alginate epimerase AlgG

Pseudomonas aeruginosa is an opportunistic pathogen that forms chronic biofilm infections in the lungs of cystic fibrosis patients. A major component of the biofilm during these infections is the exopolysaccharide alginate, which is synthesized at the inner membrane as a homopolymer of 1-4-linked β-D-mannuronate. As the polymer passages through the periplasm, 22-44% of the mannuronate residues are converted to α-L-guluronate by the C5-epimerase AlgG to produce a polymer of alternating β-D-mannuronate and α-L-guluronate blocks and stretches of polymannuronate. To understand the molecular basis of alginate epimerization, the structure of Pseudomonas syringae AlgG has been determined at 2.1-Å resolution, and the protein was functionally characterized. The structure reveals that AlgG is a long right-handed parallel β-helix with an elaborate lid structure. Functional analysis of AlgG mutants suggests that His(319) acts as the catalytic base and that Arg(345) neutralizes the acidic group during the epimerase reaction. Water is the likely catalytic acid. Electrostatic surface potential and residue conservation analyses in conjunction with activity and substrate docking studies suggest that a conserved electropositive groove facilitates polymannuronate binding and contains at least nine substrate binding subsites. These subsites likely align the polymer in the correct register for catalysis to occur. The presence of multiple subsites, the electropositive groove, and the non-random distribution of guluronate in the alginate polymer suggest that AlgG is a processive enzyme. Moreover, comparison of AlgG and the extracellular alginate epimerase AlgE4 of Azotobacter vinelandii provides a structural rationale for the differences in their Ca(2+) dependence.

Potential role of biofilms in deep cervical abscess

OBJECTIVES

Deep neck abscesses are complex head & neck problems that can lead to significant complications including life threatening infections. It is understood that the pathology of these infections is primarily polymicrobial. Although broad spectrum antibiotics can be effective for small abscesses, larger abscesses can be recalcitrant and difficult to treat with antibiotics. It has been demonstrated for several infectious diseases, including some of head & neck, that biofilm phenotypes present a unique model for recurrence and chronicity of infectious diseases. It is suspected that biofilm phenotypes could play a crucial role in the recalcitrance of large deep neck abscesses. This study presents initial evidence indicating the presence of polymicrobial biofilms in deep neck space infections.

METHODS

Fourteen samples obtained via biopsy of abscess walls from deep neck spaces of patients undergoing surgical drainage. Eight patients were male and 6 were female. All but one patient were pediatric with ages ranging from 18 months to 32 years. All samples were processed and analyzed with scanning electron microscopy.

RESULTS

Electron micrographs of 12 out of 14 specimens showed discrete biofilm architecture with individual bacteria, both rods and cocci, embedded within the matrix. This was starkly different from tissue surfaces devoid of biofilms.

CONCLUSIONS

This initial evidence suggests that biofilm phenotypes could play a role in the pathogenesis and recalcitrance of deep neck infections, particularly in larger abscesses.

Assessment of Biofilm Formation and Resistance to Imipenem and Ciprofloxacin among Clinical Isolates of Acinetobacter baumannii in Tehran

Background:

Biofilms are communities of bacteria attached to the surfaces in an extracellular polymeric matrix which are associated with many chronic infections in humans. Acinetobacter spp. are emerging as a major cause of nosocomial infections and Acinetobacterbaumannii is the predominant species associated with this kind of infections.

Objectives:

In the present study, the potential of biofilm formation of clinical isolates, A. baumannii, was assessed by using crystal violet method. Furthermore, susceptibility pattern of these strains to ciprofloxacin and imipenem was determined.

Methods and Materials:

Biofilm formation by 75 A. baumannii isolates was evaluated by using microtiter plate and tube methods and crystal violet staining. Tube method was carried out under static and shaking conditions. Then, the susceptibility of isolates to ciprofloxacin and imipenem was determined.

Results:

Results showed that in tube method under shaking, 22% of clinical isolates were strong biofilm producers while 23% of them were not able to form biofilms. In this experiment, 18% and 42% of isolates were considered as moderate and weak biofilm-forming strains, respectively. In microtiter plate tests, 18% of strains were strong-biofilm producers and 25% of them were notable biofilm producers. In this assessment, 10% and 47% were considered as moderate and weak biofilm-forming isolates, respectively. The susceptibility tests, using microdilution method, confirmed that 92% of these isolates were resistant and 6.6% were susceptible to ciprofloxacin, although these results for imipenem were 68% and 24%, respectively.

Conclusions:

It can be concluded that most of A. baumannii isolates can form biofilm in microtiter plate and tube. The results also verified that most of these isolates were resistant to ciprofloxacin and imipenem.

Automatic microfiber filtration (AMF) of surface water: impact on water quality and biofouling evolution

In the current study we examined the impact of thread filtration using an automatic microfiber filter on Lake Kinneret water quality and as a new application to control biofouling over time. We found that automatic microfiber filtration (AMF) reduced total iron and aluminum in water by over 80%. Particle analysis (>2 μm) revealed a total particle removal efficiency of ≈ 90%, with AMF removal efficiency increasing with increasing particle size and decreasing particle circularity. Regarding microbiological parameters, AMF did not affect bacterial counts or composition in the water. However, it did control biofilm evolution and affected its microbial community composition. AMF controlled biofilm over time by maintaining premature biofilms of less than 10 μm mean thickness compared to biofilms of unfiltered water (up to 60 μm mean thickness). In addition, biofilms developing in AMF filtered water contained relatively low levels of extracellular polymeric substances. While biofilms of unfiltered water were dominated by Proteobacteria (≤ 50%) followed by Bacteroidetes (20-30%) during all 4 weeks of the experiment, biofilms of AMF filtered water were dominated by Proteobacteria (≤ 90%) and especially Alphaproteobacteria after 2 weeks, and Chloroflexi (≈ 60%) after 4 weeks. The decrease in Bacteroidetes might originate from removal of transparent exopolymer particles, which are occasionally colonized by Bacteroidetes. The increase in Alphaproteobacteria and Chloroflexi was explained by these robust groups' ability to adjust to different environments.

Application of laser scanning microscopy for the analysis of oral biofilm dissolution by different endodontic irrigants

BACKGROUND

Multi-specie biofilms are highly resistant to antimicrobials due to cellular interactions found in them. The purpose of this study was to evaluate, by confocal laser scanning microscopy, the biofilm dissolution effectiveness of different irrigant solutions on biofilms developed on infected dentin in situ.

MATERIALS AND METHODS

A total of 120 bovine dentin specimens infected intraorally (30/group) were treated by the following solutions: 2% of chlorhexidine digluconate, 1%, 2.5% and 5.25% of sodium hypochlorite (NaOCl). The solutions were utilized for 5, 15 and 30 min with 2 experimental volumes 500 μL and 1 mL. All the samples were stained using an acridine orange and the biofilm thickness before (control group) and after the experiments were evaluated, utilizing a confocal microscope at ×40. The Mann-Whitney U and the nom-parametric Kruskal-Wallis Dunns tests were utilized to determine the influence of the volume and to perform the comparisons among the groups respectively. The significance level was set at P < 0.05.

RESULTS

Statistical differences were not found among the control and the 2% chlorhexidine digluconate groups at any experimental period (P > 0.05). The biofilm dissolution treated with 1% NaOCl was directly proportional to the exposure time (P < 0.05). The higher values of biofilm dissolution were found in 2.5% and 5.25% NaOCl groups (P > 0.05).

CONCLUSION

The higher exposure times and concentrations of NaOCl were not sufficient to dissolve 100% of the biofilm. However, all NaOCl solutions were more effective than 2% chlorhexidine digluconate to dissolve organic matter.

Effects of a Novel Dental Gel on Plaque and Gingivitis: A Comparative Study

Objectives

The goal of this prospective, randomized, controlled, double-blinded study was to evaluate the effects of a novel dental gel on plaque and gingival health. The dental gel was designed to (1) break up and prevent re-accumulation of microbial biofilm, and (2) inhibit metal mediated inflammation.

Materials and Methods

Twenty-five subjects with moderate gingival inflammation (Löe and Silness Gingival Index ≥2) and pocket depths <4 were randomly assigned to brush twice daily for 21 days with the test or the control dental gel. On Days 0, 7, 14 and 21, plaque levels (Quigley-Hein, Turesky Modification Plaque Index), gingival inflammation (Löe and Silness Gingival Index) and gingival bleeding (modified Sulcus Bleeding Index) were determined by one blinded, investigator using a pressure sensitive probe.

Results

After 3 weeks, all 3 clinical indices were significantly improved in both groups (P<0.05) and significantly lower in the test group (P<0.05).

Conclusion

The novel dental gel formulation was provided effective plaque control and reduced gingival inflammation.

Clinical Relevance

A novel dentifrice formulation may be an effective tool for plaque removal and maintaining gingival health.

Pre-exposure to nitrite in the absence of ammonium strongly inhibits anammox

Anaerobic ammonium oxidizing bacteria (Anammox) are known to be inhibited by their substrate, nitrite. However, the mechanism of inhibition and the physiological conditions under which nitrite impacts the performance of anammox bioreactors are still unknown. This study investigates the role of pre-exposing anammox bacteria to nitrite alone on their subsequent activity and metabolism after ammonium has been added. Batch experiments were carried out with anammox granular biofilm pre-exposed to nitrite over a range of concentrations and durations in the absence of ammonium. The effect of pre-exposure to nitrite alone compared to nitrite simultaneously fed with ammonium was evaluated by measuring the anammox activity and the accumulation of the intermediate, nitric oxide. The results show that the inhibitory effect was more dramatic when bacteria were pre-exposed to nitrite in absence of ammonium, as revealed by the lower activity and the higher accumulation of nitric oxide. The nitrite concentration causing 50% inhibition was 53 and 384 mg N L(-1) in the absence or the presence of ammonium, respectively. The nitrite inhibition was thus 7.2-fold more severe in the absence of ammonium. Biomass exposure to nitrite (25 mg N L(-1)), in absence of ammonium, led to accumulation of nitric oxide. On the other hand when the biomass was exposed to nitrite in presence of ammonium, accumulation of nitric oxide was only observed at much higher nitrite concentrations (500 mg N L(-1)). The inhibitory effect of nitrite in the absence of ammonium was very rapid. The rate of decay of the anammox activity was equivalent to the diffusion rate of nitrite up to 46% of activity loss. The results taken as a whole suggest that nitrite inhibition is more acute when anammox cells are not actively metabolizing. Accumulation of nitric oxide in the headspace most likely indicates disruption of the anammox biochemistry by nitrite inhibition, caused by an interruption of the hydrazine synthesis step.

Microbial biofilm modulation by ultrasound: current concepts and controversies

Biofilm elimination is often necessary during antimicrobial therapy or industrial medical manufacturing decontamination. In this context, ultrasound treatment has been frequently described in the literature for its antibiofilm effectiveness, but at the same time, various authors have described ultrasound as a formidable enhancer of bacterial viability. This discrepancy has found no solution in the current literature for around 9 years; some works have shown that every time bacteria are exposed to an ultrasonic field, both destruction and stimulation phenomena co-exist. This co-existence proves to have different final effects based on various factors such as: ultrasound frequency and intensity, the bacterial species involved, the material used for ultrasound diffusion, the presence of cavitation effects and the forms of bacterial planktonic or biofilm. The aim of this work is to analyze current concepts regarding ultrasound effect on prokaryotic cells, and in particular ultrasound activity on bacterial biofilm.

A simple and inexpensive device for biofilm analysis

The Calgary Biofilm Device (CBD) has been described as a technology for the rapid and reproducible assay of biofilm susceptibilities to antibiotics. In this study a simple and inexpensive alternative to the CBD was developed from polypropylene (PP) microcentrifuge tubes and pipette tip boxes. The utility of the device was demonstrated using Candida glabrata, a yeast that can develop antimicrobial-resistant biofilm communities. Biofilms of C. glabrata were formed on the outside surface of microcentrifuge tubes and examined by quantitative analysis and scanning electron microscopy. Growth of three C. glabrata strains, including a clinical isolate, demonstrated that biofilms could be formed on the microcentrifuge tubes. After 24 h incubation the three C. glabrata strains produced biofilms that were recovered into cell suspension and quantified. The method was found to produce uniform and reproducible results with no significant differences between biofilms formed on PP tubes incubated in various compartments of the device. In addition, the difference between maximum and minimum counts for each strain was comparable to those which have been reported for the CBD device.

Subtilase SprP exerts pleiotropic effects in Pseudomonas aeruginosa

The open reading frame PA1242 in the genome of Pseudomonas aeruginosa PAO1 encodes a putative protease belonging to the peptidase S8 family of subtilases. The respective enzyme termed SprP consists of an N-terminal signal peptide and a so-called S8 domain linked by a domain of unknown function (DUF). Presumably, this DUF domain defines a discrete class of Pseudomonas proteins as homologous domains can be identified almost exclusively in proteins of the genus Pseudomonas. The sprP gene was expressed in Escherichia coli and proteolytic activity was demonstrated. A P. aeruginosa ΔsprP mutant was constructed and its gene expression pattern compared to the wild-type strain by genome microarray analysis revealing altered expression levels of 218 genes. Apparently, SprP is involved in regulation of a variety of different cellular processes in P. aeruginosa including pyoverdine synthesis, denitrification, the formation of cell aggregates, and of biofilms.

The effect of antifungal combination on transcripts of a subset of drug-resistance genes in clinical isolates of Candida species induced biofilms

Biofilm formation is often associated with increased Candida resistance toward antifungal agents. Therefore, the current study aimed to assess the incidence of biofilm formation among Candida isolates and to investigate the effect of high doses of fluconazole {FLC}, voriconazole {VOC} and amphotericin B {AMB}, singly and in combination on mature biofilms. Moreover, it aimed to assess the expression of selected genes (CDR1, KRE1 and SKN1) responsible for Candida biofilm resistance. The study included 49 patients; samples were collected from the King Khalid Hospital, Riyadh, Saudi Arabia. Isolates were prepared for biofilm formation and quantification using 0.4% (w/v) crystal violet. Minimum Inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) were conducted by the broth microdilution method. Biofilm eradication was evaluated using counting, XTT stain intensity and observed under the inverted microscope. Selected genes were evaluated in Candida biofilms under the effect of antifungal exposure using QPCR. The major isolates were Candida albicans (65.3%) followed by Candida tropicalis and Candida glabrata. 77.6% of the strains were biofilm formers. AMB showed susceptibility in 87.8% of isolates, followed by VOC (77.6%) and FLC (67.3%). MIC50 and MIC90 were (0.03, 0.125), (0.5, 8), (2, >128) μg/ml for AMB, VOC and FLC, respectively. 34.7% and 18.4% of the isolates were antagonistic to AMB/FLC and AMB/VOC, respectively. Mature biofilms of ten selected isolates were found resistant to FLC (1000 μg/ml). VOR and AMB concentration required to inhibit biofilm formation was 16-250 fold higher than the MIC for planktonic cells. Isolates showed significant reduction with antifungal combination when compared with the untreated controls (p value ⩽ 0.01), or using fluconazole alone (p value ⩽ 0.05). High doses of the antifungals were employed to assess the effect on the persisters' selected gene expression. Marked over expression of SKN1 and to a lesser extent KRE1 was noticed among the mature biofilms treated with AMB alone or in combination after 1 h of exposure, and SKN1 expression was even more sharply induced after 24 h. No statistically significant over expression of CDR1 was observed in biofilms after exposure to high doses of FLC, VOC or any of the combinations used.

The three Aspergillus fumigatus CFEM-domain GPI-anchored proteins (CfmA-C) affect cell-wall stability but do not play a role in fungal virulence

Fungal cell-wall proteins containing the conserved fungal CFEM domain have been implicated in host-pathogen interactions and virulence. To determine the role of these proteins in the mold pathogen Aspergillus fumigatus, we deleted the entire family of three CFEM-containing genes (CfmA-C), singly and in all combinations. We found an additive increase in the susceptibility of the single, double and triple ΔCfm mutants towards the chitin/β-glucan-microfibril destabilizing compounds Congo Red (CR) and Calcofluor White (CFW), indicating that the A. fumigatus CFEM proteins are involved in stabilizing the cell wall. No defects in growth or germination were observed, indicating that CFEM proteins do not have an essential role in the morphogenesis of A. fumigatus. Unlike in Candida albicans, the A. fumigatus CFEM proteins were not implicated in heme uptake or biofilm formation. The ΔTriple-Cfm deletion strain did not exhibit altered virulence in either insect or murine models of infection, suggesting that cell-wall proteins containing the conserved fungal CFEM domain are not a significant virulence factor in A. fumigatus.

Comparison of the vaginal microbial communities in women with recurrent genital HSV receiving acyclovir intravaginal rings

Vaginally administered antiviral agents may reduce the risk of HIV and HSV acquisition. Delivery of these drugs using intravaginal rings (IVRs) holds the potential benefits of improving adherence and decreasing systemic exposure, while maintaining steady-state drug levels in the vaginal tract. Elucidating how IVRs interact with the vaginal microbiome constitutes a critical step in evaluating the safety of these devices, as shifts the vaginal microbiome have been linked with several disease states. To date, clinical IVR trials have relied on culture-dependent methods that omit the high diversity of unculturable microbial population. Longitudinal, culture-independent characterization of the microbiota in vaginal samples from 6 women with recurrent genital HSV who used an acyclovir IVR was carried out and compared to the communities developing in biofilms on the IVR surface. The analysis utilized Illumina MiSeq sequence datasets generated from bar-coded amplicons of 16S rRNA gene fragments. Specific taxa in the vaginal communities of the study participants were found to be associated with the duration of recurrent genital HSV status and the number of HSV outbreaks. Taxonomic comparison of the vaginal and IVR biofilm communities did not reveal any significant differences, suggesting that the IVRs were not systematically enriched with members of the vaginal microbiome. Device usage did not alter the participants' vaginal microbial communities, within the confines of the current study design. Rigorous, molecular analysis of the effects of intravaginal devices on the corresponding microbial communities shows promise for integration with traditional approaches in the clinical evaluation of candidate products.

Polymicrobial wound infections: pathophysiology and current therapeutic approaches

Acute and chronic wounds represent a very common health problem in the entire world. The dermal wounds are colonized by aerobic and anaerobic bacterial and fungal strains, most of them belonging to the resident microbiota of the surrounding skin, oral cavity and gut, or from the external environment, forming polymicrobial communities called biofilms, which are prevalent especially in chronic wounds. A better understanding of the precise mechanisms by which microbial biofilms delay repair processes together with optimizing methods for biofilm detection and prevention may enhance opportunities for chronic wounds healing. The purpose of this minireview is to assess the role of polymicrobial biofilms in the occurrence and evolution of wound infections, as well as the current and future preventive and therapeutic strategies used for the management of polymicrobial wound infections.

Natural antifouling compounds produced by a novel fungus Aureobasidium pullulans HN isolated from marine biofilm

A fungus, Aureobasidium pullulans, was isolated from marine biofilm and identified. A bioassay-guided fractionation procedure was developed to isolate and purify antifouling compounds from A. pullulans HN. The procedure was: fermentation broth-aeration and addition of sodium thiosulfate-graduated pH and liquid-liquid extraction-SPE purification-GC-MS analysis. Firstly, the fermentation broth was tested for its toxicity. Then it was treated with aeration and addition of sodium thiosulfate, and its toxicity was almost not changed. Lastly, antifouling compounds were extracted at different pH, the extract had high toxicity at pH 2 but almost no toxicity at pH 10, which suggested the toxicants should be fatty acids. The EC50 of the extract against Skeletonema costatum was 90.9 μg ml(-1), and its LC50 against Balanus amphitrete larvae was 22.2 μg ml(-1). After purified by HLB SPE column, the EC50 of the extract against S. costatum was 49.4 μg ml(-1). The myristic and palmitic acids were found as the main toxicants by GC-MS.

Influence of milk components in establishing biofilm mediated bacterial mastitis infections in cattle: a fractional factorial approach

Biofilm formation is one of the factors responsible for antibiotic resistance. The involvement of biofilm formation in bacterial mastitis is well known. Milk composition varies during the lactation period and certain pathogens are producing more number of mastitis cases during particular periods of lactation. The present study elucidates the effects of different milk components on biofilm formation and the persistence of infection. The Plackett Burman screening design has been chosen for assessing the significance. Biofilm production of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were assessed by crystal violet assay. Dipotassium hydrogen phosphate had a significant effect on biofilm formation by S. aureus (MTCC 1430) whereas it was pH in the case of biofilm formation by P. aeruginosa (NCIM 5029). Other independent factors were found to be insignificant.

Staphylococcal biofilm formation as affected by type acidulant

Staphylococcal growth and biofilm formation in culture medium where pH was lowered with weak organic (acetic and lactic) or strong inorganic (hydrochloric) acids were studied. The effects were evaluated by biomass measurements, cell-surface hydrophobicity, scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM). The results demonstrated that the inhibition was related to type of acidulant and pH value. At pH 5.0, the antibacterial effect was more pronounced in the presence of acetic acid (58-60% growth reduction) compared with that in the presence of lactic (7-16% growth reduction) and hydrochloric acids (23-24% reduction). The biofilm biomass of Staphylococcus aureus and Staphylococcus epidermidis was reduced by 92, 85, 63, and 93, 87, 81% after exposition to acetic, lactic, and hydrochloric acids, respectively. Increasing the pH from 5.0 to 6.0 resulted in a noticeable reduction in the effectiveness of acids. A minor cells hydrophobic character was also documented. The SEM and CLSM revealed a poorly structured and thinner biofilm compared with the dense and multilayered control. Acidic environment could have important implications for food-processing system to prevent bacterial colonization and control biofilm formation. The findings of this study lead to consider the rational use of the type of acid to achieve acidic environments.

A novel role of the vacuolar calcium channel Yvc1 in stress response, morphogenesis and pathogenicity of Candida albicans

C. albicans is a common opportunistic pathogen, causing both superficial and life-threatening systemic infections. Calcium signaling is an intriguing aspect in its physiology, attributing to the roles in stress response and morphogenesis. Until recently, little was known about the mechanisms by which the calcium signaling-associated elements affect its pathogenicity. In this study, we found that Yvc1, a member of the transient receptor potential (TRP) family, localized on the vacuolar membrane. The yvc1Δ/Δ mutant displayed decreased ability of stress response, morphogenesis and attenuated virulence. The Spitzenkörper required for polarized growth were not detected in the hyphal tip of this mutant, suggesting a key role of Yvc1 in hyphal polarized growth and re-orientation to host signals. This study demonstrates, for the first time, that the putative vacuolar calcium channel Yvc1 plays an important role in C. albicans infection and survival in host tissues, which is associated with its pleiotropic effects in several fungal physiological processes, including stress response, morphogenesis, and polarized growth.

Multi-technique approach to assess the effects of microbial biofilms involved in copper plumbing corrosion

Microbially influenced corrosion (MIC) is recognized as an unusual and severe type of corrosion that causes costly failures around the world. A microbial biofilm could enhance the copper release from copper plumbing into the water by forming a reactive interface. The biofilm increases the corrosion rate, the mobility of labile copper from its matrix and the detachment of particles enriched with copper under variable shear stress due to flow conditions. MIC is currently considered as a series of interdependent processes occurring at the metal-liquid interface. The presence of a biofilm results in the following effects: (a) the formation of localized microenvironments with distinct pH, dissolved oxygen concentrations, and redox conditions; (b) sorption and desorption of labile copper bonded to organic compounds under changing water chemistry conditions; (c) change in morphology by deposition of solid corrosion by-products; (d) diffusive transport of reactive chemical species from or towards the metal surface; and (e) detachment of scale particles under flow conditions. Using a multi-technique approach that combines pipe and coupon experiments this paper reviews the effects of microbial biofilms on the corrosion of copper plumbing systems, and proposes an integrated conceptual model for this phenomenon supported by new experimental data.

Low metabolic activity of biofilm formed by Enterococcus faecalis isolated from healthy humans and wild mallards (Anas platyrhynchos)

It is widely known that Enterococcus faecalis virulence is related to its biofilm formation. Although Enterococci are common commensal organisms of the gastrointestinal tract, the difference between commensal and pathogen strains remain unclear. In this study, we compare the biochemical profile of the biofilms formed by two groups of medical and two groups of commensal strains. The medical strains were isolated as pathogens from infections of urinary tract and other infections (wounds, pus and bedsores), and the commensal strains were taken from faeces of healthy volunteers and faeces of wild mallards (Anas platyrhynchos) living in an urban environment. The properties of biofilms formed by medical and commensal strains differed significantly. Commensal strains showed lower metabolic activity and glucose uptake and higher biofilm biomass than the medical ones. Consistent with glucose uptake experiments, we found that the glucose dehydrogenase gene was more expressed in medical strains. These results indicate that higher metabolic activity and lower protein concentration of E. faecalis cells within biofilms are formed during infections.

Nanoparticles and the control of oral infections

The potential of antimicrobial nanoparticles to control oral infections is reviewed. Such particles can be classified as having a size no greater than 100 nm and are produced using traditional or more novel techniques. Exploitation of the toxic properties of nanoparticles to bacteria, fungi and viruses, in particular metals and metal oxides, as well as their incorporation into polymeric materials have increased markedly over the past decade. The potential of nanoparticles to control the formation of biofilms within the oral cavity, as a function of their biocidal, anti-adhesive and delivery capabilities, is now receiving close attention. Latest insights into the application of nanoparticles within this field, including their use in photodynamic therapy, will be reviewed. Possible approaches to alter biocompatibility and desired function will also be covered.

Phenol-soluble modulins

PSMs are a recently discovered family of short, amphipathic, α-helical peptides in staphylococci. Several PSMs are key virulence determinants, particularly in highly virulent Staphylococcus aureus strains. PSMα peptides of S. aureus facilitate neutrophil lysis after phagocytosis, and are key contributors to several infection types, including skin infection and bacteremia. Furthermore, all PSMs contribute to biofilm structuring and the dissemination of biofilm-associated infection. Cytolytic PSMs as produced by S. aureus appear to have evolved from original functions in the non-infectious lifestyle of staphylococci. The surfactant properties of PSMs, which they all share, are believed to facilitate growth on epithelial surfaces. The basic role of PSMs in staphylococcal physiology is underscored, for example, by their exceptionally strict and direct control by quorum-sensing and the presence of a dedicated secretion system. Targeting PSMs for anti-staphylococcal drug development may be a promising approach to overcome the problems associated with widespread antibiotic resistance in staphylococci.

Nanostructuring carbon fibre probes for use in central venous catheters

A carbon fibre probe is described which utilises the oxidation of an endogenous biomarker to provide diagnostic information on the condition of intravascular access lines. The probe surface was modified through anodic oxidation to provide a high selectivity towards urate which was used as a redox probe through which the pH could be determined. A Nernstian response (-60 mV/pH) was obtained which was free from the interference of other redox species common to biofluids. The electroanalytical performance of the probe has been optimised and the applicability of the approach demonstrated through testing the responses in whole blood.

Azithromycin Reduces the Production of α-hemolysin and Biofilm Formation in Staphylococcus aureus

Staphylococcus aureus causes a broad range of life-threatening diseases in humans. This bacterium produces a large number of extracellular virulence factors that are closely associated with specific diseases which are controlled by quorum sensing. In this study, we show that azithromycin was active against methicillin-resistant Staphylococcus aureus (MRSA) strains with MICs ranged from 32 to 64 μg/mL. Azithromycin at subinhibitory concentration, markedly reduced the production of α-hemolysin at (1/16MIC, 1/8MIC) and biofilm formation at (1/16MIC, 1/8MIC), respectively. The results indicated that sub-inhibitory concentrations of azithromycin decreased the production of α-hemolysin and biofilm formation in MRSA in a dose-dependent manner. Therefore, azithromycin may be useful in the treatment of α-hemolysin producing and biofilm formation MRSA infections.

A polysaccharide lyase from Stenotrophomonas maltophilia with a unique, pH-regulated substrate specificity

Polysaccharide lyases (PLs) catalyze the depolymerization of anionic polysaccharides via a β-elimination mechanism. PLs also play important roles in microbial pathogenesis, participating in bacterial invasion and toxin spread into the host tissue via degradation of the host extracellular matrix, or in microbial biofilm formation often associated with enhanced drug resistance. Stenotrophomonas maltophilia is a Gram-negative bacterium that is among the emerging multidrug-resistant organisms associated with chronic lung infections as well as with cystic fibrosis patients. A putative alginate lyase (Smlt1473) from S. maltophilia was heterologously expressed in Escherichia coli, purified in a one-step fashion via affinity chromatography, and activity as well as specificity determined for a range of polysaccharides. Interestingly, Smlt1473 catalyzed the degradation of not only alginate, but poly-β-D-glucuronic acid and hyaluronic acid as well. Furthermore, the pH optimum for enzymatic activity is substrate-dependent, with optimal hyaluronic acid degradation at pH 5, poly-β-D-glucuronic acid degradation at pH 7, and alginate degradation at pH 9. Analysis of the degradation products revealed that each substrate was cleaved endolytically into oligomers comprised predominantly of even numbers of sugar groups, with lower accumulation of trimers and pentamers. Collectively, these results imply that Smlt1473 is a multifunctional PL that exhibits broad substrate specificity, but utilizes pH as a mechanism to achieve selectivity.

Genetic determinants of virulence - Candida parapsilosis

The global epidemiology of fungal infections is changing. While overall, Candida albicans remains the most common pathogen; several institutions in Europe, Asia and South America have reported the rapid emergence to predominance of Candida parapsilosis. This mini-review examines the impact of gene deletions achieved in C. parapsilosis that have been published to date. The molecular approaches to gene disruption in C. parapsilosis and the molecularly characterized genes to date are reviewed. Similar to C. albicans, factors influencing virulence in C. parapsilosis include adherence, biofilm formation, lipid metabolism, and secretion of hydrolytic enzymes such as lipases, phospholipases and secreted aspartyl proteinases. Development of a targeted gene deletion method has enabled the identification of several unique aspects of C. parapsilosis genes that play a role in host-pathogen interactions - CpLIP1, CpLIP2, SAPP1a, SAPP1b, BCR1, RBT1, CpFAS2, OLE1, FIT-2. This manuscript is part of the series of works presented at the "V International Workshop: Molecular genetic approaches to the study of human pathogenic fungi" (Oaxaca, Mexico, 2012).

Biofilm-dependent airway infections: a role for ambroxol?

Biofilms are a key factor in the development of both acute and chronic airway infections. Their relevance is well established in ventilator associated pneumonia, one of the most severe complications in critically ill patients, and in cystic fibrosis, the most common lethal genetic disease in Caucasians. Accumulating evidence suggests that biofilms could have also a role in chronic obstructive pulmonary disease and their involvement in bronchiectasis has been proposed as well. When they grow in biofilms, microorganisms become multidrug-resistant. Therefore the treatment of biofilm-dependent airway infections is problematic. Indeed, it still largely based on measures aiming to prevent the formation of biofilms or remove them once that they are formed. Here we review recent evidence suggesting that the mucokinetic drug ambroxol has specific anti-biofilm properties. We also discuss how additional pharmacological properties of this drug could be beneficial in biofilm-dependent airway infections. Specifically, we review the evidence showing that: 1-ambroxol exerts anti-inflammatory effects by inhibiting at multiple levels the activity of neutrophils, and 2-it improves mucociliary clearance by interfering with the activity of airway epithelium ion channels and transporters including sodium/bicarbonate and sodium/potassium/chloride cotransporters, cystic fibrosis transmembrane conductance regulator and aquaporins. As a whole, the data that we review here suggest that ambroxol could be helpful in biofilm-dependent airway infections. However, considering the limited clinical evidence available up to date, further clinical studies are required to support the use of ambroxol in these diseases.

Hemagglutination and biofilm formation as virulence markers of uropathogenic Escherichia coli in acute urinary tract infections and urolithiasis

INTRODUCTION

Urinary tract infections (UTI) are a major public health concern in developing countries. Most UTIs are caused by E. coli, accounting for up to 90% of community-acquired UTIs (CAUTI). Recurrent UTI is considered as a major risk factor for urolithiasis. Virulence factors like adhesins and biofilm have been extensively studied by authors on UPEC isolated from recurrent UTI. The studies on isolates from infection stones in kidney are scanty. In a prospective study, we aimed to determine the expression of Haemagglutinins, (Type 1 and P fimbriae), Biofilm production and resistance pattern to common antibiotics of Uropathogenic E.coli (UPEC) isolates from Community acquired Acute Urinary Tract Infection(CAUTI) and Urolithiasis.

MATERIALS AND METHODS

A total of 43 UPEC isolates, 23 mid-stream urine (MSU) samples from patients with CAUTI attending Out Patient Departments and 20 from renal calculi of urolithiasis patients at the time of Percutaneous nephrolithostomy (PCNL) were included in the study and the expression of Haemagglutinins,(Type 1 and P fimbriae), Biofilm production and resistance pattern to common antibiotics was assessed.

RESULTS

A total of 43 UPEC isolates 23 from CAUTI and 20 from renal calculi were tested for production of biofilm and hemagglutinins. In CAUTI, biofilm producers were 56.52% and hemagglutinins were detected in all isolates 100%. In urolithiasis, biofilm producers were 100% but hemagglutinins were detected only in 70% of isolates. All isolates were resistant to multiple antibiotics used. CAUTI isolates were susceptible to 3(rd) generation cephalosporins, whereas urolithiasis isolates were resistant to 3(rd) generation cephalosporins and 25% were Extended Spectrum Beta Lactamases ESBL producers.

CONCLUSIONS

HA mediated by type 1 fimbriae plays an important role in CAUTI (P < 0.001 highly significant), whereas, in chronic conditions like urolithiasis, biofilm plays an important role in persistence of infection and the role of hemagglutinins is less.

Hypoxia induces abnormal larval development and affects biofilm-larval interaction in the serpulid polychaete Hydroides elegans

Hydroides elegans, a worldwide fouling polychaete, can spawn throughout the year, but its recruitment drops during summer when hypoxia prevails. Here, the influence of hypoxia on larval development and settlement of H. elegans was investigated. Results showed that larval development was compromised at 1mg O2 l(-1) with a lower proportion of competent larvae and a higher proportion of malformed larvae, probably due to reduction in clearance rate. Regarding larval settlement, although most of the larvae were reluctant to settle at 1mg O2 l(-1), regardless of the biofilm nature, they settled quickly within 24h in response to the resumption of dissolved oxygen. Furthermore, only about 5% of the larvae settled on the biofilms developed under hypoxia, regardless of dissolved oxygen levels of the seawater. The delayed larval development and potential alteration of biofilm nature owing to hypoxia explained why the recruitment of H. elegans declines during summer.

Mercury induced community tolerance in microbial biofilms is related to pollution gradients in a long-term polluted river

The net toxicity of different forms of mercury, in the long-term during their transformation processes, leads to the selection of resistant bacterial cells and this result in community tolerance which is pollution induced. Accordingly, based on profiles of a bacterial community structure, analysis of Hg resistant culturable bacteria and quantification of merA genes, we assessed development of pollution induced community tolerance in a mercury-polluted gradient in the Idrijca River. TTGE analysis did not show effects of mercury pollution to bacterial community diversity, while quantification of merA genes showed that merA genes can be correlated precisely (R(2)=0.83) with the total concentration of mercury in the biofilm microbial communities in the pollution gradient.

Community behavior and amyloid-associated phenotypes among a panel of uropathogenic E. coli

Uropathogenic Escherichia coli (UPEC) are the major causative agents of urinary tract infection and engage in a coordinated genetic and molecular cascade to colonize the urinary tract. Disrupting the assembly and/or function of virulence factors and bacterial biofilms has emerged as an attractive target for the development of new therapeutic strategies to prevent and treat urinary tract infection, particularly in the era of increasing antibiotic resistance among human pathogens. UPEC vary widely in their genetic and molecular phenotypes and more data are needed to understand the features that distinguish isolates as more or less virulent and as more robust biofilm formers or poor biofilm formers. Curli are extracellular functional amyloid fibers produced by E. coli that contribute to pathogenesis and influence the host response during urinary tract infection (UTI). We have examined the production of curli and curli-associated phenotypes including biofilm formation among a specific panel of human clinical UPEC that has been studied extensively in the mouse model of UTI. Motility, curli production, and curli-associated biofilm formation attached to plastic were the most prevalent behaviors, shared by most clinical isolates. We discuss these results in the context on the previously reported behavior and phenotypes of these isolates in the murine cystitis model in vivo.

Effects of surfactant and Zn (II) at various concentrations on microbial activity and ethylbenzene removal in biotricking filter

The effects of Tween-20, a non-ionic surfactant, and Zn (II) on microbial activity and removal performance for ethylbenzene in a biotrickling filter (BTF) were evaluated. Batch experiments were conducted to evaluate the surfactant and Zn (II) at various concentrations for their toxicity to microorganisms, and results indicated that Tween-20 was beneficial to microbial activity at all the tested concentration, while Zn (II) affected adversely when the concentration overpassed 5.0mgL(-1). Then effects of the two additives on removal efficiency of ethylbenzene were evaluated in a BTF at an empty-bed retention time of 30s and an ethylbenzene concentration of 1100mgm(-3). Results showed that the optimal concentrations of Tween-20 and Zn (II) were about 12 and 1.0mgL(-1), respectively. Compared to the results when neither of the two additives was added, Tween-20 improved ethylbenzene removal efficiency from 67% to 86% at the optimal condition, while on that basis, Zn (II) just increased the removal efficiency from 86% to 90%. The promoting effects of the two additives on recovering microbial activity and removing excessive biomass were also observed in this article.

Nanotechnology as a therapeutic tool to combat microbial resistance

Use of nanoparticles is among the most promising strategies to overcome microbial drug resistance. This review article consists of three parts. The first part discusses the epidemiology of microbial drug resistance. The second part describes mechanisms of drug resistance used by microbes. The third part explains how nanoparticles can overcome this resistance, including the following: Nitric oxide-releasing nanoparticles (NO NPs), chitosan-containing nanoparticles (chitosan NPs), and metal-containing nanoparticles all use multiple mechanisms simultaneously to combat microbes, thereby making development of resistance to these nanoparticles unlikely. Packaging multiple antimicrobial agents within the same nanoparticle also makes development of resistance unlikely. Nanoparticles can overcome existing drug resistance mechanisms, including decreased uptake and increased efflux of drug from the microbial cell, biofilm formation, and intracellular bacteria. Finally, nanoparticles can target antimicrobial agents to the site of infection, so that higher doses of drug are given at the infected site, thereby overcoming resistance.

A kinetic study of biohydrogen production from glucose, molasses and cheese whey by suspended and attached cells of Thermotoga neapolitana

Batch tests of H2 production from glucose, molasses and cheese whey by suspended and immobilized cells of Thermotoga neapolitana were conducted to develop a kinetic model of the process. H2 production was inhibited by neither H2 (up to 0.7 mg L(-1)) nor O2 (up to 0.2 mg L(-1)). The H2 specific rates obtained at different substrate concentrations were successfully interpolated with Andrew's inhibition model. With glucose and molasses, biofilms performed better than suspended cells. The suspended-cell process was successfully scaled-up to a 19-L bioreactor. Assays co-fed with molasses and cheese whey led to higher H2 productivities and H2/substrate yields than the single-substrate tests. The simulation of the suspended-cell continuous-flow process indicated the potential attainment of H2 productivities higher than those of the batch tests (up to 3.6 mmol H2 h(-1) L(-1) for molasses and 0.67 mmol H2 h(-1) L(-1) for cheese whey) and allowed the identification of the optimal dilution rate.