Effect of nutrient limitation on adhesion characteristics of Pseudomonas aeruginosa

Short communication: evaluation of an endotoxin challenge and intraruminal bacterial inoculation model to induce liver abscesses in Holstein steers

Holstein steers (n = 40; initial body weight [BW] = 96.0 ± 10.5 kg) were individually housed in a climate-controlled barn to evaluate potential models for the genesis of liver abscesses (LA). In this 2 × 2 factorial, steers were balanced by BW and randomly assigned to one of two treatments: 1) intravenous saline injection followed by intraruminal bacterial inoculation with Fusobacterium necrophorum subsp. necrophorum (1 × 109 colony forming unit [CFU]/mL) and Salmonella enterica serovar Lubbock (1 × 106 CFU/mL; CON; n = 20 steers); or 2) intravenous injection with 0.25 µg/kg BW of lipopolysaccharide (LPS; Escherichia coli O111:B4) followed by intraruminal bacterial inoculation of F. necrophorum subsp. necrophorum (1 × 109 CFU/mL) and S. enterica serovar Lubbock (1 × 106 CFU/mL; LBI; n = 20 steers) and 1 of 2 harvest dates (3 or 10 d post LPS infusion). Body weights were recorded on days -4, -1, 3, and 10, and blood was collected for hematology on days -4, 3, and 10, relative to LPS infusion on day 0. Intraruminal bacterial inoculation occurred on day 1. Steers from each treatment group were harvested at two different time points on day 3 or 10 to perform gross pathological examination of the lung, rumen, liver, LA (if present), and colon. Feed disappearance was less for LBI than CON (P < 0.01); however, BW did not differ (P = 0.33) between treatments. Neither treatment nor time differed for hematology (P ≥ 0.13), and no gross pathological differences were noted in the lung, liver, LA, or colon (P ≥ 0.25). A treatment × harvest date interaction was noted for ruminal pathology in which LBI had an increased percentage of abnormal rumen scores on day 3 (P < 0.01). These results suggest that an LPS challenge in combination with intraruminal bacterial inoculation of pathogens commonly isolated from LA was not sufficient to induce LA in steers within 3 or 10 d (P = 0.95) when compared to CON. Further evaluation is needed to produce a viable model to investigate the genesis and prevention of LA in cattle.

External ocular surface and lens microbiota in contact lens wearers with corneal infiltrates during extended wear of hydrogel lenses

OBJECTIVES

To determine whether carriage of microbes on the contact lens or ocular surfaces during extended wear (EW) with soft hydroxyethyl methacrylate (HEMA)-based contact lenses predisposes the wearer to adverse events.

METHODS

Participants (non-contact lens wearers) were enrolled in a clinical study involving wear of HEMA-based hydrogel lenses on a six night EW basis with weekly replacement. Type and number of bacteria colonizing the lower lid margins, upper bulbar conjunctiva, and contact lenses during EW after one night, 1 week, 1 month, and thereafter every 3 months for 3.5 years were determined. The association of bacteria with adverse responses was compared between carriers (defined as having significant microbes cultured from two or more samples with 1 year) and noncarriers, and the strength of the association was estimated using multivariate logistic regression.

RESULTS

Carriers of gram-positive bacteria on lenses (particularly coagulase negative staphylococci or Corynebacterium spp.) were approximately three and eight times more likely to develop contact lens-induced peripheral ulcers (CLPUs) and asymptomatic infiltrates (AIs), respectively. Staphylococcus aureus was most frequently isolated from lenses during CLPU. Carriers of gram-negative bacteria on lenses were five times more likely to develop contact lens-induced acute red eye (CLARE). Haemophilus influenzae was isolated most frequently from lenses during CLARE and AI events.

CONCLUSIONS

Bacterial carriage on contact lenses during EW predisposes the wearer to the development of corneal inflammatory events including CLARE, CLPU, and AI.

Analysis of the Pseudomonas putida CA-3 proteome during growth on styrene under nitrogen-limiting and non-limiting conditions

Pseudomonas putida CA-3 is a styrene-degrading bacterium capable of accumulating medium-chain-length polyhydroxyalkanoate (mclPHA) when exposed to limiting concentrations of a nitrogen source in the growth medium. Using shotgun proteomics we analysed global proteome expression in P. putida CA-3 supplied with styrene as the sole carbon and energy source under N-limiting (condition permissive for mclPHA synthesis) and non-limiting (condition non-permissive for mclPHA accumulation) growth conditions in order to provide insight into the molecular response of P. putida CA-3 to limitation of nitrogen when grown on styrene. A total of 1761 proteins were identified with high confidence and the detected proteins could be assigned to functional groups including styrene degradation, energy, nucleotide metabolism, protein synthesis, transport, stress response and motility. Proteins involved in the upper and lower styrene degradation pathway were expressed throughout the 48 h growth period under both nitrogen limitation and excess. Proteins involved in polyhydroxyalkanoate (PHA) biosynthesis, nitrogen assimilation and amino acid transport, and outer membrane proteins were upregulated under nitrogen limitation. PHA accumulation and biosynthesis were only expressed under nitrogen limitation. Nitrogen assimilation proteins were detected on average at twofold higher amounts under nitrogen limitation. Expression of the branched-chain amino acid ABC transporter was up to 16-fold higher under nitrogen-limiting conditions. Branched chain amino acid uptake by nitrogen-limited cultures was also higher than that by non-limited cultures. Outer membrane lipoproteins were expressed at twofold higher levels under nitrogen limitation. This was confirmed by Western blotting (immunochemical detection) of cells grown under nitrogen limitation. Our study provides the first global description of protein expression changes during growth of any organism on styrene and accumulating mclPHA (nitrogen-limited growth).

Differential lipopolysaccharide core capping leads to quantitative and correlated modifications of mechanical and structural properties in Pseudomonas aeruginosa biofilms

Bacterial biofilms are responsible for the majority of all microbial infections and have profound impact on industrial and geochemical processes. While many studies documented phenotypic differentiation and gene regulation of biofilms, the importance of their structural and mechanical properties is poorly understood. Here we investigate how changes in lipopolysaccharide (LPS) core capping in Pseudomonas aeruginosa affect biofilm structure through modification of adhesive, cohesive, and viscoelastic properties at an early stage of biofilm development. Microbead force spectroscopy and atomic force microscopy were used to characterize P. aeruginosa biofilm interactions with either glass substrata or bacterial lawns. Using isogenic migA, wapR, and rmlC mutants with defined LPS characteristics, we observed significant changes in cell mechanical properties among these strains compared to wild-type strain PAO1. Specifically, truncation of core oligosaccharides enhanced both adhesive and cohesive forces by up to 10-fold, whereas changes in instantaneous elasticity were correlated with the presence of O antigen. Using confocal laser scanning microscopy to quantify biofilm structural changes with respect to differences in LPS core capping, we observed that textural parameters varied with adhesion or the inverse of cohesion, while areal and volumetric parameters were linked to adhesion, cohesion, or the balance between them. In conclusion, this report demonstrated for the first time that changes in LPS expression resulted in quantifiable cellular mechanical changes that were correlated with structural changes in bacterial biofilms. Thus, the interplay between architectural and functional properties may be an important contributor to bacterial community survival.

Antecedent growth conditions alter retention of environmental Escherichia coli isolates in transiently wetted porous media

The physical transport of Escherichia coli in terrestrial environments may require control to prevent its dissemination from potential high-density sources, such as confined animal feedlot operations. Biobarriers, wherein convective flows carrying pathogens pass through a porous matrix with high retentive capacity, may present one such approach. Eight environmental E. coli isolates were selected to conduct operational retention tests (ORT) with potential biobarrier materials Pyrax or dolomite, or silica glass as control. The conditions in the ORT were chosen to simulate conditioning by manure solutes, a pulse application of a bacterial load followed by rainfall infiltration, and natural drainage. Removal was limited, and likely caused by the relatively high velocities during drainage, and the conditioning of otherwise favorable adhesion sites. Flagella-mediated motility showed the strongest correlation to biobarrier retention. Significant variability was observed across the E. coli isolates, but consistently higher retention was observed for cells with external versus intestinal pregrowth histories. E. coli O157:H7 was retained the least with all examined matrices, while E. coli K-12 displayed moderate retention and may not serve as representative model strain. Pyrax is a good candidate biobarrier material given its superior removal ability across the tested E. coli strains.

Abnormal cell division caused by inclusion bodies in E. coli; increased resistance against external stress

Inclusion body formation occurs naturally in prokaryotic cells, but is particularly common when heterologous foreign proteins are overexpressed in bacterial systems. The plant disease virus protein CMV 3a (cucumber mosaic virus movement protein) and the 56 kDa Orientia tsutsugamushi (OT56) protein (an outer membrane protein), which causes tsutsugamushi disease, were expressed in Escherichia coli, and found to form inclusion bodies. Confocal laser scanning microscopy revealed that these inclusion bodies are localized at the cellular poles within E. coli. Cells expressing inclusion bodies appeared to be interconnected, and divided abnormally. The clustered cells exhibited biofilm-like characteristics in that the interior cells of the community were protected by the antibiotic resistance of the outer cells. We compared the number of colony-forming units in inclusion body-forming versus non-forming E. coli to demonstrate the effects of lysozyme, sonication or antibiotic treatment. E. coli clustering provided significantly improved protection against cell disruption/lysis by physical and biochemical stress. This is the first report that shows that abnormal cell division caused by inclusion body formation can cause cellular clustering, resulting in improved resistance to stress in vitro.

Temperature and nutrient effects on Campylobacter jejuni attachment on multispecies biofilms on stainless steel

Campylobacterjejuni is a thermophilic microaerophilic pathogen that is commonly found in the intestinal tract of chickens. In this study, attachment of C. jejuni 1221gfp in biofilms on stainless steel was assessed at various temperatures and with reduced nutrients. Bacteria collected from a saline rinse of processed broiler chicken carcasses were used to form initial biofilms. The whole carcass rinse (WCR) biofilms were formed by incubation of the bacteria for 16 h at 13, 20, 37, and 42 degrees C on stainless steel coupons in tryptic soy broth (TSB). The resulting biofilms were stained with Hoechst 33258 stain and visualized by epifluorescence microscopy. WCR biofilms formed at 13 degrees C yielded the highest surface area coverage (47.6%), and the lowest coverage (2.1%) was attained at 42 degrees C. C. jejuni transformed to produce green fluorescent protein (gfp) was allowed to attach to the preexisting biofilms (from WCR incubated for 16 h) at each of the four temperatures, and attached cells were enumerated by visualization with an epifluorescence microscope. Attachment of C. jejuni 1221gfp did not significantly differ (P > 0.05) among the four temperatures. C. jejuni 1221gfp was cultured only from coupons with biofilms formed at 13 and 20 degrees C. For nutrient limitation experiments, WCR biofilms were allowed to grow in 10- and 50-fold diluted TSB at 20 and 37 degrees C for 48 h. The WCR biofilm surface area coverage (approximately 2%) was greater at 37 degrees C than at 20 degrees C for both TSB concentrations. C. jejuni 1221gfp was incubated with the WCR biofilm for 48 h at 20 and 37 degrees C, and attached cells were enumerated. Attachment was significantly higher (P < 0.05) only for the treatments with 1:10 TSB at 20 degrees C and 1:50 TSB at 37 degrees C. Under reduced-nutrient conditions, C. jejuni 1221gfp was cultured only from biofilms formed at 20 degrees C. Under the conditions tested, the attachment of C. jejuni 1221gfp on stainless steel and biofilms was affected by a combination of temperature and nutrient availability, but C. jejuni culturability was affected solely by temperature.

Nutritional cues control Pseudomonas aeruginosa multicellular behavior in cystic fibrosis sputum

The sputum (mucus) layer of the cystic fibrosis (CF) lung is a complex substrate that provides Pseudomonas aeruginosa with carbon and energy to support high-density growth during chronic colonization. Unfortunately, the CF lung sputum layer has been difficult to mimic in animal models of CF disease, and mechanistic studies of P. aeruginosa physiology during growth in CF sputum are hampered by its complexity. In this study, we performed chromatographic and enzymatic analyses of CF sputum to develop a defined, synthetic CF sputum medium (SCFM) that mimics the nutritional composition of CF sputum. Importantly, P. aeruginosa displays similar phenotypes during growth in CF sputum and in SCFM, including similar growth rates, gene expression profiles, carbon substrate preferences, and cell-cell signaling profiles. Using SCFM, we provide evidence that aromatic amino acids serve as nutritional cues that influence cell-cell signaling and antimicrobial activity of P. aeruginosa during growth in CF sputum.

Investigating the surface properties of Escherichia coli under glucose controlled conditions and its effect on aggregation

Bacteria exist as aggregates or in biofilms to help with adaptation and protection from environmental stresses. The hypothesis that is tested in this paper is that the relative presence of glucose in the media, at the beginning of the growth phase, influences the surface chemistry of the cell, which as a consequence reduces the tendency for the cells to interact and form aggregates. In this study, we used Escherichia coli (E. coli) MG1655 as a model organism and measured the change in the surface chemistry of cells harvested at different growth phases, which had been cultured in Luria-Bertani media with and without the addition of glucose, using potentiometric titration and infrared spectroscopy. Cells, cultivated with the additional supplement of glucose at the beginning of the growth phase, displayed a higher concentration of bacterial surface functional groups and a variation in outer membrane proteins. As a consequence, the tendency for cell-to-cell attachment was significantly reduced. Our findings therefore revealed that glucose limits aggregation in E. coli MG1655 by altering the concentration of functional groups from macromolecules present on the bacterial surface.

Attachment of Listeria monocytogenes, Escherichia coli O157:H7 and Pseudomonas aeruginosa on food soiled plastic surfaces

This study investigated the ability of three different pathogens, Escherichia coli O157:H7, Listeria monocytogenes and Pseudomonas aeruginosa, to attach food soiled (salad dressing, cooking oil, milk and yogurt) polyvinyl chloride (PVC) plastic. The pre-soiled PVC coupons were incubated with 10(8) CFU/cm2 of each bacterium in 50% tryptic soy broth for 6 h to allow attachment. It was found that the effect of food products was not significant while the effect of bacterial strain was highly significant (p = 0.0005). Mean attachment ofP. aeruginosa (5.5 log CFU/cm2) to pre-soiled coupons was the highest (p < 0.05), compared to L. monocytogenes (5.0 log CFU/cm2) and E. coli O157:H7 (4.5 log CFU/cm2). This study indicates the capability of each bacterial pathogen, E. coli O157:H7, L. monocytogenes or P. aeruginosa, to equally attach to different pre-soiled PVC surfaces. P. aeruginosa showed the greatest potential to attach to PVC when compared to E. coli O157:H7 and L. monocytogenes.

Bacterial outer membrane protein analysis by electrophoresis and microchip technology

Outer membrane proteins are indispensable components of bacterial cells and participate in several relevant functions of the microorganisms. Changes in the outer membrane protein composition might alter antibiotic sensitivity and pathogenicity. Furthermore, the effects of various factors on outer membrane protein expression, such as antibiotic treatment, mutation, changes in the environment, lipopolysaccharide modification and biofilm formation, have been analyzed. Traditionally, the outer membrane protein profile determination was performed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Converting this technique to capillary electrophoresis format resulted in faster separation, lower sample consumption and automation. Coupling capillary electrophoresis with mass spectrometry enabled the fast identification of bacterial proteins, while immediate quantitative analysis permitted the determination of up- and downregulation of certain outer membrane proteins. Adapting capillary electrophoresis to microchip format ensured a further ten- to 100-fold decrease in separation time. Application of different separation techniques combined with various sensitive detector systems has ensured further opportunities in the field of high-throughput bacterial protein analysis. This review provides an overview using selected examples of outer membrane proteins and the development and application of the electrophoretic and microchip technologies for the analysis of these proteins.

Adhesion of Pseudomonas aeruginosa and Staphylococcus epidermidis to Silicone???Hydrogel Contact Lenses

PURPOSE

The purpose of this study is to compare the adhesion capabilities of the most important etiologic agents of microbial ocular infection to the recently available silicone-hydrogel lenses with those to a conventional hydrogel lens.

METHODS

In vitro static adhesion assays of Pseudomonas aeruginosa 10,145, Staphylococcus epidermidis 9142 (biofilm-positive), and 12,228 (biofilm-negative) to two extended-wear silicone-hydrogel lenses (balafilcon A and lotrafilcon A), a daily wear silicone-hydrogel lens (galyfilcon A) and a conventional hydrogel (etafilcon A) were performed. To interpret the adhesion results, lens surface relative hydrophobicity was assessed by water contact angle measurements.

RESULTS

P. aeruginosa and S. epidermidis 9142 exhibited greater adhesion capabilities to the extended wear silicone-hydrogel lenses than to the daily wear silicone- and conventional hydrogel lenses (p < 0.05). No statistical differences were found between the adhesion extent of these strains to galyfilcon A and etafilcon A. The biofilm negative strain of S. epidermidis adhered in larger extents to the silicone-hydrogel lenses than to the conventional hydrogel (p < 0.05), but in much lower amounts than the biofilm-positive strain. The water contact angle measurements revealed that the extended wear silicone-hydrogel lenses are hydrophobic, whereas the daily wear silicone- and conventional hydrogel lenses are hydrophilic.

CONCLUSIONS

As a result of their hydrophobicity, the extended wear silicone-hydrogel lenses (lotrafilcon A and balafilcon A) may carry higher risk of microbial contamination than both the hydrophilic daily wear silicone-hydrogel lens, galyfilcon A and the conventional hydrogel lens, etafilcon A.

Identification of oligopeptide permease (opp) gene cluster inVibrio fluvialisand characterization of biofilm production byoppAknockout mutation

Oligopeptides play important roles in bacterial nutrition and signaling. The oligopeptide permease (opp) gene cluster was cloned from Vibrio fluvialis. The V. fluvialis opp operon encodes five proteins: OppA, B, C, D and F. The deduced amino acid sequence of these proteins showed high similarity with those from other Gram-negative bacteria. To investigate whether OppA is involved in biofilm production, an oppA knockout mutant was constructed by homologous recombination. The oppA mutant produced more abundant biofilm than the wild type in BHI medium. When both strains were grown in minimal medium, we could not detect biofilm formation. However, it was found that the biofilm productivity of the oppA mutant was two folds greater than that of the wild type in minimal medium containing peptone or tryptone. This variation in biofilm production was demonstrated by scanning electron microscopy (SEM). In minimal medium containing C-sources, both strains produced some biofilm without significant difference in the biofilm productivity. Complementation of oppA gene with the plasmid pOAC2, which contains oppA ORF plus promoter regions, was sufficient to restore growth rate and biofilm to the wild type. These results suggest that the OppA protein is involved in uptake of peptides and affects biofilm productivity.

Adhesion of a Pseudomonas putida strain isolated from a paper machine to cellulose fibres

The adhesion to cellulose fibres of a strain of Pseudomonas putida isolated from a paper machine was studied under different environmental conditions. The physicochemical properties of both P. putida cells and cellulose fibres were also determined to better understand the adhesion phenomenon. Adhesion was rapid (1 min) and increased with time, cell concentration and temperature (from 25 to 40 degrees C), indicating that bacterial adhesion to cellulose fibres is essentially governed by a physicochemical process. The P. putida cell surface was negatively charged, as shown by electrophoretic mobility measurements, and was hydrophilic due to a strong electron-donor character, as shown by the microbial adhesion to solvents method. Cellulose fibres were shown to be hydrophilic by contact angle measurements using the capillary rise method. These results suggest the importance of Lewis acid-base interactions in the adhesion process. In various ionic solutions (NaCl, KCl, CaCl(2) and MgCl(2)), adhesion increased with increasing ionic strength up to 10-100 mM, indicating that, at low ionic strength, electrostatic interactions were involved in the adhesion process. An increase in the C/N ratio of the growth medium (from 5 to 90) decreased adhesion but this could not be related to changes in physicochemical properties, suggesting that other factors may be involved. In practice, temperature, ionic strength and nitrogen concentration must be taken into consideration to reduce bacterial contamination in the paper industry.

High diversity among environmental Escherichia coli isolates from a bovine feedlot

Approximately 280 Escherichia coli isolates were isolated from a bovine feedlot at the University of Connecticut campus via enrichment in lauryl tryptose broth and random selection from MacConkey plates. The E. coli subspecies diversity was estimated by employing whole-cell BOX-PCR genomic fingerprints. A total of 89 distinct operational taxonomic units (OTUs) were identified by employing a criterion of 85% fingerprint similarity as a surrogate for an OTU, while the Chao1 index estimated the E. coli population richness at 128 OTUs. One genotype (at a similarity level of 60%) dominated the population at 66% regardless of sampling depth or location, while no significant vertical distribution pattern was observed in terms of genotype, mobility, antibiotic resistance profile, or biofilm-forming ability. Motility, measured by a soft agar assay, had a very broad range among the E. coli population and was positively correlated with biofilm-forming ability in minimal medium (Spearman's rank correlation coefficient r = 0.619, P < 10(-4)) but not in Luria broth. Only an estimated 48% of the population possessed gene agn43, which encodes Ag43, a phase-variable outer membrane protein that has been implicated in biofilm formation in minimal medium. We observed significantly more biofilm formation in both minimal medium and Luria broth for agn43(+) strains, with a larger effect in minimal medium. This study represents an exhaustive inventory of extant E. coli population diversity at a bovine feedlot and reveals significant subspecies heterogeneity in interfacial behavior.

Mucin degradation mechanisms by distinct Pseudomonas aeruginosa isolates in vitro

Pseudomonas aeruginosa has emerged as an important causative agent of bacterial keratitis, a rapidly progressive ocular condition that may result in blindness. Secretory mucin forms the main constituent of the precorneal tear film, a three-layer film on the ocular surface protecting the underlying corneal epithelium from potential pathogens. The purpose of the present study was to compare mucin degradation mechanisms between ocular P. aeruginosa strains. Mucin degradation was assessed by agarose electrophoresis, lectin blotting, and size exclusion chromatography. The results indicate that certain P. aeruginosa strains (Paer12, ATCC 15442, 6294, and Paer25) had depleted mucin from the culture supernatant and that this was contingent on the inherent ability of these isolates to produce proteases. Non-protease-producing strains (Paer1 and Paer3) did not appreciably degrade mucin. Further, galactosidase, N-acetylglucosaminidase, and N-acetylgalactosaminidase activities were detected in some strains, suggesting the operation of further mechanisms of mucin degradation by P. aeruginosa. Mucin degradation by P. aeruginosa also seemed to be for the acquisition of nutrients, as a growth advantage was observed in mucin-depleting strains over nondepleting strains in the long term. It is postulated that the degradation of mucin serves to collapse the mucin barrier and its associated network containing antibacterial tear components and to provide energy for sustained bacterial growth.

Application of proteomics to Pseudomonas aeruginosa

The recent completion of the Pseudomonas Genome Project, in conjunction with the Pseudomonas Community Annotation Project (PseudoCAP) has fast-tracked our ability to apply the tools encompassed under the term 'proteomics' to this pathogen. Such global approaches will allow the research community to answer long-standing questions regarding the ability of Pseudomonas aeruginosa to survive diverse habitats, its high intrinsic resistance to antibiotics and its pathogenic nature towards humans. Proteomics provides an array of tools capable of confirming the expression of Open Reading Frames (ORF), the relative levels of their expression, the environmental conditions required for this expression and the sub-cellular location of the encoded gene-products. Since proteins are important cellular effectors, the biological questions we pose can be defined in terms of changes in protein expression detectable by separation to purity using two-dimensional gel electrophoresis (2-DGE) and relation to gene sequences via mass spectrometry. As such, we can compare strains with well-characterized phenotypic differences, growth under a variety of stresses, protein interactions and complexes and aid in defining proteins of unknown function. While the complete genome has only recently been finished, a number of studies have already utilized this information and examined various protein gene-products using proteomics. This review summarizes the application of proteomics to P. aeruginosa and highlights potential areas of future research, including overcoming the traditional technical limitations associated with 2-DGE. More focused approaches that target sub-cellular fractions ('sub-proteomes') prior to 2-DGE can provide further functional information. A review of current and previous proteomic projects on P. aeruginosa is presented, as well as theoretical considerations of the importance of sub-proteomic approaches to enhance these investigations.

Polyclonal human antibodies reduce bacterial attachment to soft contact lens and corneal cell surfaces

Bacterial keratitis due to Pseudomonas aeruginosa is a potentially serious complication of extended-wear contact lens use. Adhesion of P. aeruginosa to soft contact lens materials or corneal endothelial cells in the presence of pooled human immunoglobulins and/or neutrophils in artificial tear fluid was studied in vitro as a potential method to treat contact lens-associated infection. Soft hydrophilic contact lens materials equilibrated in sterile saline were soaked in artificial tear fluid for 18 h prior to use. P. aeruginosa IFO 3455 was added to groups of lenses or confluent cultured bovine corneal endothelial cells with varying amounts of human polyclonal immunoglobulin (IgG) and human blood neutrophils or serum albumin as a control. After 2 or 4 h incubation, adherent viable bacteria on lenses were quantified. Fluorescence microscopy was used to assess bacterial adherence to bovine corneal endothelial cells in the presence and absence of IgG and neutrophils. Various concentrations of albumin had no effect on adhesion. Human immunoglobulin solutions (25 mg/ml) reduced P. aeruginosa adhesion by nearly 1 log and 2 logs after 2 and 4 h incubations, respectively. Neutrophils in combination with 25 mg/ml IgG reduced bacterial adhesion approximately 1 log over reduction in adhesion by neutrophils alone. Diluted human IgG (10 mg/ml) did not significantly decrease bacterial adhesion after 2 or 4 h, but did reduce adhesion in combination with human neutrophils at both time points. Similar reductions in amounts of fluorescently labeled bacteria adhered to cultured monolayers of corneal endothelial cells under these conditions were qualitatively observed.

Pseudomonas aeruginosa outer membrane protein F is an adhesin in bacterial binding to lung epithelial cells in culture

Adherence to host cells is a crucial step by which bacteria initiate an infection but the bacterial determinants of the process are, as yet, poorly understood. In an effort to identify bacterial adhesins responsible for Pseudomonas aeruginosa binding to host cells, we identified porin F (OprF) from the outer membrane of P. aeruginosa as adhesin for human alveolar epithelial (A549) cells. Bacterial adhesion assays with (35)S-labeled wild type P. aeruginosa and its isogenic mutant strain lacking OprF showed that the mutant strain binds 43% less than the wild type to A549 cells (P<0.01). In addition, bacterial binding is significantly reduced (P<0.01) when either A549 cells were pretreated with purified OprF or if bacteria were pre-incubated with a monoclonal antibody to OprF. Finally, ligand binding experiments in which purified OprF protein was added to A549 monolayers showed saturable binding. These data indicate that OprF contributes to bacterial adherence to A549 epithelial cells and could facilitate Pseudomonas interactions with the epithelium, including colonization of the airway epithelium or the initiation of pulmonary infection.

Bacterial interactions with contact lenses; effects of lens material, lens wear and microbial physiology

Contact lens wear is a successful form of vision correction. However, adverse responses can occur during wear. Many of these adverse responses are produced as a consequence of bacterial colonization of the lens. The present study demonstrated that during asymptomatic contact lens wear lenses are colonized by low levels of bacteria with gram-positive bacteria, such as coagulase negative staphylococci, predominating. Gram-negative bacteria are frequently the causative agents of adverse responses during contact lens wear. Measuring the adhesion of different strains and/or species of bacteria to different contact lens materials demonstrated considerable differences. In particular. Pseudormonas aeruginosa strains Paerl and 6294 and Aeromonas hydrophilia strain Ahyd003 adhered in larger numbers to the highly oxygen permeable contact lenses Balafilcon A compared to hydrogel lenses manufactured from either Etafilcon A or HEMA. Furthermore, after Balafilcon A lenses had been worn for 6 h during the day bacteria were able to adhere in greater numbers to the worn lenses compared to the unworn lenses with increases in adhesion ranging from 243% to 1393%. However, wearing Etafilcon A lenses usually resulted in a decrease in adhesion (22-48%). Bacteria were able to grow after adhesion to lenses soaked in artificial tear fluid and formed biofilms, visualized by scanning confocal microscopy. Chemostat grown bacterial cultures were utilized to enable control of bacterial growth conditions and bacteria were shown to adhere in the greatest numbers if grown under low temperature (25 degrees C compared to 37 degrees C). The changes in growth temperature was shown. using 2D gel electrophoresis, to change the experssion of cell-surface proteins and, using ID gel electrophoresis, to change the expression of surface lipopolysaccharide of P. aeruginosa Paerl. Thus, these surface changes would have been likely to have mediated the increased adhesion to Etafilcon A contact lenses.

Complementing genomics with proteomics: the membrane subproteome of Pseudomonas aeruginosa PAO1

With the completion of many genome projects, a shift is now occurring from the acquisition of gene sequence to understanding the role and context of gene products within the genome. The opportunistic pathogen Pseudomonas aeruginosa is one organism for which a genome sequence is now available, including the annotation of open reading frames (ORFs). However, approximately one third of the ORFs are as yet undefined in function. Proteomics can complement genomics, by characterising gene products and their response to a variety of biological and environmental influences. In this study we have established the first two-dimensional gel electrophoresis reference map of proteins from the membrane fraction of P. aeruginosa strain PA01. A total of 189 proteins have been identified and correlated with 104 genes from the P. aeruginosa genome. Annotated membrane proteins could be grouped into three distinct categories: (i) those with functions previously characterised in P. aeruginosa (38%); (ii) those with significant sequence similarity to proteins with assigned function or hypothetical proteins in other organisms (46%); and (iii) those with unknown function (16%). Transmembrane prediction algorithms showed that each identified protein sequence contained at least one membrane-spanning region. Furthermore, the current methodology used to isolate the membrane fraction was shown to be highly specific since no contaminating cytosolic proteins were characterised. Preliminary analysis showed that at least 15 gel spots may be glycosylated in vivo, including three proteins that have not previously been functionally characterised. The reference map of membrane proteins from this organism is now the basis for determining surface molecules associated with antibiotic resistance and efflux, cell-cell signalling and pathogen-host interactions in a variety of P. aeruginosa strains.