Biomedical subjects

M D Willcox

Publications and source records attributed to M D Willcox.

At least 55 records · Page 3Linked to original sources

PubMed1998

A relatively small change in sodium chloride concentration has a strong effect on adhesion of ocular bacteria to contact lenses.

Adhesion of bacteria to hydrogel lenses is thought to be an initial step of ocular colonization allowing evasion of normal host defences. The salt concentration of media is an important parameter controlling microbial adhesion. Salinity varies from 0.97% NaCl equivalents in the open eye to 0.89% in the closed eye state. In this study, the effect of sodium chloride in the concentration range of 0.8-1.0% (w/v) NaCl on adhesion of ocular bacteria to soft contact lenses was investigated using a static adhesion assay. Pseudomonas aeruginosa was found to adhere to lenses in significantly greater amounts than Serratia marcescens, Flavobacterium meningosepticum, Stenotrophomonas maltophilia and Staphylococcus intermedius. Increasing NaCl from 0.8% to 1.0% (w/v) increased adhesion of all bacteria tested. This adhesion was strong since the organisms could not be removed by washing in low ionic buffer. Adhesion of these organisms did not correlate with their cell surface properties as determined by bacterial adhesion to hydrocarbons (BATH) and retention on sepharose columns.

Bacterial Adhesion↗

PubMed1998

Effectiveness of two methods of denture sterilization.

Species of Candida and in particular Candida albicans may be involved in the aetiology of denture stomatitis. Studies have shown that Candida and other oral micro-organisms including Streptococcus gordonii are associated with denture plaque; hence denture hygiene is an important factor in the prevention and treatment of the disease. The aim of this investigation was to test in vitro the efficacy of two methods of denture sterilization: (1) microwave irradiation and (2) sodium hypochlorite soak. Twenty upper acrylic dentures were prepared for microbiological assay; 10 were inoculated with C. albicans H1 and 10 with S. gordonii LGR2. Within each group, five dentures were tested in a domestic microwave oven for optimal exposure time and temperature to ensure sterilization; the five control dentures were not microwaved. Microbiological analyses showed that the inoculated dentures became sterile after six min of irradiation at medium setting (2450 MHz, 350 W). Damage to the microorganisms after microwave irradiation was clearly visible by scanning electron microscopy (SEM). Following the same protocol as above, experimental dentures were soaked for 8 h in either 0.02%, or 0.0125% sodium hypochlorite solution and control dentures soaked in distilled water. Microbiological analyses showed that the experimental dentures inoculated with C. albicans H1 became sterile. By contrast, those inoculated with S. gordonii LGR2 did not become sterile, and the SEM procedures confirmed these findings. The results of this study indicate that microwaving may be a more effective method of denture sterilization than denture soaking in sodium hypochlorite. However, compared with microwaving, hypochlorite reduces the levels of residual non-viable micro-organisms attached to the denture surface.

Acrylic Resins↗

PubMed1998

Tear changes in contact lens wearers following overnight eye closure.

PURPOSE: Tear protein composition alters during eye closure, by becoming rich in secretory IgA (sIgA) and certain complement proteins. This may reflect altered ocular defense mechanisms during eye closure. Since overnight wear of contact lenses (CLs) is associated with an increased risk of corneal infection and inflammation, this study aimed to quantify tear protein changes with overnight soft CL wear. METHODS: Non-stimulated tears were collected from 9 CL wearers prior to CL wear (baseline), after daily CL wear, and after 8 h sleep. Lenses were removed following wear and were extracted in 80% urea at 95 degrees C. Secretory IgA, complement C3 and C4, were measured using ELISA and total protein using the Pierce BCA assay. Assays were performed on tear samples and CL extracts. RESULTS: Baseline tear protein concentrations were: 0 total tear protein (9.37 +/- 2.97 mg/mL), C3 (4.4 +/- 2.1 micrograms/mL), C4 (0.1 +/- 0.1 micrograms/mL), and sIgA (0.84 +/- 0.34 mg/mL). There were no differences in any protein levels between daily CL wear and no CL wear (p > 0.05). Following sleep, protein concentrations were: total tear protein (43.64 +/- 24.30 mg/mL), C3 (72.5 +/- 49.9 micrograms/mL), C4 (6.7 +/- 5.2 micrograms/mL), and sIgA (5.53 +/- 5.15 mg/mL). Total protein extracted from CLs after daily wear was 90 +/- 27 micrograms/CL and, after overnight wear, 152 +/- 24 micrograms/CL. Negligible levels of C3, C4 and sIgA were recovered from CL extracts. CONCLUSIONS: Uncomplicated daily use of soft CLs does not appear to alter certain tear proteins compared with baseline levels. Uptake of these proteins by the CL does not appear to deplete the tear protein levels. Overnight levels of all tear proteins were increased, compared to daily CL wear.

Adult↗

PubMed1998

Modulation of bacterial adhesion to hydrogel contact lenses by albumin.

PURPOSE: The purpose of this investigation was to measure the abilities of Pseudomonas aeruginosa and Staphylococcus epidermidis strains to adhere to two hydrogel lens materials and measure the effect of a protein-coated surface on the number of adhered bacteria. METHODS: Proteins absorbed to contact lenses during sleep were extracted, subjected to sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), and probed for the presence of albumin. Bacterial adhesion was measured by counting bacteria adherent to contact lenses coated in vitro in increasing concentrations of albumin, examining the ability of albumin in solution to prevent adhesion to albumin-coated lenses, and examining the topography of bacterial adhesion by electron microscopy. RESULTS: Albumin adsorbed to lenses during overnight wear. In vitro studies demonstrated that Polymacon lenses adsorbed more albumin than Etafilcon A lenses. In general, the numbers of adherent bacteria increased with increasing concentration of albumin. Bacteria adhered in higher numbers to Polymacon lenses than Etafilcon A (p < 0.05). P. aeruginosa showed an increased adhesion as the amount of albumin on Etafilcon A lenses increased. There was a decrease in numbers of bacteria adhering per milligram of albumin as the level of albumin increased on Polymacon lenses. Cells tended to adhere to "deposits" on albumin-coated lenses. DISCUSSION: Albumin adsorbed onto the surface of contact lenses modulated the ability of P. aeruginosa and S. epidermidis to adhere. P. aeruginosa is commonly associated with contact lens-associated microbial keratitis, where bacterial adhesion to contact lenses is believed to be an important first step in the pathogenesis of the disease.

Adsorption↗

PubMed1998

Identification and enumeration of staphylococci from the eye during soft contact lens wear.

PURPOSE: An extensive study was conducted to identify and enumerate staphylococcal microbiota found on ocular sites during asymptomatic soft contact lens (SCL) wear. METHODS: A biochemical identification system separately grouped the eight clinically relevant staphylococci. Total counts and isolation frequencies from SCLs and ocular sites were evaluated. RESULTS: The epidermidis group was the most numerous isolate from extended wear (EW) lenses; the capitis/warneri group was the most numerous (p < 0.05) from daily wear (DW) lenses. In both DW and EW, the greatest isolation frequency (p < 0.05) was recorded for the capitis/warneri group. The remaining six groups were isolated infrequently and in low numbers. DISCUSSION: These results show that, in addition to Staphylococcus epidermidis, other staphylococcal species may be important members of the normal microbiota of the ocular surface during SCL wear. Furthermore, an increase and a shift in staphylococcal microbiota between DW and EW regimes was highlighted.

Adult↗

PubMed1998

Interactions of bacteria with contact lenses: the effect of soluble protein and carbohydrate on bacterial adhesion to contact lenses.

PURPOSE: During contact lens wear, components in the tear film adsorb to the contact lens surface to form a protein-rich coating. In this study, we investigated the importance of these components in bacterial adhesion to contact lenses. METHODS: Five strains of bacteria were tested for their ability to adhere to contact lenses (patient-worn; coated with lactoferrin, lysozyme, or an artificial tear formulation; or left uncoated) in the presence of various solutes (protein, carbohydrate). Bacterial adhesion was quantified by both a total count (light microscopy) and viable count (culturing on agar). RESULTS: None of the solutes were found to competitively inhibit bacterial adhesion to worn contact lenses. However, lactoferrin was observed to kill bacteria attached to worn contact lenses. CONCLUSIONS: We could find no evidence to indicate that bacterial adhesion to contact lenses is mediated by specific interactions between bacteria and contact lens-bound tear components. The interaction between attached bacteria and lactoferrin may be important in initiating inflammatory responses to contact lens wear.

Aeromonas hydrophila↗

PubMed1998

Interactions between Candida species and platelets.

Candida spp. are able to cause disseminated disease in immunocompromised patients. This study examined the interactions of Candida spp. with platelets, complement and polymorphonuclear leucocytes (PMNLs). With the exception of C. albicans, all other Candida spp., including a C. albicans strain previously classified as C. stellatoidia, aggregated human platelets at a ratio of yeast cells: platelets of 1:80. Usually, those species and strains that aggregated platelets were either killed or prevented from growing in platelet-rich plasma indicating that the aggregation released microbicidal or microbistatic substances that were active against Candida spp. All Candida spp. were resistant to attack by complement in 50% serum. However, all species activated complement as determined by the presence of C3 fragments on their surface, in particular a 195-kDa fragment corresponding to C3c, two fragments at 67 and 40 kDa corresponding to iC3b, and a 33-kDa fragment corresponding to C3d. When strains were tested for their ability to stimulate the release of pro-inflammatory substances from platelets and PMNLs, it was found that most strains stimulated PMNLs to release interleukin(IL)-8 but not IL-1beta or leucotriene B4. The ability of C. albicans to evade complement-mediated killing and not to aggregate platelets may contribute to the survival of this species in the blood during vascular infections.

Anticoagulants↗

PubMed1998

Synergic antistaphylococcal properties of lactoferrin and lysozyme.

Staphylococcus epidermidis colonises a wide range of implanted prosthetic devices, but rarely contact lenses -- despite a similarity in material composition. A conceivable explanation for this anomaly is the action of the tear defences, including the constitutive proteins lactoferrin and lysozyme. Therefore this study investigated the effect of lactoferrin, lysozyme and serum on the growth of S. epidermidis isolates in artificial tear fluid. Whether supplemented with serum alone or serum with either apolactoferrin or lysozyme, this medium induced a similar, strain-variable effect. However, simultaneous addition of these proteins induced a greater bactericidal or bacteristatic effect. Of those strains killed by the concerted action of apolactoferrin and lysozyme, the absence of serum led to a further increase in the bactericidal effect, whereas strains displaying bacteriostasis were unaffected by serum. Iron saturation of lactoferrin reversed the antimicrobial synergy of apolactoferrin and lysozyme. These results show synergy between lactoferrin and lysozyme which is dependent on the iron limitation of lactoferrin. As a bactericidal mechanism, this synergy is augmented by serum, but bacteriostasis remains unaffected by serum supplemention. Thus, the combination of lysozyme and lactoferrin may partly explain the low level of contact lens colonisation by S. epidermidis in vivo.

Apoproteins↗

PubMed1998

Does Acanthamoeba protect Pseudomonas aeruginosa from the bactericidal effects of contact lens disinfecting systems?

PURPOSE: The aim of this study was to test the hypothesis that Pseudomonas aeruginosa that have been internalized in Acanthamoeba are protected against the action of contact lens disinfecting solutions. METHODS: The experiments were divided into two parts. First, five commercially available disinfecting solutions, hydrogen peroxide and non-peroxide based, were tested for their efficacy against four strains of P. aeruginosa and one strain of A. castellanii. Cells were inoculated into working concentrations of disinfecting solutions, incubated for 18 h and the numbers of viable bacteria or amoeba were analysed after appropriate growth on agar plates. Second, two strains of P. aeruginosa were allowed to interact with A. castellanii for 4 h prior to addition to disinfecting solutions. The numbers of P. aeruginosa after incubation with the disinfecting solutions were measured after growth on agar plates. RESULTS: In general, disinfecting solutions containing hydrogen peroxide were most effective against the micro-organisms. Solutions containing only traces of polyaminopropyl biguanide were least effective. CONCLUSIONS: For strains of P. aeruginosa, the presence of the amoebae did not protect the bacteria against the disinfecting agents. The amoeba appeared to kill the bacteria, perhaps using them as a food source.

Acanthamoeba↗

PubMed1998

Effect of tear secretory IgA on chemotaxis of polymorphonuclear leucocytes.

PURPOSE: The aim of the present study was to examine the effect of tear and purified colostrum secretory IgA (sIgA) on polymorphonuclear leucocyte (PMN) chemotaxis. METHODS: The chemotactic effect of tear and purified sIgA for PMN was studied using a modified Boyden chamber. Tears treated with anti-human IgA, complement-inactivated tears and albumin were used as controls. RESULTS: The data indicate that both tear and purified sIgA are highly chemotactic for PMN. Anti-sIgA antibodies reduced the chemotactic effect of closed-eye tears (34%) and tear collected during ocular inflammation. CONCLUSION: The massive recruitment of PMN in tears during sleep may be partially attributed to the increased levels of tear sIgA. This may play an important role in protecting the eye against bacterial infection.

Chemotaxis, Leukocyte↗

PubMed1998

Candida-associated denture stomatitis. Aetiology and management: a review. Part 1. Factors influencing distribution of Candida species in the oral cavity.

Candida species are yeasts and within the oral cavity, Candida albicans is the most frequently isolated. There is clear evidence that C. albicans adheres to oral surfaces including acrylic dentures and mucosa. The mechanisms of attachment differ, with candidal adhesion to inert surfaces under the control of hydrophobic and electrostatic forces and adhesion to mucosa dependent on a number of complex ligand-recognition systems. Other factors within the oral environment such as saliva, pH, bacteria and hyphal formation have been shown to influence adhesion of candida species to surfaces in the mouth.

Acrylic Resins↗

PubMed1998

Candida-associated denture stomatitis. Aetiology and management: a review. Part 2. Oral diseases caused by Candida species.

Certain systemic conditions and/or defects in the immune system may predispose the host to oral candidal infection and the commonest form of oral candidosis is candida-associated denture stomatitis. Until recently there has been controversy concerning the aetiology of the disease. Although some earlier investigators linked denture stomatitis with trauma or bacterial infection, others had isolated Candida albicans from the mouths of patients with the condition. Current studies indicate that denture stomatitis lesions are associated with the detection of candida species while other factors such as denture hygiene, trauma, systemic diseases and deficiencies of the immune system may be involved.

Bacterial Infections↗

PubMed1998

Candida-associated denture stomatitis. Aetiology and management: a review. Part 3. Treatment of oral candidosis.

Treatment of oral candidosis with topical antifungal agents such as nystatin and amphotericin B is effective initially. However, medication can produce side effects in some patients and when therapy is stopped the condition can recur. Alternative treatment involving the use of antiseptics and disinfecting agents has been shown to play an important role in the control of dental plaque. The use of sodium hypochlorite as an overnight denture soak has been shown to eliminate denture plaque and recent investigations have demonstrated that microwave irradiation of dentures at a specified setting and exposure time is bactericidal and candidacidal.

Anti-Infective Agents, Local↗

PubMed1998

Different strains of Pseudomonas aeruginosa isolated from ocular infections or inflammation display distinct corneal pathologies in an animal model.

PURPOSE: The present investigation sought to define the responses of mouse eyes to challenge with three different strains of P. aeruginosa isolated from human corneas or contact lenses: two different strains produced an ulcerative keratitis, and one strain produced contact lens-induced acute red eye (CLARE). METHODS: The corneas of BALB/c mice were inoculated with three different strains of P aeruginosa. The strains were allowed to interact with the corneas for up to 24 h. In addition, strain Paerl, isolated from CLARE, was subjected to in vitro assays to measure its ability to invade corneal epithelial cells, or to produce cytotoxicity in these cells. Both these assays used cultured rabbit corneal epithelial cells. RESULTS: Both MK isolates were able to infect the corneas of mice, but the CLARE isolate was non-infective. The predominant response to infection with the cytotoxic strain was severe corneal edema and infiltration of the corneal stroma with polymorphonuclear leukocytes (PMNs). The predominant response with the invasive MK isolate was corneal ulceration and infiltration with PMNs. The CLARE strain produced only low levels of PMN infiltration. In in vitro assays the CLARE strain was non-invasive and non-cytotoxic. CONCLUSIONS: This study has identified that P. aeruginosa produces at least three different types of corneal pathology and that not all strains are able to infect mouse corneas.

Animals↗

PubMed1997

Establishment of the human reflex tear two-dimensional polyacrylamide gel electrophoresis reference map: new proteins of potential diagnostic value.

To understand the changes in protein expression associated with various physiological states as well as the development of pathological eye disease, we have begun to map the protein components of normal human reflex tears. An analytical reference map of normal human reflex tears was created using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) with pH 3.5-10 immobilized pH gradients (IPGs). Micropreparatively loaded gels were transferred to polyvinylidene difluoride (PVDF) and analysed by a combination of N-terminal sequence tagging and amino acid compositional analysis. Thirty spots were sequence tagged, resulting in identification of six different proteins (lipocalin, lysozyme, lactotransferrin, zinc-alpha-2 glycoprotein, cystatin S, cystatin SN) that matched to entries in the SWISS-PROT database. A group of N-terminally blocked proteins was clearly identified from SWISS-PROT by amino acid analysis, isoelectric point (pI) and molecular weight (Mr). A number of highly expressed protein components remain unidentified despite being subjected to amino acid analysis and Edman sequencing. A majority of the abundant proteins showed varying degrees of charge heterogeneity attributed to post-translational processing such as glycosylation and N-terminal truncation. We have identified a previously undescribed protein that we have named lacryglobin. This protein displays strong homology with mammaglobin, a protein overexpressed in breast cancer. The discovery of this homologue in tears offers the potential for disease diagnosis by screening tear fluid proteins.

Databases, Factual↗

PubMed1997

Fibronectin concentration in tears of contact lens wearers.

The tears of soft contact lens wearers (wearing lenses on an extended were schedule) were analysed for the amount of fibronectin, albumin and total protein. Tears were collected during the day without stimulation and the levels were then compared to levels in non-contact lens wearers tears. The level of fibronectin in the tears of contact lens wearers (120 ng ml-1) was significantly higher than in the tears of non-contact lens wearers (21 ng ml-1; P < 0.01). There were no differences in the amount of albumin or total protein. When contact lens wearers were divided into those subjects who carried significant levels of bacteria on their contact lenses and non-carriers, the amount of fibronectin and albumin was found to be higher in the tears of bacterial carriers (P < 0.03), whereas the amount of total protein remained the same. The fibronectin in the tears and on the contact lens may predispose subjects to contamination by bacteria and thus increase the risk of inflammatory or infectious diseases associated with bacterial contamination of contact lenses.

Adult↗

PubMed1997

Potential sources of bacteria that are isolated from contact lenses during wear.

PURPOSE: The aim of this paper was to determine the possible contamination sources of contact lenses during wear. METHODS: Potential sources of the microbiota that colonized hydrogel contact lenses during wear were examined. The microorganisms that colonize contact lenses were grown, identified, and compared to those microorganisms that colonized the lower lid margins, upper bulbar conjunctiva, hands, and contact lens cases of contact lens wearers. In addition, the incidence of contamination of the domestic water supply in the Sydney area was obtained, and this was compared to the incidence of colonization of contact lenses by microorganisms in general and gram-negative bacteria in particular. RESULTS: There was a wide diversity of bacteria that were isolated from each site sampled. Coagulase-negative staphylococci and Propionibacterium spp. were the most common isolates from all ocular sites examined, and constituted the normal ocular microbiota. Other bacteria, including members of the families Enterobacteriaceae and Pseudomonadaceae, were isolated infrequently from all sites, but most frequently from contact lens cases. Statistical analysis revealed that there was a correlation between the isolation of bacteria from the contact lens and the lower lid margin (p < 0.001). Analysis of this correlation revealed that this was true for the normal microbiota. A correlation was also noted between the colonization of contact lenses by gram-negative bacteria and contamination of the domestic water supply. DISCUSSION: This study has demonstrated that the likely route for the normal ocular microbiota colonizing contact lenses is via the lid margins, whereas colonization by gram-negative bacteria, including potential agents of microbial keratitis, is likely to be from the domestic water supply.

Bacteria↗

PubMed1997

Microbial contamination of hydrogel contact lenses.

Bacterial contamination of contact lenses (CLs) may contribute to CL-related corneal infection and inflammation. This study reports CL biota over time during daily and extended wear. Microbial contamination of a 58% water, ionic hydrogel CL and a 38% water, non-ionic hydrogel CL was evaluated in an Australian and an Indian population. Fifty wearers were repeatedly sampled over 18 months. Overnight CL use did not alter the frequency of positive cultures, nor the spectrum of organisms compared with daily CL wear. There were no differences in type and frequency of CL contamination between the CL types. Positive cultures were more frequently recovered from the Indian population compared with the Australian population. Streptococcus spp. and Propionibacterium spp. were more frequently isolated from the Australian population. Fungi and Bacillus spp. were more frequently isolated from the Indian population. Normal CL biota alone cannot explain the increased rate of infection and inflammation in extended wear.

Bacillus↗