Isolation of conjunctival mucin and differential interaction with Pseudomonas aeruginosa strains of varied pathogenic potential

Impact of Exposomes on Ocular Surface Diseases

Ocular surface diseases (OSDs) are significant causes of ocular morbidity, and are often associated with chronic inflammation, redness, irritation, discomfort, and pain. In severe OSDs, loss of vision can result from ocular surface failure, characterised by limbal stem cell deficiencies, corneal vascularisation, corneal opacification, and surface keratinisation. External and internal exposomes are measures of environmental factors that individuals are exposed to, and have been increasingly studied for their impact on ocular surface diseases. External exposomes consist of external environmental factors such as dust, pollution, and stress; internal exposomes consist of the surface microbiome, gut microflora, and oxidative stress. Concerning internal exposomes, alterations in the commensal ocular surface microbiome of patients with OSDs are increasingly reported due to advancements in metagenomics using next-generation sequencing. Changes in the microbiome may be a consequence of the underlying disease processes or may have a role in the pathogenesis of OSDs. Understanding the changes in the ocular surface microbiome and the impact of various other exposomes may also help to establish the causative factors underlying ocular surface inflammation and scarring, the hallmarks of OSDs. This review provides a summary of the current evidence on exposomes in various OSDs.

Analysis of Conjunctival Sac Microbiome in Dry Eye Patients With and Without Sjögren's Syndrome

Purpose

To analyze the conjunctival sac microbial communities in patients with Sjögren's syndrome-associated dry eyes (SSDE) and non-Sjögren's syndrome-associated dry eyes (NSSDE), compared with normal controls (NC).

Methods

Conjunctival sac swab samples from 23 eyes of SSDE, 36 eyes of NSSDE, and 39 eyes of NC were collected. The V3–V4 region of the 16S ribosomal RNA (rRNA) gene high-throughput sequencing was performed on an Illumina MiSeq platform and analyzed using Quantitative Insights Into Microbial Ecology (QIIME). Alpha diversity was employed to analyze microbiome diversity through Chao1 and Shannon indexes. Beta diversity was demonstrated by the principal coordinates analysis (PCoA) and Partial Least Squares Discrimination Analysis (PLS-DA). The relative abundance was bioinformatically analyzed at the phylum and genus levels.

Results

The alpha diversity was lower in patients with dry eye disease (Shannon index: NC vs. SSDE: P = 0.020, NC vs. NSSDE: P = 0.029). The beta diversity showed divergent microbiome composition in different groups (NC vs. SSDE: P = 0.001, NC vs. NSSDE: P = 0.001, NSSDE vs. SSDE: P = 0.005). The top 5 abundant phyla were Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota, and Cyanobacteria in all three groups. The top five abundant genera included Acinetobacter, Staphylococcus, Bacillus, Corynebacterium, and Clostridium_sensu_stricto_1. The relative microbiome abundance was different between groups. The Firmicutes/Bacteroidetes (F/B) ratio was 6.42, 7.31, and 9.71 in the NC, NSSDE, and SSDE groups, respectively (NC vs. SSDE: P = 0.038, NC vs. NSSDE: P = 0.991, SSDE vs. NSSDE: P = 0.048).

Conclusion

The diversity of conjunctival sac microbiome in patients with NSSDE and SSDE was diminished compared with NC. The main microbiome at the phylum and genus level were similar between groups, but the relative abundance had variations. The Firmicutes/Bacteroidetes ratio was higher in the SSDE group.

The impact of Lactococcus lactis (probiotic nasal rinse) co-culture on growth of patient-derived strains of Pseudomonas aeruginosa

BACKGROUND

The Lactococcus strain of bacteria has been introduced as a probiotic nasal rinse for alleged salubrious effects on the sinonasal bacterial microbiome. However, data regarding interactions with pathogenic bacteria within the sinuses are lacking. The purpose of this study is to assess the interaction between L. lactis and patient-derived Pseudomonas aeruginosa, an opportunistic pathogen in recalcitrant chronic rhinosinusitis (CRS).

METHODS

Commercially available probiotic suspension containing L. lactis W136 was grown in an anaerobic chamber and colonies were isolated. Colonies were co-cultured with patient-derived P. aeruginosa strains in the presence of porcine gastric mucin (mimicking human mucus) for 72 hours. P. aeruginosa cultures without L. lactis served as controls. Colony forming units (CFUs) were compared.

RESULTS

Six P. aeruginosa isolates collected from 5 CRS patients (3 isolates from cystic fibrosis [CF], 1 mucoid strain) and laboratory strain PAO1 were co-cultured with L. lactis. There was no statistical difference in CFUs of 5 P. aeruginosa isolates grown with L. lactis compared to CFUs without presence of L. lactis. CFU counts were much higher when the mucoid strain was co-cultured with L. lactis (CFU+L.lactis = 1.9 × 108 ± 1.44 × 107, CFU-L.lactis = 1.3 × 108 ± 8.9 × 106, p = 0.01, n = 7). L. lactis suppressed the growth of 1 P. aeruginosa strain (CFU+L.lactis = 2.15 × 108 ± 2.9 × 107, CFU-L.lactis = 3.95 × 108 ± 4.8 × 106, p = 0.03, n = 7).

CONCLUSION

L. lactis suppressed the growth of 1 patient P. aeruginosa isolate and induced growth of another (a mucoid strain) in in vitro co-culture setting in the presence of mucin. Further experiments are required to assess the underlying interactions between L. lactis and P. aeruginosa.

Tear film, contact lenses and tear biomarkers

This article summarises research undertaken since 1993 in the Willcox laboratory at the University of New South Wales, Sydney on the tear film, its interactions with contact lenses, and the use of tears as a source of biomarkers for ocular and non-ocular diseases. The proteome, lipidome and glycome of tears all contribute to important aspects of the tear film, including its structure, its ability to defend the ocular surface against microbes and to help heal ocular surface injuries. The tear film interacts with contact lenses in vivo and interactions between tears and lenses can affect the biocompatibility of lenses, and may be important in mediating discomfort responses during lens wear. Suggestions are made for follow-up research.

Non-invasive objective and contemporary methods for measuring ocular surface inflammation in soft contact lens wearers - A review

Contact lens wear is one of the primary risk factors for the development of ocular surface inflammatory events. The purpose of this review is to examine and summarize existing knowledge on the mechanisms of contact lens related ocular surface inflammation and the evidence for the effectiveness of current objective methods to measure ocular surface inflammation. Contact lens wear is postulated to trigger an inflammatory response on the ocular surface due to mechanical, chemical, hypoxic stress, or by the introduction of microbes and their toxins. Apart from the traditional signs of inflammation, such as swelling, oedema, redness and heat, on the ocular surface, other methods to measure ocular surface inflammation in sub-clinical levels include tear inflammatory mediator concentrations, conjunctival cell morphology, and corneal epithelial dendritic cell density and morphology. Tear inflammatory mediator concentrations are up- or down-regulated during contact lens wear, with or without the presence of associated inflammatory events. There is higher conjunctival cell metaplasia observed with contact lens wear, but changes in goblet cell density are inconclusive. Dendritic cell density is seen to increase soon after initiating soft contact lens wear. The long term effects of contact lens wear on dendritic cell migration in the cornea and conjunctiva, including the lid wiper area, require further investigation. Currently patient factors, such as age, smoking, systemic diseases and genetic profile are being studied. A better understanding of these mechanisms may facilitate the development of new management options and strategies to minimize ocular surface inflammation related to contact lens wear.

Evaluation of patients with dry eye disease for conjunctival Chlamydia trachomatis and Ureaplasma urealyticum

AIM

To determine the possibility of the development of dry eye disease (DED) as a result of persistent infection with Chlamydia trachomatis and Ureaplasma urealyticum in the conjunctiva of patients.

METHODS

This study was conducted on 58 patients of age range 20-50y, diagnosed with DED confirmed by Schirmer I test and tear breakup time. The non-dry eye control group included 27 subjects of the same age. Ocular specimens were collected as conjunctival scrapings and swabs divided into three groups: the first used for bacterial culture, the second and third taken to detect Chlamydia trachomatis and Ureaplasma urealyticum by direct fluorescent antibody (DFA) assay and polymerase chain reaction (PCR) method.

RESULTS

Chlamydia trachomatis was detected in 65.5% and 76% of DED patients by DFA and PCR methods respectively. Ureaplasma urealyticum was found in 44.8% of DED infected patients using the PCR method. Both organisms were identified in only 37.9% of DED patients found to be infected. Control subjects had a 22% detection rate of Chlamydia trachomatis by DFA assay versus a 7% detection rate by PCR; while Ureaplasma urealyticum was detected in 3.7% of the controls by PCR method. The conjunctival culture revealed that gram positive microorganisms represented 75% of isolates with coagulase negative Staphylococci the most common (50%) followed by Staphylococcus aureus (20%), whereas gram negative microorganisms occurred in 25% of cases, isolating Moraxella spp. as the most frequent organism.

CONCLUSION

Our results tend to point out that Chlamydia trachomatis and Ureaplasma urealyticum were detected in a moderate percentage of patients with DED, and could be a fair possibility for its development. PCR is more reliable in detecting Chlamydia trachomatis than DFA technique. The presence of isolated conjunctival bacterial microflora can be of some potential value.

Histopathological Studies on Rabbits Infected by Bacteria Causing Infectious Keratitis in Human through Eye Inoculation

AIM

This study aimed to investigate the pathogenic effect of bacteria causing infectious keratitis among patients through experimental study conducted on rabbits' eyes with the aid of histopathology as eye infection is a common disease in developing countries that may complicate to loss of vision.

METHODOLOGY

100 swab samples were collected from human infected eyes, at Qassim region during 2012, for the isolation of Pseudomonas aeruginosa and Staphylococcus aureus. The isolated pathogenic bacteria were tested to various antibiotics using some selected antibiotics discs through agar-well diffusion method. Then, experimental study conducted on 27 rabbits. The rabbits were divided randomly into three equal groups, each containing 9 rabbits. Rabbits of group (1) served as control group (Negative Control) and their eyes were inoculated with the buffer only. Rabbits of group (2) were inoculated through eyes with the isolated Pseudomonas aeruginosa. Rabbits of group (3) were inoculated through eyes with the isolated Staphylococcus aureus.

RESULTS

Out of 100 collected swab samples from human infected eyes, Pseudomonas aeruginosa and Staphylococcus aureus were isolated with a total percentage of 25.21% and 15.65%; respectively and used in this study. Both bacterial isolates were sensitive to Gentamicin and Cefuroxime. Clinically, experimentally infected rabbits by Pseudomonas aeruginosa, revealed varying degree corneal abrasions, corneal abscess and dense corneal opacity. Histopathologically, at 3(rd) day post-infection (PI), the cornea revealed polymorpho-nuclear cells infiltration with loss of the outer epithelial lining. At 7(th) day PI, neutrophils were seen in the stroma. At 15(th) day PI, proliferation of fibroblasts and new vascularisation were seen in the stroma. Clinically, rabbits experimentally infected with Staphylococcus aureus, revealed corneal ulcers and focal abscesses. Histopathologically, at 3(rd) and 7(th) day PI, the cornea revealed edema and infiltration of leukocytes. At 15(th) day PI, hyperplasia of corneal epithelium and proliferation of keratocytes were evident. The liver and kidneys of experimented rabbits revealed no remarkable histopathological alterations along the period of experiment.

CONCLUSION

Pseudomonas aeruginosa and Staphylococcus aureus are common eye infection in human, both induced severe lesions in the eyes of rabbits that could interfere with vision, therefore, strict measures to control these infections in human is recommended.

The adhesion of Pseudomonas aeruginosa to high molecular weight human tear film species corresponds to glycoproteins reactive with Sambucus nigra lectin

Pseudomonas aeruginosa is a pathogen gaining prevalence in contact lens-related corneal ulcers. Tear outflow protects the ocular surface, where high molecular weight tear glycoproteins bind bacteria for removal from the eye. The purpose of the present study was to identify glycoproteins in human tears involved in the adhesion of ocular P. aeruginosa isolates. Basal human tears were applied to a bacterial adhesion assay involving electrophoretic separation of tear components, transfer to nitrocellulose and incubation with biotin-labelled bacteria. Glycoproteins were further characterised using lectin profiling. The results showed large-dimension agarose gels were imperative for the detection of at least four glycoproteins with a migration >200 kDa, including species not previously identified. P. aeruginosa 6294 preferentially bound to a well-defined glycoprotein near the origin of the gel that, unlike other glycoproteins >200 kDa, reacted with Sambucus nigra lectin (sialic acid alpha2-6) but not WGA lectin (N-acetylglucosamine, sialic acid alpha2-3). Adhesion did not involve free biotin label or hydrophobic interactions. Also, the pre-incubation of separated tear glycoproteins with S. nigra lectin increased subsequent adhesion of 6294 to this tear glycoprotein. The less virulent Paer1 strain showed diffuse adhesion in the S. nigra-reactive region at the gel origin. In conclusion, an overlay adhesion assay was developed that identified slow-migrating sialylated glycoprotein species in human tears preferentially bound by P. aeruginosa ocular strains, and S. nigra lectin seemed to enhance the interaction. The study provides a basis for direct investigation of bacterial adhesion to glycoproteins with an apparent migration >200 kDa in tear fluid.

Mucins and contact lens wear

PURPOSE

This study was designed to determine whether long-term tolerant contact lens (CL) wear causes changes in the expression of mucin mRNA by the conjunctival epithelium and mucin protein content in tears and to determine whether specific mucins adhere to contact lenses.

METHODS

Twenty long-term (> or = 5 years ) and tolerant CL wearers (2 with hard and 18 with soft contact lenses) were compared with 23 non-CL wearers. One hour after CL removal, tear fluid was collected after instillation of 60 microL of sterile water onto the ocular surface, and protein concentration was determined. Impression cytology was performed on the bulbar temporal region of conjunctiva to collect cells for RNA isolation. Real-time polymerase chain reaction was performed using TaqMan primer and probes for MUC1, 4, 5AC, and 16. ELISA was performed on the collected tears to detect MUC5AC and the mucin carbohydrate epitope H185. For the analysis of adherent mucins on CL, discarded daily-wear contact lenses were collected, rinsed, and incubated overnight at 4 degrees C in mucin isolation buffer. Immunoblot analysis of adherent mucins was performed to detect MUC1, 4, 5AC, 16, and H185.

RESULTS

No significant changes in the levels of mucin mRNA from impression cytology samples were detected when comparing CL and non-CL wearers. The amount of total protein in tears collected from CL wearers (39.9 +/- 27.2 microg) was significantly less than that from non-CL wearers (95.1 +/- 73.8 microg, P = 0.001). The level of MUC5AC mucin and the H185 epitope in tears per unit protein in CL wearers was not significantly different from non-CL wearers. Low levels of membrane-associated mucins, the secreted mucin MUC5AC, and the carbohydrate epitope, H185, were detected in protein extracts from discarded CLs. Compared with MUC1, 4, and 5AC, there was less MUC16 adherent to the CLs.

CONCLUSION

Neither mucin mRNA expression by conjunctival epithelia nor mucin content per unit protein in tears was altered by long-term tolerant CL wear; however, the amount of protein in the tears was significantly less. Shed membrane-associated mucins and the goblet cell mucins adhere to CLs.

Stopping Bacterial Adhesion: A Novel Approach to Treating Infections

Adhesion and colonization are prerequisites for the establishment of bacterial pathogenesis. The prevention of adhesion is an attractive target for the development of new therapies in the prevention of infection. Bacteria have developed a multiplicity of adhesion mechanisms commonly targeting surface carbohydrate structures, but our ability to rationally design effective antiadhesives is critically affected by the limitations of our knowledge of the human 'glycome' and of the bacterial function in relation to it. The potential for the future development of carbohydrate-based antiadhesives has been demonstrated by a significant number of in vitro and in vivo studies. Such therapies will be particularly relevant for infections of mucosal surfaces where topical application or delivery is possible.