Severe sclerokeratitis due to Pseudomonas aeruginosa in noncontact-lens wearers

Increased tolerance to commonly used antibiotics in a Pseudomonas aeruginosa ex vivo porcine keratitis model

Introduction. Bacterial keratitis, particularly caused by Pseudomonas aeruginosa, is challenging to treat because of multi-drug tolerance, often associated with the formation of biofilms. Antibiotics in development are typically evaluated against planktonic bacteria in a culture medium, which may not accurately represent the complexity of infections in vivo.Hypothesis/Gap Statement. Developing a reliable, economic ex vivo keratitis model that replicates some complexity of tissue infections could facilitate a deeper understanding of antibiotic efficacy, thus aiding in the optimization of treatment strategies for bacterial keratitis.Methodology. Here we investigated the efficacy of three commonly used antibiotics (gentamicin, ciprofloxacin and meropenem) against Pseudomonas aeruginosa cytotoxic strain PA14 and invasive strain PA01 using an ex vivo porcine keratitis model.Results. Both strains of P. aeruginosa were susceptible to the MIC of the three tested antibiotics. However, significantly higher concentrations were necessary to inhibit bacterial growth in the minimum biofilm eradication concentration (MBEC) assay, with both strains tolerating concentrations greater than 512 mg l-1 of meropenem. When MIC and higher concentrations than MBEC (1024 mg l-1) of antibiotics were applied, ciprofloxacin exhibited the highest potency against both P. aeruginosa strains, followed by meropenem, while gentamicin showed the least potency. Despite this, none of the antibiotic concentrations used effectively cleared the infection, even after 18 h of continuous exposure.Conclusions. Further exploration of antibiotic concentrations and aligning dosing with clinical studies to validate the model is needed. Nonetheless, our ex vivo porcine keratitis model could be a valuable tool for assessing antibiotic efficacy.

Genomic and metabolic versatility of Pseudomonas aeruginosa contributes to its inter-kingdom transmission and survival

Pseudomonas aeruginosa is one of the most versatile bacteria with renowned pathogenicity and extensive drug resistance. The diverse habitats of this bacterium include fresh, saline and drainage waters, soil, moist surfaces, taps, showerheads, pipelines, medical implants, nematodes, insects, plants, animals, birds and humans. The arsenal of virulence factors produced by P. aeruginosa includes pyocyanin, rhamnolipids, siderophores, lytic enzymes, toxins and polysaccharides. All these virulent elements coupled with intrinsic, adaptive and acquired antibiotic resistance facilitate persistent colonization and lethal infections in different hosts. To date, treating pulmonary diseases remains complicated due to the chronic secondary infections triggered by hospital-acquired P. aeruginosa. On the contrary, this bacterium can improve plant growth by suppressing phytopathogens and insects. Notably, P. aeruginosa is one of the very few bacteria capable of trans-kingdom transmission and infection. Transfer of P. aeruginosa strains from plant materials to hospital wards, animals to humans, and humans to their pets occurs relatively often. Recently, we have identified that plant-associated P. aeruginosa strains could be pathologically similar to clinical isolates. In this review, we have highlighted the genomic and metabolic factors that facilitate the dominance of P. aeruginosa across different biological kingdoms and the varying roles of this bacterium in plant and human health.

Genetic and environmental determinants of surface adaptations in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a well-studied Gram-negative opportunistic bacterium that thrives in markedly varied environments. It is a nutritionally versatile microbe that can colonize a host as well as exist in the environment. Unicellular, planktonic cells of P. aeruginosa can come together to perform a coordinated swarming movement or turn into a sessile, surface-adhered population called biofilm. These collective behaviours produce strikingly different outcomes. While swarming motility rapidly disseminates the bacterial population, biofilm collectively protects the population from environmental stresses such as heat, drought, toxic chemicals, grazing by predators, and attack by host immune cells and antibiotics. The ubiquitous nature of P. aeruginosa is likely to be supported by the timely transition between planktonic, swarming and biofilm lifestyles. The social behaviours of this bacteria viz biofilm and swarm modes are controlled by signals from quorum-sensing networks, LasI-LasR, RhlI-RhlR and PQS-MvfR, and several other sensory kinases and response regulators. A combination of environmental and genetic cues regulates the transition of the P. aeruginosa population to specific states. The current review is aimed at discussing key factors that promote physiologically distinct transitioning of the P. aeruginosa population.

Etiology, Pathogens, Clinical Features and Treatment of Bacterial Scleritis

We retrospectively reviewed literature reports on pathogens, clinical features, diagnosis, treatment, and clinical and visual outcomes in patients with bacterial scleritis over the past decade. Eye surgery and trauma are the most common causes of bacterial infections. Subtenon triamcinolone acetonide injection, intravitreal ranibizumab, and wearing contact lenses are also causes of bacterial scleritis. Pseudomonas aeruginosa is the most common pathogenic microorganism causing bacterial scleritis. Mycobacterium tuberculosis ranks second. The main symptoms of bacterial scleritis are red and painful eyes. The patient's visual acuity decreased significantly. Bacterial scleritis caused by Pseudomonas aeruginosa often manifests as necrotizing scleritis, tuberculous scleritis and syphilitic scleritis are mostly nodular scleritis. Bacterial scleritis often involves the cornea, and approximately 37.6% (32 eyes) of patients had corneal bacterial infection. Hyphema was present in 18.8% (16 eyes). Elevated intraocular pressure was observed in 36.5% (31 eyes) of patients. Bacterial culture was an effective method of diagnosis. Most bacterial scleritis cases require both aggressive medical and surgical treatment, and the drug choice must be based on antibiotic susceptibility testing.

Plant-associated Pseudomonas aeruginosa strains harbour multiple virulence traits critical for human infection

Introduction. Pseudomonas aeruginosa causes fatal infections in immunocompromised individuals and patients with pulmonary disorders.Gap Statement. Agricultural ecosystems are the vast reservoirs of this dreaded pathogen. However, there are limited attempts to analyse the pathogenicity of P. aeruginosa strains associated with edible plants.Aim. This study aims to (i) elucidate the virulence attributes of P. aeruginosa strains isolated from the rhizosphere and endophytic niches of cucumber, tomato, eggplant and chili;and (ii) compare these phenotypes with that of previously characterized clinical isolates.Methodology. Crystal-violet microtitre assay, swarm plate experiment, gravimetric quantification and sheep blood lysis were performed to estimate the biofilm formation, swarming motility, rhamnolipid production and haemolytic activity, respectively, of P. aeruginosa strains. In addition, their pathogenicity was also assessed based on their ability to antagonize plant pathogens (Xanthomonas oryzae, Pythium aphanidermatum, Rhizoctonia solani and Fusarium oxysporum) and kill a select nematode (Caenorhabditis elegans).Results. Nearly 80 % of the plant-associated strains produced rhamnolipid and exhibited at least one type of lytic activity (haemolysis, proteolysis and lipolysis). Almost 50 % of these strains formed significant levels of biofilm and exhibited swarming motility. The agricultural strains showed significantly higher and lower virulence against the bacterial and fungal pathogens, respectively, compared to the clinical strains. In C. elegans, a maximum of 40 and 100% mortality were induced by the agricultural and clinical strains, respectively.Conclusion. This investigation shows that P. aeruginosa in edible plants isolated directly from the farm express virulence and pathogenicity. Furthermore, clinical and agricultural P. aeruginosa strains antagonized the tested fungal phytopathogens, Pythium aphanidermatum, Rhizoctonia solani and Fusarium oxysporum. Thus, we recommend using these fungi as simple eukaryotic model systems to test P. aeruginosa pathogenicity.

Rhizospheric and endophytic Pseudomonas aeruginosa in edible vegetable plants share molecular and metabolic traits with clinical isolates

AIM

Pseudomonas aeruginosa, a leading opportunistic pathogen causing hospital-acquired infections, is also commonly found in agricultural settings. However, there are minimal attempts to examine the molecular and functional attributes shared by agricultural and clinical strains of P. aeruginosa. This study investigates the presence of P. aeruginosa in edible vegetable plants (including salad vegetables) and analyses the evolutionary and metabolic relatedness of the agricultural and clinical strains.

METHODS AND RESULTS

Eighteen rhizospheric and endophytic P. aeruginosa strains were isolated from cucumber, tomato, eggplant, and chili directly from the farms. The identity of these strains was confirmed using biochemical and molecular assays. The genetic and metabolic traits of these plant-associated P. aeruginosa isolates were compared with clinical strains. DNA fingerprinting and 16S rDNA-based phylogenetic analyses revealed that the plant- and human-associated strains are evolutionarily related. Both agricultural and clinical isolates possessed plant-beneficial properties, including mineral solubilization to release essential nutrients (phosphorous, potassium, and zinc), ammonification, and the ability to release extracellular pyocyanin, siderophore, and indole-3 acetic acid.

CONCLUSION

These findings suggest that rhizospheric and endophytic P. aeruginosa strains are genetically and functionally analogous to the clinical isolates. In addition, the genotypic and phenotypic traits do not correlate with plant sources or ecosystems.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reconfirms that edible plants are the potential source for human and animal transmission of P. aeruginosa.

Scleral Melting in a Patient With Carotid Artery Obstruction

PURPOSE

To report a case of severe scleral melting in a patient with carotid artery obstruction.

METHODS

This is an observational case report. We reviewed the patient's chart and the available literature on ocular melting and ocular ischemia.

RESULTS

A 71-year-old man with a history of carotid vascular disease and a blind left eye due to a previous vascular accident developed scleral melting of the right eye. Despite frequent lubricants, systemic immunosuppressives, and repeated conjunctiva transplants, the thinning progressed and his visual acuity deteriorated. Intensive screening for possible underlying diseases revealed no infectious or collagen vascular disease. Magnetic resonance angiography, however, showed a subtotal obstruction of the right internal carotid artery. Further investigations revealed coronary artery obstruction. Carotid surgery combined with coronary artery bypass grafting was performed, and a stable ocular situation was achieved.

CONCLUSIONS

Although a causal factor cannot always be determined, corneoscleral melting should be regarded as a manifestation of underlying systemic or ocular disorders. In the absence of more common causes of corneoscleral melting, a thorough workup is warranted and might reveal life-threatening disorders.

Posterior scleritis secondary to Pseudomonas aeruginosa keratitis

PURPOSE

To report a case of Pseudomonas aeruginosa keratitis that progressed to posterior scleritis.

METHODS

Observational case report.

RESULTS

A 64-year-old woman was treated for P. aeruginosa keratitis. Twelve days later, she was diagnosed with posterior scleritis and treated with oral ciprofloxacin. Her condition progressed, ultimately resulting in enucleation. Histopathology confirmed posterior scleritis, a previously unreported complication of P. aeruginosa keratitis.

CONCLUSION

P. aeruginosa keratitis may progress to posterior scleritis, a potentially devastating complication.

Scleritis

Scleritis is typically a severe painful inflammatory process centered in the sclera that may involve the cornea, adjacent episclera, and underlying uvea; it poses a significant threat to vision. Careful clinical history taking, detailed ocular examination, appropriate investigation for ocular disease with or without underlying systemic disease, and timely intervention with the use of immunosuppressant drugs when necessary, has improved the long-term outcome for patients with this disease.

Anterior scleritis: three case reports and a review of the literature

BACKGROUND

Scleritis is a rare ocular condition involving vasculitis. It can result in severe ocular morbidity and has a high association with underlying systemic disease and mortality. Management can be challenging and under-diagnosis is a concern. Treatment usually requires systemic medications and co-management with a medical specialist in the appropriate field to manage any underlying systemic etiology.

METHODS

Three cases are presented: idiopathic nodular scleritis with complete recovery; bilateral, diffuse anterior scleritis with rheumatoid arthritis; and scleromalacia perforans treated with chemotherapeutic agents and co-managed with a rheumatologist. A search of the English language literature is reported, also.

RESULTS

The reported cases exemplify much of our knowledge regarding scleritis. The literature review focuses on the challenges of an accurate diagnosis and management. Management is challenging and, although standards exist, controversy remains. The literature discusses the relationship of scleritis to underlying systemic disease and the significant implication of this association.

CONCLUSION

Knowledge of scleritis may aid in determining a timely and accurate diagnosis and treatment of both the ocular and any underlying systemic conditions, thus decreasing morbidity and mortality.