ABSTRACT
PURPOSE: To elucidate the reservoirs of Pseudomonas aeruginosa keratitis associated with contact lens (CL) wear by using a molecular genotyping method. METHOD: Ten P. aeruginosa isolates obtained from two young adult patients with infectious keratitis associated with CL wear were studied. These were isolated from corneal specimens, conjunctival swabs, discharges, CL storage cases, and the living environment of the two patients. Species identification was performed with an Oxi/Ferm Tube II system using well-separated colonies on MacConkey and NAC agar plates. We employed molecular genotyping by pulsed-field gel electrophoresis. RESULTS: We isolated three (one each from a corneal scraping, discharge, and a CL storage case) P. aeruginosa samples from patient 1, and seven (one each from the conjunctival swab, CL storage case, and the patient's fingers, and four from the patient's room) from patient 2. Pseudomonas aeruginosa of environmental origin could not be obtained from the house of patient 1. The genotypes of two P. aeruginosa isolates, from corneal scraping and discharge, were identical to that of the isolate from the CL storage case belonging to patient 1. In patient 2, the isolates from the eye and the CL storage case showed the identical genotype, which was different from those of the environmental isolates. CONCLUSION: Our results suggest that the causative P. aeruginosa strains in cases of infectious keratitis associated with CL wear originate in contaminated CL storage cases. However, it is still unclear whether the environmental strains in the patients' houses also cause keratitis.
Subject(s)
Contact Lenses/microbiology , Corneal Ulcer/microbiology , Equipment Contamination , Eye Infections, Bacterial/microbiology , Pseudomonas Infections/microbiology , Pseudomonas aeruginosa/isolation & purification , Adult , Conjunctiva/microbiology , Disease Reservoirs , Disposable Equipment/microbiology , Electrophoresis, Gel, Pulsed-Field , Genotype , Humans , Male , Molecular Biology , Pseudomonas aeruginosa/genetics , Young AdultABSTRACT
The hydrodynamic theory of dentine hypersensitivity proposes that external stimuli cause dentinal fluid movement within dentinal tubules thereby triggering mechanosensitive nerves and eliciting a pain response. The aim of this study was to employ X-ray microtomography (XMT) to monitor diffusion of caesium acetate through dentine to investigate the extent to which transport occurs within the primary tubules compared to that through branched microtubules believed to run perpendicular to the direction of the primary dentinal tubules. 2.0-mm thick coronal dentine disks masked to leave half of the upper surface exposed were imaged by XMT, initially in water, which was then replaced with an aqueous solution of 0.50 mol l(-1) caesium acetate. Further XMT images were acquired after 1 and 6 days immersion. The XMT images were used to measure the change in the X-ray linear attenuation coefficient resulting from caesium acetate ingress into dentine. There was clearly considerable ingress of caesium acetate into the dentine lying below the exposed surface, but considerably less beneath the sealed surface, suggesting that diffusive transport occurs predominantly in the direction of the primary dentinal tubules, with no significant lateral transport. Primary tubules are clearly the dominant transmission route for triggering the mechanosensitive nerves present at the dentine-pulp interface, and for delivery of nerve desensitising agents.
