Paul R Badenoch

Bacteria commonly isolated from keratitis specimens retain antibiotic susceptibility to fluoroquinolones and gentamicin plus cephalothin

Purpose:  Patients presenting with presumed infective keratitis were studied to determine predisposing factors, the current susceptibilities of the bacterial isolates to a range of relevant antibiotics, the success rate of topical antibiotic treatment of keratitis and predictors of failure of topical therapy.

Pythium insidiosum keratitis confirmed by DNA sequence analysis.

Editor,— Pythium insidiosum is an unusual but serious ocular pathogen. Although the organism grows as a mycelium in tissue, it is not a member of the fungal kingdom and its identification can be a challenge for a routine laboratory. We report a case of Pythium keratitis in which the organism was confirmed by nucleic acid sequencing. ### CASE REPORT A 32 year old man was referred from Kuala Lumpur having suffered with intractable keratitis of the left eye for 4 weeks. He gave a history of diabetes, disposable contact lens wear, and swimming in the Kelang River. Routine microbiological investigations had been negative. At presentation to Flinders Medical Centre, he was on topical antibacterial, antifungal, and antiamoebic medication. He had a large epithelial defect, a deep stromal infiltrate approaching the limbus, and hypopyon (Fig 1, top). His visual acuity was hand movements and there was considerable pain. The drops were stopped and corneal scrapings were taken. Gram and Giemsa stains were negative. A biopsy was performed the following day and hyphae were observed in sections. A filamentous organism appeared in cultures of the original scrapings. There was no response to continued antifungal treatment and a penetrating graft was performed 4 days after the biopsy. Postoperatively, the patient received oral itraconazole and …

Corneal virulence, cytopathic effect on human keratocytes and genetic characterization of Acanthamoeba.

Acanthamoeba keratitis is a sight-threatening complication of corneal trauma or contact lens wear. Although the majority of corneal isolates of Acanthamoeba belong to Group II in the Pussard-Pons classification based on cyst morphology, they have been placed in at least six species and their genetic relatedness is uncertain. The aim of this study was to determine the virulence of, and the relationship among, strains derived from the cornea, the nasal mucosa, and other environmental sources. To assess virulence, 10(4) trophozoites of each strain were incubated with monolayers of human corneal fibroblasts. By day 7, 12 of 29 strains tested had induced significant cytopathic changes. In addition, inocula of 10(4) cysts or trophozoites with 10(6) Corynebacterium xerosis were injected into the corneas of Porton rats; 11 amoebic strains induced infection within 7 days. The correlation between the virulence of trophozoites in vitro and in vivo was 86%. Using allozyme electrophoresis, 23 Acanthamoeba strains clustered into 5 major phylogenic divisions. Three divisions contained one or more strains that were virulent in the rat cornea. Virulent Pussard-Pons Group II strains clustered tightly to a fixed allelic difference of 13.6%. The eight corneal isolates clustered to 33%, dividing into three lineages. Five avirulent nasal isolates were strongly differentiated from other Group II strains. The results were not in accord with species designations based primarily on morphological criteria. These data suggest that particular subsets of Acanthamoeba strains are virulent in the human cornea.

Antimicrobial susceptibility of 19 Australian corneal isolates of Acanthamoeba

Purpose: To determine the in vitro drug susceptibility of Australian corneal isolates of Acanthamoeba and to correlate the results with patient treatment and visual outcome.

Acanthamoeba keratitis. Resolution after epithelial debridement.

Two patients presented with dendritiform epithelial irregularities of the cornea that were unresponsive to topical acyclovir. Both were soft contact lens wearers who had practiced inadequate lens hygiene. Acanthamoeba was cultured from a shallow corneal biopsy of one patient and from the contact lens of the other. Epithelial debridement resolved the condition in both patients without concomitant treatment with antiamoebic agents.

Pythium insidiosum keratitis in an Australian child

A 3‐year‐old girl from the Northern Territory developed suppurative keratitis after swimming in pools. A mycelial organism suspected to be Pythium insidiosum was cultured. Treatment with polyhexamethylene biguanide and voriconazole for 5 days was unsuccessful, and a corneal graft was performed. The infection was cleared and when last seen 14 months after surgery the patient had a stable graft and useful vision. The identification of the organism was confirmed by rRNA gene sequencing. P. insidiosum is an oomycete, an organism more closely related to kelp than to fungi. Masses of hyphae were seen in sections and, for the first time, the ultrastructure of P. insidiosum in human tissue is described. The staining characteristics of cultured hyphae were assessed; lactofuchsin and acridine orange were found to be the most useful methods. Although the diagnosis of P. insidiosum keratitis is not difficult, and the organism is susceptible in vitro to a number of antimicrobial agents, early corneal transplantation remains the treatment of choice.

Capnocytophaga canimorsus endophthalmitis following cataract surgery.

An elderly man developed endophthalmitis 1 week after cataract extraction and lens implantation. Intraocular samples were collected and the patient received intravitreal vancomycin and ceftazidime, and topical tobramycin. A Gram stain of vitreous humour revealed spindle‐shaped Gram‐negative bacilli. He was then given systemic clindamycin and topical ofloxacin. Capnocytophaga canimorsus, a member of the oral flora of dogs and cats, was cultured after 3 days. The infection resolved leaving the patient with a visual acuity of 6/60. An attempt was made to culture the organism from the mouth of the patients pet dog. This was unsuccessful and the source of the infection remains unknown.

Serratia ficaria endophthalmitis.

ABSTRACT We report a case of Serratia ficaria endophthalmitis in a 73-year-old man. The patients ocular history included a chemical burn, glaucoma, and corneal transplantation. S. ficaria is part of the fig tree ecosystem and is rarely isolated from clinical specimens. When it has been previously implicated as an agent of disease, the patients have been treated successfully and there have been no complications. In our patient, however, the infection resulted in the loss of the infected eye. This case illustrates that S. ficaria infection in a compromised patient can have serious consequences.

Acanthamoeba Encephalitis: Isolation of Genotype T1 in Mycobacterial Liquid Culture Medium

ABSTRACT We report a case of Acanthamoeba encephalitis diagnosed from an antemortem brain biopsy specimen, where the organism was first isolated in mycobacterial liquid medium and first identified by using a sequence generated by a commercial panfungal sequencing assay. We correlate susceptibility results with clinical outcome.

Acanthamoeba lenticulata keratitis in a hard contact lens wearer

patient saw a different doctor at each encounter. The misdiagnosis of posterior subcapsular cataract, by two experienced practitioners, as pseudophakic posterior capsular opacification is difficult to explain but entirely preventable. Incomplete mydriasis may have been contributory. Importantly, ineffective communication was a major contributing factor in the cascade of events. In general, the language barrier in clinical encounters can be overcome by using professional interpreters and translated information leaflets. These are available in most hospitals but may be underutilized. Reliance on ad hoc interpreters, usually family members, is associated with a greater likelihood of errors of potential consequence. The hazards of ineffective communication can be compounded by pooled waiting lists. Pooling for laser procedures and cataract surgery relies on a shared care model whereby teams or practitioners who recommend surgery may not necessarily perform it. As in this case, the resultant lack of continuity of care and reduced responsibility can be detrimental to outcome. Achieving high standards of care while addressing inequalities in sociolinguistically diverse settings requires emphasis on culturally competent communication. Electronic health records, specifically designed for ophthalmology, should be widely implemented as a means of facilitating continuity of care and enhancing safety. In this case, an electronic health record displaying the patient’s status as phakic or awaiting cataract surgery could have spared the consequences of misdiagnosis. To our knowledge, this is also the first report of the consequences of unintended phakic YAG capsulotomy.