Failure of chemotherapy in the first reported cases of Acanthamoeba keratitis in Pakistan.

Acanthamoeba keratitis is a painful and progressive infection of the cornea that can result in loss of vision. Here, for the first time in Pakistan, we report two cases of Acanthamoeba keratitis. The first patient was a 37-year-old female who presented with severe itching, redness, pain, along with loss of vision. The patient was a regular soft contact lens wearer. The second patient was a 25-year-old female who had been using soft contact lenses for the past two years. She presented with a burning sensation and extreme pain, along with loss of vision. Both patients were treated for a possible microbial keratitis with topical moxifloxacin hydrochloride drops, vancomycin drops, propamidine isethionate ointment, amphotericin B drops, and amikacin drops. However, the response was inadequate and both patients were referred for corneal transplant. Acanthamoeba castellanii was isolated by placing contact lenses and contact lens cases on non-nutrient agar plates containing a lawn of non-invasive Escherichia coli K-12 HB101 bacteria. The polymerase chain reaction (PCR) using genus-specific probes confirmed the identity of Acanthamoeba spp., whereas the morphological characteristics of trophozoites and cysts were suggestive of A. castellanii in both cases. With growing use of contact lenses for vision correction/cosmetic use coupled with sub-standard lens care in this region and the possibility of non-contact lens-associated Acanthamoeba keratitis, a need for increased awareness of this sight-threatening infection is discussed further.

Acanthamoeba keratitis cluster: an increase in Acanthamoeba keratitis in Australia.

BACKGROUND: This study was undertaken in response to an increase in the number of patients treated for Acanthamoeba keratitis at a tertiary referral hospital in Brisbane, Australia. Incidence and patient characteristics were investigated over a 4-year period. METHODS: A retrospective consecutive case series study was performed on patients with Acanthamoeba keratitis presenting to the Princess Alexandra Hospital between January 2003 and March 2007. RESULTS: Nine cases of Acanthamoeba keratitis were identified over 12 months from March 2006 to March 2007 compared with four cases over the previous 37 months from January 2003 to February 2006. This was an increase from 0.07 cases per 1000 outpatient visits to 0.42 per 1000 (P = 0.003). Of the 13 cases, 11 patients used soft contact lenses of which two used monthly extended overnight wear silicone hydrogel lenses. Of the five patients who specified the type of contact lens solution they had used, three reported using AMO Complete Moistureplus Multipurpose solution, one reported using the AMO Complete Comfortplus Multipurpose solution and one was unsure which type of AMO Complete solution they were using. CONCLUSIONS: There has been a significant increase in incidence of cases of Acanthamoeba keratitis presenting to our institution. The type of contact lens solution and the use of silicon hydrogel lenses combined with extended overnight wear may play a role; however, the significance is unclear given the small numbers for analysis. Further study of incidence and patient characteristics is warranted to identify risk factors and causes for the rising incidence.

Acanthamoeba keratitis and contact lens wear.

Acanthamoeba keratitis is a rare but serious complication of contact lens wear that may cause severe visual loss. The clinical picture is usually characterised by severe pain, sometimes disproportionate to the signs, with an early superficial keratitis that is often misdiagnosed as herpes simplex virus (HSV) keratitis. Advanced stages of the infection are usually characterised by central corneal epithelial loss and marked stromal opacification with subsequent loss of vision. In this paper, six cases of contact lens-related Acanthamoeba keratitis that occurred in Australia and New Zealand over a three-year period are described. Three of the patients were disposable soft lens wearers, two were hybrid lens wearers and one was a rigid gas permeable lens wearer. For all six cases, the risk factors for Acanthamoeba keratitis were contact lens wear with inappropriate or ineffective lens maintenance and exposure of the contact lenses to tap or other sources of water. All six patients responded well to medical therapy that involved topical use of appropriate therapeutic agents, most commonly polyhexamethylene biguanide and propamidine isethionate, although two of the patients also subsequently underwent deep lamellar keratoplasty due to residual corneal surface irregularity and stromal scarring. Despite the significant advances that have been made in the medical therapy of Acanthamoeba keratitis over the past 10 years, prevention remains the best treatment and patients who wear contact lenses must be thoroughly educated about the proper use and care of the lenses. In particular, exposure of the contact lenses to tap water or other sources of water should be avoided.

[Painless acanthamoeba keratitis]. / Schmerzlose Akanthamöbenkeratitis.

A 37-year-old contact lens wearer was treated for herpes simplex keratitis. After an initial improvement the keratitis became much worse. An annular infiltrate gave rise to the suspicion of acanthamoeba keratitis even though the patient was not in pain. This diagnosis was confirmed by histological and microbiological examination of the corneal disc after keratoplasty. Acanthamoeba keratitis should be considered even in the absence of pain, especially when the patients are contact lens wearers.

Enhanced attachment of acanthamoeba to extended-wear silicone hydrogel contact lenses: a new risk factor for infection?

PURPOSE: To establish if silicone hydrogel (S-H) contact lenses could be a risk factor for Acanthamoeba infection by facilitating the attachment of trophozoites to their surface and transfer to the cornea and to determine the effect Acanthamoeba culture technique, patient wear, and Pseudomonas biofilm coating have on attachment to the S-H lens. DESIGN: Experimental material study. PARTICIPANTS AND CONTROLS: Attachment to a S-H lens was compared with that of a conventional hydrogel control lens. Sixteen replicates were carried out for both lens types under each test condition. METHODS: Unworn S-H (PureVision; Bausch & Lomb, Kingston-Upon-Thames UK) and conventional hydrogel (Acuvue; Vistakon, Johnson & Johnson, Jacksonville, FL USA) lens quarters were incubated for 90 minutes in suspensions of liquid or plate-cultured Acanthamoeba castellanii trophozoites. Unworn, worn, and Pseudomonas biofilm coated S-H and hydrogel quarters were incubated for 90 minutes with plate-cultured trophozoites. MAIN OUTCOME MEASURES: Trophozoites attached to one surface of each lens quarter were counted by direct light microscopy. Logarithmic transformation of data allowed the use of a parametric analysis of variance. RESULTS: Lens polymer had a significant effect on attachment (P < 0.001), with higher numbers of trophozoites attaching to the S-H lens. Culture technique also had a significant effect on attachment (P = 0.013), with higher numbers of liquid-cultured organisms attaching to both lens types. A significant increase in attachment was demonstrated with worn and Pseudomonas biofilm-coated hydrogel lenses (P < 0.001); however, this difference was not seen with the S-H lens. CONCLUSIONS: Acanthamoebal attachment to the S-H lenses was significantly greater than to the conventional hydrogel. Liquid-cultured trophozoites demonstrated a higher affinity for the lenses tested. Wear and bacterial biofilm coating had no effect on attachment to S-H lenses. The increased attachment found with the S-H lens may be an inherent characteristic of the polymer or a side effect of the surface treatment procedure to which the lenses are exposed. It is possible that S-H lenses are at greater risk of promoting Acanthamoeba infection if exposed to the organism because of the enhanced attachment characteristic of this new material.