Clofazimine-induced bull's-eye retinopathy.

Bull's-eye retinopathy has multiple associations. We report a case of bull's-eye retinopathy presumed to be secondary to clofazimine (Lamprene) treatment of a 30-year-old patient with acquired immunodeficiency syndrome (AIDS). Pretreatment baseline eye exam of this patient was normal except for bilateral cotton-wool spots. However, follow-up exam 5 months later revealed bilateral anterior pigmentary corneal deposits in a whorl pattern, a presumed infectious retinitis in the left eye, and bilateral annular macular pigmentary abnormalities. The patient was taken off clofazimine treatment, but died 1 month later. The authors suggest that patients being treated with clofazimine be examined for drug-related corneal and retinal lesions.

False susceptibility of enterococci to aminoglycosides with blood-enriched Mueller-Hinton agar for disk susceptibility testing.

Disk diffusion susceptibility tests for enterococci are frequently modified by adding 5% sheep blood (SB) to Mueller-Hinton agar; the performance standards from the National Committee for Clinical Laboratory Standards sanction this addition. Susceptibility testing of aminoglycoside antibiotics is not recommended for enterococci; in actual practice, however, some laboratories do include aminoglycoside antibiotics routinely, and others may test upon request or in selected situations. In examining 50 clinical isolates of enterococci, SB-enriched Mueller-Hinton agar frequently gave enlarged zone sizes that falsely indicated susceptibility (72% for gentamicin and tobramycin), with the average increase in zone size being 6.3 and 7.6 mm, respectively. Comparison agar dilution MICs demonstrated uniform resistance, with or without added SB. The effect was shown to be caused by heme in concentrations as low as 0.03 micrograms/ml, which, when combined with aminoglycoside antibiotics, caused a synergistic growth inhibition of the enterococci, resulting in larger aminoglycoside antibiotic zones. We postulate that the heme effect is related to a catalytic cleavage of intracellular H2O2 and resultant lipid peroxidation. No other organism or antimicrobial agent tested demonstrated a similar effect, although other investigators have shown a similar phenomenon with the broad-spectrum cephalosporins. Because enterococci grow well and give accurate susceptibility results on Mueller-Hinton agar without SB supplementation and because of the spectrum of definable problems with a number of antimicrobial agents, we recommend that enterococci routinely be tested without SB.

Melanocytoma: nomenclature, pathogenesis, natural history and treatment.

A melanocytoma (magnocellular nevus) is a benign pigmented tumor that may arise wherever uveal melanocytes are present. The most commonly observed site is on or adjacent to the optic nerve head. In the past this tumor was frequently misdiagnosed as a malignant melanoma and many unnecessary enucleations were carried out. Its clinical features are now well recognized and, fortunately, specimens of melanocytomas are rarely received in ocular pathology laboratories today. A review of the literature concerning this tumor is presented, with special reference to the changing concepts in nomenclature, pathogenesis, natural history, and treatment that have evolved in the past one hundred years. We also define the clinical and histopathological features of this tumor.

Malignant transformation of an optic nerve melanocytoma.

A 47-year-old woman who had had a flat, hyperpigmented lesion of the optic disc and juxtapapillary choroid for at least 17 years experienced acute visual loss. This was caused by rapid growth of a pigmented tumour emanating from the original lesion. Histopathological examination of the enucleated globe revealed a large malignant melanoma originating from a melanocytoma (magnocellular nevus) within the optic nerve and peripapillary choroid. This case represents a very rare instance of malignant transformation of a normally benign tumour.

Anterior segment complications and neovascular glaucoma following implantation of a posterior chamber intraocular lens.

Lens implantation is now a highly successful operation. Although follow-up over 5 to 10 years with posterior chamber lenses is incomplete, the complication rate appears to be as low or lower than other lens styles. We present an exception: a clinicopathologic analysis of a globe, enucleated 4 years postoperatively, which in spite of uneventful implantation of a posterior chamber lens, developed neovascular glaucoma. Microscopic studies suggest several mechanisms for this rare complication including deep erosion of a prolene loop into the ciliary body, anterior segment ischemia, and breakdown of the blood-aqueous barrier. Scanning microscopy showed cracking of this deeply embedded loop, a finding we interpret as possible stress cracking and/or oxidation. The more flexible loops now used in modern lenses may decrease the chance of deep erosion. Implantation of a loop in the capsular bag may minimize the danger of both erosion and loop degradation. Patients should be followed long-term in order to recognize and treat these rare, but potentially disastrous complications.

Membrane filter contact technique for bacteriological sampling of moist surfaces.

We used a membrane filter contact technique to pick up and grow bacteria from artificially contaminated surfaces. We were able to recover individual colony-forming units (CFU) of Staphylococcus aureus from a moist agar surface more efficiently with 3- and 5- micron membrane filters than with Rodac plates, velvet pads, velveteen pads, or smaller-pore membrane filters. The effective transfer of bacteria with the 3- and 5-micron membrane filters was 0.96 +/- 0.04 (standard error of the mean) and 0.99 +/- 0.04, respectively, as compared to 0.49 +/- 0.03 for Rodac plates, 0.09 +/- 0.01 velvet pad imprints, 0.05 +/- 0.01 for velveteen pad imprints, 0.27 +/- 0.02 for velvet pad rinses, 0.005 +/- 0.001 for velveteen pad rinses, 0.39 +/- 0.02 for 0.45-micron filters, and 0.85 +/-0.05 for 1.2 micron filters. In addition, the recovery of S. aureus from contaminated bovine muscle surfaces with the 5-microns membrane filter was similar to that of quantitative dilutions of biopsy material and was significantly higher than the recovery from Rodac plates. The 5-microns membrane filters on a paddle recovered 52 +/- 5 CFU/cm2 from artificially contaminated bovine skeletal muscle, the quantitative dilutions of biopsy recovered 69 +/- 5 CFU/cm2, and the Rodac plate recovered 5 +/- 3 CFU/cm2. Sampling of moist surfaces by the membrane filter contact technique is easy to perform and highly efficient; our data suggest that it could be employed for cultures of clinical surfaces such as surgical wounds or burns.