Limulus lysate assay for early detection of certain Gram-negative corneal infections

Endotoxemia: methods of detection and clinical correlates

As an assay for endotoxin, the Limulus amebocyte lysate assay has several desirable properties: sensitivity, specificity, and potential for adaptation to a quantitative format. Several modifications have been developed to enhance its potential for clinical application. The modifications that allow quantitative measurement of endotoxin and also improve its application to blood samples are described in this review. In fluids other than blood, the detection of endotoxin with the Limulus amebocyte lysate assay can be used as an aid to identify the presence of gram-negative bacteria, and the assay has established utility. With blood, however, there are a range of factors that interfere with the detection of endotoxemia and there are disparate views with respect to the diagnostic and prognostic significance of the test results. In general, the clinical significance of the finding of endotoxemia broadly parallels the frequency and importance of gram-negative sepsis in the patient groups studied and a decline in endotoxin levels accompanies clinical improvement. However, with therapies designed to reduce levels of endotoxin, or to antagonize its effects, it is unclear whether clinical improvement occurs as a consequence of changes in the levels of endotoxemia.

Corneal biopsy. Indications, techniques, and a report of a series of 87 cases

Corneal biopsy can be an effective aid in establishing diagnoses in a variety of infections, dystrophic and degenerative conditions, corneal manifestations of systemic diseases, and drug-induced changes. Preoperative planning and proper preparation of the tissue are stressed. In a series of 87 cases, the indications for biopsy were ulcerative keratitis in 42 cases, nonulcerative lesions in 25 cases, dystrophic and degenerative processes in 15 cases, and corneal manifestations of systemic diseases in 5 cases. Of the 42 cases of ulcerative keratitis, the presence of bacteria, fungi, and Acanthamoeba organisms was excluded in 33 instances (79%). Organisms observed in 9 (21%) of the 42 ulcerative cases included 4 with bacteria, 3 with fungi, and 1 each with Acanthamoeba organisms and virus.

Automation of the Limulus amoebocyte lysate test by using the Abbott MS-2 microbiology system

A rapid, automated method for the performance of the Limulus amoebocyte lysate endotoxin assay has been developed by using the Abbott MS-2 Microbiology System. This instrument automatically determines sequential changes in the optical density of up to 176 samples at 1- or 5-min increments during a 1-h assay period. Graphic representation of optical density changes can be viewed on a cathode-ray tube or reproduced by using a hard-copy printer. Limulus amoebocyte lysate preparations that were obtained from different commercial producers and that had similar endotoxin sensitivities by the conventional gelation method varied somewhat in reactivity when determinations were based upon rate changes in optical density. Lysates from Associates of Cape Cod, Difco Laboratories, and M. A. Bioproducts were the most readily adaptable to the MS-2 System. Use of the MS-2 system increased the sensitivity of these preparations from 60- to 250-fold, and as little as 1 pg/ml was detected. Adaptation of the MS-2 instrument for this purpose provides an objective, reproducible, automated method for the performance of Limulus amoebocyte lysate tests on a variety of fluids.