The signal-to-noise ratio (S/N) in magnetic resonance imagining is one of the variables that must be measured when comparing the relative performance of different techniques. Although various investigators and official groups have proposed different methods for measuring S/N, these are generally not practical for use by a physician working in a clinical situation. The authors present a simple method that should serve for estimating S/N in most cases.

In investigating six cases of blastomycosis in two school groups that had separately visited an environmental camp in northern Wisconsin in June 1984, we identified a large outbreak of the disease and isolated Blastomyces dermatitidis from soil at a beaver pond near the camp. Of 89 elementary-school children and 10 adults from the two groups, 48 (51 percent) of the 95 evaluated in September had blastomycosis. Of the cases, 26 (54 percent) were symptomatic (the median incubation period was 45 days; range, 21 to 106 days). No cases were identified in 10 groups that visited the camp two weeks before or after these two groups. A review of camp itineraries, a questionnaire survey, and environmental investigation showed that blastomycosis occurred in two of four groups that visited a beaver pond and in none of eight groups that did not. Walking on the beaver lodge (P = 0.008) and picking up items from its soil (P = 0.05) were associated with illness. Cultures of soil from the beaver lodge and decomposed wood near the beaver dam yielded B. dermatitidis. We conclude that B. dermatitidis in the soil can be a reservoir for human infection.

One hundred ninety-four patients with cryptococcal meningitis were enrolled in a multicenter, prospective, randomized clinical trial to compare the efficacy and toxicity of four as compared with six weeks of combination amphotericin B and flucytosine therapy. Among 91 patients who met preestablished criteria for randomization, cure or improvement was noted in 75 percent of those treated for four weeks and in 85 percent of those treated for six weeks. The estimated relapse rate for the four-week regimen was higher--27 as compared with 16 percent--whereas the incidence of toxic effects for the two regimens was similar--44 as compared with 43 percent. Among 23 transplant recipients, 4 of 5 treated for four weeks relapsed, leading to the decision to treat the rest of the group for six weeks. Only 3 of the 18 treated for six weeks relapsed. In a third group of 80 patients, the protocol was not followed during the initial four weeks, and these patients were not randomized. Thirty-eight died or relapsed. Multifactorial analysis of pretreatment factors for all 194 patients identified three significant predictors (P less than 0.05) of a favorable response: headache as a symptom, normal mental status, and a cerebrospinal fluid white-cell count above 20 per cubic millimeter. These and other findings in this study are consistent with the view that the four-week regimen should be reserved for patients who have meningitis without neurologic complications, underlying disease, or immunosuppressive therapy; a pretreatment cerebrospinal fluid white-cell count above 20 per cubic millimeter and a serum cryptococcal antigen titer below 1:32; and at four weeks of therapy, a negative cerebrospinal fluid India ink preparation and serum and cerebrospinal fluid cryptococcal-antigen titers below 1:8. Patients who do not meet these criteria should receive at least six weeks of therapy.

Pythiosis occurs in animals and humans who encounter aquatic habitats that harbor Pythium insidiosum. Drug therapy for deeply invasive infections with this organism has been ineffective in humans and animals; patients have been cured only by radical surgical debridement. A 2-year-old boy developed periorbital cellulitis unresponsive to antibiotic and antifungal therapy. The cellulitis extended to the nasopharynx, compromising the airway and necessitating a gastrostomy for feeding. P. insidiosum was isolated from surgical biopsy specimens of the affected tissue. On the basis of in vitro susceptibility studies of the isolate, the patient was treated with a combination of terbinafine and itraconazole. The infection resolved over a period of a few months. The patient remained well 1.5 years after completing a 1-year course of therapy. Cure of deep P. insidiosum infection is feasible with drug therapy.

Pythium insidiosum sp. nov., the etiologic agent of pythiosis, a cosmopolitan disease of horses, cattle, and dogs, is described and illustrated. Pythiosis (5) is a cosmopolitan granulomatous disease of horses, cattle, and dogs (10, 16, 17, 18) that is caused by a long-unnamed "phycomycete." (The term pythiosis was proposed in 1980 by Chandler et al. [5] as a more appropriate name for the equine disease variously referred to as bursatii, Florida horse leeches, granular dermatitis, hyphomycosis destruens equi, phycomycosis, phycomycotic granuloma, and swamp cancer.) It is probable that the first reports referring to this disease were those of Smith (20) and Drouin (9), who observed the mycelial nature of the etiologic agent. Although the organism could be cultured, it could not be identified, as it did not sporulate. de Haan and Hoogkamer (7) gave an extensive description of several cases of diseased horses in Indonesia and named the disease hyphomycosis destruens. This name was extended by de Haan (6) to hyphomycosis destruens equi. In a publication by Bridges and Emmons (4), the etiologic agent was called Hyphomyces destruens. It was not clear from that publication whether the authors intended to introduce a new binomial or only a provisional name they were anticipating to validate in the future (see reference 21, article 34.1b). The binomial was proposed without a Latin description (21, article 36), and the nomenclatural type was not designated for H. destruens (21, article 37). The binomial H. destruens, therefore, was in direct violation of articles 34.1b, 36, and 37 of the International Code of Botanical Nomenclature (21). Bridges and Emmons considered H. destruens to be a phycomycete (zygomycete) on the basis of its morphology in equine tissue as well as its broad, branched, sparsely septate to coenocytic, nonsporulating mycelium in cultures. They could not induce sporulation when H. destruens was grown on a wide variety of media. They speculated that the fungus they had studied "may be a species of Mortierella." Austwick and Copland (1) reported that isolates recovered from horses afflicted with swamp cancer in Papua, New Guinea, formed biflagellate zoospores. Zoospore formation occurred when the isolates, grown on Sabouraud dextrose agar, were transferred to a sterilized aqueous medium of rotten maize silage. They concluded that H. destruens was a phycomycete belonging to the Pythiaceae in the Peronosporales and that it could be included in the genus Pythium Pringsheim. These investigators also stated that "Further work is in progress to establish whether it is a recognized or new species." However, additional work on the identity of this oomycete of the kingdom Protoctista was not published.