Roberts, Glenn D.

An enzymatic method involving a protease (pronase) for the elimination of interference factors in the latex test for cryptococcal antigen was developed and compared with dithiothreitol treatment. The two were equivalent in their ability to remove interference factors; however, the enzymatic method generally yielded higher titers. The method is simple, requires only 20 min, and makes the latex test for cryptococcal antigen specific.

Immunocytoadherence was investigated as a method of detecting active histoplasmosis in two groups of infected New Zealand white rabbits. Yeast-phase Histoplasma capsulatum was given intravenously to one group and intratracheally to the other. There was a striking correlation between the clinical condition of the animals and the number of rosettes seen. This number increased as the infection progressed and decreased as it regressed. The immunocytoadherence technique might be of value in detecting active histoplasmosis, and investigation in humans is warranted.

ABSTRACT We studied the recovery of 1,270 fungal isolates from 176,144 Isolator blood cultures (0.72% positive) on bacterial and fungal media, under routine and differing incubation conditions. Except with Histoplasma capsulatum , chocolate agar incubated for only 3 days proved to be an excellent medium for the recovery of fungi from the Isolator system.

ABSTRACT In a large multicenter study involving six major study sites in the United States, Canada, and Europe, the susceptibilities of 272 Mycobacterium tuberculosis strains to classical second-line antituberculosis (anti-TB) drugs (capreomycin, cycloserine, ethionamide, and kanamycin) and newer compounds (amikacin, clofazimine, ofloxacin, and rifabutin) were determined by the radiometric BACTEC 460 procedure and the conventional proportion method on Middlebrook 7H10 agar. Previously established critical concentrations for classical second-line anti-TB drugs were compared with several concentrations in liquid medium to establish equivalence. MICs of newer compounds determined in liquid medium were either the same or up to four times lower than those determined in agar medium. After establishing critical concentrations (breakpoints) in the extended testing of clinical isolates, we obtained an excellent overall correlation between the two systems, with no errors with amikacin, kanamycin, and ofloxacin and very few major or very major errors with the other drugs; however, for cycloserine, no breakpoint concentration could be recommended due to repeatedly inconsistent results by both methods. Based on these data we conclude that the BACTEC 460 procedure is a simple and rapid method requiring 4 to 8 days on average to generate accurate antimicrobial susceptibility testing (AST) results for eight anti-TB drugs other than those considered primary ones. These data not only fill a major gap of knowledge regarding the critical test concentrations of secondary anti-TB drugs but also provide a baseline for future evaluations of M. tuberculosis AST with the more recently developed, nonradiometric broth-based culture systems.

ABSTRACT Eighty-four cerebrospinal fluid (CSF) samples from different children who presented with signs and symptoms of meningitis were evaluated for the presence of Mycobacterium tuberculosis complex organisms by the Gen-Probe Amplified Mycobacterium tuberculosis Direct Test (MTD; Gen-Probe, San Diego, Calif.). All CSF samples had negative acid-fast smears by the Ziehl-Neelsen staining method. M. tuberculosis was recovered from five samples. M. tuberculosis did not grow from 19 additional samples, but the samples were from patients who fulfilled specific clinical and laboratory criteria for probable tuberculous meningitis (TBM). The remaining samples ( n = 60) were from patients with other infections or noninfectious causes of meningitis. The results of the MTD were interpreted as positive or negative on the basis of recommended cutoff values for respiratory specimens. These results were interpreted as true or false positives or true or false negatives on the basis of the results of M. tuberculosis culture or whether the patient fulfilled criteria for probable TBM. The Gen-Probe MTD was 33% sensitive and 100% specific for detecting M. tuberculosis complex organisms in these 84 CSF samples. If the cutoff values for positive results were decreased for the MTD (≥11,000 versus ≥30,000 relative light units), the sensitivity increased to 83% and the specificity remained 100%. These results for the MTD are encouraging considering that TBM is a highly fatal disease and difficult to diagnose by conventional laboratory techniques.

ABSTRACT The ability to identify yeast isolates by the new enzymatic RapID Yeast Plus System was compared to the ability to identify yeast isolates by the API 20C system. A total of 447 yeast isolates representing Blastoschizomyces capitatus , 17 Candida spp., 5 Cryptococcus spp., Geotrichum spp., 2 Hanseniaspora spp., Hansenula anomala , Hansenula wingei , 3 Rhodotorula spp., Saccharomyces cerevisiae , Sporobolomyces salmonicolor , Trichosporon beigelii , and 2 Prototheca spp. were evaluated. Also, five quality control strains ( Candida spp. and Cryptococcus laurentii ) with well-documented reactivities by the RapID Yeast Plus System were used. Each isolate was evaluated by both methods with a 48-h culture grown at 30°C on Sabouraud dextrose agar (Emmons modification) by following the recommendations of the manufacturers. The RapID Yeast Plus System enzymatic reactions were read after 4 h of incubation, and the API 20C carbohydrate assimilation identification profiles were obtained after 72 h of incubation. There was good (95.7%) agreement between the identifications obtained by the two methods with the eight common Candida spp. and with Cryptococcus neoformans . The agreement was lower when the emerging Candida spp. and other yeast-like pathogens were tested (79.1 and 75.2%, respectively). These preliminary data suggest the potential utility of the RapID Yeast Plus System for use in the clinical laboratory for the rapid identification of common yeast pathogens as well as certain new and emerging species.

Fungal infections of the immunocompromised host are being seen with greater frequency than ever before. In addition, a growing list of unusual and unexpected etiologic agents presents a unique and difficult challenge to the clinician and microbiologist. The clinical manifestations of opportunistic fungal infections are often not characteristic and, in many instances, may prevent a rapid diagnosis from being made. Clinical microbiology laboratories should consider any organism as a potential etiologic agent. This requires that all fungi recovered from immunocompromised patients be thoroughly identified and reported so that their clinical significance may be assessed. This review presents a brief discussion of the clinical and laboratory aspects of some fungal infections seen in this important group of patients.

A polyurethane elastomer was microbiologically evaluated in vitro for its potential use in resilient denture liners. Specimens were immersed in suspensions of ten selected oral microorganisms; this was followed by viable cell counts at intervals during a 16-week period. Results indicated that the polyurethane neither supported the growth of the organisms nor was it degraded.