P G Standard

Immuno-identification of cultures of fungi pathogenic to man.

Because isolates of the fungal pathogensBlastomyces dermatitidis. Coccidioides immitis, Histoplasma capsulatum, andParacoccidioides brasiliensis frequently vary widely in gross and microscopic features and are often difficult or impossible to convert to their tissue forms, a simple diagnostic procedure not dependent upon sporulation is needed to identify them specifically and rapidly. The exoantigen technique has been found to meet this need effectively. On the basis of studies with 166Histoplasma spp. isolates, 128C. immitis isolates, 59B. dermatitidis isolates, 30P. brasiliensis isolates, and 181 saprophytes, we determined that the exoantigen test is valuable for the presumptive identification of the four fungal pathogens studied. All of the positive reactions have correlated with the cultural, histologic, or other available laboratory data, and we are unaware of any false positive or flase negative reactions.

Deoxyribonucleic Acid Hybridization Studies of Exophiala dermatitidis and Exophiala jeanselmei

Exophiala dermatitidis and Exophiala jeanselmei share similar morphological features and have been confused with each other. To clarify the relationship between the two fungi, we conducted a deoxyribonucleic acid (DNA)‐DNA hybridization study using a dot blot method. Between E. dermatitidis and E. jeanselmei, only a very low level of DNA relatedness was seen and it was confirmed that these two fungi are distinct species based on DNA similarity. Close correspondence of DNA from the isolates of E. dermatitidis was obtained, whereas the isolates of E. jeanselmei were divided into 6 groups according to their DNA similarity and a possibility was shown that E. jeanselmei is composed of genetically heterogeneous groups. The subdivision of the species E. jeanselmei by the DNA‐DNA hybridization method was in agreement with serotyping exoantigens. This result suggests that DNA‐DNA hybridization studies provide an excellent tool for the identification and grouping of pathogenic dematiaceous fungi.

Exoantigen tests for the immunoidentification of fungal cultures

Exoantigen tests for the immunoidentification of fungal pathogens are playing a new and significant role in the diagnostic laboratory. Properly performed and controlled exoantigen tests lead to rapid, accurate identification of cultures of many fungal pathogens. The tests are particularly valuable in identifying dimorphic pathogens that are difficult to convert or with atypical cultures. We review the value of exoantigen tests for identifying mycelial form fungi: Aspergillus spp. Blastomyces dermatitidis, Coccidioides immitis, Exophiala jeanselmei, Histoplasma spp., Paracoccidioides brasiliensis, Penicillium marneffei, Pseudallescheria boydii, Sporothrix schenckii, Wangiella dermatitidis and certain dermatophytes. We discuss procedures for performing the tests and sources of error.

Reliability of exoantigens for differentiating Blastomyces dermatitidis and Histoplasma capsulatum from Chrysosporium and Geomyces species

A recent study suggested that Chrysosporium species have the same diagnostic antigens as Histoplasma capsulatum and Blastomyces dermatitidis and, thus, compromise the antigenic identification of these pathogens. In light of these findings, studies were undertaken to determine the reliability of the exoantigen tests for identifying B. dermatitidis and H. capsulatum organisms from cultures. Sixty-three slant or shake culture extracts, or both, were derived from C. asperatum, C. keratinophilum, C. parvum, C. pruinosum, C. parvum var. crescens, Geomyces (Chrysosporium) pannorus, B. dermatitidis, and H. capsulatum. These were analyzed by use of a commercial exoantigen kit and exoantigen test reagents obtained from a commercial source. The results of these analyses were compared with those obtained with Centers for Disease Control reagents. Many of the extracts derived from nonpathogenic fungi produced nonspecific precipitin bands when reacted with the kit and reference antisera, particularly the B. dermatitidis antisera. None, however, produced antigens identical to the specific B. dermatitidis A and H. capsulatum H and M antigens. Our findings indicate that the properly controlled immunoidentification procedure is 100% specific for B. dermatitidis and H. capsulatum, and that cross-reacting antigens derived from morphologically similar saparophytic fungi do not pose identification problems.

Evaluation of commercial serologic test reagents for immunoidentification of medically important aspergilli

We evaluated commercial serodiagnostic test reagents from Greer Laboratories (GL), Lenoir, NC; Immuno-mycologics, Inc. (IMI), Norman, OK; and Scott Laboratories (SL), Fiskville, RI; for their ability to detect Aspergillus spp. exoantigens and group them in their proper series. We detected 87 culture extracts from coded cultures of Aspergillus groups and heterologous fungi against anti-A. fumigatus, A. flavus, A. nidulans, A. niger, and A. terreus sera in the presence of their corresponding antigens. Parallel control studies were performed using serological reagents from both laboratories. The IMI reagents accurately grouped all the isolates. The A. nidulans and A. terreus reactions, however, were significantly weaker than those noted with the control reagents. GL and SL do not supply A. nidulans and A. terreus reagents. Their available reagents correctly grouped the A. fumigatus, A. flavus, and A. niger isolates. Our results indicate that the commercial serodiagnostic reagents for aspergillosis can be effectively used to accurately immunoidentify the medically important Aspergillus spp.

Obituary: Haley, Leanor Davidson

Dr. Leanor Davidson Haley, 75, died May 19, 1996, after a long illness. Dr. Haley was a friend to anyone involved with medical mycology in the clinical laboratory regardless of the size of the laboratory or number of specimens processed. Dr. Haley was tireless in her training efforts for all medical laboratory personnel; medical technologists, microbiologists, dermatologists, pathologists, etc. She taught numerous field courses in medical mycology which were based on Centers for Disease Control and Prevention (CDC) curriculum and research, and wrote training manuals and manuscripts. She was a consultant to anyone who needed help with medical mycological problems. Dr. Haley developed the first audio-tutorial course in general medical mycology at the CDC. This training procedure allowed her to reach many more laboratory workers than she could with home-based studies and field lectures. However, the tutorial procedure did not distract from her other responsibilities. This teaching strategy was so successtul that she developed a tutorial course for the isolation and identification of systemic fungalpathogens, and another course designed to teach dermatologists the necessary tenets of mycology essential for their certification and for daily use in their office practice. Dr. Haley, a medical technologist by training, received her Ph.D. from Duke University in 1949. She left Duke to take a teaching and research position at Yale University Medical School, as the first woman in the Department of Microbiology, where she remained for 17 years. She was recruited to become the Mycology Training Branch Chief, CDC, Atlanta, Georgia in 1968; a position she held for 20 years until retirement. While at CDC she held joint appointments at Emory University Departments of Dermatology and Pathology for 18 years. During her professional career of over 35 years, Dr. Haley was a member of a number of professional societies in which she held many offices. Among these was Sigma Xi, an honorary organization for promotion of research in science, American Association of the Advancement of Science and Whos Who in American Women. She was a pioneer in clinical mycology and is recognized internationally for her excellence in teaching and research. We feel extremely fommate in having had the opportunity to work and train with Dr. Haley. Through the years we developed a personal, as well as professional relationship. Her knowledge and friendship will by missed by many.