A total of 126 Candida albicans strains were enzymatically evaluated by the. API ZYM system. .... Humble, M. W., A. King, and I. Philips. 1977. API ZYM, a simple ...
JOURNAL OF CLINICAL MICROBIOLOGY, Aug. 1983, p. 430-431 0095-1 137/83/080430-02$02.00/0 Copyright © 1983, American Society for Microbiology
Vol. 18, No. 2
Preliminary Investigation of Candida albicans Biovars M. CASAL ROMAN* AND M. J. LINARES SICILIA Department of Microbiology, School of Medicine, Cordoba Univ,ersity, Cordoba, Spain
Received 6 December 1982/Accepted 27 April 1983
A total of 126 Candida albicans strains were enzymatically evaluated by the API ZYM system. Four enzymatically based groups of C. albicans are recognized.
Candida albicans is the most frequently isolated opportunistic human pathogen (8). Infections caused by C. albicans vary widely in their clinical manifestations (9). The incidence of candidiasis is increasing because of such factors as prolonged broad-spectrum antibiotic therapy, hematological disorders, immunological problems, immunosuppressive therapies, parenteral alimentation and intravenous catheters, parenteral dialysis, and organ transplants (3, 9). C. albicans has two serotypes, serotypes A and B (5), which have been shown to be related to resistance to 5-fluorocytosine (1, 7). This study was undertaken to evaluate the API ZYM system as a potential method to enzymatically characterize C. albicans isolates. A total of 126 C. albicans isolates isolated from human specimens were purified and identified by standard mycological techniques (2, 4, 10). Of the 126 isolates studied, 63 were obtained from vaginal exudates, 29 from urine, 21 from sputum, 5 from nasopharynx specimens, 1 from a bronchial aspirate, 1 from a nasal specimen, 1 from a nail, 1 from a subfrenic abscess, 1 from a stool specimen, and 3 from mouth cultures. Enzyme activity was evaluated by means of the API ZYM system (8). Each plastic strip contained 20 cupules, 19 of which had different substrates, and the last cupule served as a negative control. The system detects the presence of alkaline phosphatase esterase (C4), lipase esterase (C8), lipase (C14), leucine arylamidase, valine arylamidase, cystine arylamidase, trypsin, chymotrypsin, acid phosphatase, phosphoamidase, cx-galactosidase, P3-galactosidase, ,B-glucuronidase, o-glucosidase, 3-glucosidase,
N-acetyl-3-glucosaminidase, ox-mannosidase,
and a-fucosidase. All cell suspensions that were obtained from cultures grown on Sabouraud glucose agar for 24 and 48 h at 28°C were adjusted to a turbidity approximating that of a McFarland no. 5 nephelometric standard. Each isolate was tested sev430
eral times on different occasions. Two drops of the suspension were added with a Pasteur pipette to each of the 20 cupules of the API ZYM system strip. Each strip was placed in a moist chamber and incubated at 37°C for 4, 5, or 6 h. After incubation, 1 drop of reagent A (25 g of Tris, 110 ml of HCl, 100 g of lauryl sulfate, and up to 1 liter of distilled water) and 1 drop of reagent B (3.5 g of Fast Blue BB and up to 1 liter of 2-methoxyethanol) was added into each cupule. The resulting colors which developed within 5 min were compared to the ZYM color chart. The enzymes exhibiting taxonomic value included leucine arylamidase, valine arylamidase, cystine arylamidase, ot-glucosidase, and N-acetyl-,3glucosaminidase (Table 1). No differences were found when the yeast had been previously cultivated on Sabouraud glucose agar or Sabouraud glucose agar plus chloramphenicol. Cultures incubated for 4 h produced results similar to those of cultures incubated for 5 to 6 h. Cells from 24- and 48-hold cultures proved to have the same enzymatic activity. All the biovars were stable on repeating the test after one year. The separation of C. albicans into biovars is useful for clinical and epidemiological reasons. Because of its simplicity, speed, and commercial availability, the API ZYM system is applicable TABLE 1. Enzymatic biovars of C. albicans Biovar
No. of strains
Enzymatic activity (API ZYM system) in cupule": 6 7 8 16 18
(%) + + + + 80 (64) + + 24 (19) + + 13 (10) + + 9 (7) + a 6, Leucine arylamidase; 7, veline arylamidase; 8, cystine arylamidase; 16, os-glucosidase; 18, N-acetylA B C D
1-glucosaminidase.
NOTES
VOL. 18, 1983
for providing diagnostic laboratories with the ability to distinguish biovars of C. albicans based on differences in their enzymatic profiles. We are grateful to M. Silva-Hutner, The College of Physicians and Surgeors of Columbia University, and M. R. McGinnis, Clinical Microbiology Laboratories, North Carolina Memorial Hospital, for their helpful advice on the preparation of this paper.
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