The Medically Important Yeasts Present in Clinical Specimens
1992; King Faisal Specialist Hospital and Research Centre; Volume: 12; Issue: 1 Linguagem: Inglês
10.5144/0256-4947.1992.57
ISSN0975-4466
Autores Tópico(s)Antifungal resistance and susceptibility
ResumoOriginal ArticlesThe Medically Important Yeasts Present in Clinical Specimens Saleh S. A. Al-HedaithyPhD Saleh S. A. Al-Hedaithy Address reprint requests and correspondence to Dr. Al-Hedaithy: Microbiology Division, Department of Pathology, College of Medicine, King Saud University, P.O. Box 2925, Riyadh 11461, Saudi Arabia. From the Microbiology Division, Department of Pathology, College of Medicine, and King Khalid University Hospital, Riyadh. Search for more papers by this author Published Online:1 Jan 1992https://doi.org/10.5144/0256-4947.1992.57SectionsPDF ToolsAdd to favoritesDownload citationTrack citations ShareShare onFacebookTwitterLinked InRedditEmail AboutABSTRACTABSTRACTIn an effort to determine the yeast species present in clinical specimens obtained from patients attending a busy Saudi hospital, the present study was undertaken. More than 1614 yeasts were isolated in culture from pathologic specimens of over 1303 patients with diverse clinical conditions. Organisms identified in 22 species of eight genera included: Candida albicans, C. parapsilosis, C. tropicalis, C. krusei, C. lipolytica, C. guilliermondii, C. pseudo-ropicalis, C. pinotolopesii, C. humicola, C. stellatoidea, C. lusitaniae, Torulopsis glabrata, T. inconspicua, T. candida, Trichosporon beigelii, T. capitatum, Saccharomyces cerevisiae, Cryptococcus neoformans, C. albidus, Rhodotorula glutinis, Hansenula anomala and Prototheca zopfii. The details of specimen types yielding these yeasts in culture are presented in the text. The most frequently isolated yeast was C. albicans, followed by T. glabrata, C. parapsilosis, C. tropicalis, T. inconspicua, C. krusei, S. cerevisiae, T. candida, and T. beigelii. Twenty isolates of six species were recovered from blood of which C. albicans was also the most common. Crytococcus neoformans was found causing cryptococcal meningitis being isolated from the CSF of an 8-year-old female patient. Future studies assessing the incidence of yeast infections in each homogeneous group of patients are recommended.IntroductionYeasts comprise a large sector of fungi with ubiquitous distribution in nature. They are by large beneficial organisms, however, some produce adverse effects on human health and/or are frequently encountered in clinical specimens known as the medically important yeasts. Among these, the species of Candida rank first in importance. A large number of medically important yeasts participate in the normal flora of skin, mouth, intestinal tract, urinary tract and vagina. However, slight changes in host cellular defenses, physiology, or normal flora may render these commensals to become pathogenic and produce disease [1]. Therefore, the significance of yeasts in naturally contaminated specimens such as sputum depends on other considerations pertaining to patient's status, while the mere presence of these organisms in normally sterile body fluids is considered significant [2]. The incidence of yeast infections in compromised individuals has increased considerably in recent years. This, together with resistance of certain yeasts to some antifungal agents, has placed emphasis on the need for spéciation of the isolated organism [3, 4]. The degree to which a laboratory should go into spéciation depends on the spectrum of the clinical setup it serves.A careful review of the literature failed to disclose any published reports on the type of yeast species encountered in clinical specimens from patients in Saudi Arabia. Hence, this study was conducted in order to establish a database on such species and it is hoped that it will stimulate future studies in assessing the pathogenic role of these organisms in various disease processes.MATERIAL AND METHODSThe study was conducted during a six month period from October 23, 1989 to April 23, 1990 in the Medical Mycology Unit at King Khalid University Hospital (KKUH) on patient specimens submitted to the Mycology Laboratory or the yielding yeasts in cultures that were submitted to the bacteriology laboratory. Yeasts isolated prior to the above mentioned period in the mycology laboratory (201 isolates) which were saved and maintained have also been included in this study. KKUH is a 649-bed hospital which provides health services to a large community offering primary and tertiary medical care.The isolated yeast was subjected to germ tube test and subcultured to Sabouraud dextrose agar (SDA), cornmeal (CMA), and SDA containing 500 μ g/ml cycloheximide and 50 μ g/ml chloramphenicol (SDA-CC). Cultures were incubated at 26 ± 1°C for 24 to 48 hours and identified simultaneously or thereafter. The yeast was identified as Candida albicans when it was germ tube positive, produced chlamydospores in CMA, and not inhibited by cycloheximide contained in the SDACC medium. The resistance to cycloheximide is included to differentiate C. albicans from C. stellatoidea[5] since the sucrose assimilation test does not differentiate the two species due to the presence of sucrose negative strains of C. albicans[6].Yeasts other than C. albicans were identified on the basis of their morphology on CMA (such as formation of pseudohyphae or hyphae, production on arthrospores and/or blastospores), carbohydrate assimilation using API 20C System (Analytab Products, Plainview, New York, USA) or the conventional auxanogram method using impregnated disks and urease test. Additionally, nitrate assimilation was performed when deemed necessary. Direct microscopic examination of Giemsa-stained smears or stained histologic sections of most of the respiratory specimens or biopsy tissue as well as India ink stain of CSF were also performed. In addition to the API 20C Index Book, identification charts were consulted for determining species identity [2, 5].RESULTSA total of 1614 yeast isolates were obtained from 1303 hospitalized and non-hospitalized patients. The isolated yeasts were identified to ten species of Candida and ten species of the genera Torulopsis, Trichosporon, Saccharomyces, Cryptococcus, Rhodotorula, and Hansenula (Tables 1 and 2). Candida spp. isolates comprised 84% of all yeasts recovered, (1360 of the 1614 total), with Candida albicans alone amounting to 72.3% of all organisms (1167). The major predisposing factors in the patients from whom specimens were collected included pregnancy, gynecological, urinary or respiratory disorders, cancer, endocrine abnormalities, surgery, infection in an otherwise healthy subject, and a few others such as systemic lupus erythematosus.Table 1. The species of Candida isolated from clinical specimens of hospitalized and non-hospitalized patients.Table 1. The species of Candida isolated from clinical specimens of hospitalized and non-hospitalized patients.Table 2. The species of yeasts other than Candida isolated from clinical specimens of hospitalized and non-hospitalized patients.Table 2. The species of yeasts other than Candida isolated from clinical specimens of hospitalized and non-hospitalized patients.Among the species of Candida, C. albicans also ranked first in frequency of isolation yielding 86% of these yeasts. Next in frequency among Candida spp. were C. parapsilosis, C. tropicalis, and C. krusei, scoring 96 (7.1%), 63 (4.6%), and 20 (1.5%), total isolations, respectively. The other Candida species were recovered infrequently (Table 1). Most of the C. albicans isolates were obtained from high vaginal swabs (HVS) followed by urine, respiratory specimens, and swabs from various other body sites. Few isolations were made from other types of specimens such as catheters, blood and others (Table 3). Candida parapsilosis was recovered more often fr.om urine then from HVS, other swabs, respiratory specimens, catheters and blood. The order of frequency of isolation of C. tropicalis was from urine, respiratory specimens, HVS and to a lesser extent from other specimens including blood. The 20 isolates of C. krusei were obtained from HVS, urine, respiratory specimens and catheter, in this order of frequency. The species C. lipolytica, C. guilliermondii, C. pseudotropicalis, C. pintolopesii, C. humicola, and C. stellatoidea were each recovered in low numbers from different specimens (Table 3).Table 3. The species of Candida isolated from various clinical specimens distributed according to the type of specimen from which they were isolated.Table 3. The species of Candida isolated from various clinical specimens distributed according to the type of specimen from which they were isolated.Species of the genus Torulopsis were next to Candida in their prevalence in clnical specimens totalling 209 isolates (13%) from 199 patients. Although by a big margin, Torulopsis glabrata was second to C. albicans in frequency of isolation comprising 164 isolates of all yeasts. T. inconspicua and T. candida were recovered in much lesser numbers (Table 2). Twenty organisms were identified to the genus Trichosporon of which 14 were of the species T. beigelii and the remaining of T. capitatum. Other yeasts isolated in culture were 19 of Saccharomyces cerevisiae, two Cryptococcus neoformans, one C. albidus, two Rhodotorula glutinis, and one Hansenula anomala (Table 2). With regard to type of specimens, Torulopsis and Saccharomyces were each isolated more frequently from HVS than other specimens, while Trichosporon recovered more from respiratory specimens than other types. Cryptococcus neoformans was isolated on two separate occasions from the cerebrospinal fluid (CSF) of one patient, and the single isolate of Cryptococcus albidus was from skin. Rhodotorula glutinis was recovered twice from HVS and urine. The only isolate of Hansenula anomala was obtained from blood (Table 4).Table 4. The species of yeasts other than Candida isolated from various clinical specimens distributed according to the type of specimen from which they were obtained.Table 4. The species of yeasts other than Candida isolated from various clinical specimens distributed according to the type of specimen from which they were obtained.Two additional species of yeasts were encountered in clinical specimens during the preparation of the manuscript and after the termination of data collection, were not included in the consecutive analysis of yeast isolation during the specified period as presented in the results tables. These were Candida lusitaniae (two isolates, from urine and HVS of two patients) and four isolates of Proto theca zopfii, one from sputum, two from urine, and one from HVS specimens of four different patients. This makes the total yeasts identified to be 22 species in eight genera.Most of the yeasts were isolated from high vaginal swabs followed by urine, respiratory specimens, other swabs, catheters, blood, then skin, in this order (Tables 3 and 4). The species recovered from blood included Candida albicans, C. parapsilosis, C. tropicalis, C. humicola, Saccharomyces cerevisiae, and Hansenula anomala, with C. albicans being the most frequently isolated (55%). Only three species were found in skin: namely, C. albicans, Trichosporon beigelii, and Cryptococcus albidus.A number of yeasts reported herein were clinically significant causing several infections in their respective hosts. These ranged from cutaneous and mucocutaneous (e.g., paronychia, oral thrush, mycotic vaginitis) to fatal disseminated disease and meningitis. One of these has already been reported [7] and the others will be presented in separate communications. As examples, the heavy infection of the skin of a one-year-old female patient by Candida albicans is shown in Figure 1. The organism was also isolated from the blood of this child with fatal disseminated candidiasis. In addition, there was one case of fatal cryptococcal meningitis in an eight-year-old female with systemic lupus erythematosus. Cryptococcus neoformans was isolated twice from two different CSF specimens of this patient (Figure 2).Figure 1. Candida albicans pseudohyphae and hyphae in the skin of a 1-year-old female with disseminated candidiasis. (PAS; original magnification, × 400.)Download FigureFigure 2. Encapsulated yeast cells of Cryptococcus neoformans isolated from cerebrospinal fluid of an 8-year-old female with systemic lupus erythematosus complicated with meningeal cryptococcosis. (India ink preparation; original magnification, × 400.)Download FigureDISCUSSIONThe number of yeasts isolated (more than 1614) from the various types of specimens of the patients with their diverse clinical conditions should be representative of the type of yeast species that would be encountered in specimens from patients in Saudi Arabia. These totaled 22 species in eight genera of yeasts, 11 of which were species of Candida and 11 of other different genera (Tables 1 and 2). A similar study on cancer patients in New York reported the isolation of 18 species in seven genera [8]. It has been found that yeasts are more prevalent in hospitalized patients than in nonhospitalized patients [9, 10]. The current investigation did not discriminate between the two patient populations.The high incidence of Candida albicans in the various specimens is not unexpected since it is the most virulent of all yeasts, in addition to being a major participant in the normal flora of various body sites [1,3,11,12]. The other species that were encountered in high numbers were Torulopsis glabrata, Candida parapsilosis, C. tropicalis, C. krusei, and Saccharomyces cerevisiae. Similar findings were reported by Kiehn et al [8] with slight modification of the order of frequency, perhaps due to the difference in the type of patients investigated. The pathogenicity of C. parapsilosis and C. tropicalis in compromised patients is well established [1,3,11,13]. These two species are considered next to C. albicans as etiologies of candidaemia. In their pediatric patients, Weems et al [13], found C. parapsilosis as the frequent cause of candidaemia. The commonly isolated species from blood in this study were C. albicans followed by C. parapsilosis and C. tropicalis. Other yeast isolates from blood included C. humicola, Saccharomyces cerevisiae, and Hansenula anomala. It is likely that these species comprise the etiologie agents of yeast septicemia in patients seen in this country. All yeasts found in the clinical specimens in this study have been reported to cause opportunistic infections to humans [1,2,4,5,7,11,13]. These included Candida krusei, C. guilliermondii, C. pseudotropicalis, Trichosporon beigelii, and Cryptococcus neoformans.Although yeast isolation from normally nonsterile specimens may indicate the possibility of being normal flora, their potential in producing infection should not be underestimated especially in patients with other syndromes or predisposing factors. It has been stated that the isolation of yeasts from multiple sites should be considered significant [3,10,11]. In a recent review article, Jones [3] suggested that the growth of Candida should be reported even when it is part of a mixed flora. The rise in yeast infections in recent years coupled with.some variation in susceptibility of different yeasts to antifungal agents and the severity of the disease produced by some of these organisms in compromised patients, emphasizes the need for identifying the isolated yeast beyond the Candida albicans step [3,4]. In this investigation only one isolate was obtained of the species C. stellatoidea indicating the rarity of this species in clinical specimens. Similarly, Kwon-Chung et al [6] found this organism to be rather rare in their study on vaginal isolates. Therefore, since C. stellatoidea is so rare, it may be justifiable to employ only germ tube test and chlamydospore production for routine C. albicans identification. However, in serious infections, all species must be fully identified.In brief, the yeasts found by the current study in the patient specimens were 22 species in the genera Candida, Torulopsis, Trichosporon, Saccharomyces, Prototheca, Cryptococcus, Rhodotorula, and Hansenula. As mentioned earlier, a number of these were found to be causing infections demonstrated by C. albicans causing disseminated candidiasis and Cryptococcus neoformans responsible for a case of cryptococcal meningitis. Evaluation of the clinical significance of these organisms in each group of patients will form the basis of a proposed communication in the near future.ARTICLE REFERENCES:1. Rippon JW. Candidiasis and the pathogenic yeasts, cryptococcosis. In: Rippon JW, ed. Medical mycology, the pathogenic fungi and the pathogenic actinomycetes, ed 2. Philadelphia: WB Saunders; 1982;484–558. Google Scholar2. Silva-Hunter M, Cooper BH. Yeasts of medical importance. In: Lennette EH, Balows A, Hausler WJ, Traunt JP, eds. Manual of clinical microbiology, ed 3. Washington, DC: Am Soc Microbiol; 1980;562–76. Google Scholar3. Jones JM. "Laboratory diagnosis of invasive candidiasis" . Clin Microbiol Rev. 1990; 3(1):32–45. Google Scholar4. Guinet R, Chanas J, Goullier A, Bonnefoy G, Ambroise-Thomas P. "Fatal septicemia due to amphoterician B-resistant Candida lusitaniae" . J Clin Microbiol. 1983; 18(2):443–4. Google Scholar5. McGinnis MR. Yeast identification. In: McGinnis MR, ed. 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"Candida detection system (CAND-TEC) to differentiate between Candida albicans colonization and disease" . J Clin Microbiol. 1986; 24(4):542–7. Google Scholar11. Martino P, Girmenia C, Venditti M, et al.. "Candida colonization and systemic infection in neutropenic patients" . Cancer. 1989; 64(10):2030–4. Google Scholar12. Burford-Mason AP, Weber JCP, Willoughby JMT. "Oral carriage of Candida albicans, ABO blood group and secretor status in healthy subjects" . J Med Vet Mycol. 1988; 26(1):49–56. Google Scholar13. Weems JJ, Chamberland ME, Ward J, et al.. "Candida parapsilosis fungemia associated with parenteral nutrition and contaminated blood pressure transducers" . J Clin Microbiol. 1987; 25(6):1029–32. Google Scholar Previous article Next article FiguresReferencesRelatedDetails Volume 12, Issue 1January 1992 Metrics History Accepted10 February 1991Published online1 January 1992 ACKNOWLEDGMENTSThe technical assistance provided by Mr. H. A. Jegede-Fadunsin and the secretarial help by Miss Ma Emma Manuzon are greatly appreciated.InformationCopyright © 1992, Annals of Saudi MedicinePDF download
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