Sabouraud Glucose Agar Research Articles

Prevalence of Cryptococcus neoformans in clinical specimens.

Cryptococcus neoformans isolated from various clinical materials in 14 cases, was identified by (1) cultivation on Sabouraud glucose agar and CHROMagar Candida, (2) microscopic examination of Indian-ink-stained preparations and (3) determination of biochemical properties (assimilation and fermentation of saccharides, assimilation of KNO3, production of urease and phenol monooxygenase). C. neoformans was determined in five specimens from paediatric patients in the intensive care unit and in nine specimens from adult patients, most frequently from liquor at meningitis (n = 3).

Adherence in tissues of immunocompromised mice of a non-mycelium producing strain of Candida albicans.

A non-mycelial strain of wild-type Candida albicans strain 3153 A was produced by repeated subculturing on Sabouraud glucose agar, and maintained on yeast extract-peptone-glucose medium resulting in hydrophobic cells at 26 degrees C and hydrophilic cells at 37 degrees C. The behaviour of cells of this strain was studied in male BALB/c mice, immunocompromised by treatment with cyclophosphamide and cortisone acetate. An ex-vivo assay of cell adherence to tissue sections of liver, spleen, kidney and lymph-nodes was used. The adherence of yeast cells at 26 and 37 degrees C was predominantly produced by hydrophobic cells and was significantly greater in spleen and liver of immunosuppressed mice compared with the organs of control animals. Adhesion was observed in the white and red pulp as well as in the marginal zone of the spleen.

The influence of alcohol disinfection of nail samples in the laboratory

Samples of two hundred finger- and toenails cultured after a 70% alcohol disinfection for 2 min were compared with non-disinfected samples cultured on a classical way. Alcohol treatment caused a significant decrease in isolation of yeast and moulds. Both organisms were cultivated at 25.5 and 31%, respectively, when not treated with alcohol, whereas the isolation rate dropped to 10 and 17.5%, respectively, after alcohol treatment. Isolation of dermatophytes decreased from 27.5 to 23.5% when alcohol disinfection was used. In conclusion, although alcohol disinfection of nail samples in the laboratory effectively decreases the isolation rate of unwanted contaminants on Sabouraud glucose agar without cycloheximide, it hampers the isolation of dermatophytes and pathogenic yeasts on cycloheximide-containing media.

Membrane filtration test for rapid presumptive differentiation of four Candida species.

A rapid enzymatic two-step test for the presumptive differentiation of four Candida species commonly occurring in various clinical samples is described. The technique involves membrane filtration of a liquid sample, followed by preincubation of the membrane filter on Sabouraud glucose agar supplemented with ticarcillin-clavulanic acid to yield microcolonies. In a separate assay step, parts of the filter are placed on absorbent pads impregnated with fluorogenic 4-methylumbelliferyl (4-MU) enzyme substrates (4-MU-N-acetyl-beta-D-galactosaminide, 4-MU-phosphate, 4-MU-pyrophosphate, and 4-MU-beta-D-galactoside) in combination with 0.1% digitonin acting as a membrane permeabilizer. The membrane filter in contact with the assay medium is incubated to allow cleavage of the enzyme substrate, resulting in fluorescent microcolonies under long-wavelength UV light. This approach, tested on 301 clinical samples, is able to presumptively differentiate C. albicans, C. glabrata, C. krusei, and C. tropicalis and to distinguish them from other Candida spp. in about 9 to 11 h. Overall agreement with the conventional methods of 94.4% (one Candida species present in the sample) to 83.8% (multiple Candida spp. present) was obtained. The false-negative rates with reference to identification by traditional methods were 1.3% (single species) and 3.8% (multiple species).

Evaluation of CHROMagar Candida for rapid screening of clinical specimens for Candida species

CHROMagar Candida is a new differential culture medium that allows selective isolation of yeasts and simultaneously identifies colonies of Candida albicans, Candida glabrata, Candida tropicalis and Candida krusei. We evaluated this medium and compared it with a reference medium, Sabouraud glucose agar, for the presumptive identification of yeast species isolated directly on the medium from 1150 clinical specimens. A total of 731 specimens showed no growth, 299 isolates (70.2%) showed growth to the same extent on both media. Forty mixed cultures were detected on both media. More than one isolate was detected in 30 of the tested specimens on either CHROMagar (26 specimens) or Sabouraud glucose agar (four specimens). We found a sensitivity of 98.8% and a specificity of 100% for C. albicans, 66.7% and 99.8% for C. tropicalis, 100% and 100% for C. krusei, and 98% and 95.7% for C. glabrata. Regarding these results, CHROMagar Candida is recommended as a useful isolation medium capable of the presumptive identification of yeasts and better detection of mixed cultures in clinical specimens.

Euphorbia hirta leaves and Musa sapientum fruits in culture media for fungi.

Two plant products, Euphorbia hirta leaves and fruits of Musa sapientum, were evaluated as principal ingredients for selective cultivation of fungi. Sapientum glucose agar supported the growth of both dermatophytic, yeast-like, and saprophytic fungi; growth on this medium compared favourably with growth on Sabouraud glucose agar, a standard mycological medium. Sporulation and pigment formation were stronger on sapientum glucose agar than on Sabouraud glucose agar, although fungal growth on the latter was more luxuriant. Addition of Euphorbia extract to mycological media remarkably enhanced fungal growth on the media, and concomitantly suppressed bacterial growth to a similar extent as did antibiotics. The results of this study suggest that Euphorbia sapientum glucose agar can safely be recommended as a cheap and efficient medium for routine isolation of fungi in both clinical and general mycological studies.

Simple, inexpensive, reliable method for differentiation of Candida dubliniensis from Candida albicans.

Candida dubliniensis is a recently described pathogenic species which shares many phenotypic features with Candida albicans, including the ability to form germ tubes and chlamydospores. These similarities have caused significant problems in the identification of C. dubliniensis by the average clinical mycology laboratory. To facilitate the differentiation of these species, we investigated the growth of 120 isolates of C. dubliniensis and 98 C. albicans isolates at 42 and 45 degrees C on Emmons' modified Sabouraud glucose agar (SGA) and 10 isolates of each species in yeast-peptone-dextrose broth. None of the C. dubliniensis isolates grew on the agar or in the broth medium at 45 degrees C, while 11 isolates were capable of growing on SGA at 42 degrees C. In contrast, all of the C. albicans isolates but one grew at 45 degrees C on or in either medium. These reproducible results clearly demonstrate that the incubation of isolates suspected to be C. dubliniensis or C. albicans at 45 degrees C provides a simple, reliable, and inexpensive method for the differentiation of the two species.

An aberrant variant of Histoplasma capsulatum var. capsulatum

We studied an aberrant culture of Histoplasma capsulatum var. capsulatum isolated from synovial fluid collected from the right elbow of a patient from Kansas. Colonies on Sabouraud glucose agar and other routine mycological media were glabrous to soft, moist, heaped, deeply folded or convoluted, and orange-brown with a white, irregular margin. Microscopically, hyphae were hyaline, septate, and branched and remained totally devoid of conidiation over a period of 2 years on all mycological media. Conversion to the yeast form was achieved on Pine's medium at 37 degrees C. Colonies at early stages of growth were smooth, moist, pasty, shiny, and orange-brown but soon became wrinkled and slightly raised and produced oval, thin-walled cells measuring 2 to 3 by to 4.5 microns which multiplied by polar budding. The identity of the isolate was further confirmed by utilizing the Accuprobe DNA and the exoantigen test for H. capsulatum var. capsulatum.

Microbiological profile of crude oil in storage tanks

Microbiological quality of crude oil storage tanks was determined. The samples were taken from crude oil storage tanks in three stations, at Ughelli, Escravos and Forcados tank farms in the Delta State of Nigeria. Two tanks were sampled at each station with samples collected from three levels of the tank, namely the oil layer, oil water interface, and effluent layer. Samples from the inner walls and bottom sediment of the only empty tank in Ughelli during the study were also taken. The total heterotrophic count of bacteria and total fungal count were obtained by plating samples on nutrient agar and sabouraud's glucose agar respectively and incubated for 14 days at 28 °C±2 °C. Oilutilizing bacteria and fungi were isolated on oil agar using fungizone and antibiotics to inhibit fungal and bacterial growth respectively. Pure cultures of bacteria and fungi were prepared on nutrient agar and sabouraud's glucose agar respectively at 28 °C±2 °C for 4 days. Isolates were identified using approved standard methods. Three bacterial genera, Pseudomonas, Proteus and Bacillus, and one actinomycete, Actinomyces and two fungal genera, Penicillium and Cunninghamella, were isolated. Pseudomonas was dominant among the bacteria (41.62%) and Penicillium dominant among the fungi (94%). It was also found that the total microbial load of the effluent layer was higher than that of the oil layer.

Application of CHROMagar Candida for rapid screening of clinical specimens for Candida albicans, Candida tropicalis, Candida krusei, and Candida (Torulopsis) glabrata

CHROMagar Candida is a new differential culture medium that allows selective isolation of yeasts and simultaneously identifies colonies of Candida albicans, C. tropicalis, and C. krusei. We evaluated the use of this medium with 316 yeast isolates including 247 isolated directly on CHROMagar from clinical material. Over 95% of stock and clinical isolates of C. albicans, C. tropicalis, and C. krusei were correctly identified on the basis of colony morphology and pigmentation on CHROMagar. Additionally, CHROMagar also allowed the identification of C. (Torulopsis) glabrata at a similar level of accuracy. The overall agreement between two observers in reading the CHROMagar plates was 95%. Growth of Candida sp. isolates on CHROMagar had no adverse effect on antifungal MICs or Vitek identification results. In parallel, cultures of 548 stool and rectal swab specimens set up on CHROMagar and Sabouraud glucose agar (SGA) were positive in 234 instances. CHROMagar was positive and SGA was negative for 11 specimens, and CHROMagar was negative and SGA was positive for 18 specimens. A single yeast species was isolated on both media from 162 specimens, and in 146 (90%) of these specimens the same species was detected on both CHROMagar and SGA. A total of 43 of the 234 positive cultures contained mixtures of yeast species. Twenty (47%) of these mixed cultures were detected only on CHROMagar. CHROMagar is extremely useful in making a rapid presumptive identification of common yeast species. This capability plus the ability to detect mixed cultures of Candida spp. promises to improve and streamline the work flow in the mycology and clinical microbiology laboratory.

Hyaluronidase and chondroitin sulphatase production by different species ofCandida

The production of hyaluronidase and chondroitin sulphatase by Candida albicans, Candida tropicalis, Candida parapsilosis, Candida guilliermondii and Candida krusei was investigated using a complex culture medium (Sabouraud glucose agar) and a chemically defined medium. Among the 63 C. albicans isolates tested, 61 (97.8%) were found to be hyaluronidase and chondroitin sulphatase producers; one isolate produced only chondroitin sulphatase and one other was unable to produce either enzyme. The second major hyaluronidase and chondroitin sulphatase producing species was C. tropicalis followed by C. guilliermondii, C. parapsilosis and C. krusei. Among the C. albicans isolates tested no relation between the source of isolation and the amount of hyaluronidase and chondroitin sulphatase produced was found.

Epidemiological analysis of Candida yeasts by pulsed-field gel electrophoresis.

The purpose of this study was to determine whether yeast isolates from mothers and their new-borns are of the same genotype. In this investigation, 103 parturient mothers and their children were examined for colonization by yeasts by sampling the vaginal secretions at delivery and by taking swabs from the oral mucosa and the anus of the children on the third day after parturition. The samples were cultured on Sabouraud glucoseagar and incubated for 48 h at 37 degrees C. Differentiation of the isolates was achieved biochemically by means of the Vitek AMS system and morphologically on rice extract agar. Subsequently DNA fingerprinting analysis was carried out by means of pulsed-field gel electrophoresis (PFGE). In six cases we could prove the presence of Candida spp. in the mothers as well as in their children. In all cases the strains isolated from mother and child showed the same banding pattern. Likewise, the strains isolated from the vaginal secretion and the vaginal epithelium of individual women were identical. The differences observed between strains isolated from different women were small to middling. This shows PFGE to be an efficient procedure to demonstrate the relation between strains derived from mothers and their newborns.

An unusual variant ofTrichophyton tonsuransvar.sulfureum

A fungus, recovered from a skin lesion of a patient, produced velvety to powdery, white to deep yellow colonies on Sabouraud glucose agar. Microscopically, it produced a large number of cylindric, smooth-walled, three- to eight-celled macroconidia but failed to produce microconidia on a variety of nutritional media such as rice grains, cornmeal dextrose, potato dextrose, Sabouraud glucose, oatmeal and lactrimel agars. It hydrolysed urea in 7 days, perforated hair in vitro and required thiamine for growth. This isolate represents an atypical variant of Trichophyton tonsurans var. sufureum subvar. perforans.

Application of neutral red staining for evaluation of the viability of dermatophytes andCandidain human skin scales

The fungal elements observed by direct microscopic examination sometimes fail to grow on subsequent culture. To elucidate the cause of this discrepancy, the viability of dermatophytes and Candida in skin scales was evaluated by neutral red staining. Autoradiographic study using 3H-thymidine confirmed that grain-positive cells (viable cells) were stained with neutral red, whereas negative cells (non-viable cells) were not stained. Taking this as a baseline, the correlation between neutral red-positive fungal elements in scales taken from 211 patients with tinea and 27 patients with cutaneous candidosis and cultures on Sabouraud glucose agar was studied. Strong positive correlations were found in both mycoses. These findings suggest that neutral red staining provides a useful method for evaluating the viability of dermatophytes and Candida in human skin scales.

Dermatophytoses in Mexico City.

We analysed 2350 biological samples from patients with a clinical diagnosis of superficial mycoses who attended outpatient services over a 7-year period. Samples of scales were processed by direct microscopic examination with 15% KOH and cultured on Sabouraud glucose agar with chloramphenicol and cycloheximide. Laboratory examination confirmed dermatophytosis in 860 (36.6%) cases, of which 80.9% were caused by Trichophyton rubrum. The most frequently observed dermatophytoses were tinea unguium (60%) and tinea pedis (25.6%). In agreement with previous observations, we demonstrate that T. rubrum continues to increase in Mexico.

The production of antifungal volatiles by Bacillus subtilis.

A strain of Bacillus subtilis which produces an antibiotic metabolite was also found to produce a volatile compound(s) which was antifungal to Rhizoctonia solani and Pythium ultimum. Growth of the fungi was severely impaired in the presence of the volatiles and physiological abnormalities of the hyphae were observed, including hyphal distortion and vacuolation. A range of media were tested for volatile production and potato dextrose agar (PDA) was found to be the most active. Temperature had a considerable effect on antifungal volatile activity with the greatest inhibition occurring at 30 degrees C. Addition of iron (III) chloride to Sabouraud's glucose agar (SGA) also enhanced the antifungal effect. The volatiles were found to be water soluble and remained active when trapped in SGA.

各種消毒薬の殺真菌効果

Fungicidal activities of six kinds of disinfectants, such as chlorhexidine digluconate (CHX), benzalkonium chloride (BAC), alkylpolyaminoethylglycine (APE), formalin (FON), cresol soap (CRS) and povidone iodine (PVI) were investigated against 8 clinical isolated fungi, which included 1 Aspergillus niger, 1 Aspergillus terreus, 2 Candida albicans, 2 Candida tropicalis, 1 Candida parapsilosis, 1 Cryptococcus neoformans, 1 Trichophyton rubrum and 1 Rhodotorula glutinis strains. Concentrations of fungal suspensions were adjusted to approximately 107CFU/ ml for A.niger, A.terreus and T.rubrum and 108-9CFU/ml for C.albicans (A), (B), C.tropicalis (A), (B), C.parapsilosis, C.neoformans and R.glutinis strains, respectivelyThe fungal suspensions with the various concentration of disinfectant were incubated at 25°C, for 15, 30, 60min.and 24 hrs, respectively.An aliquot (0.1ml) was inoculated onto the Sabouraud-glucose agar plates, and the growth was observed after 7 days of incubation at 25°C. Among the 5 strains tested, A.niger was the most resistant one to all disinfectants examined, and 0.4% concentration of CHX, APE or CRS was found to be effective against A. niger strain for lhr.It was considered that BAC, FON or PVI was more effective against the fungi tested than CHX, APE or CRS in short time.

The preservation of fungal cultures by lyophilization

A method for the preservation of fungal strains is presented. The cultures are grown on Sabouraud glucose agar in glass ampoules and lyophilized without further processing. By this method the macroscopical morphology of the cultures is preserved, so that these can be used immediately without recultivation as reference cultures. All tested mould and yeast strains remained viable over the six months duration of the experiment, whereas the dermatophyte strains could only partially be recultivated.

Sabouraud('s) agar

'Sabouraud glucose agar' is the name recommended for present-day versions of the medium originally designed by Raymond Sabouraud. The title 'Sabouraud glucose agar' implies a medium comprising 1% (w:v) peptone, 4% (w:v) glucose and 1.5-2.0% (w:v) agar with a final pH of 5.6 and should not be applied to any other formulation, in the interests of inter-laboratory reproducibility. Use of the word 'dextrose' as a synonym for 'glucose' is not recommended. The colony forms, microscopic characteristics and other physiological properties of fungi cultivated on Sabouraud glucose agar may vary considerably according to the type of peptone used in the medium. The type of agar chosen and the conditions of autoclave sterilization are further obstacles to true standardization of this widely used mycological culture medium.

Prevalence ofTrichosporon beigelii. Colonization of normal perigenital skin

Although the natural habitat of Trichosporon species is considered to be the soil, the role of normal skin in the carriage of Trichosporon beigelii is unknown. The purpose of this study was to determine the prevalence of T. beigelii colonization on normal perigenital skin. Inguinal skin scrapings were obtained from 322 asymptomatic volunteers. There were 261 males and 61 females ranging in age from 18 to 89; 136 were white, 134 were black, and 52 were Hispanic. Specimens were cultured on Sabouraud's glucose agar containing 500 micrograms ml-1 chloramphenicol, and incubated at 23-26 degrees C for up to 4 weeks. The overall incidence of T. beigelii colonization was 12.4%. However, this varied with patient's age, sex, race and socioeconomic background. The highest prevalence (27.1%) was found in black males who attended a Veterans Affairs hospital. The prevalence was lowest in females (1.6%), and no patients who attended a private clinic were colonized. It was concluded that T. beigelii colonizes normal skin with some regularity.