Comparative performance of the RapID Yeast Plus System and the API 20C AUX Clinical Yeast System

Etiological agents of fungal endophthalmitis: diagnosis and management

Endophthalmitis caused by fungi is commonly diagnosed around the world in apparently healthy and immunocompromised individuals. An accurate clinical diagnosis for endophthalmitis confirmed by laboratory techniques is essential for early treatment with antifungal drugs, such as amphotericin B, imidazoles, and other antifungals. Here, we review endophthalmitis caused by fungi according to its classification into endogenous fungal endophthalmitis (EFE) and exogenous fungal endophthalmitis (EXFE). EFE is caused by endogenously acquired fungi, whereas the traumatic implantation of opportunistic fungal pathogens is the main feature of EXFE. We highlight the most important etiologies causing endophthalmitis and the steps required for a rapid diagnosis and management.

Breakthrough disseminated cryptococcosis during micafungin therapy

Echinocandins are not active against basidiomycetous yeasts, such as Cryptococcus neoformans, Trichosporon, and Rhodotorula species, and zygomycosis. We present a patient with renal failure and candidemia, who developed a breakthrough fungal infection with cryptococcemia and cryptococcuria while receiving micafungin therapy.

Isolation of Cryptococcus neoformans and other opportunistic fungi from pigeon droppings

BACKGROUND

Invasive fungal infections cause considerable morbidity and mortality in immunocompromised hosts. Pigeon droppings could especially be a potential carrier in the spread of pathogenic yeasts and mold fungi into the environment. The objective of this study was to isolation of Cryptococcus neoformans and other opportunistic fungi from pigeon droppings.

MATERIALS AND METHODS

One hundred twenty samples of pigeon droppings were suspended 1:10 in saline solution and then cultured. Identification of C. neoformans was performed on bird seed agar, presence of a capsule on India ink preparation, urease production on urea agar medium and RapID yeast plus system. The identification of candida species was based on micro-morphological analysis on corn meal-Tween 80 agar, RapID yeast plus system and growth in CHROMagar candida. The identification of other fungi was based on macromorphologic, microscopic, biochemical and physiological characteristics.

RESULTS

The highest frequency of yeasts and mold fungi were observed in Candida albicans 6.6% and Penicillium spp. 25%. The frequency rate of C. neoformans isolation was 2.5%.

CONCLUSION

Several types of fungi are present in pigeon droppings that can spread in environment and transmit to children and elderly as well as immunocompromised patients who are at increased risk of contracting opportunistic diseases.

Evaluation of the commercial rapid trehalose test (GLABRATA RTT) for the point of isolation identification of Candida glabrata isolates in primary cultures

Candidaemias account for 10-20% of nosocomial bloodstream infections depending on the study. Whilst Candida albicans remains the most frequently isolated species, Candida glabrata may be responsible for as many as 10-25% of all candidaemias. Moreover, C. glabrata is generally less susceptible to the azole antifungals than the majority of other pathogenic yeast species. Thus, a rapid test for the specific identification of isolates of C. glabrata would be useful for patient management if it could be performed at point of isolation, on primary cultures grown on standard mycological media directly from patient specimens. Under certain conditions, C. glabrata rapidly hydrolyses trehalose into glucose. The GLABRATA RTT kit allows detection of the preformed enzyme responsible for this action. This study has assessed GLABRATA RTT as an identification tool specifically at point of isolation. Sixty test isolates were evaluated: 39 clinical isolates of C. glabrata identified at the UK Mycology Reference Laboratory, examples of the recently described genetic relatives of C. glabrata, Candida nivariensis (n = 6) and Candida bracarensis (n = 1), and a selection of other common pathogenic yeast species (n = 14). The test provided results within 30 min. Although 77% (30/39) of confirmed C. glabrata isolates were correctly identified by GLABRATA RTT (positive trehalase test), 23% (9/39) of isolates gave negative or equivocal results. All other yeast species gave negative results. The performance of GLABRATA RTT in this study is compared to previous evaluations of the test which employed isolates pre-cultured on specialised media and to other existing conventional identification methodologies.

Improved identification of yeast species directly from positive blood culture media by combining Sepsityper specimen processing and Microflex analysis with the matrix-assisted laser desorption ionization Biotyper system

Current methods for identification of yeast from blood cultures may take several days after these microorganisms have been observed by Gram stain smears from positive blood cultures. We explored the use of a matrix-assisted laser desorption ionization (MALDI) Biotyper system in combination with Sepsityper specimen processing and Microflex analysis for improved detection and identification of yeast species directly from positive blood culture specimens demonstrating yeast-like organisms by Gram stain. The limit of detection of yeast species in blood culture medium was determined to be 5.9 × 10(5) CFU, with intra- and interstrain coefficients of variation of 1.8 to 3.6% and 2.9%, respectively. A total of 42 yeast-containing positive blood culture specimens were processed, and the identification results were compared to those obtained by routinely used phenotypic methods. Specimens with discrepant results between the Biotyper and phenotypic methods were identified on the basis of internal transcribed spacer region sequencing. The MALDI Biotyper system correctly identified the 42 specimens to species level, including 28 (66.7%) Candida albicans, 8 (19.0%) Candida parapsilosis, and 5 (11.9%) Candida tropicalis isolates and 1 (2.4%) Cryptococcus neoformans isolate. The entire procedure, from specimen extraction to final result reporting, can be completed within 1 h. Our data indicated that the Sepsityper specimen processing and Microflex analysis by the MALDI Biotyper system provide a rapid and reliable tool for yeast species identification directly from positive blood culture media.

Enzymatic substrates in microbiology

Enzymatic substrates are powerful tools in biochemistry. They are widely used in microbiology to study metabolic pathways, to monitor metabolism and to detect, enumerate and identify microorganisms. Synthetic enzymatic substrates have been customized for various microbial assays, to detect an expanding range of both new enzymatic activities and target microorganisms. Recent developments in synthetic enzymatic substrates with new spectral, chemical and biochemical properties allow improved detection, enumeration and identification of food-borne microorganisms, clinical pathogens and multi-resistant bacteria in various sample types. In the past 20 years, the range of synthetic enzymatic substrates used in microbiology has been markedly extended supporting the development of new multi-test systems (e.g., Microscan, Vitek 2, Phoenix) and chromogenic culture media. The use of such substrates enables an improvement in time to detection and specificity over conventional tests that employ natural substrates. In the era of intense developments in molecular biology, phenotypic tests involving enzymatic substrates remain useful to analyse both simple and complex samples. Such tests are applicable to diagnostic and research laboratories all over the world.

Invasive Japanese beetles facilitate aggregation and injury by a native scarab pest of ripening fruits

Invasive species' facilitation, or benefiting, of native species is rarely considered in biological invasion literature but could have serious economic consequences should a non-native herbivore facilitate injury by a native pest of high-value crops. Japanese beetle (JB), Popillia japonica, a polyphagous scarab, facilitates feeding by the obligate fruit-feeding native green June beetle (GJB), Cotinis nitida, by biting into intact grape berries that GJB, which has blunt spatulate mandibles, is otherwise unable to exploit. Here, we show JB further facilitates GJB by contaminating fruits with yeasts, and by creating infection courts for yeasts associated with GJB, that elicit volatiles exploited as aggregation kairomones by GJB. Traps baited with combinations of grapes and beetles were used to show that fruits injured by JB alone, or in combination with GJB, become highly attractive to both sexes of GJB. Such grapes emit high amounts of fermentation compounds compared with intact grapes. Beetle feeding on grape mash induced the same volatiles as addition of winemaker's yeast, and similar attraction of GJB in the field. Eight yeast species were isolated and identified from JB collected from grapevine foliage. Establishment and spread of JB throughout fruit-growing regions of the United States is likely to elevate the pest status of GJB and other pests of ripening fruits in vineyards and orchards.

Yeast identification--past, present, and future methods

The focus of this review is the evolution of biochemical phenotypic yeast identification methods with emphasis on conventional approaches, rapid screening tests, chromogenic agars, comprehensive commercial methods, and the eventual migration to genotypic methods. As systemic yeast infections can be devastating and resistance is common in certain species, accurate identification to the species level is paramount for successful therapy and appropriate patient care.

Evaluation of VITEK 2 and RapID yeast plus systems for yeast species identification: experience at a large clinical microbiology laboratory

A total of 750 clinical yeast isolates were evaluated by two identification systems, VITEK 2 and RapID Yeast Plus, using sequence analysis of the rRNA gene internal transcribed spacer regions as the reference method. The VITEK 2 and RapID systems correctly identified 737 (98.2%) and 716 (95.5%) isolates, respectively.

[Evaluation of the API20C AUX system for the identification of clinically important yeasts]

Fifty yeasts belonging to the genera Candida, Pichia, Saccharomyces, Cryptococcus, Rhodotorula and Trichosporon were identified by classical methods and by the API 20C AUX system. The commercial system correctly identified 92% of the species, with the need for additional tests in 16% of cases. The results were interpreted with good, very good and excellent identification.

Yeast identification in the clinical microbiology laboratory: phenotypical methods

Emerging yeast pathogens are favoured by increasing numbers of immunocompromised patients and by certain current medical practices. These yeasts differ in their antifungal drug susceptibilities, and rapid species identification is imperative. A large variety of methods have been developed with the aim of facilitating rapid, accurate yeast identification. Significant recent commercial introductions have included species-specific direct enzymatic colour tests, differential chromogenic isolation plates, direct immunological tests, and enhanced manual and automated biochemical and enzymatic panels. Chromogenic isolation media demonstrate better detection rates of yeasts in mixed cultures than traditional media, and allow the direct identification of Candida albicans by means of colony colour. Comparative evaluation of rapid methods for C. albicans identification, including the germ tube test, shows that chromogenic media may be economically advantageous. Accurate tests for single species include the Bichrolatex Albicans and Krusei Color tests, both immunologically based, as well as the Remel Rapid Trehalose Assimilation Broth for C. glabrata. Among broad-spectrum tests, the RapID Yeast Plus system gives same-day identification of clinical yeasts, but performance depends on inoculum density and geographic isolate source. The API 20 C AUX system is considered a reference method, but newer systems such as Auxacolor and Fungichrom are as accurate and are more convenient. Among automated systems, the ID 32 C strip, the Vitek Yeast Biochemical Card and the Vitek 2 ID-YST system correctly identify >93% of common yeasts, but the ID-YST is the most accurate with uncommon yeasts, including C. dubliniensis. Spectroscopic methods such as Fourier transformed-infrared spectroscopy offer potential advantages for the future. Overall, the advantages of rapid yeast identification methods include relative simplicity and low cost. For all rapid methods, meticulous, standardized multicenter comparisons are needed before tests are fully accepted.