SciELO - Scientific Electronic Library Online

vol.52 issue3Geographical distribution and intra-domiciliary capture of sylvatic triatomines in La Convención province, Cusco, PeruDengue in an elderly patient author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand




Related links


Revista do Instituto de Medicina Tropical de São Paulo

On-line version ISSN 1678-9946

Rev. Inst. Med. trop. S. Paulo vol.52 no.3 São Paulo May/June 2010 



Differentiation of Candida dubliniensis from Candida albicans with the use of killer toxins


Avaliação das toxinas killer na diferenciação entre Candida albicans e Candida dubliniensis



Liliane A. ScheidI; Débora A. Nunes MarioI; Elizabeth Maria Heins-VaccariII; Janio Morais SanturioIII; Sydney Hartz AlvesI,III

ICurso de Pós graduação em Ciências Farmacêuticas. Universidade Federal de Santa Maria. Santa Maria, RS, Brasil
IIFaculdade de Medicina. Universidade de São Paulo. São Paulo, SP, Brasil
IIIDepartamento de Microbiologia e Parasitologia. Universidade Federal de Santa Maria, Santa Maria, RS, Brasil

Correspondence to




The aim of this study was to report the ability of killer toxins, previously used as biotyping techniques, as a new tool to differentiate C. albicans from C. dubliniensis. The susceptibility of C. albicans and C. dubliniensis to killer toxins ranged from 33.9 to 93.3% and from 6.67 to 93.3%, respectively.

Keywords: Killer toxins; Biotyping: Candida dubliniensis.


Avaliou-se a capacidade das toxinas killer, previamente utilizadas na biotipagem de C. albicans, como método para diferenciar C. albicans de C. dubliniensis. A susceptibilidade de C. albicans e C. dubliniensis às toxinas killer variou de 33,9% a 93,3% para C. albicans e de 6,67% a 93,3% para C. dubliniensis.



Killer toxins are glucoprotein compounds secreted by Hansenula and Picchia strains, which may cause pores in the cytoplasmatic membrane of the Candida albicans, inhibiting its growth. Because the susceptibility of C. albicans to killer toxins is variable, the phenomenon was employed as a method to biotype different C. albicans strains2,3,6. In recent years, biotyping techniques have been advantageously substituted by molecular methods.

Since 1995 when C. dubliniensis was proposed as a new species of Candida genera, many techniques have been studied in order to phenotypically differentiate this species from C. albicans because both species are germ tube positive and form chlamydospores in corn meal agar14.

Nowadays, the definitive identification of C. dubliniensis requires molecular methods and thus old phenotypic tests have been re-evaluated, as well as new tests having been proposed for phenotypic identification. Among them, we can emphasize: niger seed agar13, sunflower agar7, sesame seed agar9 based on chlamydoconidia production, and colonial morphology. Other tests include absence of opacity on Tween 80 agar4, coaggregation of C. dubliniensis with Fusobacterium nucletaum5, inability of C. dubliniensis to grow in hypertonic broth (NaCl 6.5%)1, and to grow at temperatures of 42 °C or 45 °C10. Among commercially disposable methods, the CHROMagar Candida8 and Bichro-Dublin Fumouze®12 are worthy of mention.

The aim of this study was to investigate the ability to differentiate C. albicans from C. dubliniensis based on susceptibilities to killer toxins as proposed by POLONELLI et al. (1983). The yeasts employed for the assays were: Hansenula sp Stumm 1034 (K1), Pichia sp Stumm 1035 (K2), Hansenula anomala UM (K3), Hansenula anomala CBS 5759 (K4), Hansenula anomala Ahearn UN 866 (K5), Hansenula californica Ahearn WC 40 (K6), Hansenula canadensis Ahearn WC 41 (K7), Hansenula dimmenae Ahearn WC 44 (K8), and Hansenula mrakit Ahearn W1C51 (K9)

The susceptibility of C. albicans and C. dubliniensis to killer toxins ranged from 33.3% to 93.3% and from 6.67% to 93.3%, respectively. Twenty-one biotypes were registered and the code numbers 111, 611, and 211 were the most frequently observed in both species. No biotypes occurred as a particular characteristic of C. dubliniensis and thus the killer toxins were unable to differentiate C. albicans from C. dubliniensis. As far as we know, this technique had not been explored until now.



1. Alves SH, Milan EP, Laet Sant'ana P, Oliveira LO, Santurio JM, Colombo AL. Hypertonic Sabouraud broth as a simple and powerful test for Candida dubliniensis screening. Diagn Microbiol Infect Dis. 2002;43:85-6.         [ Links ]

2. Bendová O. The killer phenomenon in yeasts. Folia Microbiol. 1986;31:422-33.         [ Links ].

3. Candido RC, Fischman O, Zaror L, Ito IY. Diferenciação de cepas de Candida albicans pelo sistema killer. Rev Soc Bras Med Trop. 1995;28:321-4.         [ Links ]

4. Dolapçi I, Tekeli A, Arikan S. Evaluation of the Tween 80 test for detection of the lipolytic activity of various Candida species and its utility in differentiation of C. albicans and C. dubliniensis. Mikrobiyol Bul. 2004;38:429-33.         [ Links ]

5. Jabra-Rizk MA, Falkler WA Jr, Merz WG, Kelley JI, Baqui AA, Meiller TF. Coaggregation of Candida dubliniensis with Fusobacterium nucleatum. J Clin Microbiol. 1999;37:1464-8.         [ Links ]

6. Kagan BL. Mode of action of yeats killer toxin: channel formation in lipid bilayer membranes. Nature. 1983;302:709-11.         [ Links ]

7. Khan ZU, Ahmad S, Mokaddas E, Chandy R. Simplified sunflower (Helianthus annus) seed agar for differentiation of Candida dubliniensis from Candida albicans. Clin Microbiol Infect. 2004;10:590-2.         [ Links ]

8. Kirkpatrick WR, Revankar SG, McAtee RK, Lopez-Ribot JL, Fothergill AW, McCarthy DI et al. Detection of Candida dubliniensis in oropharyngeal samples from human immunodeficiency virus-infected patients in North America by primary CHROMagar Candida screening and susceptibility testing of isolates. J Clin Microbiol 1998;36:3007-12.         [ Links ]

9. Loreto ES, Bolzan AR, Linares CE, Boff E, Santurio JM, Alves SH. Evaluation of 5 new media containing extracts of seeds applied to Candida dubliniensis screening. Diagn Microbiol Infect Dis. 2006;55:191-3.         [ Links ]

10. Pinjon E, Sullivan D, Salkin I, Shanley D, Coleman D. Simple, inexpensive, reliable method for differentiation of Candida dubliniensis. J Clin Microbiol. 1998;36:2093-5.         [ Links ]

11. Polonelli L, Archibusacci C, Sestito M, Morace G. Killer system: a simple method for differentiating Candida albicans strains. J Clin Microbiol. 1983;17:774-80.         [ Links ]

12. Sahand IH, Moragues MD, Robert R, Quindós G, Pontón J. Evaluation of Bichro-Dubli Fumouze to distinguish Candida dubliniensis from Candida albicans. Diagn Microbiol Infect Dis. 2006;55:165-7.         [ Links ]

13. Staib P, Morschhauser J. Chlamydospore formation on Staib agar as a species-specific characteristics of Candida dubliniensis. Mycoses. 1999;42:521-4.         [ Links ]

14. Sullivan D, Coleman D. Candida dubliniensis: characteristics and identification. J Clin Microbiol. 1998;36:329-34.         [ Links ]



Correspondence to:
Sydney Hartz Alves
Rua dos Andradas 1985/201
97010-033 Santa Maria, RS, Brasil

Received: 2 February 2010
Accepted: 6 May 2010

Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License