Differential growth inhibition as a tool to increase the discriminating power of killer toxin sensitivity in fingerprinting of yeasts

Abstract

A panel of 27 cell-free crude killer toxin preparations were used in fingerprinting 45 Saccharomyces cerevisiae and 11 Saccharomyces exiguus strains. The differential sensitivity to different mycocins was evaluated both as binary data matrix (presence^absence of killing effect), and by considering the growth inhibition areas (measured by agar diffusion well bioassay). The first approach gave an individual fingerprinting of 68% of sensitive strains, whereas the second gave a total and reproducible (P 6 0.01) discrimination of all tested strains. ß

Discrimination between Candida albicans and Other Pathogenic Species of the Genus Candida by Their Differential Sensitivities to Toxins of a Panel of Killer Yeasts

“…Therefore, the resistance of C. albicans isolates to the actions of the killer toxin panel can be considered an objective basis on which to differentiate the isolates from those belonging to other species of the same genus. In addition, in agreement with previous reports (4,5,12), the presence of different clusters of non-C. albicans strains characterized by different sensitivity patterns may also represent an alternative approach in the identification of subspecific entities ( Table 1).…”

“…Compared with data obtained by the use of several commercial identification kits, as reported in the literature (7,8,10,11,13), the identification efficiency of the killer yeast method was also on the same order, but at a significantly lower cost per test. As previously demonstrated (4,5), the method proposed here is extremely sensitive and accurate, the interpretation of results is generally easy and unequivocal, and the method is definitely less subjective than the GT assay (7) and is applicable in the laboratory by technicians untrained in mycology and lacking skill in microscopy. In order to reduce the 48-h incubation time, the procedure may be revised with only a reasonable increase in total cost.…”

“…Because of the recent success of using killer systems for inter-and intraspecific discrimination of ascomycetous and basidiomycetous yeasts (4,5,9,12,14), we evaluated a killer toxin panel by using 314 members of the genus Candida, including 91 isolates of C. albicans and 223 isolates of non-C. albicans species.…”

“…Similar to previous reports (4,5), the differential killer toxin sensitivity patterns were condensed into a "killer sensitivity index," where each one of the four yeasts capable of inhibiting the growth of a given strain was indicated by its reference number, while absence of activity was recorded as 0.…”

Yeast Killer Toxins: Fundamentals and Applications

“…Subsequently, the principle was extended by the inclusion of more killer strains, the use of partially purified toxins and computer-aided data analysis, resulting in an improvement in reproducibility (Polonelli et al 1985;Buzzini and Martini 2000;Buzzini et al 2003Buzzini et al , 2007. Killer toxin sensitivity patterns (KSPs) were shown to discriminate not only different C. albicans strains but also different species of other pathogenic yeasts (Morace et al 1984;Polonelli et al 1985).…”