Tomato juice as a potential replacement for human serum in germ tube test assay

Abstract

Candida albicans (C. albicans) is the most common opportunistic fungal pathogen often isolated from clinical samples. Traditionally, the differentiation of C. albicans from other Candida species is performed through the germ tube test using human serum. The aim of this study was to assess the use of tomato juice of “Thilina” variety for the differentiation of C. albicans from other non albicans species. This study was carried out using 66 Candida isolates including five Candida standards. Candidal suspension (100 μl) equals to 0.5 McFarland was mixed with 1 ml of fresh human serum and 1 ml of tomato juice, separately. Test tubes were incubated at 37 ºC and the observations were made at 15 minute intervals for two hours. The tomato juice exhibited 97% sensitivity, 100% specificity, 97% positive predictive value, 100% negative predictive value and higher positive correlation (R2 > 0.6) in producing results. There was no statistically significant difference (P = 0.05) in the meantime of initial germ tube production when tomato juice was compared with the routine serum medium. For the first time the study strongly suggests that human serum can be replaced by juice of “Thilina” variety of tomato for the differentiation of C. albicans from non albicans species.

Keywords

• tomato juice
• <i>candida albicans</i>
• differentiation
• germ tube formation
• human serum