Abstract :
Introduction: Candida albicans, a predominant yeast pathogen can be easily distinguished from other
non-albicans species in a diagnostic laboratory based on their property to produce germ tubes using human
serum as a routine substrate. As usage of human serum is accompanied with risk of transmission of bloodborne
viral infections, several other media were employed by many clinical laboratories. The aim of this
study was to evaluate the efficacy of four commonly used non-serum liquid media relative to fresh human
serum in germ tube (GT) productivity among various Candida isolates.
Materials and Methods: A total of 146 Candida isolates (96 C. albicans; 47 C. tropicalis; 3 C.
dubliniensis) identified by conventional methods were assessed for germ tube production in five types of
media namely peptone water, Mueller Hinton broth, Trypticase soy broth, Brain Heart infusion broth and
fresh human serum . Results obtained in different media for germ tube production in all Candida isolates
were analysed for sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV)
and accuracy.
Results: All the Candida isolates showed 100% specificity and PPV in all the five-liquid media. Highest
performance in germ tube production (96%) in C. albicans isolates was found in Trypticase soy broth
followed by fresh human serum (95%). Trypticase soy broth was shown to have 96% sensitivity and 97%
accuracy for germ tube formation comparable to human serum with 95% sensitivity and 96.5% accuracy.
Conclusion: Trypticase soy broth can be suggested as a choice medium for GT production in diagnostic
mycology.
Keyword :
Trypticase soy broth, Peptone water germ tube production test sensitivity specificity