Comparison of 12 liquid media for germ tube production of Candida albicans and C-tropicalis

WOS: 000247263400007PubMed ID: 17576320Infections caused by yeast of the genus Candida are the most common fungal infections, being Candida albicans the most common isolated species among them. The rapid identification of this yeast is mostly based on the production of germ tube in human or animal serum. This study describes the use of 12 different liquid media for germ tube production at 2, 2.5, 3 and 4 h. We examined 193 yeasts, including 157 (81.3%) C. albicans and 36 (18.7%) Candida tropicalis for the production of germ tube. The germ tube production of C. albicans was mostly observed in human serum (98%) followed by rabbit serum (89.8%), brain heart infusion broth (84%) and sheep serum (74.5%) at 2 h. An incubation time exceeding 2 h i.e. 2.5 h or later, C. tropicalis strains were observed to produce germ tubes. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for germ tube production of human serum at 2 h were 98%, 100%, 100% and 92.3% respectively. In all tested sera, an incubation period of more than 2 h improves the sensitivity, but decreases the specificity as well as PPV and NPV of germ tube test (GTT). In conclusion, human serum was observed to be the most appropriate medium to be preferred for GTT, with an incubation period of 2 h

Use of Nucleic Acid Probes for Identification of Mycobacterium tuberculosis Directly from MB/BacT Bottles

The feasibility of using nucleic acid probes directly from positive MB/BacT broth to identify mycobacteria was determined in this study. A total number of 2,727 specimens were cultured into the MB/BacT (Organon Teknika) automated system and on conventional Loweinstein-Jensen (LJ) slants. The Gen-Probe AccuProbe culture identification tests (DNA probes) were used on samples from bottles which were identified as positive for mycobacteria by MB/BacT. Samples of positive MB/BacT broth (0.1 ml) were used directly in the broth culture method for the DNA probes as published by Gen-Probe. Centrifugation of the contents of the bottle was not done prior to probe testing. The number of mycobacteria detected by MB/BacT and LJ was 253 (221 isolates of M. tuberculosis and 32 isolates of mycobacteria other than M. tuberculosis [MOTT]). A total of 96.4% (213 of 221) of the bottles growing M. tuberculosis produced a positive direct DNA probe result for M. tuberculosis complex. One hundred percent (16 of 16) of the bottles growing M. gordonae produced a positive direct DNA probe result for M. gordonae. A total of 3.6% (8 of 221) of the bottles growing M. tuberculosis did not yield a positive direct DNA probe result for M. tuberculosis complex. The testing of subcultures made onto solid media from the positive bottles by AccuProbe identified six of these eight M. tuberculosis isolates. Two (0.9%) M. tuberculosis isolates gave a negative result for the M. tuberculosis probe test applied on the MB/BacT broth and its subculture. The rest of the positive MB/BacT bottles growing MOTT (16 of 32) were negative for M. gordonae, M. avium, M. intracellulare, and M. kansasii probes. The sensitivity and specificity of AccuProbe for the identification of M. tuberculosis and M. gordonae directly from MB/BacT broth were 96.4 and 100% for M. tuberculosis and 100 and 100% for M. gordonae, respectively. The direct testing of positive MB/BacT broth by AccuProbe, without prior centrifugation, allows for the accurate and rapid identification of M. tuberculosis and M. gordonae