Comparative Evaluation of Standard Dilution Method and Commercial Kit for Frozen Plate Antifungal Susceptibility Testing of Yeasts Using 200 Clinical Isolates

A longitudinal study of Candida bloodstream infections in a Japanese university hospital: species distribution, drug susceptibility, clinical features, and mortality predictors

We aimed to detect possible changes in Candida species distribution over time and to know the antifungal susceptibility profile of isolates obtained from patients with bloodstream infection (BSI) due to this pathogen. Risk factors associated with 30-day mortality were also assessed. We conducted a retrospective cohort study of patients diagnosed with Candida BSI at a Japanese university hospital from 2013 to 2021. The change in the distribution pattern of the Candida spp. isolated was examined by considering three successive sub-periods of 3 years each. Risk factors for 30-day mortality were determined using Cox regression analysis. In the entire study period, Candida albicans was the most frequent species (46.7%), followed by Candida glabrata (21.5%) and Candida parapsilosis (18.7%). There was no change in Candida species distribution comparing the three sub-periods analyzed. All isolates were susceptible to micafungin, and most were susceptible to fluconazole, except for C. glabrata. No isolates were resistant to amphotericin B or voriconazole. The overall 30-day mortality was 40.2%. Univariate analysis revealed an association between 30-day mortality and central venous catheter (CVC) removal at any time, high Pitt bacteremia score (PBS), and high Charlson comorbidity index (CCI). Multivariate Cox analysis found that high PBS was the only independent predictor of 30-day mortality; subsequent multivariate Cox regression demonstrated that early CVC removal significantly reduced 30-day mortality. Candida species distribution and antifungal susceptibility profile in our hospital remained similar from 2013 to 2021. Early CVC removal may improve candidemia outcomes.

Multicenter Evaluation of Commercial Frozen Plates for Microdilution Broth Antifungal Susceptibility Testing of Yeasts and Comparison of MIC Limits Recommended in NCCLS M27-A2

A commercial kit, Frozen Plate for Antifungal Susceptibility Testing of Yeasts, Eiken (Eiken Chemical Co., Ltd., Tokyo), was tested in a multi-institute study to evaluate the agreement between interinstitute MICs and National Committee for Clinical Laboratory Standards (NCCLS) M27-A2 recommendation limits of MIC value. The kit was reported as a method equivalent to the standardized guidelines for antifungal susceptibility testing by the Committee for Clinical Laboratory Standards-1994, the Japanese Society for Medical Mycology, and which is widely used in Japan for amphotericin B, flucytosine, fluconazole, miconazole, and itraconazole. The degrees of inter-institute and NCCLS agreements were good to excellent especially with 48-hr incubation for all antifungal agents. However, the percent agreements to NCCLS recommendations against itraconazole were poor. Overall, MIC values obtained using the frozen plate antifungal susceptibility testing kit, with 48-hr incubation, were thought to be reliable and convenient alternatives to the data obtained by the NCCLS M27-A2 reference macrodilution and microdilution method. This kit will allow matching of results between international laboratories. However, the MIC value for itraconazole requires careful interpretation.

[A study for testing the antifungal susceptibility of yeast by the Japanese Society for Medical Mycology (JSMM) method. The proposal of the modified JSMM method 2009]

The Japanese Society for Medical Mycology (JSMM) method used for testing the antifungal susceptibility of yeast, the MIC end point for azole antifungal agents, is currently set at IC(80). It was recently shown, however that there is an inconsistency in the MIC value between the JSMM method and the CLSI M27-A2 (CLSI) method, in which the end- point was to read as IC(50). To resolve this discrepancy and reassess the JSMM method, the MIC for three azoles, fluconazole, itraconazole and voriconazole were compared to 5 strains of each of the following Candida species: C. albicans, C. glabrata, C. tropicalis, C. parapsilosis and C. krusei, for a total of 25 comparisons, using the JSMM method, a modified JSMM method, and the CLSI method. The results showed that when the MIC end- point criterion of the JSMM method was changed from IC(80) to IC(50) (the modified JSMM method) , the MIC value was consistent and compatible with the CLSI method. Finally, it should be emphasized that the JSMM method, using a spectrophotometer for MIC measurement, was superior in both stability and reproducibility, as compared to the CLSI method in which growth was assessed by visual observation.

Antifungal drug susceptibility of Cryptococcus neoformans from clinical sources in Nairobi, Kenya

The serotypes and mating types of 80 clinical isolates of Cryptococcus neoformans from Kenya were studied and subjected to broth microdilution susceptibility testing to amphotericin B (AMP), flucytosin, fluconazole (FLC), itraconazole (ITC) and miconazole (MCZ). The isolates included C. neoformans var. grubii- 75 of 80 (serotype A; 93.7%), C. neoformans var. neoformans- three of 80 (3.8%) and C. neoformans var. gattii- two (serotype B; 2.5%). Mating experiment confirmed all the isolates to be alpha-mating type. Seventy-eight (97.5%) of the isolates had minimum inhibitory concentration (MIC) of < or =0.5 microg ml(-1) to AMP and at 1 microg ml(-1), 100% of the isolates were inhibited. Flucytosin resistance was observed in 21% with MIC in which 90% of the isolates were inhibited (MIC90) of 64 microg ml(-1). Only 23.8% of the strains were susceptible to FLC with 65% susceptible dose-dependent (SDD) and 11.2% resistant. Itraconazole susceptibility was 61.3% while the rest were either SDD or resistant. The MIC90 for ITC and MCZ were 0.5 and 2 microg ml(-1) respectively. The study reports the serotypes, mating types and highlights the existence of azoles resistance in C. neoformans in Nairobi which calls for antifungal drug resistance surveillance as prophylactic use of FLC increases because of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) epidemic in sub-Saharan Africa.