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 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.

Fusarium napiforme systemic infection: case report with molecular characterization and antifungal susceptibility tests

Introduction

During the last decades, Fusarium spp. has been reported as a significant cause of disease in humans, especially in immunocompromised patients, who have high risk of invasive life-threatening disease. Fusarium species usually reported as cause of human disease are F. solani, F. oxysporum and F. verticillioides.

Case description

We describe the second case in the literature of disseminated fusariosis caused by Fusarium napiforme, that occurred in a 60-year-old woman with multiple myeloma after subsequent cycles of chemotherapy.

Discussion and Evaluation

We identified the F. napiforme not only by standard morphologic criteria by macroscopic and microscopic characteristics, but also confirmed by molecular biology methods, including sequencing. The antifungal susceptibility of the F. napiforme isolates were tested to seven antifungal drugs; the azoles were the most active drug against all the isolates tested.

Conclusions

Fusarium spp. are of relevance in medical mycology, and their profiles of low susceptibility to antifungal drugs highlight the importance for faster and more accurate diagnostic tests, what can contribute to an earlier and precise diagnosis and treatment.

Antifungal susceptibilities of Cryptococcus neoformans cerebrospinal fluid isolates from AIDS patients in Kenya

Poor susceptibility of Cryptococcus neoformans to fluconazole (FLC) is a matter of concern among clinicians in Africa. The emergence of resistance to FLC was recently reported in Kenya, but it is not known whether it is widespread. Thus, there is need for more antifungal drug susceptibility studies in Kenya. The aim of this study was to measure the in vitro antifungal drug susceptibilities of incident C. neoformans isolates from acquired immunodeficiency syndrome patients in Kenya. Antifungal susceptibility testing was performed in 67 C. neoformans isolates by broth microdilution method as outlined in the Clinical and Laboratory Standards Institute document M27-A3 using FLC, amphotericin B (AMB), voriconazole (VOR), ravuconazole (RAV) and flucytosine (5-FC). Isolates were grown on l-canavanine glycine bromothymol blue medium for serotype identification. Six per cent of the isolates were identified as C. neoformans var. gattii serotype B or C and 94% as C. neoformans var. neoformans. All isolates tested were susceptible to AMB, VOR and RAV (100%), and high susceptibilities were seen to FLC (97%), and 5-FC (90%). Only 3% and 10% of the isolates' susceptibility to FLC and 5-FC, respectively, was dose-dependent or intermediate. These results demonstrate high susceptibilities of incident C. neoformans isolates to FLC and AMB, antifungals used for treatment of cryptococcal meningitis in Kenya.

Comparison of genotypes between environmental and clinical isolates of Cryptococcus neoformans var. grubii based on microsatellite patterns

We applied multilocus microsatellite typing (MLMT) method to investigate the genetic relation between Cryptococcus neoformans var. grubii clinical and environmental isolates in São Paulo, Brazil. This MLMT method includes three functional gene sequences of C. neoformans var. grubii, which are dispersed on three chromosomes. In all, 89 strains (36 clinical and 53 environmental isolates) were analyzed. Of 36 clinical strains, 20 belonged to a major type of MLMT-13 (55.6%). They were mainly isolated from clinical specimens. About 52.8% of strains from the environment belong to a major type of MLMT-36, which are indigenous to environments and which were not isolated from clinical samples. Thus, we recognized two genotypes that distinguish majority of clinical and environmental strains. No differences were found in antifungal susceptibility and capsule size between major environmental and clinical MLMT types.

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.

[Studies on the correlation of the method currently used by the Japanese Society for Medical Mycology and its modified method with the NCCLS M27-A2 microdilution method for azole susceptibility testing of Candida species]

To evaluate the currently used Japanese Society for Medical Mycology (JSMM) method for testing the azole susceptibility of yeasts, the activities of fluconazole and itraconazole were tested against recently collected clinical isolates of Candida spp. (n=946) and compared with the National Committee for Clinical Laboratory Standards (NCCLS) M27-A2 microdilution reference method. Favorable correlation with the M27-A2 method was not seen for isolates of C. albicans, C. tropicalis or other Candida spp., particularly their trailing-growth isolates. However, the degree of correlation and agreement of MIC values were markedly improved when testing was performed by the modified JSMM method in which the end-point to be read was changed from IC80 (for the current JSMM method) to IC50. These results suggest that there is an urgent need to revise the current JSMM method.