Evaluation of a Novel Laboratory Candiduria Screening Protocol in the Intensive Care Unit

Effect of various concentrations of common organic solvents on the growth and proliferation ability of Candida glabrata and their permissible limits for addition in drug susceptibility testing

Objectives

Dimethyl sulfoxide (DMSO), acetone, ethanol, and methanol are organic solvents commonly used for dissolving drugs in antimicrobial susceptibility testing. However, these solvents have certain antimicrobial activity. Currently, standardized criteria for the selection and dosage of drug solvents in drug susceptibility testing research are lacking. The study aims to provide experimental evidence for the selection and addition limit of drug solvents for the in vitro antifungal susceptibility test of Candida glabrata (C. glabrata).

Methods

According to the recommendation of the Clinical and Laboratory Standards Institute (CLSI) M27-A3, a 0.5 McFarland C. glabrata suspension was prepared and then diluted 1:1,000. Next, a gradient dilution method was used to prepare 20%, 10%, 5%, and 2.5% DMSO/acetone/ethanol/methanol. The mixture was plated onto a 96-well plate and incubated at a constant temperature of 35 °C for 48 h. The inhibitory effects of DMSO, acetone, ethanol, and methanol on C. glabrata growth and proliferation were analyzed by measuring optical density values at 600 nm (OD600 values).

Results

After 48 h incubation, the OD600 values of C. glabrata decreased to different extents in the presence of the four common organic solvents. The decrease in the OD600 values was greater with increasing concentrations within the experimental concentration range. When DMSO and acetone concentrations were higher than 2.5% (containing 2.5%) and methanol and ethanol concentrations were higher than 5.0% (containing 5.0%), the differences were statistically significant compared with the growth control wells without any organic solvent (P < 0.05).

Conclusion

All four organic solvents could inhibit C. glabrata growth and proliferation. When used as solvents for drug sensitivity testing in C. glabrata, the concentrations of DMSO, acetone, ethanol, and methanol should be below 2.5%, 2.5%, 5%, and 5%, respectively.

Rapid preparation of Candida genomic DNA: combined use of enzymatic digestion and thermal disruption

Nucleic acid based molecular technologies are the most promising tools for the early diagnosis of Candida infection. A simple and effective DNA preparation method is of critical for standardizing and applying molecular diagnostics in clinic laboratories. The goal of this study was to develop a Candida DNA preparation method that was quick to do, easy to perform, and bio-safe. Snailase and lyticase were screened and combined in this work to enhance the lysis of Candida cells. The lysis solution composition and metal bath were optimized to boost amplification efficiency and biosafety. A duplex real-time PCR was established to evaluate the sensitivity and specificity of the preparation method. Using the supernatant from the rapid preparation method as templates, the duplex PCR sensitivities for five common Candida species were determined to be as low as 10⁰ CFUs. When compared to conventional preparation methods, the samples prepared by our method showed higher PCR detection sensitivity. PCR identification and ITS sequencing were 100% consistent, which was better than biochemical identification. This study demonstrates a rapid method for Candida DNA preparation that has the potential to be used in clinical laboratories. Meanwhile, the practical application of the method for clinical samples needs to be proven in future investigations.

Candida spp. co-infection in COVID-19 patients with severe pneumonia: Prevalence study and associated risk factors

Background

Invasive fungal infections (IFI) are increasing in prevalence in recent years. In the last few months, the rise of COVID-19 patients has generated a new escalation in patients presenting opportunistic mycoses, mainly by Aspergillus. Candida infections are not being reported yet.

Objectives

We aimed to determine the prevalence of systemic candidiasis in patients admitted to ICUs due to severe pneumonia secondary to SARS-CoV-2 infection and the existence of possible associated risk factors that led these patients to develop candidiasis.

Patients/methods

We designed a study including patients with a confirmed diagnosis of COVID-19.

Results

The prevalence of systemic candidiasis was 14.4%, and the main isolated species were C. albicans and C. parapsilosis. All patients that were tested positive for Candida spp. stayed longer in the ICU in comparison to patients who tested negative. Patients with candidiasis had higher MuLBSTA score and mortality rates and a worse radiological involvement. In our study, Candida spp. isolates were found in patients that were submitted to: tocilizumab, tocilizumab plus systemic steroids, interferon type 1β and Lopinavir-Ritonavir.

Conclusions

Results suggested a high prevalence of systemic candidiasis in severe COVID-19-associated pneumonia patients. Patients with Candidiasis had the worst clinical outcomes. Treatment with tocilizumab could potentialize the risk to develop systemic candidiasis.