Comparison between MALDI-TOF MS and MicroScan in the identification of emerging and multidrug resistant yeasts in a fourth-level hospital in Bogotá, Colombia

Identification and antifungal susceptibility patterns of reference yeast strains to novel and conventional agents: a comparative study using CLSI, EUCAST and Sensititre YeastOne methods

Objectives

The aim of this study was to identify and determine the MICs of 13 antifungal drugs, including the novel agents ibrexafungerp, manogepix and rezafungin, against 22 laboratory reference strains from 14 different Candida spp. and allied yeast genera using the EUCAST, CLSI and Sensititre™ YeastOne™ (SYO) methods.

Results

Complete agreement between molecular and proteomics methods was observed for identification. The compounds with the greatest in vitro activity, as indicated by the lowest geometric mean MIC (GM), were manogepix (GM: 0.01), isavuconazole (GM: 0.05) and rezafungin (GM: 0.03-0.07). The overall essential agreement (EA) (within ±0 to ±2 2-fold dilutions) between the reference methods, EUCAST and CLSI, was 95%, with results ranging from 82% (ibrexafungerp) to 100% (amphotericin B, anidulafungin, fluconazole, 5-flucytosine and micafungin). Regarding EA for EUCAST and CLSI compared with SYO, values were 91% and 89%, respectively. Nevertheless, when the MIC values were transformed into log2, significant differences were observed (e.g. fluconazole, ibrexafungerp and 5-flucytosine). At the species level, Candidozyma auris and Candida duobushaemulonii exhibited the highest number of cases with significant differences when comparing the three techniques for each antifungal.

Conclusions

The high EA observed reinforces the reliability of EUCAST, CLSI and SYO in guiding antifungal therapy. However, the differences in EA, particularly for ibrexafungerp and 5-flucytosine, highlight the importance of continued evaluation of these methodologies to ensure consistency. Given that antifungal susceptibility testing plays a critical role in treatment decisions, understanding these variations is essential to prevent potential misclassification of susceptibility profiles, which could impact clinical outcomes.

The Mass Spectrometry Revolution in Clinical Microbiology Part 1: History and Current Applications

The introduction of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has revolutionized infectious disease diagnostics over the past decade. In this review, we will first explore the history of how the once disparate fields of mass spectrometry (MS) and clinical microbiology inextricably merged. We will then review the rapid growth as well as current applications of MALDI-TOF MS in clinical microbiology. In the accompanying review, we will discuss some of the exciting and emerging applications of MS in pathogen detection, identification, and characterization.

Antimicrobial Resistance Profiles of Staphylococcus Isolated from Cows with Subclinical Mastitis: Do Strains from the Environment and from Humans Contribute to the Dissemination of Resistance among Bacteria on Dairy Farms in Colombia?

Staphylococcus is a very prevalent etiologic agent of bovine mastitis, and antibiotic resistance contributes to the successful colonization and dissemination of these bacteria in different environments and hosts on dairy farms. This study aimed to identify the antimicrobial resistance (AMR) genotypes and phenotypes of Staphylococcus spp. isolates from different sources on dairy farms and their relationship with the use of antibiotics. An antimicrobial susceptibility test was performed on 349 Staphylococcus strains (S. aureus, n = 152; non-aureus staphylococci (NAS), n = 197) isolated from quarter milk samples (QMSs) from cows with subclinical mastitis (176), the teats of cows (116), the milking parlor environment (32), and the nasal cavities of milk workers (25). Resistance and multidrug resistance percentages found for S. aureus and NAS were (S. aureus = 63.2%, NAS = 55.8%) and (S. aureus = 4.6%, NAS = 11.7%), respectively. S. aureus and NAS isolates showed resistance mainly to penicillin (10 IU) (54.1% and 32.4%) and ampicillin (10 mg) (50.3% and 27.0%) drugs. The prevalence of AMR Staphylococcus was higher in environmental samples (81.3%) compared to other sources (52.6-76.0%). In S. aureus isolates, the identification of the blaZ (83.9%), aacAaphD (48.6%), ermC (23.5%), tetK (12.9%), and mecA (12.1%) genes did not entirely agree with the AMR phenotype. We conclude that the use of β-lactam antibiotics influences the expression of AMR in Staphylococcus circulating on dairy farms and that S. aureus isolates from the environment and humans may be reservoirs of AMR for other bacteria on dairy farms.

Typing of Candida spp. from Colonized COVID-19 Patients Reveal Virulent Genetic Backgrounds and Clonal Dispersion

Advances in the knowledge of the pathogenesis of SARS-CoV-2 allowed the survival of COVID-19 patients in intensive care units. However, due to the clinical characteristics of severe patients, they resulted in the appearance of colonization events. Therefore, we speculate that strains of Candida spp. isolated from COVID-19 patients have virulent genetic and phenotypic backgrounds involved in clinical worsening of patients. The aim of this work was to virutype Candida spp. strains isolated from colonized COVID-19 patients, analyze their genomic diversity, and establish clonal dispersion in care areas. The virulent potential of Candida spp. strains isolated from colonized COVID-19 patients was determined through adhesion tests and the search for genes involved with adherence and invasion. Clonal association was done by analysis of intergenic spacer regions. Six species of Candida were involved as colonizing pathogens in COVID-19 patients. The genotype analysis revealed the presence of adherent and invasive backgrounds. The distribution of clones was identified in the COVID-19 care areas, where C. albicans was the predominant species. Evidence shows that Candida spp. have the necessary genetic tools to be able colonize the lungs, and could be a possible causal agent of coinfections in COVID-19 patients. The detection of dispersion of opportunistic pathogens can be unnoticed by classical epidemiology. Epidemiological surveillance against opportunistic fungal pathogens in COVID-19 patients is an immediate need, since the findings presented demonstrate the potential virulence of Candida spp.

Laboratory Diagnostic Methods and Antibiotic Resistance Patterns of Staphylococcus aureus and Escherichia coli Strains: An Evolving Human Health Challenge

Raw ground meat is known as a transmission vehicle for biological agents that may be harmful to human health. The objective of the present study was to assess microbiological quality of the ground meats. A total of 280 samples of local and imported chilled meats were randomly collected from retail shops in Buraydah City, Saudi Arabia. The meat samples were microbiologically analyzed using standard methods, peptide mass fingerprinting (PMF) technique, MicroScan Walkaway System (MicroScan) and qPCR System. The imported meat was more bacterially contaminated than local meat, with variable contamination degrees of Staphylococcus aureus (40.33%), Escherichia coli (36.13%), Hafnia alvei (7.56%), Pseudomonas spp. (6.72%), Salmonella spp. (5.88%) and Aeromonas spp. (3.36%). PMF verified all the isolated bacteria by 100%, compared to 75-95% achieved by MicroScan. The gene encoding flagellin (fliC) was recognized in 67.44% of E. coli strains, while the thermonuclease (nuc) and methicillin resistance (mecA) genes were detected in 100% S. aureus and 39.6% of methicillin-resistant S. aureus (MRSA) strains, respectively. The S. aureus and E. coli strains were highly resistant to multiple antibiotics (e.g., ampicillin, amoxicillin-clavulanic acid and cephalothin). For identifying various foodborne pathogens, PMF has been recognized as a powerful and precise analytical method. In light of the increasing use of PMF to detect multidrug-resistant bacteria, this study emphasizes the need for improved ways of treating and preventing pathogens, as well as setting up monitoring systems to guarantee hygiene and safety in meat production.

Species identification, antifungal susceptibility profiles and biofilm formation attributes of Rhodotorula isolates from ocular infections

BACKGROUND

Members of genus Rhodotorula are widely distributed in nature and have been traditionally considered non-pathogenic. Last few decades have seen the yeast as an emerging pathogen. We observed increase in numbers of Rhodotorula isolates from ocular infections in last few years, thus this prospective study was planned.

OBJECTIVES

To identify the species of Rhodotorula isolates from ocular infections. To know the antifungal susceptibilities and study the biofilm formation attributes of the isolates.

MATERIALS AND METHODS

Rhodotorula isolates were speciated using conventional methods, Matrix Assisted Laser Desorption and Ionisation - Time of Flight (MALDI- TOF) and sequencing of ITS region of ribosomal DNA. Antifungal susceptibility testing (AFST) was done using disc diffusion and E-test. Biofilm formation was studied using XTT [2,3-bis (2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetra-zolium-5-carboxanilide] assay.

RESULTS

Twenty four isolates (92.3%) were identified as R. mucilaginosa and two as R. Minuta. AFST showed high MICs against Fluconazole, Amphotericin-B, Caspofungin, Micafungin and Flucytosine; MIC distribution from low to very high against Voriconazole, Itraconazole and Natamycin; and very low MICs against Posaconazole 57.7% of isolates were strong biofilm producers, 23.1% were moderate, and 19.2% were non producers.

CONCLUSIONS

This is the first prospective study on species distribution, antifungal susceptibility and biofilm production attributes of Rhodotorula isolates from ocular infections; also first time demonstrating the utility of proteomics based MALDI-TOF in diagnosing Rhodotorula up to species level. The study has shown high MICs against the conventional azoles, Amphotericin-B and Flucytosine. However, low MICs against Posaconazole and Natamycin give a hope for their possible therapeutic use.

Impact of calmodulin inhibition by fluphenazine on susceptibility, biofilm formation and pathogenicity of caspofungin-resistant Candida glabrata

BACKGROUND

In recent decades, Candida glabrata has emerged as a frequent cause of life-threatening fungal infection. In C. glabrata, echinocandin resistance is associated with mutations in FKS1/FKS2 (β-1,3-glucan synthase). The calmodulin/calcineurin pathway is implicated in response to antifungal stress and calcineurin gene disruption specifically reverses Fks2-mediated resistance of clinical isolates.

OBJECTIVES

We evaluated the impact of calmodulin inhibition by fluphenazine in two caspofungin-resistant C. glabrata isolates.

METHODS

C. glabrata isolates were identified by ITS1/ITS4 (where ITS stands for internal transcribed spacer) sequencing and the echinocandin target FKS1/FKS2 genes were sequenced. Susceptibility testing of caspofungin in the presence of fluphenazine was performed by a modified CLSI microbroth dilution method. The effect of the fluphenazine/caspofungin combination on heat stress (37°C or 40°C), oxidative stress (0.2 and 0.4 mM menadione) and biofilm formation (polyurethane catheter) was analysed. A Galleria mellonella model using blastospores (1 × 109 cfu/mL) was developed to evaluate the impact of this combination on larval survival.

RESULTS

F659del was found in the FKS2 gene of both resistant strains. In these clinical isolates, fluphenazine increased susceptibility to caspofungin and reduced their thermotolerance. Furthermore, the fluphenazine/caspofungin combination significantly impaired biofilm formation in an in vitro polyurethane catheter model. All these features participated in the increasing survival of infected G. mellonella after combination treatment in comparison with caspofungin alone.

CONCLUSIONS

In a repurposing strategy, our findings confirm that calmodulin could provide a relevant target in life-threatening fungal infectious diseases.

Matrix-Assisted Laser Desorption Ionization Time-of-Flight for Fungal Identification

Many studies have shown successful performance of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for rapid yeast and mold identification, yet few laboratories have chosen to apply this technology into their routine clinical mycology workflow. This review provides an overview of the current status of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for fungal identification, including key findings in the literature, processing and database considerations, updates in technology, and exciting future prospects. Significant advances toward standardization have taken place recently; thus, accurate species-level identification of yeasts and molds should be highly attainable, achievable, and practical in most clinical laboratories.

In-house protocol and performance of MALDI-TOF MS in the early diagnosis of bloodstream infections in a fourth-level hospital in Colombia: Jumping to full use of this technology

BACKGROUND

Bloodstream infections (BSIs) are a major cause of mortality in hospitalized patients. Rapid diagnosis is crucial because any delay in the antimicrobial treatment is associated with an increase in adverse patient outcomes. The application of matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) technology directly to blood cultures permits earlier identification of BSIs and facilitates treatment management.

METHODS

A total of 470 positive blood cultures from patient samples were analyzed using Standard Aerobic/F and Anaerobic/F blood culture media. Isolates were identified using conventional identification methods and by the direct method using the MALDI-TOF MS system.

RESULTS

In 470 blood cultures, the direct method showed good identification results (420/470, 89%); specifically, accurate species and genus identification in 283/470 (60%), and only correct genus identification in 137/470 (29%). The direct protocol had better performance for Gram-negative compared to Gram-positive bacteria (97% vs 76%) and was unable to identify the positive blood cultures for both yeasts and some bacteria, mostly Gram-positive (50/470).

CONCLUSIONS

The protocol used here gave good and reliable results, being available up to 24 h earlier, while also leading to better use of MALDI-TOF.

Is the superbug fungus really so scary? A systematic review and meta-analysis of global epidemiology and mortality of Candida auris

BACKGROUND

Candida auris is a new pathogen called "superbug fungus" which caused panic worldwide. There are no large-scale epidemiology studies by now, therefore a systematic review and meta-analysis was undertaken to determine the epidemic situation, drug resistance patterns and mortality of C. auris.

METHODS

We systematically searched studies on the clinical report of Candida auris in Pubmed, Embase and Cochrane databases until October 6, 2019. A standardized form was used for data collection, and then statics was performed with STATA11.0.

RESULTS

It showed that more than 4733 cases of C. auris were reported in over 33 countries, with more cases in South Africa, United States of America, India, Spain, United Kingdom, South Korea, Colombia and Pakistan. C. auirs exhibited a decrease in case count after 2016. Clade I and III were the most prevalent clades with more cases reported and wider geographical distribution. Blood stream infection was observed in 32% of the cases, which varied depending on the clades. Resistance to fluconazole, amphotericin B, caspofungin, micafungin and anidulafungin in C. auris were 91, 12, 12.1, 0.8 and 1.1%. The overall mortality of C. auris infection was 39%. Furthermore, subgroup analyses showed that mortality was higher in bloodstream infections (45%), and lower in Europe (20%).

CONCLUSIONS

Over 4000 cases of C. auris were reported in at least 33 countries, which showed high resistance to fluconazole, moderate resistance to amphotericin B and caspofungin, high sensitivity to micafungin and anidulafungin. The crude mortality for BSI of C. auris was 45% which was similar to some drug-resistant bacteria previously reported. In conclusion, C. auris displayed similar characteristics to some drug resistance organisms. This study depicts several issues of C. auris that are most concerned, and is of great significance for the clinical management.

Evaluation of the Autof MS1000 mass spectrometer in the identification of clinical isolates

BACKGROUND

To evaluate the accuracy and performance of the Autof MS1000 mass spectrometer in bacteria and yeast identification, 2342 isolates were obtained from microbial cultures of clinical specimens (e.g. blood, cerebrospinal fluid, respiratory tract samples, lumbar puncture fluid, wound samples, stool, and urine) collected in 2019 in Henan Provincial People's Hospital. Repetitive strains from the same patient were excluded. We tested the Autof MS1000 and Bruker Biotyper mass spectrometry systems and the classical biochemical identification system VITEK 2/API 20C AUX. Inconsistencies in strain identification among the three systems were identified by 16S rDNA and gene sequencing.

RESULTS

At the species level, the Autof MS1000 and Bruker Biotyper systems had isolate identification accuracies of 98.9 and 98.5%, respectively. At the genus level, the Autof MS1000 and Bruker Biotyper systems were 99.7 and 99.4% accurate, respectively. The instruments did not significantly differ in identification accuracy at either taxonomic level. The frequencies of unreliable identification were 1.1% (26/2342) for the Autof MS1000 and 1.5% (34/2342) for the Bruker Biotyper. In vitro experiments demonstrated that the coincidence rate of the Autof MS1000 mass spectrometer in the identification of five types of bacteria was > 93%, the identification error rate was < 3%, and the no identification rate was 0. This indicates that the Autof MS1000 system is acceptable for identification.

CONCLUSIONS

The Autof MS1000 mass spectrometer can be utilised to identify clinical isolates. However, an upgradation of the database is recommended to correctly identify rare strains.

Development and Validation of an in-House Library of Colombian Candida auris Strains with MALDI-TOF MS to Improve Yeast Identification

: Background: Candida auris is characterized for having a high genetic variability among species. MALDI-TOF MS library contains spectra from only three strains of C. auris, which makes difficult the identification process and gives low scores at the species level. Our aim was to construct and validate an internal library to improve C. auris identification with Colombian clinical strains.

METHODS

From 30 clinical strains, 770 mass spectra were obtained for the construction of the database. The validation was performed with 300 strains to compare the identification results in the BDAL and C. auris Colombia libraries.

RESULTS

Our library allowed a complete, 100% identification of the evaluated strains and a significant improvement in the scores obtained, showing a better performance compared to the Bruker BDAL library.

CONCLUSIONS

The strengthening of the database is a great opportunity to improve the scoring and C. auris identification. Library data are available via ProteomeXchange with identifier PXD016387.