Evaluation of Vitek 2 for identification of yeasts in the clinical laboratory

Changing Trends of Candida Species and Antifungal Susceptibility Profile of Candida Bloodstream Isolates: A 5-Year Retrospective Survey

Background: Candida species have emerged as one of the most common causes of bloodstream infections (BSIs). There are limited data on the distribution of Candida spp. and susceptibility by year. Objectives: In this study, we analyzed changes in the distribution of Candida spp. and their antifungal susceptibility profiles from blood cultures. Methods: Records from January 2016 to December 2020 were obtained from the microbiology laboratory in Istanbul. Antifungal susceptibility tests were performed using the VITEK 2 compact system and evaluated according to EUCAST breakpoints. A total of 241 unique candidemia episodes were included in this study. Results: Candida albicans was the predominant pathogen (n = 95, 39.42%), followed by C. parapsilosis (n = 82, 34.02%), C. glabrata (n = 18, 7.47%), C. tropicalis (n = 17, 7.05%), C. krusei (n = 15, 6.22%), and other Candida spp. (n = 14, 5.79%). There was no statistically significant difference in the percentage of episodes of Candida spp. After data analysis, a tendency to shift from C. albicans to C. parapsilosis was observed in the period analyzed in this study. Candida albicans was the most common species in intensive care units (ICUs), hematology and hemopoietic stem cell transplantation units, and surgical clinics, with C. parapsilosis predominant in medical clinics. In general, micafungin susceptibility was the highest, and fluconazole was the lowest. There was reduced sensitivity to fluconazole and voriconazole for C. albicans and C. parapsilosis over 5 years. Conclusions: Detecting changes in the distribution of Candida spp. and antifungal susceptibility over time will lead to the selection of appropriate empirical therapy and monitor phenomena of antifungal resistance. Empirical treatment with antifungal agents is associated with high costs, toxicities, and risk of antifungal resistance. Therefore, it is mandatory to determine and monitor Candida spp. and antifungal susceptibility testing to select appropriate antifungal agents.

Identification of candida albicans and nonalbicans candida resistant species in tobacco users and oral squamous cell carcinoma patients: Comparison of HiCrome agar and automated VITEK 2 system

Introduction:

Candida is most common fungal pathogen in the immunocompromised and medically ill patients. Higher prevalence of Candida albicans has been reported in tobacco users and oral squamous cell carcinoma (OSCC) patients which may be due to immunosuppression. Recently, emergence of nonalbicans candida (NAC) species resistant to conventional antifungal treatment has been observed that requires accurate identification of organisms at species level for reduction of progression of suspicious oral lesions toward malignancy.

Aims and Objectives:

To detect and compare the prevalence of C. albicans and NAC species smokeless tobacco chewers, histopathologically confirmed oral squamous cell carcinoma patients and the normal individuals. Effectiveness of automated Vitek 2 system in comparison to HiCrome agar color media in the identification of the candida species was also evaluated.

Methodology:

One hundred and fifty patients (90 males, 60 females) aged between 20 and 76 years were divided into three groups: Group I individuals with habit of chewing Gutka, and betel quid/pan masala with or without tobacco, Group II individuals with clinically and histopathologically confirmed oral squamous cell carcinoma and Group III comprised of controls. Salivary samples were cultured on HiCrome agar color media and results were compared with those of Vitek 2 system in the accurate identification of candida species. Data were statistically analyzed and Chi-square test was used to estimate the effectiveness of color and Vitek method in the identification of candida species in all the three groups. P < 0.05 was considered to be statistically significant.

RESULTS:

HiCrome agar color method identified six candida isolates C. albicans, Candida tropicalis, Candida krusei and Candida glabrata isolates in all the three groups, with 0.00 unidentified organisms (P = 0.00001) whereas VITEK 2 system identified five isolates of candida; C. albicans, Candida famat, Candida ciferri, Candida gulleri, C. tropicalis, unidentified organisms were observed in 26% of subjects. Further confirmation by supplemental tests indicated the presence of two or three organisms of different species/or subspecies with low reactivity biopattern. Higher incidence of opportunistic infections was seen in Group II OSCC patients (P = 0.00001).

Conclusion:

The results suggested that there is shift toward NAC species, with higher species diversity in OSCC patients followed by gutka, betel quid/pan masala with or without tobacco users. Conventional agar media culture methods of species identification should be used in conjunction with automated Vitek 2 method for better control of candida-associated oral cancer.

Current Aspects in the Biology, Pathogeny, and Treatment of Candida krusei, a Neglected Fungal Pathogen

Fungal infections represent a constant and growing menace to human health, because of the emergence of new species as causative agents of diseases and the increment of antifungal drug resistance. Candidiasis is one of the most common fungal infections in humans and is associated with a high mortality rate when the fungi infect deep-seated organs. Candida krusei belongs to the group of candidiasis etiological agents, and although it is not isolated as frequently as other Candida species, the infections caused by this organism are of special relevance in the clinical setting because of its intrinsic resistance to fluconazole. Here, we offer a thorough revision of the current literature dealing with this organism and the caused disease, focusing on its biological aspects, the host-fungus interaction, the diagnosis, and the infection treatment. Of particular relevance, we provide the most recent genomic information, including the gene prediction of some putative virulence factors, like proteases, adhesins, regulators of biofilm formation and dimorphism. Moreover, C. krusei veterinary aspects and the exploration of natural products with anti-C. krusei activity are also included.

Candida Bloodstream Infection: Changing Pattern of Occurrence and Antifungal Susceptibility over 10 Years in a Tertiary Care Saudi Hospital

Background

Candida has emerged as one of the most important pathogens that cause bloodstream infection (BSI).Understanding the current Candida BSI trends, the dominant species causing disease and the mortality associated with this infection are crucial to optimize therapeutic and prophylaxis measures.

Objectives

To study the epidemiology and to evaluate the risk factors, prognostic factors, and mortality associated with candidemia and to compare these findings with previously published studies from Saudi Arabia.

Design

A retrospective medical record review.

Setting

Tertiary hospital in Riyadh.

Patients and Methods

The analysis included all cases of Candida blood stream infection who are >18 years old over the period from 2013 to 2018. Continuous variables were compared using the parametric T-test while categorical variables were compared using the Chi-squared test.

Main Outcome Measure

Incidence, resistance, and hospital outcomes in Candida blood stream infection.

Sample Size

324 patients.

Results

Three hundred and twenty-four episodes of Candida blood stream infections were identified. Median age of patients was 49.7 SD ± 28.1 years, and 53% of patients were males. More than half of the patients had an underlying disease involving the abdomen or laparotomy, 78% had an indwelling intravenous catheter, and 62% had suffered a bacterial infection within 2 weeks prior to candidemia. Candida albicans represents 33% of all isolates with decreasing trend overtime. There was an increase in the number of nonalbicans Candida overtime with Candida tropicalis in the lead (20%). Use of broad spectrum antibiotics (82%), prior ICU admission (60%) and use of central venous catheters (58%) were the most prevalent predisposing factors of candidemia. Azole resistance was variable overtime. Resistance to caspofungin remained very low (1.9%). Fourteen days crude mortality was 37% for ICU patients and 26.7% in non-ICU patients, while hospital crude mortality was 64.4% and 46.7%, respectively.

Conclusion

There is an increasing trend of nonalbicans Candida blood stream infection. Fluconazole resistance remained low to C. albicans. Most isolates remain susceptible to caspofungin, voriconazole, and amphotericin B. Candida bloodstream infection is associated with high 14-day hospital mortality.

Predicting candidemia in the internal medicine wards: a comparison with gram-negative bacteremia-a retrospectives study

INTRODUCTION

Risk factors for candidemia in the internal medicine wards (IMW) are poorly characterized. Their elucidation might assist in early diagnosis and treatment.

OBJECTIVES

We aimed to elucidate predictors of candidemia in the IMWs comparing them to patients with gram-negative bacteremia (GNB).

METHODS

A retrospective study of consecutive patients with candidemia in IMWs in Beilinson hospital (2007-2016) was performed. Patient demographics, comorbidities, and clinical characteristics were documented. The comparator group was GNB patients.

RESULTS

Sixty-two patients with candidemia were compared with 178 patients with GNB. Candidemic patients were younger and with less body mass index > 20 kg/m² (73 ± 15 vs. 78 ± 10, P = 0.01; 44% vs. 60%, P = <0.0001,respectively). In multivariate model, underweight, prior cephalosporin use, and central venous catheters (CVCs) were significantly associated with candidemia [odds ratio (OR) = 0.2, 95% confidence interval (CI) 0.07-0.4; OR = 4, 95% CI 1.3-11; and OR = 4, 95% CI 1.5-12, respectively].

CONCLUSION

Underweight, recent cephalosporin exposure, and CVCs were statistically significant predictors of candidemia in the IMW. Using these predictors might aid in recognizing high-risk patients for candidemia in the IMWs, leading to earlier appropriate empirical treatment.

Chronic use of oral iron supplements is associated with poor clinical outcomes in patients with gram-negative bacteremia

An unabsorbed dietary iron supplementation can modify the colonic microbiota equilibrium and favor the growth of pathogenic strains over barrier strains. Nevertheless, the impact of oral iron supplements (OIS) use on the clinical outcomes of patients with gram-negative bacteremia (GNB) has not been evaluated. To explore the impact of OIS on the outcomes of patients with GNB. A retrospective study conducted in a tertiary hospital including patients with GNB during 2011-2016. The entire cohort was divided into chronic OIS users (study group) and nonusers (control group). The two groups were compared for the study outcomes, septic shock at presentation, length of hospital stay (LOS), and short-term mortality. The study cohort included 232 patients; 44 patients in the study group and 188 in the control one. There was no any significant difference in demographic and comorbidities characteristics between the two groups. Escherichia coli comprised the majority of bacteria (69%), while the urinary tract was the main source of the bacteremia. OIS alone and after adjustment was significantly associated with septic shock at presentation (OR = 2, CI95% [1.03-5], p = 0.04 and OR = 5, CI95% [1.4-15], p = 0.01, respectively). By multivariate analysis, OIS was significantly associated with 30-day mortality (OR = 3, CI95% [1.05-7], p = 0.04), but had no impact on LOS (16 + 23 vs. 12 + 15, p = 0.9). There is a significant association between chronic OIS exposure and increased adverse outcomes in patients with GNB. These findings might have important clinical implications.

Identification of Fungal Pathogens in Otomycosis and Their Drug Sensitivity: Our Experience

Introduction  Otomycosis is a common problem in otolaryngology practice. However, we usually encounter some difficulties in its treatment because many patients show resistance to antifungal agents, and present high recurrence rate. Objectives  To determine the fungal pathogens that cause otomycosis as well as their susceptibility to the commonly used antifungal agents. Additionally, to discover the main reasons for antifungal resistance. Methods  We conducted an experimental descriptive study on 122 patients clinically diagnosed with otomycosis from April 2016 to April 2017. Aural discharge specimens were collected for direct microscopic examination and fungal culture. In vitro antifungal susceptibility testing was performed against the commonly used antifungal drugs. We tested the isolated fungi for their enzymatic activity. Results  Positive fungal infection was found in 102 samples. The most common fungal pathogens were Aspergillus and Candida species, with Aspergillus niger being the predominant isolate (51%). The antifungal susceptibility testing showed that mold isolates had the highest sensitivity to voriconazole (93.48%), while the highest resistance was to fluconazole (100%). For yeast, the highest sensitivity was to nystatin (88.24%), followed by amphotericin B (82.35%), and the highest resistance was to terbinafine (100%), followed by Itraconazole (94.12%). Filamentous fungi expressed a high enzymatic ability, making them more virulent. Conclusion  The Aspergillus and Candida species are the most common fungal isolates in otomycosis. Voriconazole and Nystatin are the medications of choice for the treatment of otomycosis in our community. The high virulence of fungal pathogens is owed to their high enzymatic activity. Empirical use of antifungals should be discouraged.

Are the Conventional Commercial Yeast Identification Methods Still Helpful in the Era of New Clinical Microbiology Diagnostics? A Meta-Analysis of Their Accuracy

Accurate identification of pathogenic species is important for early appropriate patient management, but growing diversity of infectious species/strains makes the identification of clinical yeasts increasingly difficult. Among conventional methods that are commercially available, the API ID32C, AuxaColor, and Vitek 2 systems are currently the most used systems in routine clinical microbiology. We performed a systematic review and meta-analysis to estimate and to compare the accuracy of the three systems, in order to assess whether they are still of value for the species-level identification of medically relevant yeasts. After adopting rigorous selection criteria, we included 26 published studies involving Candida and non-Candida yeasts that were tested with the API ID32C (674 isolates), AuxaColor (1,740 isolates), and Vitek 2 (2,853 isolates) systems. The random-effects pooled identification ratios at the species level were 0.89 (95% confidence interval [CI], 0.80 to 0.95) for the API ID32C system, 0.89 (95% CI, 0.83 to 0.93) for the AuxaColor system, and 0.93 (95% CI, 0.89 to 0.96) for the Vitek 2 system (P for heterogeneity, 0.255). Overall, the accuracy of studies using phenotypic analysis-based comparison methods was comparable to that of studies using molecular analysis-based comparison methods. Subanalysis of studies conducted on Candida yeasts showed that the Vitek 2 system was significantly more accurate (pooled ratio, 0.94 [95% CI, 0.85 to 0.99]) than the API ID32C system (pooled ratio, 0.84 [95% CI, 0.61 to 0.99]) and the AuxaColor system (pooled ratio, 0.76 [95% CI, 0.67 to 0.84]) with respect to uncommon species (P for heterogeneity, <0.05). Subanalysis of studies conducted on non-Candida yeasts (i.e., Cryptococcus, Rhodotorula, Saccharomyces, and Trichosporon) revealed pooled identification accuracies of ≥98% for the Vitek 2, API ID32C (excluding Cryptococcus), and AuxaColor (only Rhodotorula) systems, with significant low or null levels of heterogeneity (P > 0.05). Nonetheless, clinical microbiologists should reconsider the usefulness of these systems, particularly in light of new diagnostic tools such as matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, which allow for considerably shortened turnaround times and/or avoid the requirement for additional tests for species identity confirmation.

Rapid identification of yeast isolates from clinical specimens in critically ill trauma ICU patients

Purpose:

The purpose was to evaluate the performance of a commercially available chromogenic Candida speciation media and the Vitek 2 ID system for the identification of medically important yeasts and yeast-like organisms in a routine clinical microbiology laboratory.

Materials and Methods:

A total of 429 non duplicate, consecutive yeast strains were included during the 3.5-year study period. The performance of the Vitek 2 ID system and a chromogenic agar medium was evaluated against the gold standard conventional phenotypic and biochemical identification method for speciation of yeast isolates from trauma patients.

Results:

Candida tropicalis (64%) was the most common Candida species, followed by Candida albicans (14%), Candida rugosa (7%), and Candida parapsilosis (6.5%). Of the 429 isolates, 183 could be identified to species level by all the three methods. Agreement between the chromogenic agar method and conventional methods was 80% for Candida tropicalis, 100% for Candida rugosa, 89% for Candida albicans, and 77% for Candida parapsilosis. Vitek 2 had lower sensitivity, with agreement of 49% for Candida tropicalis, 100% for Candida rugosa, 39% for Candida albicans, and 31% for Candida parapsilosis.

Conclusion:

Thus, in long-term ICU patients, an increasing trend of isolating nonalbicans Candida spp. continues. The chromogenic agar medium is a convenient and economic method to identify commonly isolated species in busy clinical microbiology laboratories.

Comparative evaluation of three commercial identification systems using common and rare bloodstream yeast isolates

The commercial yeast identification systems API ID32C, Auxacolor, and Vitek were evaluated using 251 molecularly identified bloodstream isolates and 2 reference strains, representing a total of 35 species (6 common and 29 rare). Correct identification rates were higher for common species (Auxacolor, 95%; API ID32C, 94%; Vitek, 92%) than for rare species (Auxacolor, 43%; API ID32C, 56%; Vitek, 64%). All systems performed equally among the former, and Vitek performed best among the latter.

Evaluation of new colorimetric vitek 2 yeast identification card by use of different source media

The new colorimetric Vitek 2 YST card was evaluated for identification of yeasts (136 strains) with respect to the influence of different source media. The Vitek 2 YST card achieved satisfactory results for all yeast species tested, with the exception of Candida guilliermondii, Candida norvegensis, Candida parapsilosis, Candida rugosa, and Candida tropicalis. After simple additional tests, 93.7% of all the strains tested were correctly identified. A significant influence of the isolation medium on the identification rate could not be observed.

Candida albicans masquerading as gram-negative bacilli in the clinical laboratory

We report misidentification of Candida albicans as Gram-negative bacilli owing to colony morphology on MacConkey agar and subsequent inoculation into GN-ID/VITEK-2. ATCC and clinical Candida strains (n = 24) masqueraded as various bacterial species when experimentally inoculated into GN-ID cards. This phenomenon should be considered when peculiar taxa or susceptibility are encountered.

Microbiological evaluation of the new VITEK 2 Neisseria-Haemophilus identification card

VITEK 2 is an automated identification system for diverse bacterial and fungal species. A new card (the Neisseria-Haemophilus [NH] card) for the identification of Neisseria spp., Haemophilus spp., and other fastidious gram-negative or gram-variable microorganisms has been developed, but its performance in a routine clinical laboratory has not yet been evaluated. In this study, a total of 188 bacterial strains belonging to the genera Actinobacillus, Campylobacter, Capnocytophaga, Cardiobacterium, Eikenella, Gardnerella, Haemophilus, Kingella, Moraxella, and Neisseria were investigated. The NH card was able to identify 171 strains (91%) correctly without the need for extra tests; one strain (0.5%) was misidentified, and five strains (2.7%) could not be classified. Eleven strains (5.8%) were identified with a low level of discrimination, and simple additional tests were required to increase the correct-identification rate to 96.8%. The results were available within 6 h. Based on these results, the new VITEK 2 NH card appears to be a good method for the identification of diverse groups of fastidious organisms, which would otherwise require testing with multiple systems. However, more work is needed to evaluate the performance of VITEK 2 with regard to Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella bacteria because of the insufficient number of strains tested in this study. Moreover, further reduction of the detection time would be desirable.

Rapid simultaneous detection and identification of six species Candida using polymerase chain reaction and reverse line hybridization assay

The aim of this study was to develop and evaluate PCR based reverse line blot (RLB) hybridization assay for rapid detection of the most common Candida isolates from clinical specimens. A pair of universal primers targeting the ITS2 region of the gene from 28S rRNA to 5.8S rRNA was designed for PCR amplification of DNA from 6 Candida species (C. albicans, C. tropicalis, C. krusei, C. glabrata, C. parapsilosis, C. dubliniensis), the reverse primer was biotin labeled. PCR products, which were 302-441 bp length, were hybridized with 6 specific oligonucleotides probes immobilized on a nylon membrane. These 6 probes proved specific (they hybridized with only their target molecules). The assay was shown to be sensitive in detecting yeast to a concentration of 10 CFU/ml. This method was used to test 100 isolates and 200 vaginal swabs. The results agreed with those of culture for all but 3 of 100 isolates. Sequencing was performed on these 3 samples and confirmed that the culture results were inaccurate. Our results show the PCR-RLB positive rate (49%) is higher than culture (39%) and smear microscopic screening (27%) (P<0.05). In conclusion, the PCR/RLB developed in this study is specific and offers increased sensitivity compared to culture for the detection of Candida species in swab specimens. Moreover, the improved detection of cases of polycandidal candidiasis is advantageous.

Evaluation of VITEK 2 and RapID yeast plus systems for yeast species identification: experience at a large clinical microbiology laboratory

A total of 750 clinical yeast isolates were evaluated by two identification systems, VITEK 2 and RapID Yeast Plus, using sequence analysis of the rRNA gene internal transcribed spacer regions as the reference method. The VITEK 2 and RapID systems correctly identified 737 (98.2%) and 716 (95.5%) isolates, respectively.