Biofilm formation and increased mortality among cancer patients with candidemia in a Peruvian reference center

BACKGROUND

Candidemia is an invasive mycosis with an increasing global incidence and high mortality rates in cancer patients. The production of biofilms by some strains of Candida constitutes a mechanism that limits the action of antifungal agents; however, there is limited and conflicting evidence about its role in the risk of death. This study aimed to determine whether biofilm formation is associated with mortality in cancer patients with candidemia.

METHODS

This retrospective cohort study included patients treated at Peru's oncologic reference center between June 2015 and October 2017. Data were collected by monitoring patients for 30 days from the diagnosis of candidemia until the date of death or hospital discharge. Statistical analyses evaluated the association between biofilm production determined by XTT reduction and mortality, adjusting for demographic, clinical, and microbiological factors assessed by the hospital routinary activities. Survival analysis and bivariate and multivariate Cox regression were used, estimating the hazard ratio (HR) as a measure of association with a significance level of p < 0.05.

RESULTS

A total of 140 patients with candidemia were included in the study. The high mortality observed on the first day of post-diagnosis follow-up (81.0%) among 21 patients who were not treated with either antifungal or antimicrobial drugs led to stratification of the analyses according to whether they received treatment. In untreated patients, there was a mortality gradient in patients infected with non-biofilm-forming strains vs. low/medium and high-level biofilm-forming strains (25.0%, 66.7% and 82.3%, respectively, p = 0.049). In treated patients, a high level of biofilm formation was associated with increased mortality (HR, 3.92; 95% p = 0.022), and this association persisted after adjusting for age, comorbidities, and hospital emergency admission (HR, 6.59; CI: 1.87-23.24, p = 0.003).

CONCLUSIONS

The association between candidemia with in vitro biofilm formation and an increased risk of death consistently observed both in patients with and without treatment, provides another level of evidence for a possible causal association. The presence of comorbidities and the origin of the hospital emergency, which reflect the fragile clinical condition of the patients, and increasing age above 15 years were associated with a higher risk of death.

Clinical Outcome of Patients with Escherichia coli Isolated from Catheter Lumens and/or Peripheral Blood Cultures: A Retrospective Analysis

BACKGROUND

Escherichia coli commonly causes catheter-related bloodstream infection (C-RBSI) in specific populations. The differential time to positivity (DTTP) technique is the recommended conservative procedure for diagnosing C-RBSIs.

METHODS

We conducted a retrospective study of episodes in which E. coli was isolated from catheter lumens obtained using the DTTP technique. Microbiological and clinical data were obtained based on the DTTP technique as either catheter colonization, C-RBSI, or non-C-RBSI.

RESULTS

A total of 89 catheter blood cultures were included, classified as follows: catheter colonization, 33.7%; C-RBSI, 9.0%; and non-C-RBSI, 57.3%. Only 15.7% of the catheters were withdrawn, with no positive catheter-tip cultures. We found no statistically significant differences in catheter type, antibiotic treatment, or clinical outcome among the groups, except for the frequency of catheter lock therapy or in the frequency of successful treatment. Mortality was associated with C-RBSI in only one patient.

CONCLUSION

E. coli bacteremia diagnosed by the DTTP technique was classified as non-catheter-related in most patients. As the majority of the catheters were retained, E. coli bacteremia could not be microbiologically confirmed as catheter-related by the catheter-tip culture. Future studies are needed to assess the profitability of the DTTP technique for diagnosing E. coli C-RBSIs.

Determination of the ability of matrix-assisted laser desorption ionization time-of-flight mass spectrometry to identify high-biofilm-producing strains

Background

The traditional method for assessing the capacity of a microorganism to produce biofilm is generally a static in vitro model in a multi-well plate using the crystal violet (CV) binding assay, which takes 96 h. Furthermore, while the method is simple to perform, its reproducibility is poor.

Objective

We evaluated whether matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) could make it possible to differentiate between high-and low-biofilm-producing microorganisms on 24-h cultures of Staphylococcus aureus and Candida albicans.

Methods

We included 157 strains of S. aureus and 91 strains of C. albicans obtained from the blood cultures of patients with bacteremia/candidemia. We tested biofilm production using the CV binding assay as the gold standard to classify strains as low or high biofilm producers. We then applied MALDI-TOF MS to create a machine learning-based predictive model using 40 strains of S. aureus and C. albicans, each with extreme absorbance values, and validated this approach with the remaining 117 and 51 strains using the random forest algorithm and the support vector machine algorithm, respectively.

Results

Overall, 81.2% of the S. aureus strains (95/117) and 74.5% of the C. albicans strains (38/51) used for validation were correctly categorized, respectively, as low and high-biofilm-producing.

Conclusion

Classification based on MALDI-TOF MS protein spectra enables us to predict acceptable information about the capacity of 24-h cultures of S. aureus and C. albicans to form biofilm.

Antimicrobial Resistance and Biofilms Underlying Catheter-Related Bloodstream Coinfection by Enterobacter cloacae Complex and Candida parapsilosis

Biofilm-associated infections are a public health concern especially in the context of healthcare-associated infections such as catheter-related bloodstream infections (CRBSIs). We evaluated the biofilm formation and antimicrobials resistance (AMR) of Enterobacter cloacae complex and Candida parapsilosis co-isolated from a CRBSI patient. Antimicrobial susceptibility of central venous catheters (CVCs) and hemoculture (HC) isolates was evaluated, including whole genome sequencing (WGS) resistome analysis and evaluation of gene expression to obtain insight into their AMR determinants. Crystal violet assay was used to assess dual biofilm biomass and microscopy was used to elucidate a microorganism’s distribution within biofilms assembled on different materials. Bacteria were multidrug-resistant including resistance to colistin and beta-lactams, likely linked to the mcr-9-like phosphoethanolamine transferase and to an ACT family cephalosporin-hydrolyzing class C beta-lactamase, respectively. The R398I and Y132F mutations in the ERG11 gene and its differential expression might account for C. parapsilosis resistance to fluconazole. The phenotype of dual biofilms assembled on glass, polystyrene and polyurethane depends on the material and how biofilms were initiated by one or both pathogens. Biofilms assembled on polyurethane were denser and richer in the extracellular polymeric matrix, and microorganisms were differently distributed on the inner/outer surface of the CVC.

Prevalence of biofilms in Candida spp. bloodstream infections: A meta-analysis

CONTEXT

Candida-related infections are nowadays a serious Public Health Problem emerging multidrug-resistant strains. Candida biofilm also leads bloodstream infections to invasive systemic infections.

OBJECTIVE

The present meta-analysis aimed to analyze Candida biofilm rate, type, and antifungal resistance among hospitalized patients between 1995 and 2020.

DATA SOURCES

Web of Science, Scopus, PubMed, and Google Scholar databases were searched for English papers using the following medical subject heading terms (MESH): "invasive candidiasis"; "bloodstream infections"; "biofilm formation"; "biofilm-related infections"; "mortality"; and "prevalence".

STUDY SELECTION

The major inclusion criteria included reporting the rate of biofilm formation and the prevalence of biofilm-related to Candida species, including observational studies (more exactly, cohort, retrospective, and case-control studies). Furthermore, data regarding the mortality rate, the geographical location of the study set, and the use of anti-fungal agents in clinical isolates were also extracted from the studies.

DATA EXTRACTION

Independent extraction of articles by 2 authors using predefined data fields, including study quality indicators.

DATA SYNTHESIS

A total of 31 studies from publicly available databases met our inclusion criteria. The biofilm formation in the data set varied greatly from 16 to 100% in blood samples. Most of the studies belonged to Europe (17/31) and Asia (9/31). Forest plot showed a pooled rate of biofilm formation of 80.0% (CI: 67-90), with high heterogeneity (Q = 2567.45, I2 = 98.83, τ2 = 0.150) in random effects model (p < 0.001). The funnel plot and Egger's linear regression test failed to find publication bias (p = 0.896). The mortality rate in Candida-related bloodstream infections was 37.9% of which 70.0% were from biofilm-associated infections. Furthermore, Candida isolates were also characterized in low, intermediate, or high biofilm formers through their level of biofilm mass (crystal violet staining or XTT assays) after a 24h growth. When comparing between countries, statistical differences were obtained (p = 0.0074), showing the lower and higher biofilm prevalence values in Italy and Spain, respectively. The prevalence of low, intermediate, and high biofilms were 36.2, 18.9, and 35.0% (p < 0.0001), respectively. C. tropicalis was the prevalent species in high biofilm formation (67.5%) showing statistically significant differences when compared to other Candida species, except for C. krusei and C. glabrata. Finally, the rates of antifungal resistance to fluconazole, voriconazole, and caspofungin related to biofilm were 70.5, 67.9 and 72.8% (p < 0.001), respectively.

CONCLUSIONS

Early detection of biofilms and a better characterization of Candida spp. bloodstream infections should be considered, which eventually will help preserve public health resources and ultimately diminish mortality among patients.

PVC grafted zinc oxide nanoparticles as an inhospitable surface to microbes

Antimicrobial Polyvinyl chloride (PVC) was obtained by covalent bonding of zinc oxide nanoparticles, which have gained important achievements in antimicrobial fields because of their auspicious properties. This was achieved by grafting mercaptopropyltrimethoxysilane onto PVC, followed by the growth of zinc oxide nanoparticles covalently bonded on the polymer surface. In this study, the relationship between the physicochemical features of modified-surface PVC and antimicrobial activity on Staphylococcus aureus and Candida albicans was investigated. Zinc oxide with controllable morphologies (rods, rod flowers, and petal flowers) was synthesized on the polymer surface by tuning merely base-type and concentration using a hydrothermal process. The antimicrobial activity was more pronounced for rod flower morphology, because of their differences in microscopic parameters such as specific Zn-polar planes. This work provides an important hint for the safe use of PVC for biomedical devices by the structure surface tuning without injuring polymer bulk properties and a reduced risk of the covalently bonded nanoparticle dispersion in the host and the environment.

Candidemia Candida albicans clusters have higher tendency to form biofilms than singleton genotypes†

The capacity of Candida spp. to form biofilms allows them to attach either to living or inert surfaces, promoting their persistence in hospital environments. In a previous study, we reported strain-to-strain variations in Candida spp. biofilm development, suggesting that some genotypes may be greater biofilm formers than others. In this study, we hypothesize that isolates pertaining to clusters may be found more frequently in the environment due to their ability to form biofilms compared to singleton genotypes. Two hundred and thirty-nine Candida spp. isolates (78 clusters) from candidemia patients admitted to 16 hospitals located in different cities and countries-and the same number of singleton genotypes used as controls-were tested in terms of biofilm formation using the crystal violet and the XTT reduction assays. Candida albicans clusters showed higher biofilm formation in comparison to singleton genotypes (P < .01). The biofilms formed by intra-hospital C. albicans clusters showed higher metabolic activity (P < .05). Furthermore, marked variability was found among species and type of cluster. We observed that the higher the number of isolates, the higher the variability of biofilm production by isolates within the cluster, suggesting that the production of biofilm by isolates of the same genotype is quite diverse and does not depend on the type of cluster studied. In conclusion, candidemia Candida spp. clusters-particularly in the case of C. albicans-show significantly more biomass production and metabolic activity than singleton genotypes.

Impact of biofilm production by Candida species and antifungal therapy on mortality of patients with candidemia

BACKGROUND AND OBJECTIVES

Few studies have investigated the clinical outcomes of patients with candidemia caused by Candida species with different levels of biofilm formation. We aimed to investigate the impact of antifungal therapy on the outcome of candidemia caused by Candida species that were categorised as low biofilm formers (LBFs), moderate biofilm formers (MBFs), and high biofilm formers (HBFs).

METHODS

Adults with candidemia caused by LBF and HBF/MBF Candida species that were susceptible to fluconazole and caspofungin were included to investigate the impact of treatment with fluconazole vs an echinocandin on 30-day crude mortality.

RESULTS

In total, 215 patients with candidemia received fluconazole and 116 patients received an echinocandin. In multivariate analysis, Pittsburgh bacteremia score ≥ 4 (adjusted odds ratio [AOR] =2.42; 95% confidence interval [CI], 1.32-4.41), malignancy (AOR = 3.45; 95% CI, 1.83-6.51), not removing the central venous catheter within 48 hours of a positive blood culture (AOR = 4.69; 95% CI, 2.61-8.45), and treatment with fluconazole for candidemia due to HBF/MBF Candida spp. (AOR = 2.23; 95% CI, 1.22-4.06) were independent factors associated with 30-day mortality. Of the 165 patients infected by HBF/MBF Candida isolates, those who received azole therapy had a significantly higher sepsis-related mortality rate than those who received echinocandin therapy (44.9% [49/109] vs 26.8% [15/56], P = .03).

CONCLUSIONS

There was a trend of an independent association between fluconazole treatment and poor outcomes in the patients infected by HBF/MBF Candida strains.

Does the composition of polystyrene trays affect Candida spp. biofilm formation?

The biofilm formation ability of Candida species seems to have a role in the prognosis of patients with candidemia. Biofilm formation is usually tested using 96 well flat bottom polystyrene microtiter plates, although the type of plastic used is not commonly reported. This study compares biofilm formation by Candida spp. on six types of plates from three brands (three non-tissue-treated and three tissue-treated). Thirty isolates of each of the following species were selected: C. albicans, C. parapsilosis, C. glabrata, C. tropicalis, as well as 15 isolates of C. krusei (n = 135 isolates) from patients with candidemia. Biofilm production was evaluated by measuring biomass production and metabolic activity. Our results show higher biomass production and metabolic activity of biofilms formed on non-tissue-treated plates in comparison to those formed on tissue-treated plates (P < .001). We only found significant differences in metabolic activity of biofilms formed on non-tissue-treated plates (P < .003). All comparisons including biofilm formation and metabolic activity among plates of the same brand yielded higher biofilm formation on non-treated plates compared to treated plates (P < .001). Significant difference in biomass production by C. parapsilosis was only seen when comparing between the various tissue-treated plastics (P < .03). In contrast, comparisons of different non-tissue-treated tray brands yielded significant metabolic activity differences for all species except for C. parapsilosis (P < .05). Biofilm formation and metabolic activity is significantly affected by the plastic composition of non-tissue-treated trays leading to increased biofilm formation.

Is biofilm production a prognostic marker in adults with candidaemia?

OBJECTIVES

The role of biofilm production in the outcome of candidaemia remains under discussion. Current evidence relies on variable biofilm detection methods while evaluating distinct clinical end points. We aimed to determine the impact of biofilm production measured by metabolic activity (MA) and biomass (BM) on the prognosis of adults with candidaemia.

METHODS

Retrospective cohort including 280 adults with candidaemia admitted from 2010 to 2016. BM was assessed using crystal violet binding stain and the XTT reduction assay was used to detect MA. Strains were classified as high and moderate-low biofilm producers according to published cut-offs. The primary outcome was overall mortality within 7 and 30 days. The secondary outcome was unfavourable prognosis defined as metastatic infection, admission to an intensive care unit due to the severity of candidaemia, or death within 30 days.

RESULTS

High BM and high MA were detected in 90 (32.1%) and 114 (40.7%) of the 280 isolates, respectively. Comparison of high and moderate-low biofilm forming isolates revealed no correlation between biofilm production and 7-day mortality (BM high 15/90 (16.7%) versus moderate-low 24/190 (12.6%); MA high 12/114 (10.5%) versus moderate-low 27/166 (16.3%)), 30-day mortality (BM high 34/90 (37.8%) versus moderate-low 61/190 (32.1%); MA high 33/114 (28.9%) versus moderate-low 62/166 (37.3%)), or unfavourable prognosis (BM high 45/90 (50.0%) versus moderate-low 73/190 (38.4%); MA high 41/114 (36.0%) versus moderate-low 77/166 (46.4%)).

CONCLUSIONS

Biofilm production was not a predictor of mortality or of unfavourable prognosis in adults with candidaemia.

The role of biofilm forming on mortality in patients with candidemia: a study derived from real world data

BACKGROUND

Evaluation of the role on patient mortality exerted by biofilm forming (BF) Candida strains, by using predictive clinical data.

METHODS

Eighty-nine strains isolated from Candida bloodstream infection, occurring in two Italian University Hospitals, were employed in this study. A random forest (RF) model was built with a procedure of iterative selection of the risk factors potentially able to predict the probability of death. The similarity between patient conditions and Bayesian clustering was calculated in order to evaluate the role of predictors in the stratification of the death risk.

RESULTS

Three different groups of patients with different probability of death were obtained with a RF approach: Group 1 (mortality in 33.3% of cases), Group 2 (death in 50% of cases), and Group 3 (mortality in 76.9% of cases). The comparison between these three groups showed that BF correlated well with increased mortality in patients, admitted for medical diagnosis, with high APACHE II score and treated with azoles. Early treatment within 24 h between candidemia diagnosis and the beginning of antifungal therapy was associated with the lowest of BF rate and mortality.

CONCLUSIONS

BF by Candida spp. seems to be clinically associated with increased mortality especially in medical patients with higher Apache II score or treated with azoles.

Exploring ecological modelling to investigate factors governing the colonization success in nosocomial environment of Candida albicans and other pathogenic yeasts

Two hundred seventy seven strains from eleven opportunistic species of the genus Candida, isolated from two Italian hospitals, were identified and analyzed for their ability to form biofilm in laboratory conditions. The majority of Candida albicans strains formed biofilm while among the NCAC species there were different level of biofilm forming ability, in accordance with the current literature. The relation between the variables considered, i.e. the departments and the hospitals or the species and their ability to form biofilm, was tested with the assessment of the probability associated to each combination. Species and biofilm forming ability appeared to be distributed almost randomly, although some combinations suggest a potential preference of some species or of biofilm forming strains for specific wards. On the contrary, the relation between biofilm formation and species isolation frequency was highly significant (R² around 0.98). Interestingly, the regression analyses carried out on the data of the two hospitals separately were rather different and the analysis on the data merged together gave a much lower correlation. These findings suggest that, harsh environments shape the composition of microbial species significantly and that each environment should be considered per se to avoid less significant statistical treatments.

The Role of Antifungals against Candida Biofilm in Catheter-Related Candidemia

Catheter-related bloodstream infection (C-RBSI) is one of the most frequent nosocomial infections. It is associated with high rates of morbidity and mortality. Candida spp. is the third most common cause of C-RBSI after coagulase-negative staphylococci and Staphylococcus aureus and is responsible for approximately 8% of episodes. The main cause of catheter-related candidemia is the ability of some Candida strains-mainly C. albicans and C. parapsilosis-to produce biofilms. Many in vitro and in vivo models have been designed to assess the activity of antifungal drugs against Candida biofilms. Echinocandins have proven to be the most active antifungal drugs. Potential options in situations where the catheter cannot be removed include the combination of systemic and lock antifungal therapy. However, well-designed and -executed clinical trials must be performed before firm recommendations can be issued.

Extracellular DNA release confers heterogeneity in Candida albicans biofilm formation

Background

Biofilm formation by Candida albicans has shown to be highly variable and is directly associated with pathogenicity and poor clinical outcomes in patients at risk. The aim of this study was to test the hypotheses that the extracellular DNA release by C. albicans is strain dependent and is associated with biofilm heterogeneity.

Results

Initially, biofilm formed by C. albicans high biofilm formers (HBF) or low biofilm formers (LBF) were treated with DNase to find whether eDNA play a role in their biofilm formation. Digestion of biofilm eDNA significantly reduced the HBF biofilm biomass by five fold compared to untreated controls. In addition, quantification of eDNA over the period of biofilm formation by SYBR green assay demonstrate a significantly higher level of 2 to 6 fold in HBF compared to LBF. Biochemical and transcriptional analyses showed that chitinase activity and mRNA levels of chitinase genes, a marker of autolysis, were upregulated in 24 h biofilm formation by HBF compared to LBF, indicating autolysis pathway possibly involved in causing variation. The biofilm biomass and eDNA release by single (∆cht2, ∆cht3) and double knockout (∆cht2/∆cht3) chitinase mutants were significantly less compared to their parental strain CA14, confirming the role of chitinases in eDNA release and biofilm formation. Correlation analysis found a positive correlation between chitinases and HWP1, suggesting eDNA may release during the hyphal growth. Finally, we showed a combinational treatment of biofilms with DNase or chitinase inhibitor (acetazolamide) plus amphotericin B significantly improved antifungal susceptibility by 2 to 8 fold.

Conclusions

Collectively, these data show that eDNA release by C. albicans clinical isolates is variable and is associated with differential biofilm formation. Digestion of biofilm eDNA by DNase may provide a novel therapeutic strategies to destabilise biofilm growth and improves antifungal sensitivity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-014-0303-6) contains supplementary material, which is available to authorized users.