Mixed bloodstream infections involving bacteria and Candida spp

Time-lapse mesoscopy of Candida albicans and Staphylococcus aureus dual-species biofilms reveals a structural role for the hyphae of C. albicans in biofilm formation

Polymicrobial infection with Candida albicans and Staphylococcus aureus may result in a concomitant increase in virulence and resistance to antimicrobial drugs. This enhanced pathogenicity phenotype is mediated by numerous factors, including metabolic processes and direct interaction of S. aureus with C. albicans hyphae. The overall structure of biofilms is known to contribute to their recalcitrance to treatment, although the dynamics of direct interaction between species and how it contributes to pathogenicity is poorly understood. To address this, a novel time-lapse mesoscopic optical imaging method was developed to enable the formation of C. albicans/S. aureus whole dual-species biofilms to be followed. It was found that yeast-form or hyphal-form C. albicans in the biofilm founder population profoundly affects the structure of the biofilm as it matures. Different sub-populations of C. albicans and S. aureus arise within each biofilm as a result of the different C. albicans morphotypes, resulting in distinct sub-regions. These data reveal that C. albicans cell morphology is pivotal in the development of global biofilm architecture and the emergence of colony macrostructures and may temporally influence synergy in infection.

Solving polymicrobial puzzles: evolutionary dynamics and future directions

Polymicrobial infections include various microorganisms, often necessitating different treatment methods than a monomicrobial infection. Scientists have been puzzled by the complex interactions within these communities for generations. The presence of specific microorganisms warrants a chronic infection and impacts crucial factors such as virulence and antibiotic susceptibility. Game theory is valuable for scenarios involving multiple decision-makers, but its relevance to polymicrobial infections is limited. Eco-evolutionary dynamics introduce causation for multiple proteomic interactions like metabolic syntropy and niche segregation. The review culminates both these giants to form evolutionary dynamics (ED). There is a significant amount of literature on inter-bacterial interactions that remain unsynchronised. Such raw data can only be moulded by analysing the ED involved. The review culminates the inter-bacterial interactions in multiple clinically relevant polymicrobial infections like chronic wounds, CAUTI, otitis media and dental carries. The data is further moulded with ED to analyse the niche colonisation of two notoriously competitive bacteria: S.aureus and P.aeruginosa. The review attempts to develop a future trajectory for polymicrobial research by following recent innovative strategies incorporating ED to curb polymicrobial infections.

Clinical characteristics and prognostic risk factors of candidemia in non-neutropenic patients: a retrospective cohort study

This study aimed to determine the clinical characteristics and the prognostic risk factors in non-neutropenic patients with candidemia. Data were retrospectively collected through the medical record information system. Non-neutropenic patients with candidemia were relatively aged, with a more than one-third rate of in-hospitalization mortality. In multivariate analysis, APACHE II score (adjusted odds ratio [aOR], 1.138; 95% confidence interval [CI], 1.067-1.213), septic shock (aOR, 5.704; 95% CI, 2.639-12.326) and RRT (aOR, 16.152; 95% CI, 2.628-99.275) (all P < 0.01) were independent related with non-survivors. In conclusion, non-neutropenic patients with candidemia have a high in-hospitalization mortality, and APACHE II, septic shock, and RRT are independently factors.

Evaluation of the Qvella FAST System and the FAST-PBC cartridge for rapid species identification and antimicrobial resistance testing directly from positive blood cultures

Blood culture diagnostics require rapid and accurate identification (ID) of pathogens and antimicrobial susceptibility testing (AST). Standard procedures, involving conventional cultivation on agar plates, may take up to 48 hours or more until AST completion. Recent approaches aim to shorten the processing time of positive blood cultures (PBC). The FAST System is a new technology, capable of purifying and concentrating bacterial/fungal pathogens from positive blood culture media and producing a bacterial suspension called "liquid colony" (LC), which can be further used in downstream analyses (e.g., ID and AST). Here, we evaluated the performance of the FAST System LC generated from PBC in comparison to our routine workflow including ID by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using Sepsityper, AST by automatized MicroScan WalkAway plus and directly inoculated disk diffusion (DD), and MICRONAUT-AM for yeast/fungi. A total of 261 samples were analyzed, of which 86.6% (226/261) were eligible for the comparative ID and AST analyses. In comparison to the reference technique (culture-grown colonies), ID concordance of the FAST System LC and Sepsityper was 150/154 (97.4%) and 123/154 (79.9%), respectively, for Gram positive; 67/70 (95.7%) and 64/70 (91.4%), respectively, for Gram negative. For AST, categorical agreement (CA) of the FAST System LC in comparison to the routine workflow for Gram-positive bacteria was 96.1% and 98.7% for MicroScan and DD, respectively. Similar results were obtained for Gram-negative bacteria with 96.6% and 97.5% of CA for MicroScan and DD, respectively. Taken together, the FAST System LC allowed the laboratory to significantly reduce the time to obtain correct ID and AST (automated MicroScan) results 1 day earlier and represents a promising tool to expedite the processing of PBC.

Clinical and Microbiological Characteristics of Candidemia Cases in Saudi Arabia

Purpose

Candidemia and antifungal resistance are major healthcare challenges. The aim of this study is to describe the frequency of candidemia cases, distribution of Candida spp., and the associated risk factors for mortality in an academic institution in Saudi Arabia over an 18-month period. We also evaluated the susceptibility patterns of Candida blood isolates.

Methods

Candidemia cases were collected from King Fahad Hospital of the University over the period between July 1st, 2020 through December 31st, 2021. They were prospectively reviewed for the preceding risk factors and antifungal (AF) susceptibility, testing results to fluconazole (FL), voriconazole (VO), itraconazole (IT), posaconazole (PO), caspofungin (CASP), anidulafungin (AND), micafungin (MYC), flucytosine (FLC) and amphotericin B (AMPB) using a broth microdilution kit (Sensititre™ YeastOne).

Results

A total of 48 candidemia isolates were included that were isolated from 43 patients. The median age of cases was 62 ± 23.3 years (60.4% males and 83% ICU patients). Independent risk factors for mortality at 30 days in candidemia patients were age, COVID-19 co-infection, and use of tocilizumab. The most commonly isolated species were C. glabrata and C. parapsilosis (22.9% each) followed by C. albicans (18.75%). AF resistance for ≥1 antifungal was detected in 39.3% of 33 cases tested, with no cross-resistance identified. Resistance rates for each AF were as follows: FL (18%), VO (6%), IT (6%), PO (9%) and AMPB (3%). No resistance was seen for echinocandins apart from one C. krusei strain showing an intermediate result for CASP.

Conclusion

The study showed an overall high rate of non-albicans Candida, with the predominance of C. parapsilosis and C. glabrata, representing a therapeutic challenge. AF resistance rate was high which emphasizes the importance of continuing surveillance and providing accurate and reliable tools in the laboratories for rapid speciation and susceptibility testing.

Diagnostic performance and clinical impact of blood metagenomic next-generation sequencing in ICU patients suspected monomicrobial and polymicrobial bloodstream infections

Introduction

Early and effective application of antimicrobial medication has been evidenced to improve outcomes of patients with bloodstream infection (BSI). However, conventional microbiological tests (CMTs) have a number of limitations that hamper a rapid diagnosis.

Methods

We retrospectively collected 162 cases suspected BSI from intensive care unit with blood metagenomics next-generation sequencing (mNGS) results, to comparatively evaluate the diagnostic performance and the clinical impact on antibiotics usage of mNGS.

Results and discussion

Results showed that compared with blood culture, mNGS detected a greater number of pathogens, especially for Aspergillus spp, and yielded a significantly higher positive rate. With the final clinical diagnosis as the standard, the sensitivity of mNGS (excluding viruses) was 58.06%, significantly higher than that of blood culture (34.68%, P<0.001). Combing blood mNGS and culture results, the sensitivity improved to 72.58%. Forty-six patients had infected by mixed pathogens, among which Klebsiella pneumoniae and Acinetobacter baumannii contributed most. Compared to monomicrobial, cases with polymicrobial BSI exhibited dramatically higher level of SOFA, AST, hospitalized mortality and 90-day mortality (P<0.05). A total of 101 patients underwent antibiotics adjustment, among which 85 were adjusted according to microbiological results, including 45 cases based on the mNGS results (40 cases escalation and 5 cases de-escalation) and 32 cases on blood culture. Collectively, for patients suspected BSI in critical condition, mNGS results can provide valuable diagnostic information and contribute to the optimizing of antibiotic treatment. Combining conventional tests with mNGS may significantly improve the detection rate for pathogens and optimize antibiotic treatment in critically ill patients with BSI.

Novel evidence on sepsis-inducing pathogens: from laboratory to bedside

Sepsis is a life-threatening condition and a significant cause of preventable morbidity and mortality globally. Among the leading causative agents of sepsis are bacterial pathogens Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes, along with fungal pathogens of the Candida species. Here, we focus on evidence from human studies but also include in vitro and in vivo cellular and molecular evidence, exploring how bacterial and fungal pathogens are associated with bloodstream infection and sepsis. This review presents a narrative update on pathogen epidemiology, virulence factors, host factors of susceptibility, mechanisms of immunomodulation, current therapies, antibiotic resistance, and opportunities for diagnosis, prognosis, and therapeutics, through the perspective of bloodstream infection and sepsis. A list of curated novel host and pathogen factors, diagnostic and prognostic markers, and potential therapeutical targets to tackle sepsis from the research laboratory is presented. Further, we discuss the complex nature of sepsis depending on the sepsis-inducing pathogen and host susceptibility, the more common strains associated with severe pathology and how these aspects may impact in the management of the clinical presentation of sepsis.

BD BACTEC™ Mycosis IC/F culture vials for fungemia diagnosis and follow-up: a retrospective study from 2013 to 2020

This retrospective study compared the BD BACTEC™ Mycosis IC/F with the BD BACTEC™ Plus Aerobic/F and BD BACTEC™ Lytic Anaerobic/F culture vials (i.e., standard vials) for fungemia diagnosis at Nîmes University Hospital, France. From 2013 to 2020, 57 blood samples were concomitantly collected in the 3 culture vial types. For 43.8% of these samples, all vials were positive for yeast. The mean time to positivity was shorter (32.0 hours vs 44.2 hours; -12.2 hours) and longer (89.4 hours vs 33.7 hours; +55.7 hours) with the BD BACTEC™ Mycosis IC/F culture vials than with the other culture vials in patients without and with antifungal treatment, respectively. Moreover 31.6% and 24.6% of samples were positive only with the standard vials and with the BD BACTEC™ Mycosis IC/F culture vials, respectively. The BD BACTEC™ Mycosis IC/F culture vials are useful for the initial fungemia diagnosis (before any treatment) because they provide faster results.

Valorization of Invasive Plant Extracts against the Bispecies Biofilm Staphylococcus aureus-Candida albicans by a Bioguided Molecular Networking Screening

Invasive plants efficiently colonize non-native territories, suggesting a great production of bioactive metabolites which could be effective antibiofilm weapons. Our study aimed to look for original molecules able to inhibit bispecies biofilm formed by S. aureus and C. albicans. Extracts from five invasive macrophytes (Ludwigia peploides, Ludwigia grandiflora, Myriophyllum aquaticum, Lagarosiphon major and Egeria densa) were prepared and tested in vitro against 24 h old bispecies biofilms using a crystal violet staining (CVS) assay. The activities of the extracts reducing the biofilm total biomass by 50% or more were comparatively analyzed against each microbial species forming the biofilm by flow cytometry (FCM) and scanning electron microscopy. Extracts active against both species were fractionated. Obtained fractions were analyzed by UHPLC-MS/MS and evaluated by the CVS assay. Chemical and biological data were combined into a bioactivity-based molecular networking (BBMN) to identify active compounds. The aerial stem extract of L. grandiflora showed the highest antibiofilm activity (>50% inhibition at 50 µg∙mL−1). The biological, chemical and BBMN investigations of its fractions highlighted nine ions correlated with the antibiofilm activity. The most correlated compound, identified as betulinic acid (BA), inhibited bispecies biofilms regardless of the three tested couples of strains (ATCC strains: >40% inhibition, clinical isolates: ≈27% inhibition), confirming its antibiofilm interest.

Incidence, clinical characteristics, risk factors and outcomes of patients with mixed Candida/bacterial bloodstream infections: a retrospective study

Purpose

The mixed Candida/bacterial bloodstream infections (mixed C/B-BSIs) is worthy of particular attention recently, and we analyzed the incidence, co-pathogens, clinical characteristics, risk factors, and outcomes of mixed C/B-BSIs compared with monomicrobial candidemia (mono-candidemia) in adult patients in China.

Methods

All hospitalized adults with candidemia were recruited for this retrospective observational study from January 1, 2013, to December 31, 2019.

Results

Of the 296 patients with candidemia, 78 cases (26.3%) were mixed C/B-BSIs. Candida albicans (C. albicans) was the most common Candida species among all candidemia, and Klebsiella pneumoniae (K. pneumoniae) was the most concomitant bacteria (30.6%), followed by Acinetobacter baumannii (A. baumannii) (12.9%) and Enterococcus faecium (E. faecium) (11.8%) in mixed C/B-BSIs. In the multivariable analysis, prior β-lactams exposure [adjusted odds ratio (aOR), 1.97; 95% confidence interval (CI), 1.01–3.87], burn injury (aOR, 6.35; 95% CI 1.82–22.21) and continuous renal replacement therapy (CRRT) (aOR, 3.00; 95% CI 1.46–6.17) were independent risk factors for mixed C/B-BSIs. Compared with mono-candidemia, patients with mixed C/B-BSIs developed with more proportion of septic shock (55.1% vs. 39.9%, P < 0.05), prolonged stay in ICU [22.0(12.0–57.0) vs. 9.5(0.0–37.0) days, P < 0.001] and longer mechanical ventilation time [19.0(4.5–40.8) vs. 6.0(0.0–24.8) days, P < 0.001]. The in-hospital mortality in patients with mixed C/B-BSIs was higher than those with mono-candidemia (59.0% vs. 34.9%, P < 0.001). Survival analysis revealed that 28-day and 60-day mortality were significantly higher in patients with mixed C/B-BSI than in those with mono-candidemia (57.7% vs. 31.7%, P < 0.001; 59.0% vs. 34.9%, P < 0.001; respectively).

Conclusions

There is a high rate of mixed C/B-BSIs cases among candidemia, and K. pneumoniae is the predominant coexisting species. Prior β-lactams exposure, burn injury, and CRRT are independent risk factors for mixed C/B-BSIs. The mortality of patients with mixed C/B-BSIs is significantly higher than those with mono-candidemia, this deserves further attention for clinicians.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-022-00538-y.

Candida albicans biofilms: antifungal resistance, immune evasion, and emerging therapeutic strategies

Candida albicans is a fungal pathogen that can form biofilms on medical devices and host tissue, resulting in serious, life-threatening infections. These fungal biofilms are inherently resistant to traditional antifungal therapies and the host immune system; therefore, biofilm-associated infections are a huge clinical challenge. This review summarizes the most important insights into C. albicans biofilm-associated antifungal drug resistance mechanisms and immune evasion strategies. In addtion, this review also discusses the strategies for antifungal drug use to combat these processes, providing further evidence for novel drugs research and clinical therapies.

Pediatric Candida Bloodstream Infections Complicated with Mixed and Subsequent Bacteremia: The Clinical Characteristics and Impacts on Outcomes

Background: Pediatricians face a therapeutic challenge when patients with Candida bloodstream infections (BSIs) simultaneously have positive bacterial culture. We aim to characterize the clinical characteristics of pediatric Candida BSIs complicated with mixed bacteremia and subsequent bacterial infections, risk factors and impacts on outcomes. Methods: All episodes of pediatric Candida BSIs between 2005 and 2020 from a medical center in Taiwan were reviewed. Mixed Candida/bacterial BSIs were defined as isolation of a bacterial pathogen from blood cultures obtained within 48 h before or after the onset of Candida BSI. The clinical features and impacts of mixed Candida/bacterial BSIs were investigated. Results: During the study period, 320 patients with a total of 365 episodes of Candida BSIs were identified and analyzed. Mixed Candida/bacterial BSIs were 35 episodes (9.6%). No significant difference was found between mixed Candida/bacterial BSIs and monomicrobial Candida BSIs in terms of patient demographics, Candida species distributions, most chronic comorbidities or risk factors. Patients with mixed Candida/bacterial BSIs were associated with a significantly higher risk of subsequent bacteremia (51.4% vs. 21.2%, p < 0.001) and a relatively higher candidemia-attributable mortality rate (37.2% vs. 22.4%, p = 0.061) than those with monomicrobial Candida BSIs. Mixed Candida/bacterial BSIs were not an independent risk factor of treatment failure or final mortality according to multivariate logistic regression analyses. Conclusions: The clinical significance of mixed Candida/bacterial BSIs in children included a longer duration of septic symptoms, significantly higher likelihood to have subsequent bacteremia, and relatively higher risk of candidemia attributable mortality.

Molecular Methodologies for Improved Polymicrobial Sepsis Diagnosis

Polymicrobial sepsis is associated with worse patient outcomes than monomicrobial sepsis. Routinely used culture-dependent microbiological diagnostic techniques have low sensitivity, often leading to missed identification of all causative organisms. To overcome these limitations, culture-independent methods incorporating advanced molecular technologies have recently been explored. However, contamination, assay inhibition and interference from host DNA are issues that must be addressed before these methods can be relied on for routine clinical use. While the host component of the complex sepsis host–pathogen interplay is well described, less is known about the pathogen’s role, including pathogen–pathogen interactions in polymicrobial sepsis. This review highlights the clinical significance of polymicrobial sepsis and addresses how promising alternative molecular microbiology methods can be improved to detect polymicrobial infections. It also discusses how the application of shotgun metagenomics can be used to uncover pathogen/pathogen interactions in polymicrobial sepsis cases and their potential role in the clinical course of this condition.

Candidemia in patients with head and neck cancer: mortality and a novel risk factor

PURPOSE

Candidemia is a bloodstream infection (BSI) by Candida spp. and is associated with high mortality. However, there have been few reports about BSI in head and neck cancer (HNC). We aimed to evaluate the impact of candidemia in patients with HNC and compared it with bacteremia.

STUDY DESIGN

A multicenter retrospective study.

METHODS

We retrospectively analyzed 83 BSI episodes in HNC (2011 to 2020) and divided them into the candidemia and bacteremia groups. We then compared the survival rate and risk factors for candidemia between the groups.

RESULTS

The overall cumulative incidence (risk) of candidemia in BSI was 12 out of 83 episodes (14.5%). The 1-year mortality for the bacteremia and candidemia groups was 33.3% and 58.3%, respectively (log-rank p = 0.041). Broad-spectrum antibiotics (odds ratio [OR]: 29.5; 95% confidence interval [CI], 2.49-350), mucositis (OR 11.0; 95% CI, 1.52-80.1), and malignant wounds (OR 79.5; 95% CI 1.33-4737) were significant risk factors for candidemia in HNC.

CONCLUSIONS

Candidemia causes high mortality in patients with HNC. To our knowledge, malignant wounds have not been previously reported as a risk factor for candidemia. For early diagnosis and treatment of candidemia, risk factors should be considered, and antifungal therapy started earlier.

Synergistic Effects of Fluconazole Combined with Doxycycline Against Dual-Species Cultures of Candida albicans and Staphylococcus epidermidis and the Mechanisms of Action

Bacterial and fungal coinfections have posed great clinical challenges in recent years, and combination therapy may be a useful way to treat these mixed infections. The objective of this study was to find an effective drug combination to treat dual-species cultures of fungi and bacteria. In this study, we focused on poorly investigated mixed cultures of Candida albicans and Staphylococcus epidermidis. In this research, we investigated the effects of fluconazole (FLC) and doxycycline (DOX) against dual-species cultures of C. albicans and S. epidermidis. Both the fractional inhibitory concentration index model and ΔE model revealed a synergistic antimicrobial effect between FLC and DOX against the four groups of dual-species cultures. Mechanistic studies revealed that the synergism of FLC and DOX against dual-species cultures may be associated with the inhibition of biofilms and calcium dysregulation. Fluconazole+doxycycline appears to be a potential drug combination for the treatment of bacterial and fungal coinfections. These findings are of great significance for overcoming clinical bacterial and fungal coinfections and might provide novel insights into drug discovery for combination therapy.

Clinical and microbiological characteristics of polymicrobial bacteremia: a retrospective, multicenter study

PURPOSE

To clarify the clinical and microbial characteristics of polymicrobial bacteremia (PMB) to contribute to improvements in clinical diagnosis and effective early treatment.

METHODS

This retrospective multicenter study used data from three acute-care hospitals in Okayama Prefecture, Japan, collected between January 2014 and March 2019. We reviewed the demographics, comorbidities, organisms isolated, infectious focus, and 30-day mortality of patients with PMB.

RESULTS

Of the 7233 positive blood cultures, 808 (11.2%) were positive for more than one organism. Of the patients with bacteremia, 507 (7.0%) had PMB, of whom 65.3% were male. Infectious foci were identified in 78.3% of the cases, of which intra-abdominal infections accounted for 47.1%. A combination of Gram-positive cocci (GPC) (chain form) and Gram-negative rods (GNR) accounted for 32.9% of the cases, and GPC/GNR and GNR/GNR patterns were significantly associated with intra-abdominal infections. The 30-day mortality rate of patients with PMB was 18.1%, with a median of 7.5 days from diagnosis to death. The mortality in patients with an infectious focus identified was significantly lower than that in patients with an unknown focus (16.3% vs. 24.5%; p = 0.031).

CONCLUSIONS

Intra-abdominal infections were the most common source of PMB, and were strongly associated with a Gram-staining combination pattern of GPC (chain form)/GNR. PMB cases with an unknown focus had a poorer prognosis, highlighting the importance of early diagnosis and appropriate treatment.

Machine-learning based prediction of prognostic risk factors in patients with invasive candidiasis infection and bacterial bloodstream infection: a singled centered retrospective study

Background

Invasive candidal infection combined with bacterial bloodstream infection is one of the common nosocomial infections that is also the main cause of morbidity and mortality. The incidence of invasive Candidal infection with bacterial bloodstream infection is increasing year by year worldwide, but data on China is still limited.

Methods

We included 246 hospitalised patients who had invasive candidal infection combined with a bacterial bloodstream infection from January 2013 to January 2018; we collected and analysed the relevant epidemiological information and used machine learning methods to find prognostic factors related to death (training set and test set were randomly allocated at a ratio of 7:3).

Results

Of the 246 patients with invasive candidal infection complicated with a bacterial bloodstream infection, the median age was 63 years (53.25–74), of which 159 (64.6%) were male, 109 (44.3%) were elderly patients (> 65 years), 238 (96.7%) were hospitalised for more than 10 days, 168 (68.3%) were admitted to ICU during hospitalisation, and most patients had records of multiple admissions within 2 years (167/246, 67.9%). The most common blood index was hypoproteinemia (169/246, 68.7%), and the most common inducement was urinary catheter use (210/246, 85.4%). Moreover, the most frequently infected fungi and bacteria were Candida parapsilosis and Acinetobacter baumannii, respectively. The main predictors of death prognosis by machine learning method are serum creatinine level, age, length of stay, stay in ICU during hospitalisation, serum albumin level, C-Reactive protein (CRP), leukocyte count, neutrophil count, Procalcitonin (PCT), and total bilirubin level.

Conclusion

Our results showed that the most common candida and bacteria infections were caused by Candida parapsilosis and Acinetobacter baumannii, respectively. The main predictors of death prognosis are serum creatinine level, age, length of stay, stay in ICU during hospitalisation, serum albumin level, CRP, leukocyte count, neutrophil count, PCT and total bilirubin level.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07125-8.

Enhanced Virulence of Candida albicans by Staphylococcus aureus: Evidence in Clinical Bloodstream Infections and Infected Zebrafish Embryos

Coinfection with Candida and Staphylococcus results in higher mortality in animal studies. However, the pathogenesis and interplay between C. albicans and S. aureus in bloodstream infections (BSIs) is unclear. This study determines the clinical features and outcomes of mixed C. albicans/S. aureus (CA/SA) BSIs and biofilm formation on pathogenesis during coinfection. Demographics and outcomes for mixed BSIs and monomicrobial candidemia were compared. Compared to 115 monomicrobial C. albicans BSIs, 22 patients with mixed CA/SA BSIs exhibited a significantly higher mortality rate and shorter survival time. In vitro and in vivo biofilm analysis showed that C. albicans accounted for the main biofilm architecture, and S. aureus increased its amount. Antibiotic tolerance in S. aureus, which adhered to Candida hyphae observed by scanning electron microscope, was demonstrated by the presence of wild-type C. albicans co-biofilm. Upregulation in exotoxin genes of S. aureus was evidenced by quantitative RT-PCR when a co-biofilm was formed with C. albicans. Mixed CA/SA BSIs result in a higher mortality rate in patients and in vivo surrogate models experiments. This study demonstrates that the virulence enhancement of C. albicans and S. aureus during co-biofilm formation contributes to the high mortality rate.

Presence of Candida tropicalis on Staphylococcus epidermidis Biofilms Facilitated Biofilm Production and Candida Dissemination: An Impact of Fungi on Bacterial Biofilms

While Staphylococcus epidermidis (SE) is a common cause of infections in implanted prostheses and other indwelling devices, partly due to the biofilm formation, Candida tropicalis (CT) is an emerging Candida spp. with a potent biofilm-producing property. Due to the possible coexistence between SE and CT infection in the same patient, characteristics of the polymicrobial biofilms from both organisms might be different from those of the biofilms of each organism. Then, the exploration on biofilms, from SE with or without CT, and an evaluation on l-cysteine (an antibiofilm against both bacteria and fungi) were performed. As such, Candida incubation in preformed SE biofilms (SE > CT) produced higher biofilms than the single- (SE or CT) or mixed-organism (SE + CT) biofilms as determined by crystal violet staining and fluorescent confocal images with z-stack thickness analysis. In parallel, SE > CT biofilms demonstrated higher expression of icaB and icaC than other groups at 20 and 24 h of incubation, suggesting an enhanced matrix polymerization and transportation, respectively. Although organism burdens (culture method) from single-microbial biofilms (SE or CT) were higher than multi-organism biofilms (SE + CT and SE > CT), macrophage cytokine responses (TNF-α and IL-6) against SE > CT biofilms were higher than those in other groups in parallel to the profound biofilms in SE > CT. Additionally, sepsis severity in mice with subcutaneously implanted SE > CT catheters was more severe than in other groups as indicated by mortality rate, fungemia, serum cytokines (TNF-α and IL-6), and kidney and liver injury. Although CT grows upon preformed SE-biofilm production, the biofilm structures interfered during CT morphogenesis leading to the frailty of biofilm structure and resulting in the prominent candidemia. However, l-cysteine incubation together with the organisms in catheters reduced biofilms, microbial burdens, macrophage responses, and sepsis severity. In conclusion, SE > CT biofilms prominently induced biofilm matrix, fungemia, macrophage responses, and sepsis severity, whereas the microbial burdens were lower than in the single-organism biofilms. All biofilms were attenuated by l-cysteine.

Mass Spectrometry Proteotyping-Based Detection and Identification of Staphylococcus aureus, Escherichia coli, and Candida albicans in Blood

Bloodstream infections (BSIs), the presence of microorganisms in blood, are potentially serious conditions that can quickly develop into sepsis and life-threatening situations. When assessing proper treatment, rapid diagnosis is the key; besides clinical judgement performed by attending physicians, supporting microbiological tests typically are performed, often requiring microbial isolation and culturing steps, which increases the time required for confirming positive cases of BSI. The additional waiting time forces physicians to prescribe broad-spectrum antibiotics and empirically based treatments, before determining the precise cause of the disease. Thus, alternative and more rapid cultivation-independent methods are needed to improve clinical diagnostics, supporting prompt and accurate treatment and reducing the development of antibiotic resistance. In this study, a culture-independent workflow for pathogen detection and identification in blood samples was developed, using peptide biomarkers and applying bottom-up proteomics analyses, i.e., so-called "proteotyping". To demonstrate the feasibility of detection of blood infectious pathogens, using proteotyping, Escherichia coli and Staphylococcus aureus were included in the study, as the most prominent bacterial causes of bacteremia and sepsis, as well as Candida albicans, one of the most prominent causes of fungemia. Model systems including spiked negative blood samples, as well as positive blood cultures, without further culturing steps, were investigated. Furthermore, an experiment designed to determine the incubation time needed for correct identification of the infectious pathogens in blood cultures was performed. The results for the spiked negative blood samples showed that proteotyping was 100- to 1,000-fold more sensitive, in comparison with the MALDI-TOF MS-based approach. Furthermore, in the analyses of ten positive blood cultures each of E. coli and S. aureus, both the MALDI-TOF MS-based and proteotyping approaches were successful in the identification of E. coli, although only proteotyping could identify S. aureus correctly in all samples. Compared with the MALDI-TOF MS-based approaches, shotgun proteotyping demonstrated higher sensitivity and accuracy, and required significantly shorter incubation time before detection and identification of the correct pathogen could be accomplished.

Deciphering the epidemiology of invasive candidiasis in the intensive care unit: is it possible?

Invasive candidiasis (IC) has emerged in the last decades as an important cause of morbidity, mortality, and economic load in the intensive care unit (ICU). The epidemiology of IC is still a difficult and unsolved enigma for the literature. Accurate estimation of the true burden of IC is difficult due to variation in definitions and limitations inherent to available case-finding methodologies. Candidemia and intra-abdominal candidiasis (IAC) are the two predominant types of IC in ICU. During the last two decades, an increase in the incidence of candidemia has been constantly reported particularly in the expanding populations of elderly or immunosuppressed patents, with a parallel change in Candida species (spp.) distribution worldwide. Epidemiological shift in non-albicans spp. has reached worrisome trends. Recently, a novel, multidrug-resistant Candida spp., Candida auris, has globally emerged as a nosocomial pathogen causing a broad range of healthcare-associated invasive infections. Epidemiological profile of IAC remains imprecise. Though antifungal drugs are available for Candida infections, mortality rates continue to be high, estimated to be up to 50%. Increased use of fluconazole and echinocandins has been associated with the emergence of resistance to these drugs, which affects particularly C. albicans and C. glabrata. Crucial priorities for clinicians are to recognize the epidemiological trends of IC as well as the emergence of resistance to antifungal agents to improve diagnostic techniques and strategies, develop international surveillance networks and antifungal stewardship programmes for a better epidemiological control of IC.

Novel dental implant modifications with two-staged double benefits for preventing infection and promoting osseointegration in vivo and in vitro

Peri-implantitis are a major problem causing implant failure these days. Accordingly, anti-infection during the early stage and subsequent promotion of osseointegration are two main key factors to solve this issue. Micro-arc oxidation (MAO) treatment is a way to form an oxidation film on the surface of metallic materials. The method shows good osteogenic properties but weak antibacterial effect. Therefore, we developed combined strategies to combat severe peri-implantitis, which included the use of a novel compound, PD, comprising dendrimers poly(amidoamine) (PAMAM) loading dimethylaminododecyl methacrylate (DMADDM) as well as MAO treatment. Here, we explored the chemical properties of the novel compound PD, and proved that this compound was successfully synthesized, with the loading efficiency and encapsulation efficiency of 23.91% and 31.42%, respectively. We further report the two-stage double benefits capability of PD + MAO: (1) in the first stage, PD + MAO could decrease the adherence and development of biofilms by releasing DMADDM in the highly infected first stage after implant surgery both in vitro and in vivo; (2) in the second stage, PD + MAO indicated mighty anti-infection and osteoconductive characteristics in a rat model of peri-implantitis in vivo. This study first reports the two-staged, double benefits of PD + MAO, and demonstrates its potential in clinical applications for inhibiting peri-implantitis, especially in patients with severe infection risk.

Candidaemia in Central Slovenia: A 12-year retrospective survey

BACKGROUND

Candida bloodstream infections (BSI) became an important invasive disease in the late 20th century, in particular among immunocompromised patients. Although considerable progress has been made in the management of patients with invasive mycoses, Candida BSI are still widespread among hospitalised patients and are associated with relatively high mortality.

OBJECTIVES

We conducted a retrospective study to evaluate patient characteristics, incidence, species distribution and antifungal susceptibility of BSI isolates of Candida spp. as well as outcomes of Candida BSI from 2001 to 2012, before the widespread use of echinocandins. This is the first epidemiological study of Candida BSI in Slovenia so far.

METHODS

All documented candidaemia cases from 2001 to 2012 in two major hospitals-University Medical Centre and Institute of Oncology in Ljubljana, Slovenia-were taken into consideration. Candida BSI were identified in 422 patients (250 male, 172 female). Laboratory and clinical data of these patients were retrospectively analysed. Mann-Whitney U test was used to compare continuous variables and Fisher's exact test or chi-squared test for categorical variables.

RESULTS AND CONCLUSIONS

The average incidence of Candida BSI was 0.524/10.000 patient-days (0,317/1000 admissions); 16/422 were younger than 1 year and 251/422 patients were over 60 years old. The most commonly isolated species were Candida albicans and Candida glabrata, followed by Candida parapsilosis. Majority of the patients had a single episode of Candida BSI, multiple episodes of Candida BSI occurred in 18/434 patients (4.1%); in 25/434 patients (5.8%) mixed Candida BSI were observed. Crude 30-day case-fatality rate was 55.4%.

Candida albicans Colonizes and Disseminates to the Gastrointestinal Tract in the Presence of the Microbiota in a Severe Combined Immunodeficient Mouse Model

Candida albicans is the leading cause of candidemia or other invasive candidiasis. Gastrointestinal colonization has been considered as the primary source of candidemia. However, few established mouse models that mimic this infection route are available. In the present study, we established a mouse model of disseminated candidiasis developed through the translocation of Candida from the gut. In this study, we developed a novel C. albicans GI colonization and dissemination animal model by using severe combined immunodeficient Rag2^–/–IL2γc^–/– (Rag2γc) mice, which lack functional T, B, NK cells, and IL2γc-dependent signaling. Rag2γc mice were highly susceptible to C. albicans gastrointestinal infection even in the presence of the gut microbiota. Within 4 weeks post infection, Rag2γc mice showed dose-dependent weight loss and disseminated candidiasis in more than 58% (7/12) of moribund mice. Histological analysis demonstrated abundant hyphae penetrating the mucosa, with significant neutrophilic infiltration in mice infected with wild-type C. albicans but not a filamentation-defective mutant. In moribund Rag2γc mice, the necrotic lesions and disrupted epithelial cells were associated with C. albicans hyphae. Notably, removal of the gut microbiota by antibiotics exacerbated the severity of fungal infection in Rag2γc mice, as demonstrated by elevated fungal burdens and accelerated weight loss and death. Furthermore, higher fungal burden and IL-1β expression were prominently noted in the stomach of Rag2γc mice. In fact, a significant increase in circulating proinflammatory cytokines, including IL-6, TNF-α, and IL-10, indicative of a septic response, was evident in infected Rag2γc mice. Additionally, Rag2γc mice exhibited significantly lower levels of IL-22 but not IFN-γ or IL-17A than wild-type B6 mice, suggesting that IL-22 plays a role in C. albicans gastrointestinal infection. Collectively, our analysis of the Rag2γc mouse model revealed features of C. albicans gastrointestinal colonization and dissemination without the interference from antibiotics or chemotherapeutic agents, thus offering a new investigative tool for delineating the pathogenesis of C. albicans and its cross-talk with the gut microbiota.

Identification of microorganisms directly from blood culture bottles with polymicrobial growth: comparison of FilmArray and direct MALDI-TOF MS

Bloodstream infections (BSIs) are related to high mortality and morbidity. Rapid administration of effective antimicrobial treatment is crucial for patient survival. Recently developed rapid methods to identify pathogens directly from blood culture bottles speed up diagnosis of BSIs. The present study compares the performance of two rapid identification methods, FilmArray and direct MALDI-TOF MS, on identifying microorganisms directly from positive blood culture bottles with polymicrobial growth. FilmArray and direct MALDI-TOF MS were performed directly on positive clinical and simulated polymicrobial blood culture bottles. Assay results were compared with standard culture methods. In total, 110 polymicrobial blood culture samples, of which 96 samples contained two microorganisms while 14 samples contained three microorganisms, were studied. FilmArray was able to identify 215/234 (92.0%) of isolates detected by the standard culture method and successfully identified all microorganisms in 88/110 (80.0%) of blood culture bottles. In contrast, direct MALDI-TOF MS was only able to identify 65/234 (27.8%) of isolates and managed to identify all microoganisms in 2/110 (2.1%) of blood culture bottles. FilmArray is a rapid method for direct identification of polymicrobial blood culture samples that can complement the conventional identification methods. Direct MALDI-TOF MS has low performance with polymicrobial samples.

Coexistence of Pseudomonas aeruginosa With Candida albicans Enhances Biofilm Thickness Through Alginate-Related Extracellular Matrix but Is Attenuated by N-acetyl-l-cysteine

Bacteria and Candidaalbicans are prominent gut microbiota, and the translocation of these organisms into blood circulation might induce mixed-organism biofilms, which warrants the exploration of mixed- versus single-organism biofilms in vitro and in vivo. In single-organism biofilms, Acinetobacter baumannii and Pseudomonas aeruginosa (PA) produced the least and the most prominent biofilms, respectively. C. albicans with P. aeruginosa (PA+CA) induced the highest biofilms among mixed-organism groups as determined by crystal violet straining. The sessile form of PA+CA induced higher macrophage responses than sessile PA, which supports enhanced immune activation toward mixed-organism biofilms. In addition, Candida incubated in pre-formed Pseudomonas biofilms (PA>CA) produced even higher biofilms than PA+CA (simultaneous incubation of both organisms) as determined by fluorescent staining on biofilm matrix (AF647 color). Despite the initially lower bacteria during preparation, bacterial burdens by culture in mixed-organism biofilms (PA+CA and PA>CA) were not different from biofilms of PA alone, supporting Candida-enhanced Pseudomonas growth. Moreover, proteomic analysis in PA>CA biofilms demonstrated high AlgU and mucA with low mucB when compared with PA alone or PA+CA, implying an alginate-related mucoid phenotype in PA>CA biofilms. Furthermore, mice with PA>CA biofilms demonstrated higher bacteremia with more severe sepsis compared with mice with PA+CA biofilms. This is possibly due to the different structures. Interestingly, l-cysteine, a biofilm matrix inhibitor, attenuated mixed-organism biofilms both in vitro and in mice. In conclusion, Candida enhanced Pseudomonas alginate–related biofilm production, and Candida presentation in pre-formed Pseudomonas biofilms might alter biofilm structures that affect clinical manifestations but was attenuated by l-cysteine.

Clinical characteristics, risk factors and outcomes of mixed Candida albicans/bacterial bloodstream infections

Purpose

The purpose of this study was to explore the clinical features, risk factors, and outcomes of mixed Candida albicans/bacterial bloodstream infections (mixed-CA/B-BSIs) compared with monomicrobial Candida albicans bloodstream infection (mono-CA-BSI) in adult patients in China.

Methods

All hospitalized adults with Candida albicans bloodstream infection (CA-BSI) were recruited for this retrospective observational study from January 1, 2013, to December 31, 2018.

Results

Of the 117 patients with CA-BSI, 24 patients (20.5%) had mixed-CA/B-BSIs. The most common copathogens were coagulase-negative Staphylococcus (CNS) (24.0%), followed by Klebsiella pneumoniae (20.0%) and Staphylococcus aureus (16.0%). In the multivariable analysis, a prior ICU stay > 2 days (adjusted odds ratio [OR], 7.445; 95% confidence interval [CI], 1.152–48.132) was an independent risk factor for mixed-CA/B-BSIs. Compared with patients with mono-CA-BSI, patients with mixed-CA/B-BSIs had a prolonged length of mechanical ventilation [17.5 (4.5, 34.8) vs. 3.0 (0.0, 24.5), p = 0.019] and prolonged length of ICU stay [22.0 (14.3, 42.2) vs. 8.0 (0.0, 31.5), p = 0.010]; however, mortality was not significantly different.

Conclusions

There was a high rate of mixed-CA/B-BSIs cases among CA-BSI cases, and CNS was the predominant coexisting species. A prior ICU stay > 2 days was an independent risk factor for mixed -CA/B-BSIs. Although there was no difference in mortality, the outcomes of patients with mixed -CA/B-BSIs, including prolonged length of mechanical ventilation and prolonged length of ICU stay, were worse than those with mono-CA-BSI; this deserves further attention from clinicians.

Mixed fungaemia: an 18-year report from a tertiary-care university hospital and a systematic review

BACKGROUND

While fungaemia caused by two or more different species of yeasts (mixed fungaemia, MF) is infrequent, it might be underestimated.

AIMS

This study aimed to determine the incidence of MF, clinical characteristics of the patients, and antifungal susceptibility profiles of the isolates with a systematic review of the literature.

SOURCES

Data sources were PubMed and Scopus.

STUDY ELIGIBILITY CRITERIA

Studies reporting ten or more mixed fungaemia episodes.

CONTENT

Study included MF episodes in adults between January 2000 and August 2018 in Hacettepe University Hospitals, Turkey. The isolation, identification and antifungal susceptibility testing (AFST) of the isolates were by standard mycological methods. Patient data were obtained retrospectively. Literature search was performed using relevant keywords according to PRISMA systematic review guidelines. A total of 32 patients with 33 MF episodes were identified. Among all fungaemia episodes, MF incidence was 3.7% (33/883). All patients had one or more underlying disorders among which solid-organ cancer (50.0%, 16/32) was the most common. Overall mortality was 51.5% (17/33). The most preferred antifungal agents for initial treatment were fluconazole (48.5%, 16/33) and echinocandins (39.4%, 13/33). Fluconazole susceptible-dose-dependent (S-DD) or -resistant Candida species were detected in 15 episodes, and an isolate of C. parapsilosis was classified as S-DD by AFST. All Candida isolates were susceptible to echinocandins. Non-candida yeasts with intrinsic resistance/reduced susceptibility to both echinocandins and fluconazole were detected in two episodes. Systematic review of the literature revealed 24 studies that reported more than ten MF episodes. Methodology was variable. Improvement of detection rates was reported when chromogenic agars were used. Most studies underlined detection of isolates with reduced susceptibility.

IMPLICATIONS

Although rare, the MF rate is affected by the detection methods, which have improved in recent years. Fluconazole and echinocandins were used for initial treatment in accordance with the current guideline recommendations; however, isolates non-susceptible to both were detected. Detection of a mixed infection offers an opportunity for optimum treatment.

Risk Prediction and Prognosis of Invasive Fungal Disease in Hematological Malignancies Patients Complicated with Bloodstream Infections

Purpose

In patients with hematologic malignancies (HM), bloodstream infections (BSI) and invasive fungal disease (IFD) remain important complications causing considerable mortality and morbidity. At present, the morbidity of IFD and the strategies to initiate antifungal treatment in HM patients with BSI remain unclear.

Patients and Methods

Patient characteristics, infection-related variables, and therapy-related features of 1374 HM patients with proven BSI from three hospitals were reviewed to investigate the epidemiology, risk factors and prognosis of IFD.

Results

The morbidity of proven and probable IFD in HM patients with BSI was 11.2%, and the mortality of those patients was 40.5%. Existing IFD risk scores were not accurate enough in distinguishing these patients benefiting from antifungal prophylaxis. Multivariate logistic regression identified age >45 years, profound neutropenia, hypoproteinemia, and use of vasopressors as independent variables associated with IFD morbidity in HM patients with BSI. In patients with proven and probable IFD patients, age >45 years, Pitt bacteremia score >3, use of vasopressors, abnormal blood coagulation, and initiation of antifungal therapy within 72 hrs after the onset of fever were independent prognostic factors. The mortality was significantly reduced in patients with high-risk factors of IFD if they initiate antifungal treatment within 72 hrs after the onset of fever compared to the patients not.

Conclusion

The morbidity and mortality of IFD increase significantly in HM patients with BSI. Early antifungal therapy may improve prognosis in HM patients with BSI complicated with IFD risk factors.

Clinical characteristics and implications of mixed candida/bacterial bloodstream infections in patients with hematological diseases

The incidence of mixed candida/bacterial blood infections (BSIs) has been reported to account for 20% of all cases of candidaemia. However, its clinical characteristics and implications in patients with hematological diseases are not clear. We conducted a retrospective case-control study of hematological patients complicated with candidaemia over the past 5-year period to identify the risk factors and clinical implications of mixed candidia/bacterial BSIs (case group) vs. monobacterial candidiasis (control group). Of all 65 enrolled patients with candidaemia, 20 cases (30.8%) met the diagnostic criteria for mixed candida/bacterial BSIs. Candida tropicalis was the most common candida species in all patients. Klebsiella pneumoniae was the most detected bacteria (35%) in case group. Previous hospital stay ≥ 28 days, organic damage during candidaemia, and positive procalcitonin (PCT) test were the risk factors of mixed candida/bacterial BSIs. Cumulative mortality of all patients enrolled was 26.2% at day 30, with significant differences between case and control group. In multivariate analysis, organic damage and granulocyte recovery were the two predictive factors for 30-day mortality. Mixed candida/bacterial BSIs are fatal complications of infection which account for a considerable part of candidaemia; multicenter and large-scale clinical studies are required in the future.

A new culture-based method for rapid identification of microorganisms in polymicrobial blood cultures by MALDI-TOF MS

Background

The application of matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) to microbial identification has allowed the development of rapid methods for identification of microorganisms directly in positive, blood cultures (BCs). These methods can yield accurate results for monomicrobial BCs, but often fail to identify multiple microorganisms in polymicrobial BCs. The present study was aimed at establishing a rapid and simple method for identification of bacteria and yeast in polymicrobial BCs from patients with bloodstream infection.

Results

The rapid method herein proposed is based on short-term culture in liquid media allowing selective growth of microorganisms recovered from polymicrobial BCs, followed by rapid identification by MALDI-TOF MS. To evaluate the accuracy of this method, 56 polymicrobial BCs were comparatively analyzed with the rapid and routine methods. The results showed concordant identification for both microbial species in 43/50 (86%) BCs containing two different microorganisms, and for two microbial species in six BCs containing more than two different species. Overall, 102/119 (85.7%) microorganisms were concordantly identified by the rapid and routine methods using a cut-off value of 1.700 for valid identification. The mean time to identification after BC positivity was about 4.2 h for streptococci/enterococci, 8.7 h for staphylococci, 11.1 h for Gram-negative bacteria, and 14.4 h for yeast, allowing a significant time saving compared to the routine method.

Conclusions

The proposed method allowed rapid and reliable microbial identification in polymicrobial BCs, and could provide clinicians with timely, useful information to streamline empirical antimicrobial therapy in critically ill patients.

Clinical Characteristics And Risk Factors In Mixed-Enterococcal Bloodstream Infections

Purpose

Although the enterococcal bloodstream infections (EBSI) are often observed in clinic, the mixed-EBSI are few reported. The aim of this study was to investigate the clinical characteristics and risk factors of mixed-EBSI in comparison with monomicrobial EBSI (mono-EBSI).

Methods

A single-center retrospective observational study was performed between Jan 1, 2013 and Dec 31, 2018 in a tertiary hospital. All patients with EBSI were enrolled, and their data were collected by reviewing electronic medical records.

Results

A total of 451 patients with EBSI were enrolled including 157 cases (34.8%) with mixed-EBSI. The most common co-pathogens were Coagulase-negative Staphylococcus (26.86%), followed by Acinetobacter baumannii (23.43%) and Klebsiella pneumoniae (8.57%). In multivariable analysis, burn injury (adjusted odds ratio [aOR], 7.39; 95% confidence interval [CI], 2.69-20.28), and length of prior hospital stay (aOR, 1.01; 95% CI, 1.00-1.02) were associated with mixed-EBSI. Patients with mixed-EBSI developed with more proportion of septic shock (19% vs. 31.8%, p=0.002), prolonged length of intensive care unit (ICU) stay [9(0,25) vs. 15(2.5,36), p<0.001] and hospital stay [29(16,49) vs. 33(18.5,63), p=0.031]. The mortality was not significantly different between mixed-EBSI and mono-EBSI (p=0.219).

Conclusion

A high rate of mixed-EBSI is among EBSI, and Acinetobacter baumannii is the second predominant co-existed species, except for Coagulase-negative Staphylococcus. Burn injury and length of prior hospital stay are independent risk factors for mixed-EBSI. Although the mortality is not different, patients with mixed-EBSI might have poor outcomes in comparison with mono-EBSI, which merits more attention by physicians in the future.

Fungal-Bacterial Interactions in Health and Disease

Fungi and bacteria encounter each other in various niches of the human body. There, they interact directly with one another or indirectly via the host response. In both cases, interactions can affect host health and disease. In the present review, we summarized current knowledge on fungal-bacterial interactions during their commensal and pathogenic lifestyle. We focus on distinct mucosal niches: the oral cavity, lung, gut, and vagina. In addition, we describe interactions during bloodstream and wound infections and the possible consequences for the human host.

Antibiofilm efficacy of curcumin in combination with 2-aminobenzimidazole against single- and mixed-species biofilms of Candida albicans and Staphylococcus aureus

Mixed fungal and bacterial biofilm associated infections of implants have been a huge challenge in health care because of the increased resistance to antimicrobials and the critical biological differences between fungi and bacteria. In this study, we evaluated the 2-aminobenzimidazole (2ABI) and curcumin (CUR) alone to inhibit planktonic cell growth, adhesion as well as single and mixed species biofilms of Candida albicans and Staphylococcus aureus on silicone. The combined effects between 2ABI and CUR on mixed species biofilm formation and pre-formed biofilm were assessed. Our work showed that 2ABI or CUR alone was effective as a sole agent, inhibiting planktonic growth, adhesion and the biofilm formation of bacteria and fungi on the silicone surface. The combination of 2ABI and CUR exhibited the enhanced effect on mixed biofilm compared to mono-drug therapy. The biofilm architecture was investigated by scanning electron microscopy (SEM) and the distinction of living/dead organisms within biofilm was examined by confocal laser scanning microscopy (CLSM). The combination activity was most potent on mixed biofilm. These results suggest the potential applicability of 2ABI and CUR to treatment of biofilm related device infections.

Rapid identification of pathogens from positive blood culture bottles with the MinION nanopore sequencer

PURPOSE

Bloodstream infections are major causes of morbidity and mortality that lead to prolonged hospital stays and higher medical costs. In this study, we aimed to evaluate the MinION nanopore sequencer for the identification of the most dominant pathogens in positive blood culture bottles.

METHODOLOGY

16S and ITS1-5.8S-ITS2 rRNA genes were amplified by PCR reactions with barcoded primers using nine clinical isolates obtained from positive blood bottles and 11 type strains, including five types of Candida species. Barcoded amplicons were mixed, and multiplex sequencing with the MinION sequencer was performed. In addition, barcoded PCR amplicons were sequenced by Sanger sequencing to validate the performance of the MinION.

RESULTS

The bacterial and Candida spp. identified by MinION sequencing, based on the highest homology of reference sequences from the NCBI gene databases, agreed with the matrix-assisted laser desorption ionization time of flight mass spectrometry results, excepting the closely related species Streptococcusand Escherichia coli. The 'pass' reads obtained within about 10 min of sequencing were sufficient to identify the pathogens. The average values of sequence identities with 1D² chemistry and the R9.5 flow cell were around 99 %; thus, frequent sequence errors did not affect species identification based on amplicon sequencing.

CONCLUSION

We have established a rapid, portable and economical technique for the identification of pathogens in positive blood culture bottles through a novel MinION nanopore sequencer amplicon sequencing scheme, which replaces traditional Sanger sequencing.

Evaluation of the Bruker® MBT Sepsityper IVD module for the identification of polymicrobial blood cultures with MALDI-TOF MS

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) considerably reduces timeframe required from initial blood culture positivity towards complete bacterial identification. However, rapid identification of polymicrobial blood cultures remains challenging. We evaluated the performances of the Bruker® MBT Sepsityper IVD module on MALDI-TOF MS for the direct identification of polymicrobial blood culture bottles. This module has the ability to give a strong indication that a sample contains a mixture of organisms and to identify two of them. Blood culture bottles considered as polymicrobial using routine subculture were collected and processed using the Sepsityper kit. MALDI-TOF MS identification was performed using the MBT Compass IVD software including the Sepsityper module. From 143 polymicrobial blood culture bottles tested, 34.3% (49/143) were completely identified by the module. Both microorganisms were more easily detected by the module in samples containing two pathogens than in samples containing two contaminants (36.8% vs 29.4%). Additionally, in more than half of the samples, the module detected 1 of the different microorganisms contained in the same vial. In these cases, with a pathogen and contaminant in the same sample, the module detected the pathogen in more than 80%. The Sepsityper module identified 14 microorganisms which were not recovered by conventional culture methods. The Bruker® MBT Sepsityper IVD module contributed to a valuable identification of polymicrobial blood cultures in more than a third of all cases. Conventional culture methods are still required to complete the results and to carry on susceptibility testing.

Fungi as Part of the Microbiota and Interactions with Intestinal Bacteria

The human microbiota consists of bacteria, archaea, viruses, and fungi that build a highly complex network of interactions between each other and the host. While there are many examples for commensal bacterial influence on host health and immune modulation, little is known about the role of commensal fungi inside the gut community. Up until now, fungal research was concentrating on opportunistic diseases caused by fungal species, leaving the possible role of fungi as part of the microbiota largely unclear. Interestingly, fungal and bacterial abundance in the gut appear to be negatively correlated and disruption of the bacterial microbiota is a prerequisite for fungal overgrowth. The mechanisms behind bacterial colonization resistance are likely diverse, including direct antagonism as well as bacterial stimulation of host defense mechanisms. In this work, we will review the current knowledge of the development of the intestinal bacterial and fungal community, the influence of the microbiota on human health and disease, and the role of the opportunistic yeast C. albicans. We will furthermore discuss the possible benefits of commensal fungal colonization. Finally, we will summarize the recent findings on bacterial-fungal interactions.

Photodynamic Antimicrobial Chemotherapy (PACT), using Toluidine blue O inhibits the viability of biofilm produced by Candida albicans at different stages of development

BACKGROUND

Candida albicans is an opportunistic fungus producing both superficial and systemic infections, especially in immunocompromised individuals. It has been demonstrated that C. albicans ability to form biofilms is a crucial process for colonization and virulence. Furthermore, a correlation between the development of drug resistance and biofilm maturation at Candida biofilms has been shown. Photodynamic Antimicrobial Chemotherapy (PACT) is a potential antimicrobial therapy that combines visible light and a non-toxic dye, known as a photosensitizer, producing reactive oxygen species (ROS) that can kill the treated cells. The objective of this study was to investigate the effects of PACT, using Toluidine Blue O (TBO) on the viability of biofilms produced by C. albicans at different stages of development.

METHODS

In this study, the effects of PACT on both biofilm formation and viability of the biofilm produced by C. albicans were studied. Biofilm formation and viability were determined by a metabolic assay based on the reduction of XTT assay. In addition, the morphology of the biofilm was observed using light microscopy.

RESULTS

PACT inhibited both biofilm formation and viability of the biofilm produced by C. albicans. Furthermore, PACT was able to decrease the number of both cells and filamentous form present in the biofilm structure. This inhibitory effect was observed in both early and mature biofilms.

CONCLUSIONS

The results obtained in this study demonstrated the potential of PACT (using TBO) as an effective antifungal therapy, including against infections associated with biofilms at different stages of development.

Identification of microorganisms grown in blood culture flasks using liquid chromatography–tandem mass spectrometry

Aim: Bloodstream infections are a common cause of disease and a fast and accurate identification of the causative agent or agents of bloodstream infections would aid the start of adequate treatment. Materials & methods: A liquid chromatography–tandem mass spectrometry (LC–MS/MS) shotgun proteomics method was developed for the identification of bacterial species directly from blood cultures that were simulated by inoculating blood culture bottles with single or multiple clinically relevant microorganisms. Results: Using LC–MS/MS, the single species were correctly identified in 100% of the blood cultures, whereas for polymicrobial infections, 78% of both species were correctly identified in blood cultures. Conclusion: The LC–MS/MS method allows for the identification of the causative agent of positive blood cultures.

Efficacy of carboxymethyl chitosan against Candida tropicalis and Staphylococcus epidermidis monomicrobial and polymicrobial biofilms

Polymicrobial biofilms with fungi and bacteria are the leading cause for the failure of medical devices and related infections. In this study, antibiofilm activities of carboxymethyl chitosan (CM-chitosan) on monomicrobial and polymicrobial biofilms of Staphylococcus epidermidis and Candida tropicalis in vitro were evaluated. CM-chitosan was effective as a sole agent, inhibiting both monomicrobial and polymicrobial biofilms in microplates and also on the silicone surface in short- and long-term periods. Biofilm architecture was investigated by scanning electron microscopy and confocal laser scanning microscopy was used to examine living/dead organisms within biofilm. CM-chitosan inhibited planktonic growth as well as adhesion. Further biofilm formation was inhibited by CM-chitosan added at 90min or 12h after biofilm initiation. CM-chitosan may serve as a possible antibiofilm agent to limit monomicrobial and polymicrobial biofilm.

Combined use of serum (1,3)-β-D-glucan and procalcitonin for the early differential diagnosis between candidaemia and bacteraemia in intensive care units

Background

This study aimed to assess the combined performance of serum (1,3)-β-d-glucan (BDG) and procalcitonin (PCT) for the differential diagnosis between candidaemia and bacteraemia in three intensive care units (ICUs) in two large teaching hospitals in Italy.

Methods

From June 2014 to December 2015, all adult patients admitted to the ICU who had a culture-proven candidaemia or bacteraemia, as well as BDG and PCT measured closely to the time of the index culture, were included in the study. The diagnostic performance of BDG and PCT, used either separately or in combination, was assessed by calculating the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive and negative likelihood ratios (LR+ and LR–). Changes from pre-test probabilities to post-test probabilities of candidaemia and bacteraemia were inferred from Fagan’s nomograms.

Results

One hundred and sixty-six patients were included, 73 with candidaemia (44%) and 93 with bacteraemia (56%). When both markers indicated candidaemia (BDG ≥80 pg/ml and PCT <2 ng/ml) they showed higher PPV (96%) compared to 79% and 66% for BDG or PCT alone, respectively. When both markers indicated bacteraemia (BDG <80 pg/ml and PCT ≥2 ng/ml), their NPV for candidaemia was similar to that of BDG used alone (95% vs. 93%). Discordant BDG and PCT results (i.e. one indicating candidaemia and the other bacteraemia) only slightly altered the pre-test probabilities of the two diseases.

Conclusions

The combined use of PCT and BDG could be helpful in the diagnostic workflow for critically ill patients with suspected candidaemia.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1763-5) contains supplementary material, which is available to authorized users.

Commensal Protection of Staphylococcus aureus against Antimicrobials by Candida albicans Biofilm Matrix

Biofilm-associated polymicrobial infections, particularly those involving fungi and bacteria, are responsible for significant morbidity and mortality and tend to be challenging to treat. Candida albicans and Staphylococcus aureus specifically are considered leading opportunistic fungal and bacterial pathogens, respectively, mainly due to their ability to form biofilms on catheters and indwelling medical devices. However, the impact of mixed-species biofilm growth on therapy remains largely understudied. In this study, we investigated the influence of C. albicans secreted cell wall polysaccharides on the response of S. aureus to antibacterial agents in biofilm. Results demonstrated significantly enhanced tolerance for S. aureus to drugs in the presence of C. albicans or its secreted cell wall polysaccharide material. Fluorescence confocal time-lapse microscopy revealed impairment of drug diffusion through the mixed biofilm matrix. Using C. albicans mutant strains with modulated cell wall polysaccharide expression, exogenous supplementation, and enzymatic degradation, the C. albicans-secreted β-1,3-glucan cell wall component was identified as the key matrix constituent providing the bacteria with enhanced drug tolerance. Further, antibody labeling demonstrated rapid coating of the bacteria by the C. albicans matrix material. Importantly, via its effect on the fungal biofilm matrix, the antifungal caspofungin sensitized the bacteria to the drugs. Understanding such symbiotic interactions with clinical relevance between microbial species in biofilms will greatly aid in overcoming the limitations of current therapies and in defining potential new targets for treating polymicrobial infections.

The fungus Candida albicans and the bacterium Staphylococcus aureus are important microbial pathogens responsible for the majority of infections in hospitalized patients and are often coisolated from a host. In this study, we demonstrated that when grown together, the fungus provides the bacterium with enhanced tolerance to antimicrobial drugs. This process was mediated by polysaccharides secreted by the fungal cell into the environment. The biofilm matrix formed by these polysaccharides prevented penetration by the drugs and provided the bacteria with protection. Importantly, we show that by inhibiting the production of the fungal polysaccharides, a specific antifungal agent indirectly sensitized the bacteria to antimicrobials. Understanding the therapeutic implications of the interactions between these two diverse microbial species will aid in overcoming the limitations of current therapies and in defining new targets for treating complex polymicrobial infections.

National Bloodstream Infection Surveillance in Switzerland 2008-2014: Different Patterns and Trends for University and Community Hospitals

OBJECTIVE To characterize the epidemiology of bloodstream infections in Switzerland, comparing selected pathogens in community and university hospitals. DESIGN Observational, retrospective, multicenter laboratory surveillance study. METHODS Data on bloodstream infections from 2008 through 2014 were obtained from the Swiss infection surveillance system, which is part of the Swiss Centre for Antibiotic Resistance (ANRESIS). We compared pathogen prevalences across 26 acute care hospitals. A subanalysis for community-acquired and hospital-acquired bloodstream infections in community and university hospitals was performed. RESULTS A total of 42,802 bloodstream infection episodes were analyzed. The most common etiologies were Escherichia coli (28.3%), Staphylococcus aureus (12.4%), and polymicrobial bloodstream infections (11.4%). The proportion of E. coli increased from 27.5% in 2008 to 29.6% in 2014 (P = .04). E. coli and S. aureus were more commonly reported in community than university hospitals (34.3% vs 22.7%, P<.001 and 13.9% vs 11.1%, P<.001, respectively). Fifty percent of episodes were community-acquired, with E. coli again being more common in community hospitals (41.0% vs 32.4%, P<.001). The proportion of E. coli in community-acquired bloodstream infections increased in community hospitals only. Community-acquired polymicrobial infections (9.9% vs 5.6%, P<.001) and community-acquired coagulase-negative staphylococci (6.7% vs 3.4%, P<0.001) were more prevalent in university hospitals. CONCLUSIONS The role of E. coli as predominant pathogen in bloodstream infections has become more pronounced. There are distinct patterns in community and university hospitals, potentially influencing empirical antibiotic treatment. Infect Control Hosp Epidemiol 2016;37:1060-1067.

Antifungal activity of extracts and isolated compounds from Buchenavia tomentosa on Candida albicans and non-albicans

AIM

This study aimed to evaluate the antifungal activity of Buchenavia tomentosa extract and bioactive compounds on six Candida species.

MATERIALS & METHODS

The antimicrobial activity of extract was evaluated using standard strains and clinical isolates. Cytotoxicity was tested in order to evaluate cell damage caused by the extract. Extract was chemically characterized and the antifungal activity of its compounds was evaluated.

RESULTS

Extract showed antifungal activity on Candida species. Candida non-albicans were more susceptible than Candida albicans. Low cytotoxicity for extract was observed. The isolated compounds presented antifungal activity at least against one Candida spp. and all compounds presented antifungal effect on Candida glabrata.

CONCLUSION

Extracts from Buchenavia tomentosa showed promising antifungal activity on Candida species with low cytotoxicity. Gallic acid, corilagin and ellagic acid showed promising inhibitory activity on Candida glabrata.

Bioinspired Polymers: Antimicrobial Polymethacrylates

Naturally occurring antimicrobial peptides have been honed by evolution over millions of years to give highly safe and efficacious antimicrobials that form part of many organisms’ immune systems. By studying these peptides to identify key aspects of structure and composition, suitable synthetic polymer mimics can be designed that hold potential as anti-infective agents. This review focusses on an important aspect of peptide mimicry, that of replicating the chemical functionality provided by key amino acids present in antimicrobial peptides. These include polymethacrylate mimics of arginine-rich and tryptophan-rich peptides. Systematic investigation of the structure–activity relationships of these polymers identifies the guanidine based poly(methylmethacrylate-co-2-guanidinoethyl methacrylate) (pMMA-co-GEMA) copolymers with low molecular weight and low methyl content as having superior activity profiles when compared with all other combinations. Unique antibiofilm activity of these polymers is also revealed in in vitro testing against monomicrobial and polymicrobial biofilms of the bacteria Staphylococcus aureus and the fungus Candida albicans. This highlights Mother Nature as an important resource in drug development and identifies the arginine-mimicking polymethacrylates as important leads for the development of a new generation of antimicrobial agents to tackle resistance.