The global picture of antifungal resistance
The Kingdom Fungi is a biodiverse and essential component of our habitable Planet. However, recent decades have seen an increase in the number of pathogenic fungi infecting natural populations and managed landscapes. In both animals and plants, this increase in fungal diseases are causing some of the most severe die-offs and extinctions ever witnessed in wild species; fungi are also increasingly recognized as presenting a worldwide threat to food security and the healthy functioning of ecosystems. In parallel, clinicians and biomedical scientists are fighting emerging fungal pathogens that infect millions of people every year and there are signs that fungi are become increasingly adapted to resist frontline antifungal therapies. Traditional approaches to studying the biology of fungal infections are currently being transformed by the growing number of high-quality assembled genomes, by world-wide surveys of population-genomic data and by new technological and informatic strategies. This talk will discuss current challenges in emerging fungal diseases in order to identify weaknesses in our armamentarium against fungal infections. Rapid progress is being made in our understanding of how to manage fungal disease in clinical and agricultural settings, however mass-deployment of antifungal drugs and the development of monocultures has brought new risks to health and biosecurity. This meeting will attempt to identify a research agenda that will allow us to improve our resilience in the face of emerging fungal disease, and will ask what patterns of fungal disease might look like in the future and whether this is predictable?
Antifungal resistance - clinical rarity or impending disaster?
Azole antifungals play an important role in the management of fungal infections. However, in the last decade azole resistance in both Candida and Aspergillus has been increasingly reported and this is potentially complicating the effective management of these diseases. Starting as a clinical rarity in the last decade of the 20th century, less than 15 years later, the potential problem of azole resistance in Aspergillus has been recognized on all continents. The higher mortality rates observed in patients with invasive aspergillosis caused by azole resistant A. fumigatus pose serious challenges to the mycologist for timely identification of resistance and appropriate therapeutic interventions. The ‘TR34/L98H’ mutation in the cyp51A gene of A. fumigatus, which is associated with azole fungicide use, is still responsible for most multi-azole resistance seen in many European countries and globally. Azole-resistant isolates carrying this mutation have been reported from both patients and the environment. Further, several newly emerging resistance mutations are recognized with the ‘TR46/Y121F/T289A’, conferring high voriconazole and variable itraconazole MICs, being now the second most common. Many more environmental resistance mutations are surfacing, adding to the emerging problem. Environmental screening and routine antifungal susceptibility testing of clinically significant isolates should be considered in order to develop guidelines for local and national purposes. Considering that azole antifungal drugs are the mainstay of (oral) therapy, especially for chronic invasive and allergic aspergillosis, emergence of resistance will have a profound impact on healthcare. This presentation highlights the global development of azole resistance in A. fumigatus and the impending clinical treatment problem.
Candida auris - epidemiology and a global threat
Candida auris is a multidrug-resistant fungus that has caused healthcare-associated outbreaks of invasive infections. First described in Japan in 2009, it has since been detected on five continents. We established an international collaboration to understand its epidemiology and then issued an alert to US healthcare facilities in June 2016 for case-finding. C. auris is an emerging healthcare-associated pathogen with high mortality. Puzzlingly, WGS analysis suggests emergence of at least 4 distinct clades with high genomic similarity within geographical regions. Unlike other Candida species, extensive drug resistance and healthcare-associated transmission appear common. Further investigation of this concerning pathogen is urgently needed.
Diagnosis and management of an outbreak of drug resistant C. auris
Candida auris is a globally emerging multidrug resistant fungal pathogen causing nosocomial transmission. The presentation describes the first outbreak of Candida auris in Europe which occurred in 2015/2016 within a single Hospital Trust in London. A total of 44 % (n = 22/50) patients developed possible or proven C. auris infection with a candidaemia rate of 18 % (n = 9/50). Environmental sampling showed persistent presence of the yeast around bed space areas. Implementation of strict infection and prevention control measures included: isolation of cases and their contacts, wearing of personal protective clothing by health care workers, screening of patients on affected wards, skin decontamination with chlorhexidine, environmental cleaning with chorine based reagents and hydrogen peroxide vapour. Genotyping with AFLP demonstrated that C. auris isolates from the same geographic region clustered. The outbreak highlights the importance of appropriate species identification and rapid detection of cases in order to contain hospital acquired transmission.
UK antifungal resistance and stewardship survey data
Increasing incidence of fungal infections, including resistant infections, the emergence of antifungal resistant pathogens such as C. auris, high drug costs and the toxicity of antifungal agents highlight the importance of monitoring national antifungal resistance trends, the use of antifungal drugs and enhancing antifungal stewardship activities.
In collaboration with national experts and professional organisations Public Health England (PHE) has established the English Programme for Antimicrobial Use and Resistance (ESPAUR) antifungal consumption and resistance surveillance subgroup to identify gaps within current antifungal surveillance schemes and explore and implement improvements to the national surveillance programme.
The ESPAUR Report 2016 extended the annual surveillance data published by presenting data on antifungal resistance, antifungal prescribing from general practice and NHS hospitals and stewardship for the first time. A summary of the report’s findings will be presented at the 12th Annual Fungal Update Meeting. The presentation will also include reference laboratory data on the latest antifungal drug susceptibility trends of key pathogens within the UK, including the emergence of azole resistance amongst isolates of Aspergillus fumigatus.
A proposed national trial of rapid tests for Candida infection in ICU
In 2015 the NIHR Health Technology Assessment (HTA) programme published a call for commissioned research on the topic of rapid tests for fungal infection. The brief specified the research question as: In patients treated for suspected fungal infection can rapid tests be used to rule out infection and guide the early discontinuation of anti-fungal treatment. Would use of these tests be cost effective?
A multidisciplinary team of experts in infection, diagnostics, critical care, research methodology, statistics and health economics was assembled, with support from a patient representative, to design a large-scale diagnostic accuracy study, including economic modelling. This is intended to definitively answer the research question in respect of Candida infection in the UK critical care setting. The proposed study will assess the accuracy and modelled cost-effectiveness of commercially-available PCR and antigen-based tests for Candida in approximately 35 intensive care units over 3 years. It is envisaged that the result will deliver a test-based algorithm for the diagnosis and treatment of ICU patients with suspected Candida infection that could be subsequently evaluated for safety, clinical and cost-effectiveness in a randomised trial.
Lancashire Cardiac Centre, a centre-of-excellence located in Blackpool, offers heart and lung treatment for the people of Lancashire, Cumbria and beyond. Our team presents a brief account of some unexpected challenges in the follow up management of fungal infection in a patient with malignant pleural mesothelioma treated at the Cardiac Centre. Malignant pleural mesothelioma carries a poor prognosis, with overall survival being on the order of 9 to 17 months after diagnosis. A combination of chemo radiotherapy (CRT) and extra-pleural pneumonectomy (EPP) has been recommended in a select group of patients. Irrespective of the combination, EPP is associated with mortality in the range of 4–15% and a complication rate as high as 62%.
Cryptococcus neoformans, Titans, and resistance to antifungals
The human fungal pathogen Cryptococcus neoformans causes 1 million infections and 600,000 deaths worldwide each year. Cryptococcus yeast proliferate in the human lung, escape the immune response, and cross the blood-brain barrier, causing severe meningitis. Immune evasion and virulence are well known to be mediated by the production of capsule and melanin. Recently, a new pathogenicity factor, the Titan cell, was described. Titan cells are large, highly polyploid cells with the capacity to bud off small aneuploid daughters. As such, Titan cells are thought to act as an important reservoir for infection. Titan cell size prevents phagocytosis, and daughter cells exhibit altered stress and drug sensitivity profiles compared to their parent strains. Finally, the presence of Titan cells is associated with increased eosinophilia and a non-protective TH2 response, as well as increased dissemination to the brain. Despite the key role Titans play in host adaptation and immune evasion, little is known about the underlying mechanisms driving Titanisation and proliferation. Recent observations suggest that Titan daughter aneuploidy underlies phenotypic variation, creating the potential for drug resistant lineages. An understanding of the molecular mechanisms underlying the yeast-Titan morphotype transition and the proliferation of Titan daughters may inform future therapeutic interventions.
Persistence of Aspergillus spores in the host environment: A hitchhiker’s guide to the mammalian lung
The human lung is continually exposed to spores of the airborne mould Aspergillus fumigatus. Inhaled spores are small enough to bypass mucociliary clearance mechanisms and reach the alveoli of the lung where interaction between host and pathogen cells can lead to fungal clearance, or to development of inflammatory or invasive fungal diseases. A. fumigatus is an accidental pathogen whose encounters with the host, although frequent, are circumstantial in nature. The capacity of this organism to cause human disease is unique amongst a cohort of several hundred related Aspergillus species and relative to closest sequenced relative there are no immediately obvious large scale genetic events which signify recent evolution of pathogenicity. However, multiple, recently evolved telomere-associated genes are preferentially upregulated in the host environment, including those which drive production of secondary metabolites. Clinical relevance of aspergillus species does not correlate with fungal growth rate, but is positively correlated with thermotolerance, and epithelial toxicity.
In recent years we have developed a programme of research which seeks the mechanistic basis of host epithelial damage. In order to find out why A. fumigatus is cytotoxic to human epithelia we have observed the interaction between host and pathogen in laboratory culture, and measured epithelial decay, lytic death of host cells, host cell signalling and cytokine degradation in response to fungal challenge. This research has revealed multiple mechanisms involved in eliciting epithelial damage, occurring at different stages of the host-pathogen interaction and involving different fungal morphotypes. In this talk I will explain how we have used laboratory experimentation to ask the following questions: Why is A. fumigatus cytotoxic to human cells? Does the host or the pathogen drive epithelial damage and how? How do pathogen-derived proteins shape the immune environment? How is damage driven in the whole animal host? Which elicitors of host damage are produced by A. fumigatus, and have they recently evolved? I will finish by introducing a new study addressing the A. fumigatus regulatory network driving epithelial damage in cultured human lung tissue and in the whole animal, and examine how this knowledge might lead to novel therapeutic interventions.
Co-infection with aspergillosis - influenza and more
Patients with aspergillosis have usually been predisposed to this infection because of some form of immunocompromise and/or underlying structural lung disease. Co-infection with other respiratory pathogens, especially viruses, likely facilitates conversion of Aspergillus spp. from coloniser to pathogen. Influenza virus is a common, often seasonal, respiratory pathogen which has various immunomodulatory effects on both innate and adaptive immune responses. There are published case series, typically patients undergoing intensive care, where there was a frequency of invasive aspergillosis complicating influenza as high as 25%. These were not necessarily the traditionally immunocompromised although prior exposure to steroids and presence of chronic obstructive pulmonary disease were evident in some cases. During an influenza epidemic in 2015 we recorded 150 hospitalised cases of ‘flu only two of whom developed invasive aspergillosis. Both were patients recovering from haematopoietic stem cell transplants. One patient later developed persistent Pseudomonas aeruginosa airway co-infection which may have contributed to the progression of his aspergillosis. The reported interactions in vitro that occur between A. fumigatus and P. aeruginosa are complex but may lead to increased airway and lung injury. One mechanistic explanation for this is increased elastase production by P. aeruginosa when in the presence of A. fumigatus. Future research should focus on prospective case series to establish the true frequency of these microbial relationships, and studies of the respiratory microbiome to gain better insights into changes occurring during co-infection.
Trained innate immunity and implications for host-fungal interactions
The inability of innate immunity to build an immunological memory, considered one of the main characteristics differentiating it from adaptive immunity, has been recently challenged by studies in plants, invertebrates, and mammals. The increasing evidence for immunological memory within innate immunity is the focus of intense investigation. Long-term reprogramming of innate immunity, that induces adaptive traits and has been termed “trained immunity,” characterizes prototypical innate immune cells such as natural killer cells and monocytes, and provides protection against reinfection in a T/B-cell-independent manner. Both specific signaling mechanisms and non-specific epigenetic effects have been implicated in mediating these effects: the role of epigenetic changes and of metabolic reprogramming towards aerobic glycolysis will be discussed. This concept represents a paradigm change in immunity and its putative role in resistance to reinfection may represent the next step in the design of future vaccines.
ECIL, ESCMID and IDSA guidelines updates 2016/2017 - compare and contrast
Looking back at two strong decades in the field of antifungal research, scientific evidence has become too extensive for the individual clinical physician to maintain a solid overview. Guidelines provide a welcome overview and help physicians in offering state-of-the-art medicine to patients in need. An ideal guideline would supply a comprehensive review of the scientific literature with unbiased recommendations based on standards of evidence-based medicine, seasoned with expert recommendations for key questions not yet addressed by clinical trials of acceptable quality. In recent years, ECIL, ESCMID, and the IDSA have published guidelines in the field that have gained significant attention in clinical mycology in the Western world. Naturally, all are based on the same data, but intend to provide different focus based on the regional epidemiology (Europe / USA) or underlying disease (leukaemia). In addition, for lack of international standardization, all use slightly different methods how to rate the reviewed evidence and how to find consensus in the guideline group. Do they actually come to different conclusions? If yes, what are the differences? Do they deliver on our expectations?
Differentiating fungal versus non-fungal pathology by CT imaging
Chest computed tomography (CT) is an essential tool for the diagnosis and management of invasive fungal diseases, but early suggestive signs of mould infection (e.g., halo sign) are transient and non-specific. CT pulmonary angiography (CTPA), the gold-standard diagnostic test for pulmonary embolism, has been proposed to improve the sensitivity and specificity of CT detection of invasive mould disease in the lung by allowing direct visualization of vessels occluded with thrombi and fungi in nodular infiltrates.
Our center has utilized CTPA as part of the routine work-up of neutropenic patients with fever who have nodular lesions identified on initial CT scans. In a prospective analysis of the first 100 imaged patients, a positive vessel occlusion sign identified by CTPA was 100% sensitive (41/41) for detection of proven or probable fungal disease exam (EORTC/MSG criteria) in patients with an evaluable study, and was positive in 49% (25/51) of patients without mycological criteria (possible mold disease). Only one false positive result was found (septic pulmonary embolus), and no patient with an established alternative diagnosis (bacterial pneumonia including P. aeruginosa, lymphoma, viral pneumonia, mixed bacterial viral pneumonia, tuberculosis, BOOP) had a positive CTPA result. Unlike serum galactomannan, the sensitivity of CTPA was not affected by antifungal prophylaxis. Adverse effects associated with CTPA were minimal with only two patients developed evidence of acute renal injury (RIFLE criteria) more than 7 days after the exam that were likely due to sepsis and/or nephrotoxic medications.
We also found that a negative occlusion sign by CTPA was uniquely associated with a low negative likelihood ratio (0.02, 95% CI 0.003-0.09) compared to other CT findings, thus supporting clinician decisions for withholding or discontinuation of empiric antifungal therapy. Indeed, patients with negative CTPA results in our center received significantly shorter courses of empiric antifungal therapy- suggesting CTPA could be a valuable tool in the support of antifungal stewardship programs.
Ongoing studies in our institute are exploring CTPA as part of an early low-dose CT protocol for imaging high-risk hematology patients within 48 hours of fever onset. Our initial experience suggests that CTPA may also be useful for differentiating fungal versus non-fungal diseases in neutropenic patients with less characteristic CT findings such as small centrilobular nodules.