MICROBIOLOGY
major source of disseminated infections. Major global IFDs include candidaemia, invasive aspergillosis, pneumocystosis and cryptococcosis, with annual mortality rates between those of TB and malaria. Diagnostic challenges drive overuse of antifungals.
Candidaemia and invasive
Pulmonary invasive aspergillosis in a post-mortem sample from a patient with interstitial pneumonia (Grocott’s methenamine silver stain).
considerations of consent, which, perhaps surprisingly, has been an issue in some studies.
As wastewater analysis has the potential to allow the screening of large parts of the population, it can be a cost- effective epidemiological tool that can have application both to well-resourced and low- and middle-income regions. Under the right circumstances, it can provide a non-invasive mechanism by which disease patterns can be studied, allowing targeting of public health resources. It also has the potential to be applied in difficult to access regions. Dr Shaw was clear that this approach, like any other, has limitations and is not always feasible or appropriate. It is important to have a clear idea of what question you are trying to answer to determine if testing wastewater is going to be an effective tool. In his last slide he discussed some of the considerations and limitations – factors such as the logistics, appropriate sampling frequency, sample sites and target pathogens or questions around optimisation and standardisation of methods. There is also the wider perspective on how sustainable/ supported these systems may be, particularly in resource-limited regions, and how to get policymakers to trust and act upon the results.
Fungal infections: advances in diagnostics Dr Riina Richardson, Honorary Consultant Mycologist and Senior Clinical Lecturer in Infectious Diseases and Medical Education, Manchester,
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brought a stimulating scientific programme to an end with a fascinating insight into the advances in the diagnosis of invasive/systemic fungal diseases (IFDs). This focused on WHO guidance on priority fungal pathogens in terms of antifungal resistance; major public health importance; major knowledge gaps in the global burden of fungal disease; and the significant regional differences in distribution and epidemiology of fungal pathogens. Dr Richardson began her talk by stating that to combat the global burden of IFD, WHO emphasises analysis and introduction of commercially available and pipeline in vitro diagnostics (IVDs) for rapid detection and susceptibility testing, with application to diagnosis from community outreach clinics to national reference laboratories. She noted that there is a plethora of IVDs available to diagnose IFD including culture-based methods (eg microscopy, biochemical methods and MALDI-ToF MS) and non-culture-based methods (eg LFDs, immunological methods and sequencing). Antifungal susceptibility testing IVDs include culture based (eg microdilution and MALDI-ToF MS) and non-culture-based (eg nucleic acid amplification techniques and sequencing).
Phenotypic test methods for detection and identification vary significantly in sensitivity and specificity, and the challenges of innate or acquired fungal resistance mechanisms and the ability of fungal pathogens to rapidly form biofilms in the human body presents a
aspergillosis (IA) are the most common IFDs in the UK associated with gastrointestinal trauma or surgery, with risk factors including immunosuppression, particularly neutropenic, and cardiothoracic ICU patients, invasive medical support and use of broad-spectrum antibiotics. The choice of diagnostic tests to rule out fungal disease and stop antifungals after starting with empirical therapy should have high negative predictive values, and those to rule in fungal disease (ie to start/withhold antifungals) should have high positive predictive values with clinically useful turnaround times. No single test or sample type can be used to diagnose IA, as a combination approach is needed, often triggered by CT findings, including microscopy, molecular and biomarker tests.
Early appropriate treatment of candidaemia is critical to a good outcome. Blood culture and PCR have low sensitivity due to low bacterial loads, but β-D-glucan is useful. It is likely that Pneumocystis pneumonia PCR will soon replace microscopy as the diagnostic gold standard with clinical performance depending upon sample type. HIV status does not affect performance and β-D-glucan can guide qPCR result interpretation.
Best patient outcomes use a multi- modal approach to clinical samples and test diagnostics with consideration given to mixed infections. Therapeutic drug monitoring for azoles allows dose adjustment and it is important to audit patient management and outcomes.
Jim Lindsay During preparation of this report, members of the committee learned of the sudden passing of Jim Lindsay, a founding member of the BSMT in 1985 and a former Secretary. Jim was a proud microbiologist and staunch supporter both of the BSMT and the diagnostics industry. We wish to take this opportunity to acknowledge his contribution and reiterate our sincere condolences to his wife and family at this sad time. A full obituary can be found on the BSMT website (
www.bsmt.org.uk).
AUGUST 2025
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