Sepsis Diagnosis

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Bacteraemia, Fungaemia and Sepsis: The conditions and their diagnosis

The bloodstream is normally a sterile environment. However it is possible for pathogenic micro-organisms such as bacteria (bacteraemia) and fungi (fungaemia) to enter the bloodstream. Such infections can arise as a result of organisms present at a localised site of infection (such as the lung or urogenital tract) finding their way into the bloodstream. It is also possible for micro-organisms present on the skin to enter the bloodstream via breaks in the skin, such as those caused by surgery or the insertion of catheters during hospital treatment.

In many cases bloodstream infections can be transient and asymptomatic. However it is also possible for the infection to persist and for Sepsis to develop. Sepsis results from a systemic immune response and can cause severe symptoms including fever, elevated heart rate and rapid breathing. It is a potentially lethal condition that is responsible for 37,000 deaths in the UK annually. In addition to being the cause of significant morbidity and mortality, dealing with Sepsis also costs the NHS £2.5 billion per year and is responsible for 30% of bed occupancy in intensive care units.

In cases of bloodstream infection, particularly sepsis, early diagnosis and therapeutic intervention are critical to facilitating effective treatment. Sepsis diagnosis and identification of the causative organism has traditionally involved phenotypic analysis of organisms isolated from positive blood cultures. However this process can take days, during which time patients may be treated with broad-spectrum antibiotics until positive pathogen identification becomes available. The scenario is further complicated by the incidence of antibiotic resistance in microbial populations, which brings additional challenges to the process of selecting the appropriate antimicrobial agent.

It is therefore unsurprising that a great deal of attention has focused on how to speed up pathogen identification so that appropriate therapy can be implemented as quickly as possible. When a blood culture is flagged as positive a gram stain is taken that can provide an indication as to the type of organism responsible for the infection. While this is helpful, tailored therapeutic intervention relies on identification to species level, which can take a further 24-48 hours using conventional techniques.

A number of approaches have been tried to speed up this process. Biochemical assays (such as the coagulase assay used to characterise Staphylococci) are widely used but are not always completely accurate and may not provide a result for several hours. Molecular assays based on RT-PCR or nanoparticles have also come onto the market, but have a limited species range and require expensive equipment.

One of the most promising technologies to come onto the market recently has been MALDI-TOF. This versatile technique can theoretically identify any organism and has been adopted by a number of clinical microbiology laboratories. While it has proven to be effective in many cases, it has also been seen to have limitations in some cases. These include identification of organisms in the case of polymicrobial bacteraemia, and the identification of organisms with more robust cell walls such as yeasts and some gram-positive bacteria.

Introducing QuickFISH

On this site we present the QuickFISH system. This technology is designed to identify a variety of pathogens directly from positive blood cultures in 20 minutes. This simple assay can be used as a stand-alone system in a clinical microbiology laboratory. However its adaptability and ability to identify pathogens in those situations where a MALDI-TOF system may encounter issues also makes it the ideal backup system for a MALDI-TOF.

As speed and accuracy are critical when reporting pathogen ID in cases of sepsis, we are proud to partner with AdvanDX to make the QuickFISH system available to clinical microbiology laboratories in the UK. We hope that the information on this web site will prove to be helpful and informative, but please feel very welcome to contact us if you would like further information about how the QuickFISH system could work for you.

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