BLOOD CULTURE
changing after-effects following a sepsis episode.3
To put this in
perspective, sepsis kills more than breast, bowel and prostate cancer combined, and doubles the amount of heart attack admissions in the UK each year.3 With the severity and rapid onset of sepsis it is imperative to diagnose and treat with minimal delay, every hospital in the UK uses the ‘Sepsis Six’ pathway, which states that blood cultures should be taken and antimicrobials administered within the first hour.3 The early initiation of effective antibiotic treatment has been proven to reduce mortality and improve clinical outcomes in patients with severe sepsis or septic shock.4
Moreover,
Retamar found a correlation between inadequate empiric therapy and increased mortality in patients with bloodstream infections.5
Same-day identification To provide effective antimicrobial therapy the associated organism needs to be identified. Same-day organism identification from a positive blood culture is already here, and various phenotypic and genotypic microbial diagnostic platforms have been used routinely within microbiology for a long time now. We now are starting to see a number of fast and effective same-day AST profiling methods to support the identification process.
As suggested same-day microbiology is crucial for potentially septic patients as correct targeted antimicrobial therapy, rather than a ‘best guess’ enables a much better patient prognosis. It also allows for targeted antimicrobial confirmation and escalation therapy and permits de- escalation of unnecessary antimicrobial usage promptly. Quick diagnostic and AST results when used in conjunction with efficient antimicrobial stewardship can ultimately provide a decrease in pharmacy costs; a reduction in hospital stay times with associated bed day savings; and most importantly a better patient prognosis. There is also a need to stop antimicrobials when they are not needed, with associated patient toxicity and increased usage leading to antimicrobial resistance (AMR). In my opinion AMR is the sleeping pandemic and will pose more of a healthcare problem than cancer in the not-too- distant future! Have a look at the O’Neill review on antimicrobial resistance where it is predicted that by 2050 over 10 million deaths may be attributed to AMR.6
Interestingly Bae, Smith and 20
skilled biomedical scientists to interpret. Furthermore, Berinson et al. suggests that RAST has clear limitations as a de-escalation tool, particularly where MDR organisms are concerned. They go on to suggest that automated assays may provide the basis for more valid escalation and de-escalation decisions at the bedside.13
Every hospital in the UK uses the ‘Sepsis Six’ pathway.
Monogue conducted a case-control study to evaluate the unnecessary use of intravenous broad-spectrum antibiotics in presumed sepsis and septic-shock patients, and concluded that only 19.3% had a confirmed bacterial infection, and a high number of patients received broad spectrum antibiotics without confirmed or suspected bacterial infection.7 Along with rising AMR rates, we know a number of organisms are adept to developing resistance mechanisms to our currently available antibiotics. This is compounded by how we use (and misuse) antibiotics around the globe. Inappropriate antibiotic use has resulted in the development of multi drug resistant (MDR) organisms. Due to the widespread distribution of these MDR organisms, empiric antimicrobial treatment can be inappropriate in up to 50% of cases,8 with dramatic clinical and economic consequences: an increase in morbidity and mortality,9
in length of stay,10 in hospital costs.9 and Notably, ICU settings
are characterised by a higher incidence of resistant and MDR organisms which increases the risk of inappropriate empiric therapy.11
Some of the most common
bacteria responsible for or associated with bacteremia, Acinetobacter, Pseudomonas and various Enterobacteriaceae, have become multidrug resistant and the WHO has included them on the list of the pathogens of critical priority in the pursuit of new therapeutic options (2017).12
Antimicrobial susceptibility testing
The need for speed has been indicated by the introduction of the EUCAST rapid antimicrobial susceptibility testing, (RAST) process. Where agar-based disc diffusion is performed directly from positive blood cultures from potential septic patients, with breakpoints for short incubation periods of four, six and eight hours. These methods can provide same-day results but are labour intensive and require
Automated rapid same- day AST platforms have been an exciting addition to the exhibition stands at both ECCMID and IBMS Congress over the last few years. These
include the Accelerate Arc, the ASTar, the dRASTTM, and the SPECIFIC REVEAL platforms, all of which I have been fortunate enough to view. In my opinion, with targeted use within the microbiology laboratory these platforms could provide a fast and efficient same day AST profile to support phenotypic/genotypic typing platforms from positive blood cultures. This could potentially be a game changer for patients with suspected sepsis. The platforms provide a fast four- to-six-hour time to result, enabling effective antimicrobial stewardship. They all work slightly differently with some using bacterial morphological changes by time lapsed imaging, flow cytometry, and sensors to detect changes in volatile organic compounds, to provide speedy AST analysis. Some require a centrifugation step, with accurate pipetting and use of MacFarland standards, while others are truly plug- and-play platforms. The range of antibiotics that can measured in an assay is impressive, with over 20 being usually available, enabling an extensive range of options for the microbiologist to advise usage on. This far outstrips the EUCAST agar-based RAST plate where a maximum of six antibiotics can be analysed on each plate. Some of the platforms also enable AST profiles on fastidious organisms like Haemophilus influenzae, and all manufacturers are committed to increasing organism coverage. Most of the platforms use extrapolation of the growth curve to determine the minimum inhibitory concentration (MIC). Although one of the platforms impressively provides a true MIC by microbroth dilution and incubation, dependant on the initial bacterial load present in the positive blood culture bottle.
Patient care benefits The beneficial clinical impact of these platforms in patients with suspected sepsis are clear to see. In a recent
FEBRUARY 2024
WWW.PATHOLOGYINPRACTICE.COM
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
