Issue 80  October 26th 2018

Entering a New Era of Blood Culture Testing Technology

In an exclusive interview, Contagion® sat down with one of the presenters, Melvin Weinstein MD, professor of medicine, pathology, and laboratory medicine, chief of the Division of Infectious Diseases, Allergy, and Immunology, and co-director of the Microbiology Laboratory at Rutgers Robert Wood Johnson Medical School, to discuss the current challenges in the laboratory diagnosis of bloodstream infections and emerging technologies that will advance the field (interview videos in the article).

Can you speak to some of the newer technologies that are emerging? The newer technologies are mostly molecular-based; they are either single-plex or multiplex Polymerase chain reaction (PCR) assays or if they’re not PCR, they are other DNA amplification techniques. There are assays that target specific organisms like Staphylococcaceae; the GeneXpert Staph SR assay, can differentiate methicillin-susceptible from methicillin-resistant Staphylococcus aureus from non-Staph aureus isolates and do that in approximately an hour, directly out of a positive blood culture model.

There are also new assays from BioFire, which is called the BCID (blood culture identification) assay, which has 27 different targets—multiple gram-positive targets, gram-negative targets, and also several Candida targets—and can detect the Klebsiella pneumoniae carbapenemase (KPC) and those results are also direct from a positive blood culture and you will get your results within about 1 hour.

There’s a similar technology, similar in concept at least, from Luminex, it’s called the Verigene; that has 30 targets—again gram-positive targets, gram-negative targets—and that technology can provide results for 6 different resistance genes for gram-negatives of the CTX-M-ESBL (CefiTaXime Extended Spectrum Beta-Lactamase), the KPC, and other carbapenemases, and also, for gram-positives, it detects the mecA gene, and also the VanA and VanB genes that confer resistance to vancomycin in enterococci.

New test rapidly identifies antibiotic-resistant 'superbugs'

A simple and inexpensive new test developed by researchers at the University of California, Berkeley, can diagnose patients with antibiotic-resistant strains of bacteria in a matter of minutes. The technique could help doctors prescribe the right class of antibiotics for each infection, and could help limit the spread of antibiotic-resistant "superbugs" that kill as many as 700,000 people worldwide each year.

The test, dubbed DETECT, spots the molecular signatures of antibiotic-resistant bacteria directly in urine samples. Unlike other techniques that are currently on the market, DETECT does not require expensive instrumentation and is simple enough to be applied in a point-of-care setting.

The DETECT technique uses an enzymatic chain reaction to boost the signal from beta-lactamases by a factor of 40,000, high enough to allow detection of the presence of these enzymes in urine samples. With DETECT, a patient who tests positive for an infection that is resistant to early-generation antibiotics can immediately be treated with a more powerful antibiotic or alternative agent.

The team tested DETECT on 40 urine samples collected from patients suspected of having a urinary tract infection, and found that approximately one-quarter of them had antibiotic-resistant infections.

24-hour cancer clinic reduces ED visits, patient costs

A 24-hour cancer clinic at Froedtert & the Medical College of Wisconsin resulted in a 26% reduction in ED utilization and high patient satisfaction, according to a presentation at the Association of Community Cancer Centers National Oncology Conference. The clinic was able to provide services which included urgent labs and basic diagnostics, such as ECG, X-ray and CT scan. The clinic included two inpatient rooms and was staffed with one hematology/oncology advanced practice provider and two nurses, or a nurse and a technician.

In its first year, the 24-hour cancer clinic reduced ED utilization for oncology patients by 26%. When comparing diagnostic utilization, patients seen in the 24-hour clinic had fewer radiology orders (11% vs. 75%), 12-lead ECG orders (4% vs. 44%) and lab orders (71% vs. 87%) than those seen in the ED.

“What we found was that some of it was just standard practice in the ED and some of it was experience with oncology,” said Tina Curtis, DNP, MBA, RN, NEA-BC, Executive Director of cancer services. “We could find the labs, or find the scans more easily than they could find them in the ED. We could talk to providers who would say, ‘I’m OK if these labs are a few hours old. I don’t need to reorder it.’ Whereas in the ED, they weren’t as comfortable.”

Fewer orders resulted in patient savings. Among patients who were admitted, those who were seen in the clinic had a median patient charge for diagnostic testing that was $2,521 less than for those seen in the ED. Among those who were discharged, diagnostic testing charges were $1,162 lower among those seen in the clinic.

One Gene Could Be Responsible for Acute Myeloid Leukemia

The EVI1 gene may be single-handedly at fault for acute myeloid leukemia (AML), according to research published in Nature Communications. Researchers from the Wilmot Cancer Institute at the University of Rochester Medical Center studied EVI1 in the hopes that a new therapy could improve survival rates for patients with AML.

The researchers were able to show, using a mouse model, how EVI1 binds to certain DNA molecules and disrupts the blood system, leading to the expansion of myeloid cells. “It’s not so pie-in-the-sky anymore to think we can interrupt the process within the genome that leads to leukemia,” senior author Archibald Perkins, MD, PhD.

When EVI1 is overexpressed, it changes the metabolism of immature blood cells, and the researchers sought to understand what happens after the gene is overexpressed and permanently turned on. When EVI1 is overexpressed, it produces 10,000 to 50,000 copies. The authors noted that “overexpression of EVI1 is virtually never seen in non-myeloid leukemias or lymphomas.” Using the mouse model, the researchers showed that skewing toward myeloid production is “dependent on DNA binding by EVI1.”

A targeted therapy that blocks EVI1’s ability to bind to other genes could provide a new approach for treating AML. Currently, the 5-year survival rate for AML is just 25%, despite the fact that treatments for other blood cancers have improved. Overexpression of EVI1 is associated with a median overall survival in AML of just 12 months.

An RNA key that unlocks innate immunity

New research from Emory University, published in the Journal of Biological Chemistry, shows that RNA molecules may be a key player in human cells' frontline defenses against viruses. Graeme Conn, the biochemistry professor who oversaw the work, studies how RNA is involved in the body's responses to infections. When a human cell senses a virus, it activates a signaling pathway: a protein called OAS gets turned on and produces a signaling molecule, which in turn activates another protein that both directly defends against the virus as well as activating other parts of the cell's innate immune system.

As it turns out, human RNA might play an important role in this pathway, specifically a human RNA molecule called nc886. The "nc" stands for "noncoding," which means this RNA molecule is not carrying instructions for building a protein. It's doing something all on its own. What it's doing, the new paper shows, is turning on OAS, thus setting off the chain of events that destroys viruses. "We saw that (nc886) wasn't just an activator of this pathway, but a very potent activator," said Brenda Calderon, who carried out the research as a graduate student in Conn's lab.

The nc886 molecule can adopt two different shapes, and one of them is much better at activating OAS than the other. This is another way in which this RNA molecule acts like a protein: its function depends strongly on its 3-D shape and structure. Although nc886 is present in all human cells, it's unknown whether the relative abundance of the immune-activating and less-active form might change in response to infection.

Getting deep into the molecular details of cells' first responses to viruses opens the door to new kinds of treatments. Calderon speculates that understanding the factors that activate this pathway may enable researchers to someday manipulate it to strengthen antiviral defenses.

'Surely a test is a test': Shock over blood results for toxic chemical

The reliability of a national blood sampling program for toxic firefighting chemicals is under question, after a private test showed more than double the level of a contaminant in a man’s blood compared to a government sample taken on the same day.

The fresh concerns over testing methods for per- and poly-fluoroalkyl chemicals [PFAS] come after Fairfax Media independently sampled a drain near a military base last year and discovered the chemicals at levels 34 times higher than those reported by authorities.

Terry Robinson, who occupies a polluted acreage near the Williamtown RAAF base, had his blood sampled twice on March 19. The government-commissioned test, seen by Fairfax Media, detected the chemical in his blood at 21 ng/ml, while the privately funded testing found more than twice that, at 49 ng/ml. The laboratories detected the chemical of the greatest concern, perfluorooctane sulfonate (PFOS), at 60 ng/ml and 70 ng/ml respectively.

The federal government is facing multiple class action lawsuits over its refusal to compensate people stranded on unsaleable properties as a result of Defence’s use of firefighting foams containing the potentially carcinogenic chemicals. The Department of Health has offered a free blood test to people living and working near contaminated military bases through a contractor - Sonic Healthcare - at a cost of more than $3 million.

New Point-of-Care Troponin Assay Can Rapidly Rule Out Heart Attack

Importance: Emergency department (ED) investigations of patients with suspected acute myocardial infarction (AMI) are time consuming, partly because of the turnaround time of laboratory tests. Current point-of-care troponin assays shorten test turnaround times but lack precision at lower concentrations. Development of point-of-care troponin assays with greater analytical precision could reduce the decision-making time in EDs for ruling out AMI.

Objective: To determine the clinical accuracy for AMI of a single troponin concentration measured on arrival to ED with a new-generation, higher precision point-of-care assay with a 15-minute turnaround time.

Main Outcomes and Measures: The primary outcome was type 1 AMI during index presentation. We compared the discrimination ability of the TnI-Nx assay with the hs-cTnI assay using the area under receiver operator characteristic curve (AUC) and sensitivity, negative predictive value, and the proportion of negative test results at thresholds with 100% sensitivity.

Results: Of 354 patients (255 [72.0%] men; mean [SD] age, 62 [12] years), 57 (16.1%) experienced an AMI. Eighty-five patients (24.0%) presented to the ED less than 3 hours after symptom onset. No difference was found between the AUC of the TnI-Nx assay (0.975 [95% CI, 0.958-0.993]) and the hs-cTnI assay (0.970 [95% CI, 0.949 to 0.990]; P = .46). A TnI-Nx assay result of less than 11 ng/L identified 201 patients (56.7%) as low risk, with a sensitivity of 100% (95% CI, 93.7%-100%) and a negative predictive value of 100% (95% CI, 98.2%-100%). In comparison, an hs-cTnI assay result of less than 3 ng/L identified 154 patients (43.5%) as low risk, with a sensitivity of 100% (95% CI, 93.7%-100%) and a negative predictive value of 100% (95% CI, 97.6%-100%).

Conclusions and Relevance: A novel point-of-care troponin assay that can produce a result 15 minutes after blood sampling had comparable discrimination ability to an hs-cTnI assay for ruling out AMI after a single blood test. Use in the ED may facilitate earlier decision making and could expedite the safe discharge of a large proportion of low-risk patients.

Saving Patients From Unnecessary Chemotherapy with a Blood Test

Right now, many cancer patients get chemotherapy after surgery to ensure that their cancer will not come back; there has not been a way to tell how likely that is. With a new test, cancer patients that don’t need that chemotherapy may now not have to receive it. Melbourne researchers created a simple blood test that can show whether or not patients need chemotherapy after surgery. If they do, the test may help indicate the dose they will need. The test is described in this video, featuring the researchers.

The test is circulating tumor DNA (ctDNA) based; it identifies bits of tumor DNA that are present in the patient’s bloodstream after surgery has excised their cancer. A trial is underway to determine whether the ctDNA level correlates with the likelihood of relapse. If a patient does not show ctDNA in their blood, they would not get chemotherapy. Those with high ctDNA levels, however, may receive aggressive chemotherapy to prevent relapse.

The trial, ongoing since 2015, showed that early stage bowel cancer patients can be grouped by high and low risk. It has been broadened to include ovarian cancer patients since 2017.

"We suspect that many women with early-stage ovarian cancer can be treated with surgery alone, but we currently treat all these patients as though their cancer may recur, with high dose chemotherapy," said Sumi Ananda, a Walter and Eliza Hall Institute clinician-researcher Associate Professor, who led the ovarian cancer trial.