Bacterial Test Well-Suited for Small, Medium Labs, Study Says

June 29, 2018 – NEW YORK (GenomeWeb) – Researchers from four clinical microbiology laboratories reported this month that the iC-GPC assay developed by Huntsville, Alabama-based iCubate is an accurate and reliable tool for the detection of the five most common gram-positive bacteria responsible for bloodstream infections.

Additionally, the test detects the presence of the three clinically relevant antibiotic resistance markers specific to methicillin-resistant Staphylococcus and vancomycin-resistant Enterococcus, they noted.

The firm’s assay and system may be particularly suitable for use in small and medium laboratories that don’t have the sophisticated technical staff or time to devote to run more technical and more expensive assays, Paul Granato, a researcher at the Laboratory Alliance of Central New York, one of the labs that evaluated the assay, said in an interview.

He added that for such labs, the iCubate system and assay could also be less expensive.

Most importantly, the use of direct detection molecular blood culture assays, such as the iC-GPC, will significantly reduce morbidity and mortality rates, shorten hospital stays, decrease costs, and favorably impact hospital antibiotic stewardship programs, the researchers noted.

Granato’s lab collaborated with investigators from Tampa General Hospital, Tampa, Florida; TriCore Laboratories, Albuquerque, New Mexico; and Medical College of Wisconsin, Milwaukee, Wisconsin. In a study published this month in the Journal of Clinical Microbiology, they noted that the assay had a 95.5 percent agreement with a Luminex gram positive assay running on its Nanosphere Verigene I system.

The iC-GPC assay was cleared by the US Food and Drug Administration and CE marked in August last year. A clinical trial is underway to evaluate a gram-negative assay on the iCubate system, a benchtop, fully integrated cartridge-based molecular diagnostic platform capable of running highly multiplexed assays using the company’s amplicon-rescued multiplex, or ARM, PCR method.

The firm’s cleared gram-positive assay is a qualitative, multiplex test for the direct detection from positive blood cultures of five of the most common gram-positive bacteria responsible for bacterial bloodstream infections — Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Enterococcus faecalis, and Enterococcus faecium. In the multicenter trial, involving testing on 1,134 patient blood culture specimens that were positive for gram-positive cocci, the assay also detected the presence of mecA, vanA, and vanB resistance determinants. Researchers tested discordant specimens using primarily reverse sequencing in an independent lab, Granato said.

Carter Wells, CEO of iCubate, said in an interview that “its assay performed as expected with results that will undoubtedly have a positive impact.” The firm soon plans to pursue FDA clearance and CE marking for the gram-negative panel. It anticipates completing regulatory work on the gram-negative assay in the coming months, and the firm has a “robust pipeline with assays” of relevance in the US and overseas, Wells said.

“Traditional methods for the diagnosis or detection of what is causing bloodstream infections, such as septicemia, take two to five days to identify the bacterium and determine what type of antibiotic would be most appropriate for the treatment of a patient,” Granato said.

The researchers noted in their paper that in recent years, diagnostic industry players have developed a range of methods for the rapid identification of bacterial pathogens in positive blood culture broths, including peptide nucleic acid fluorescence in situ hybridization (PNA-FISH), MALDI-TOF mass spec, real-time PCR, and microarray analysis. They noted that these systems are capable of identifying a bacterial agent as a cause of bloodstream infection within one to several hours after a positive culture has been identified.

That has led to reductions in the time to appropriate antimicrobial therapy, length of stay in hospitals, mortality rates, and cost of care. They have also contributed to patient care by detecting the presence of resistance gene markers for methicillin resistance, vancomycin resistance, extended-spectrum beta-lactamases, and carbapenemases.

In addition to the iCubate and Luminex systems and assays for identifying bloodstream infections, the FDA is evaluating and has cleared a number of competing tests.

On Thursday, GenMark Diagnostics said that it had applied to the FDA for clearance of its ePlex Blood Culture ID – Gram Positive (BCID-GP) panel. It is the first of three blood culture panels being developed on the ePlex molecular sample-to-answer system for the diagnosis and management of bloodstream infections that can lead to sepsis, the firm said.

Accelerate Diagnostics’ Pheno system and kits for bloodstream infection identification and antimicrobial susceptibility testing received FDA clearance in February 2016. In May, the FDA cleared T2 Biosystems’ T2Bacteria Panel, which detects species of bacteria directly from whole-blood samples from patients with potential bloodstream infections in roughly five hours.

However, the clinical trial researchers noted that drawbacks exist for the iC-GPC Assay and for molecular diagnostics in general. For example, the iC-GPC assay doesn’t cover all of the causative organisms of bloodstream infection, they said.

But the assay’s design also has advantages. It operates in a single closed system disposable cassette and therefore requires only a few minutes of setup time, they noted. Its closed system also eliminates the potential of carryover contamination between assays, and the system’s processor can simultaneously handle random access processing of up to four cassettes on its small-footprint instrument platform. A lab requiring higher throughput can link processors to a single reader, leading to the iC-GPC assay providing “a significantly affordable alternative,” particularly for small- to medium-sized healthcare institutions, the researchers noted.

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