Lateral flow assay for detecting colonization by Streptococcus agalactiae

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DESCRIPTION (provided by applicant): Streptococcus agalactiae, a.k.a. group B streptococcus (GBS), is one of the leading causes of morbidity, and mortality among newborns. We propose to develop a molecular assay for GBS using our proprietary helicase dependent amplification (HDA), and a lateral flow strip embedded in a device that encloses the reaction vessel to prevent contamination of the laboratory by amplicons. HDA is similar to the polymerase chain reaction (PCR) in that it uses two primers to exponentially amplify nucleic acids. Like PCR, HDA assays can use a competitive internal control; i.e., a template DNA of known concentration spiked into the raw sample that can be amplified by the same primers as the analyte, but detected separately. Unlike PCR, HDA is entirely isothermal, and thus does not require costly thermocyclers. In fact we routinely use water baths to perform assays. The objectives for Phase I are to: 1) Validate the sensitivity and specificity of the assay with a panel of DNA samples from near neighbor strains, as well as strains commonly found in the sampling sites. 2) Evaluate the performance of the filtration sample preparation method proposed in the body with clinical specimens from Dr. Gary Procop, University of Miami Medical Center (UMMC). 3) Develop a clinical plan & a pre-IDE for review by the Food and Drug Administration (FDA) for a multi-site clinical study to seek regulatory clearance for sale of the assay for human diagnostics. The milestone for this Phase I is to deliver a pre-IDE to FDA. Comments from FDA will be used to design a clinical study during Phase II. We believe our proposed assay system can obtained the moderate degree of complexity designation from the FDA. Indeed, to obtain such a designation, a system manufacturer must obtain a score of 12 of less when answering 7 questions covering: user knowledge, user training, reagent preparation, operational steps, testing materials, troubleshooting, and result interpretation. The answer to these 7 questions can receive a score of 1 or 3. We estimate our proposed system could get a score of 11. Considering our assay system will not require costly instrumentation and plastic disposables, we believe we can offer a useful alternative to the Xpert GBS(tm), if we can obtain FDA clearance for our test. Support from NIAID is essential to reaching this goal. PUBLIC HEALTH RELEVANCE: Group B streptococcus (GBS) infection of newborns usually takes place in the birth canal and can lead to sepsis, pneumonia, and meningitis. GBS infection of neonates is estimated to cost roughly $300 million in additional healthcare costs. The current "standard of care" is to screen all women at 35 to 37 weeks of gestation, and to eradicate GBS in colonized women. Despite this aggressive approach, invasive early-onset disease incidence has only declined by 34% in the US. Risk factors for early-onset invasive GBS in the newborns are: rupture of membranes more than 18 h before delivery, a febrile mother during labor, preterm delivery, and a history of GBS disease in a previous delivery. Current practice it to prescribe prophylactic antibiotics to mothers with the aforementioned risk profile, even in the absence of evidence of colonization by GBS. Premature rupture of membranes (PROM) occurs in approximately one third of preterm births and it increases the potential for perinatal infection because of its association with brief latency between membrane rupture, and delivery. Preterm pregnancies only represent 7% to 11% of births, but account for 32% to 38% of early-onset GBS disease because the mother was not tested prior to labor. CDC estimates that there are 500,000 pre-term births, and 143,000 births from mothers that received no pre-natal care in the United States. When culture is performed at the time of delivery, it seldom provides a sufficiently rapid turnaround time to influence the decision of whether or not to initiate antimicrobial therapy. A rapid test is clearly needed to test women just before delivery. Unfortunately, current rapid test options are insensitive, too slow, or too costly. Some culture-based tests allow for relatively rapid detection of GBS colonization in heavily colonized women. For example, the FDA cleared StrepB Carrot Broth" (Hardy Diagnostics, Santa Maria, CA) can detect heavy GBS colonization in as little as 6 hours after inoculation of the culture. FDA cleared probe based nucleic acid tests to detect GBS grown in cluture are also commercially available. Unfortunately, 6 hours is too long in many situations. Cepheid's GeneXpert System has obtained FDA clearance for use in laboratories cleared for performing test with "a moderate degree of complexity". This test can yield results in less than 1 hour, but it is far more costly than the slower alternatives. Some physicians have questioned the economic justification for the test. We propose to offer a lower cost molecular assay with an intermediate assay time of ~1 to 2 hours that should also be eligible for being categorized as a moderate degree of complexity assay by FDA.