A rapid detection test for Exserhilum rostratum, the fungus primarily responsible for 39 deaths among patients injected last year with a contaminated steroid medication, has been developed by a research team led by David S. Perlin, PhD, Executive Director of the Public Health Research Institute (PHRI) at the University of Medicine and Dentistry of New Jersey-New Jersey Medical School. Details of the test have been published online by the Journal of Clinical Microbiology.
To date, clinicians and public health officials have been limited in their ability to detect the fungus in clinical samples such as cerebrospinal fluid, because the fungus tends not to be free-floating in the samples. The newly developed test improves on existing detection methods by using molecular beacon technology in a real-time polymerase chain reaction (PCR) assay. Through this approach, investigators have been able to detect a wide range of genomic DNA from E. rostratum, even in samples where abundant human DNA was also present. Fungal DNA has been reliably detected in amounts as small as 100 fg (femtograms, which are quadrillionths of a gram). The assay also detected DNA sequences from several related species of fungi, while tests of lab samples containing other species of fungi produced negative results, indicating a high level of specificity for the assay.
Perlin says, "The assay is a highly sensitive and robust method for early detection of the fungus in patients who might be infected but do not yet show symptoms, and also to monitor the progress of ongoing medical treatment." For critically ill patients, rapid diagnosis is essential and this assay has the potential to detect the presence of infecting fungus in less than two hours. "It is estimated that some 13,534 people received injections that might have exposed them to this fungus during the recent outbreak," notes Perlin. "We don't know the exact timeline for development of disease, and so we are not sure whether these patients are still are at risk. Using an assay such as this to detect possible infection in those patients could ease their minds if results are negative, or lead them to receive therapy in time to prevent future illness if results are positive."