Accelr8 Technology Corporation announced study results today that were presented at the joint sessions of the 48 th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC, www.icaac.org) and the Infectious Diseases Society of America (IDSA, www.idsociety.org), October 25-29 in Washington, DC.
The purpose of the study was to characterize a rapid test run on Accelr8 ' s BACcel diagnostic system to detect a broad multiple antibiotic resistance mechanism known as " ESBL, " which stands for " extended spectrum beta-lactamase. " This type of resistance includes hundreds of variant enzymes produced by pathogenic bacteria. The enzymes destroy almost all drugs in the beta-lactam antibiotic class, which is the largest single family of antibiotics and contains more than 50 different types. Beta-lactams include penicillins and cephalosporins. They are the most widely prescribed antibiotics and most favored because of their speed, potency, and safety. ESBLs represent one of the most threatening, rapidly spreading, complex forms of drug resistance according to IDSA and the CDC (US Centers for Disease Control and Prevention). Organisms that express ESBLs also tend to carry additional resistance mechanisms against other antibiotic families. Therefore ESBLs also serve as markers of multiple drug resistance (MDR) or " superbugs. "
Standard culture-based confirmation tests for ESBLs typically require 2-3 days to perform. Using pure clinical strains, the new study demonstrated reportable test results in 90 to 180 minutes. The test achieved sensitivity of 96% and specificity of 96%, on 53 positive and 73 negative (control) strains. The test used the same agents as standard tests, but performed with high speed and accuracy through the use of automated microscopy and image analysis of small numbers of immobilized individual bacteria.
The research investigators included scientists from the Barnes-Jewish Hospital and the Washington University in St. Louis School of Medicine (St. Louis, MO), and from Accelr8. The study analyzed bacterial strains previously characterized for ESBL expression, and control strains that lacked the resistance enzymes. Species included Klebsiella pneumoniae and E. coli , which commonly infect ICU patients. These species are leading members of a large family of bacteria that account for approximately 25% to 35% of serious hospital infections.
The company had previously presented results for two different tests designed for " Staph " infections (including MRSA). The new test expands the diagnostic spectrum into a larger class of organisms known as " Gram-negative " bacteria that are more numerous than " Staph " in the ICU, more highly resistant, more difficult to identify, and more difficult to treat. Accelr8 plans to add more tests for the other problematic resistance types found in the same pathogen groups. Accelr8 also plans to expand with a third category of highly resistant bacteria that includes Pseudomonas and Acinetobacter . This latter category accounts for as many as one-third of dangerous ICU infections that are the most difficult to diagnose and treat.
According to David Howson, Accelr8's president, " these new results make the BACcel system the first rapid platform to demonstrate realistic potential to simultaneously analyze all of the most dangerous bacteria in the ICU. This is the first reported practical rapid test to address Gram-negative bacteria. We have achieved unprecedented speed with high accuracy on resistance types whose nature precludes alternative rapid diagnostic technology such as gene identification. When we add the test time to the short time needed for sample preparation and organism identification, the total time to result is well within our original goal of 8 hours after receiving a specimen. In addition, the numbers of bacteria required for accurate analysis are well within the range available directly from a specimen without prior culturing. This progress supports our commitment to expand the BACcel system ' s analytical spectrum and achieve our performance objectives. "