Rapid Identification of Bacteria and Candida from Blood Culture Bottles using the Ibis Sterile Fluid Bacterial Assay
Wed 3:00 PM - Track 1: New Advances
Erin M. Johnson
University of Arizona
Erin M. Johnson, Department of Chemistry and Biochemistry, University of Arizona, Tucson AZ
Donna M. Wolk, Clinical Pathology, University of Arizona/Bio5 Institute, Tucson AZ
Desiree R. Johnson, University of Arizona/Bio5 Institute, Tucson AZ
Andrew E. Clark, University of Arizona/Bio5 Institute, Tucson AZ
Lorraine L. Dominguez, University Medical Center, Tucson AZ
Vicki H. Wysocki, Department of Chemistry and Biochemistry, University of Arizona, Tucson AZ
The ability to rapidly identify the causative agent in blood-borne infections is paramount to clinical microbiology, as it has the ability to reduce both incurred costs and the rate of mortality from patients with bacteremia. Traditional methods currently employed for the definitive identification of pathogenic bacteria and yeast from blood culture bottles rely heavily on phenotypic biochemical profiles such as from PNA FISH or Vitek cards, which can be time consuming to acquire and have difficulty in resolving mixtures of contaminating bacteria. The Ibis Sterile Fluid Bacterial and Candida Assay (SFBCA) has the ability to rapidly identify virtually any bacteria or yeast using broad range amplification of microbial DNA by polymerase chain reaction coupled to electrospray ionization mass spectrometry. This assay contains 18 primer pairs, focusing on variable regions as well as antibiotic resistance genes. The mass spectrometric signal of each amplicon can be used to unambiguously derive base compositions of the target sequence, which can be compared to a database for organism classification.

The SFBCA was used to accurately identify gram positive and negative bacteria and yeast cultivated from 200 BacT/ALERT SN aerobic and FN anaerobic blood culture bottles after extraction with the Qiagen EZ-1 Whole Blood Assay with concordance on the genus and species level. These identifications were then compared to results from phenotypic evaluation after subculture as a reference to determine the incidence of concordance of the SFBCA results. Of the 172 bottles sampled, 94% were identified correctly. The majority of discordant results are due to skin flora, which was underrepresented in the database containing common blood borne pathogens. This assay was capable of a positive identification from bottle to result in approximately 6 hours, demonstrating its potential as a rapid and accurate method for the evaluation of bacterial and Candida species from blood culture bottles in a single multiplexed method. Furthermore, the lack of a need for subculturing prior to evaluation demonstrates the efficiency in resolving mixed bacterial contaminations, also showing a strong benefit for clinical use.

Supported by:
National Institutes of Health Grant U54-AI065359 (Pacific Southwest Regional Center for Excellence)
National Institutes of Health Chemistry-Biology Interface Training Grant T32GM008804 to E.M.J.
Abbott Molecular / Ibis Biosciences