Identification of Burkholderia Cepacia Complex Isolates by MALDI-TOF MS from Burkholderia Cepacia Selective Agar
Jolanta Jedrzkiewicz, Mark Fisher. University of Utah, Salt Lake City, UT
Background: Despite modern advances in the management of cystic fibrosis patients, Burkholderia cepacia remains a troublesome diagnosis. The prognosis is much worse for cystic fibrosis patients colonized with members of the B. cepacia complex (Bcc), especially after lung transplantation. Therefore, correct identification of the Bcc is extremely important for appropriate management. The B. cepacia complex can be difficult to identify because of its heterogeneous colony morphology and ambiguous metabolic profiles. Specialized media such as Burkholderia cepacia Selective Agar (BCSA) is often used to improve the isolation of Bcc, however additional testing is required to confirm an isolate belongs to the Bcc. Confirmatory testing may include extended biochemical panels, 16S rRNA gene sequencing, or more recently, Matrix-assisted laser desorption-ionization time-of flight mass spectrometry (MALDI-TOF MS) analysis. MALDI-TOF MS compares spectral patterns from unknown isolates to a database of known spectra. Previous studies have shown variability in MALDI-TOF identification of bacteria from selective media. Within this study, we evaluated the performance of MALDI-TOF identification of Bcc isolates grown on BCSA.
Design: We examined 31 Bcc isolates previously identified using 16S sequencing. Isolates were plated on Columbia sheep blood agar (SBA) or BCSA and incubated aerobically at 350C. Isolates were harvested from both media and were prepared using both direct smear and extraction methods. MALDI-TOF scores and identifications were compiled and mean scores compared by the students t-test.
Results: Most isolates scored >2.0, consistent with species-level identification. All samples were identified as species belonging to the B. cepacia complex. On average, samples analyzed after extraction yielded higher scores than direct smear samples. There was not a statistically significant difference between scores from SBA and BCSA groups by either sample preparation method.
Conclusions: Our data suggest that B. cepacia may be successfully identified directly from BCSA without the need to first subculture to nonselective media.
Wednesday, March 6, 2013 9:30 AM
Poster Session V # 248, Wednesday Morning