Rapid identification of bacteria in positive blood culture broths by matrix-assisted laser desorption ionization-time of flight mass spectrometry.
Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry is a rapid, accurate method for identifying bacteria and fungi recovered on agar culture media. We report herein a method for the direct identification of bacteria in positive blood culture broths by MALDI-TOF mass spectrometry. A total of 212 positive cultures were examined, representing 32 genera and 60 species or groups. The identification of bacterial isolates by MALDI-TOF mass spectrometry was compared with biochemical testing, and discrepancies were resolved by gene sequencing. No identification (spectral score of < 1.7) was obtained for 42 (19.8%) of the isolates, due most commonly to insufficient numbers of bacteria in the blood culture broth. Of the bacteria with a spectral score of > or = 1.7, 162 (95.3%) of 170 isolates were correctly identified. All 8 isolates of Streptococcus mitis were misidentified as being Streptococcus pneumoniae isolates. This method provides a rapid, accurate, definitive identification of bacteria within 1 h of detection in positive blood cultures with the caveat that the identification of S. pneumoniae would have to be confirmed by an alternative test.
Stevenson
Lindsay G
LG
Microbiology Service, Department of Laboratory Medicine, Clinical Center, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892-1508, USA.
Drake
Steven K
SK
Murray
Patrick R
PR
D016470:Bacteremia / Q000175:diagnosis* / Q000382:microbiology; D001419:Bacteria / Q000737:chemistry* / Q000145:classification* / Q000254:growth & development / Q000302:isolation & purification*; D015373:Bacterial Typing Techniques; D001431:Bacteriological Techniques / Q000379:methods*; D006801:Humans; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*