Session Type: ePosters
Session Title: ePosters
Authors(s): G. Caruana, A. Croxatto, G. Prod'hom, G. Greub
Authors Affiliations(s): Lausanne University Hospital, Switzerland
Background:
Rapid BACpro II (Nittobo) is a promising method to obtain a microbial pellet from positive blood cultures for MALDI-TOF bacterial identification, but the extraction step prevents bacterial viability, which is pivotal for some analyses such as rapid 3rd-generation-cephalosporin resistance detection. We investigated the performances of rapid BACpro II modified procedure to identify bacteria (i) before and after protein extraction and (ii) with the Sepsytiper module (STM) compared to the classic (Bruker) MALDI-TOF module.
Methods:Rapid Bacpro II manufacturer procedure was modified by adding 50μl of purified water to the bacterial pellet after the second centrifugation, to obtain sufficient material for both extraction (25μl) and analyses on viable pellet (25μl). MALDI-TOF was performed directly on the pellet and after protein extraction and identifications were classified as follows: i) species level for scores ≥2 (classic), or ≥ 1.8 (STM) ii) genus level for scores ≥1.7 and <2 (classic) or ≥1.7 and <1.8 (STM), iii) unclassified for scores <1.7. Final MALDI-TOF-based identifications obtained from cultured colonies were considered as gold standard.
Results:Overall, 529 monobacterial positive blood vials were analyzed. For rapid BACpro II without protein extraction and using the classic MALDI-TOF module, we obtained scores at species level in 172 (32%), at genus level in 121 (24%) and no identification in 236 (45%) subjects, compared to 352 (67%), 102 (19%) and 75 (14%) using the new modified procedure, respectively. In a sub-analysis of 315 vials comparing classic MALDI-TOF module with STM before extraction, we obtained identification at species level in 74 (24%) versus 141 (45%), identification at genus level in 72 (23%) versus 16 (5%) and no identification in 169 (54%) versus 158 (50%) samples, respectively (Fig. 1.A). Similarly, after extraction we obtained scores at species level in 198 (63%) versus 268 (85%), genus level in 63 (20%) versus 9 (3%) and no identification in 54 (17%) versus 38 (12%) subjects, respectively (Fig. 1B).
Conclusions:The use of STM can further increase the MALDI-TOF based identification rates, both before and after protein extraction, but this latter step remains necessary for Rapid BACpro II method to reach an acceptable proportion of high scores of identification.
Keyword(s): Blood culture, Bacterial pellet, MALDI-TOF mass spectrometrySession Type: ePosters
Session Title: ePosters
Authors(s): G. Caruana, A. Croxatto, G. Prod'hom, G. Greub
Authors Affiliations(s): Lausanne University Hospital, Switzerland
Background:
Rapid BACpro II (Nittobo) is a promising method to obtain a microbial pellet from positive blood cultures for MALDI-TOF bacterial identification, but the extraction step prevents bacterial viability, which is pivotal for some analyses such as rapid 3rd-generation-cephalosporin resistance detection. We investigated the performances of rapid BACpro II modified procedure to identify bacteria (i) before and after protein extraction and (ii) with the Sepsytiper module (STM) compared to the classic (Bruker) MALDI-TOF module.
Methods:Rapid Bacpro II manufacturer procedure was modified by adding 50μl of purified water to the bacterial pellet after the second centrifugation, to obtain sufficient material for both extraction (25μl) and analyses on viable pellet (25μl). MALDI-TOF was performed directly on the pellet and after protein extraction and identifications were classified as follows: i) species level for scores ≥2 (classic), or ≥ 1.8 (STM) ii) genus level for scores ≥1.7 and <2 (classic) or ≥1.7 and <1.8 (STM), iii) unclassified for scores <1.7. Final MALDI-TOF-based identifications obtained from cultured colonies were considered as gold standard.
Results:Overall, 529 monobacterial positive blood vials were analyzed. For rapid BACpro II without protein extraction and using the classic MALDI-TOF module, we obtained scores at species level in 172 (32%), at genus level in 121 (24%) and no identification in 236 (45%) subjects, compared to 352 (67%), 102 (19%) and 75 (14%) using the new modified procedure, respectively. In a sub-analysis of 315 vials comparing classic MALDI-TOF module with STM before extraction, we obtained identification at species level in 74 (24%) versus 141 (45%), identification at genus level in 72 (23%) versus 16 (5%) and no identification in 169 (54%) versus 158 (50%) samples, respectively (Fig. 1.A). Similarly, after extraction we obtained scores at species level in 198 (63%) versus 268 (85%), genus level in 63 (20%) versus 9 (3%) and no identification in 54 (17%) versus 38 (12%) subjects, respectively (Fig. 1B).
Conclusions:The use of STM can further increase the MALDI-TOF based identification rates, both before and after protein extraction, but this latter step remains necessary for Rapid BACpro II method to reach an acceptable proportion of high scores of identification.
Keyword(s): Blood culture, Bacterial pellet, MALDI-TOF mass spectrometry