IADR Abstract Archives
Performance of MALDI-TOF MS for human Capnocytophaga identification
Objectives: The human Capnocytophaga species (C. gingivalis, C. granulosa, C. haemolytica, C. leadbetteri, C. ochracea, C. sputigena, and Capnocytophaga genospecies AHN8471) are Gram-negative, capnophilic, thin rod-shaped bacteria. They are common members of the resident oral microbiota but can also act as opportunistic pathogens in various infections, such as abscesses, septicemia, and adverse pregnancy outcomes. We aimed to examine, for the first time, the performance of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for identifying human Capnocytophaga species.
Methods: Six type strains and one clinical strain confirmed by 16S rRNA sequencing were used as references. Altogether 106 salivary isolates, originating from 25 healthy women, were presumptively identified as Capnocytophaga spp. based on their colony and cell morphologies and routine biochemical tests. All isolates were examined with MALDI-TOF MS (Bruker Daltonics, Bremen, Germany) using the Microflex LT instrument and MALDI Biotyper software version 3.1. Specific cut-off scores were used to determine the genus level (1.700-1.999) and species level (≥2.000) identification. The isolates with a log score of <2.000 were retested using the ethanol-formic acid extraction protocol.
Results: Of the 113 tested isolates, 50 (44.2%) were identified with direct spotting. Spotting was repeated for 36 (31.9%), and ethanol-formic acid extraction was further used for the rest of the isolates. The performance of MALDI-TOF MS to identify Capnocytophaga to the genus level was excellent with 100.0% accuracy, while an identification rate of 90.3% was achieved to the species level; 11 strains, representing C. ochracea (n=6), C. haemolytica (n=2), C. sputigena (n=1), C. leadbetteri (n=1), and Capnocytophaga genospecies AHN8471 (n=1), remained within the low cut-off score. Notably, the latter two species are missing from the current MALDI BioTyper database.
Conclusions: MALDI-TOF MS constitutes a promising diagnostic tool for identifying human Capnocytophaga species. However, an upgrade in the database is needed.
Methods: Six type strains and one clinical strain confirmed by 16S rRNA sequencing were used as references. Altogether 106 salivary isolates, originating from 25 healthy women, were presumptively identified as Capnocytophaga spp. based on their colony and cell morphologies and routine biochemical tests. All isolates were examined with MALDI-TOF MS (Bruker Daltonics, Bremen, Germany) using the Microflex LT instrument and MALDI Biotyper software version 3.1. Specific cut-off scores were used to determine the genus level (1.700-1.999) and species level (≥2.000) identification. The isolates with a log score of <2.000 were retested using the ethanol-formic acid extraction protocol.
Results: Of the 113 tested isolates, 50 (44.2%) were identified with direct spotting. Spotting was repeated for 36 (31.9%), and ethanol-formic acid extraction was further used for the rest of the isolates. The performance of MALDI-TOF MS to identify Capnocytophaga to the genus level was excellent with 100.0% accuracy, while an identification rate of 90.3% was achieved to the species level; 11 strains, representing C. ochracea (n=6), C. haemolytica (n=2), C. sputigena (n=1), C. leadbetteri (n=1), and Capnocytophaga genospecies AHN8471 (n=1), remained within the low cut-off score. Notably, the latter two species are missing from the current MALDI BioTyper database.
Conclusions: MALDI-TOF MS constitutes a promising diagnostic tool for identifying human Capnocytophaga species. However, an upgrade in the database is needed.