Burden of Emerging Anaerobes in the MALDI-TOF and 16S RRNA Gene Sequencing Era

The isolation of anaerobes from patients has declined in recent years, whereas their detection by molecular techniques has increased. In the present work, we analyzed the application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and 16S rRNA gene sequencing to routine identification of anaerobes in clinical microbiology laboratory. We identified 544 isolates of 79 species by routine culture from deep samples in our hospital. MALDI-TOF MS allowed identification of 332 isolates (61%). The remaining 212 (39%) were identified by 16S rRNA gene sequencing, allowing identification of 202 at the species level. The most common anaerobes were Propionibacterium spp. (12%), Finegoldia magna (4%), Fusobacterium spp. (6%) and Bacteroides spp. (6%). However, among the 79 identified species, seven were new species or genera, including two Prevotella conceptionensis, a species previously detected by our team by amplification and sequencing, five Anaerococcus sp. and one Prevotella sp. Beyond the identification of these new species, we also identified several uncommon or previously not described associations between species and specific pathologic conditions. MALDI-TOF MS-based identification, which will become more effective with future spectra database improvement, will be likely responsible of a burden of emerging anaerobes in clinical microbiology.