title: Anaerobic blood culture isolates in a Norwegian university hospital: identification by MALDI-TOF MS vs 16S rRNA sequencing and antimicrobial susceptibility profiles.
abstract: We investigated 197 anaerobic isolates recovered from blood cultures in the period 2009-2013. The isolates included were Bacteroides spp., Clostridium spp., Prevotella spp., Fusobacterium spp. and Gram-positive anaerobic cocci (GPAC). Identification results by MALDI-TOF MS were compared to those obtained by 16S rRNA sequencing, and the MICs of benzylpenicillin, clindamycin, piperacillin-tazobactam, meropenem and metronidazole were determined by Etests. The MALDI-TOF MS correctly identified 94.9% of the anaerobes to the genus level, and 86.8% to the species level, with errors mainly among the non-fragilis Bacteroides spp. and GPAC. About 73.3% of the isolates were non-susceptible to penicillin, mainly due to high resistance rates in the Bacteroides spp. (99.2%) and Prevotella spp. (69.2%). About 18.5% of the isolates were clindamycin resistant. Piperacillin-tazobactam had an excellent activity against all anaerobes except the non-fragilis Bacteroides spp., of which 43.8% were non-susceptible. The clinical significance of such a high resistance rate is unclear. Meropenem and metronidazole were the most active antibiotics, with 96.9% and 97.9% of the isolates being susceptible.
authors.affiliation: Department of Microbiology and Infection Control, Akershus University Hospital, Lørenskog, Norway.
authors.forename: Nina
authors.initials: N
authors.lastname: Handal
authors.affiliation: Department of Microbiology and Infection Control, Akershus University Hospital, Lørenskog, Norway.
authors.forename: Silje
authors.initials: S
authors.lastname: Bakken Jørgensen
authors.affiliation: Department of Multidisciplinary Laboratory Medicine and Medical Biochemistry, Unit of Gene Technology, Akershus University Hospital, Lørenskog, Norway.
authors.forename: Hege
authors.initials: H
authors.lastname: Smith Tunsjø
authors.affiliation: Department of Microbiology and Infection Control, Akershus University Hospital, Lørenskog, Norway.
authors.forename: Bjørn Odd
authors.initials: BO
authors.lastname: Johnsen
authors.affiliation: Department of Microbiology and Infection Control, Akershus University Hospital, Lørenskog, Norway.
authors.forename: Truls Michael
authors.initials: TM
authors.lastname: Leegaard
mesh_terms: D000890:Anti-Infective Agents / Q000627:therapeutic use; D001421:Bacteria, Anaerobic / Q000187:drug effects / Q000302:isolation & purification*; D001424:Bacterial Infections / Q000188:drug therapy / Q000235:genetics* / Q000382:microbiology*; D006785:Hospitals, University; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D017423:Sequence Analysis, RNA / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
chemical_list: D000890:Anti-Infective Agents; D012336:RNA, Ribosomal, 16S
keywords: Anaerobic bacteria; MALDI-TOF; antimicrobial susceptibility