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Anaerobic blood culture isolates in a Norwegian university hospital: identification by MALDI-TOF MS vs 16S rRNA sequencing and antimicrobial susceptibility profiles.

Authors
  • 1
  • 1
  • 2
  • 1
  • 1
  • 1 Department of Microbiology and Infection Control, Akershus University Hospital, Lørenskog, Norway. , (Norway)
  • 2 Department of Multidisciplinary Laboratory Medicine and Medical Biochemistry, Unit of Gene Technology, Akershus University Hospital, Lørenskog, Norway. , (Norway)
Type
Published Article
Journal
Apmis
1600-0463
Publisher
Wiley Blackwell (Blackwell Publishing)
Publication Date
Volume
123
Issue
9
Pages
749–758
Identifiers
DOI: 10.1111/apm.12410
PMID: 26123879
Source
Medline
Keywords
License
Unknown

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.

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