Rapid AST in bloodcultures

Rapid AST directly from blood culture bottles

EUCAST has published recommendations for short incubation (4, 6 and 8 hours) AST directly from positive blood culture bottles:

  • direct inoculation of disk diffusion plates (MH, MH-F) using 100 - 150 ┬ÁL directly from a positive blood culture bottle (BD, bioMerieux and Thermo Fisher).
  • no centrifugation or dilution of the inoculum - streak plates as for standard EUCAST disk diffusion.
  • shortened incubation - 4, 6 and 8 hours with breakpoints adapted to each incubation time.
  • zone diameters are read from the front of the plate after removal of the lid.
  • breakpoints for each species and each reading time.
  • identity of species must be known prior to interpretation of AST results.
  • the method is currently validated for the following species.

    • Escherichia coli
    • Klebsiella pneumoniae
    • Pseudomonas aeruginosa
    • Staphylococcus aureus
    • Streptococcus pneumoniae
    • Enterococcus faecalis and Enterococcus faecium
    • Acinetobacter baumannii (added 2 May, 2019)

  • a positive blood culture bottle should be processed 0 - 18 hours after the positive signal.
  • each species has its own TAB in the table and each reading time (4, 6 and 8 hours) its own section.
  • not all zone diameters can be read after 4 hours. Read again after 6 and 8 hours. Incubation can not be extended over night. If needed, perform a regular AST overnight.
  • read zone diameters ONLY when an obvious zone edge can be identified - otherwise re-incubate and read after 6 or 8 hours. 
  • the breakpoint table is specific for EUCAST Rapid AST - do not use the regular breakpoint table and do not use for rapid AST on an inoculum prepared from colonies.

 

Ongoing work (to be finalised 2019-20):

  • Interpretive criteria for more antibiotics than those currently available (2019-20).