Blood culture liaison process – advice by organism type- Gram negatives

Under construction (May 2020)

SECOND CLINICIAN CALL: Confirmed culture identification with susceptibility available

  • Prior to calling, check the isolate antibiogram to see that species and susceptibility are consistent with each other – see EUCAST Expert rules which provide intrinsic resistance characters by species, including unusual phenotypes.
  • If possible speak to the same clinician who you initially contacted about the Gram stain result (look at your diary record !). Make sure your interaction has an proper formality about it – this is essential for building clinician respect for the laboratory service. See previous posting concerning ISBAR process.
  • Document additional clinical data required for completion of an Bloodstream infection event record after your contact (refer to this example template for these records with definitions of key data items).

Specific advice by organism:

Enteric Gram negative – an Enterobacterales species – e.g. E. coli, Klebsiella species, Enterobacter species

  • Identification – consider these species in two main groups- E. coli,  Klebsiella and Proteus mirabilis and similar vs Enterobacter and similar species – the so-called ‘ESCPM’ group (Enterobacter cloacae, Serratia, Citrobacter freundii, Providencia and Morganella species).   Bacteraemia with these species is almost never due to sample contamination. However, beware of post mortem blood cultures which will frequently isolate Gram negatives of no significance.
  • Main presentations – Work through with the clinician on the phone the potential likely sources for the bacteraemia. Source control is an essential part of management.  The most common source is the urinary tract followed by biliary sepsis/cholecystitis, gastrointestinal infection and other intra-abdominal sepsis including diverticular disease. Healthcare-associated events may be due to catheter-associated UTI, central line-associated bacteraemia or ventilator-associated pneumonia.
  • Core antibiotics include

Salmonella Typhi and Paratyphi

Pseudomonas aeruginosa

Acinetobacter baumannii

Haemophilus influenzae

Neisseria meningitidis

  • Drug of choice benzylpenicillin (single dose of ceftriaxone will usually eradicate nasopharyngeal/throat carriage)
  • Duration of treatment 3-5 days (there is strong evidence from New Zealand studies that 3 days is sufficient)
  • Public Health notification if required

Environmental Gram negatives- Alcaligenes, Acinetobacter 

  • Isolation of these is not infrequent and whilst they may sometimes represent contamination, the more likely scenario is central line sepsis or ventilator-associated pneumonia.
  • Therapy will depend on susceptibilities. Combination therapy unnecessary unless dealing with certain multi-resistant strains.

About mdjkf

Microbiologist and Infectious Diseases Physician
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