Positive blood culture clinician liaison process (microbiology) part 1

Stop press: Gram stain appearance and implications ver 2 2020 Ferguson


  • Always note down all clinician discussions in a large personal diary or preferably on the electronic pathology record for the patient’s sample if this exists.
  • Categorise and record the clinical relevance of the positive culture – a standard template to be shared soon.

Improve blood culture collection practice

Phone notification – use ISBAR 

  • I introduce yourself – “I am the Pathology Registrar” and make sure you know who you are talking to – ask their name and record it in your notes.
  • S “I am calling you about a positive blood culture on your patient x.”
  • B Ask the clinician for some background on the patient – what is wrong with them, what antimicrobials are they on already? What doses are being used?
  • A Work out your assessment of the situation; is this a significant blood culture isolate? If so are the antibiotics the patient is on ok for the job? Are the doses appropriate?
  • R Make a recommendations- these might include- change of drug, dose, advice that you will call them when the susceptibilities are ready etc.

Remember, in order for your advice to be respected, some formality in your communication style with the clinician is worthwhile – be systematic as above.  The clinician needs to know that you are really on their side (and the patient’s).

FIRST CALL- Positive Gram stain result available

  • visit the lab every morning to check for new positive cultures and results of identification and susceptibility for previous events
  • where possible access results from other micro benches for the patient to know what had grown
  • white cell count – often helps to know this to help judge the significance of the event
  • also check liver function tests for adults with Gram negative sepsis (? cholestatic picture c/w biliary sepsis)

Gram stain shows Gram Positive Cocci resembling staph

  • await 4 hour initial tube coagulase reaction from the bottle sediment. Only contact doctor if coagulase positive.
  • need to form an idea of likely source of infection; is there a surgically drainable collection, is it endocarditis, is an intravascular line responsible? S. aureus in blood cultures is rarely a contaminant, though this occurs more often in children.
  • empiric treatment-wise, if MRSA accounts for more than 20% of positive S. aureus blood culture presentations, flucloxacillin is not going to be a good idea and an alternative is required –  intravenous vancomycin most usually. In PNG where vancomycin not currently available, IV chloramphenicol is required.

GPC (strep)

  • Two possibilities- Streptococcus species or Enterococcus species.
  • Generally IV benzylpenicillin or amoxycillin will be ok. If it sounds like a lobar pneumonia and GPC (diplococci) resembling pneumococcus then ensure that dose of benpen is sufficient- 1.8g 4hrly for severe cases best.

Gram positive rod

  • Possibilities include- Bacillus (usually large rectangular shape), Clostridium, Corynebacterium (smaller, clumps in chinese character type appearance), Listeria.
  • Most frequently- contamination – however, have to be careful that Listeria and B. anthracis are properly considered during workup.

Gram negative rod

  • Most usually represent significant isolates. See Part 2.
  • Correlate with other lab results (e.g. urine culture, liver fx tests)

Gram negative diplococcus

  • Assume N. meningitidis although occasionally Moraxella or Acinetobacter will turn up and these may be contaminants. Acinetobacter– see environmental Gram negatives below.


  • Most frequently will represent Candida species. Line sepsis (central line) most often. Haematology patients may get disseminated disease. Intravenous drug users may also present with candidaemia.

About mdjkf

Microbiologist and Infectious Diseases Physician
This entry was posted in Module - Blood cultures. Bookmark the permalink.

1 Response to Positive blood culture clinician liaison process (microbiology) part 1

  1. mdjkf says:

    Reblogged this on Microbiology and Infectious Diseases postgraduate teaching (PRIDA) and commented:

    Updated summary of Gram stain appearances, microbiological and clinical implications. Updated blood culture collection and liaison approach.


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