Table 1

Characteristics of microorganisms commonly isolated from blood culture

StainingMorphologyArrangementPossible identification
Gram-positiveCocciClusters
  • Staphylococcus spp.,

    for example, Staphylococcus aureus, CoNS

  • Micrococcus spp.

CocciChains
  • Streptococcus spp.

  • Enterococcus spp.

CocciPairs (diplococci)
  • Streptococcus pneumoniae

Bacilli//rods
  • Listeria spp.

  • Corynebacterium spp.

  • Clostridium spp. (anaerobe)

Large, budding
  • Yeasts, for example, Candida spp.

Gram-negativeCocciPairs (diplococci)
  • Neisseria spp.,

    for example, Neisseria meningitidis

  • Moraxella catarrhalis

Coccobacilli
  • Haemophilus spp.,

    for example, Haemophilus influenzae

Bacilli/rods
  • Escherichia coli

  • Other coliforms,

    for example, Klebsiella, Enterobacter spp.

  • Pseudomonas spp.

  • Bacteroides spp. (anaerobe)

Ziehl–Neelsen or auramine positiveBacilli (acid-fast)
  • Mycobacterium spp.

  • CoNS, coagulase-negative Staphylococcus.