Short Incubation of Positive Blood Cultures on Solid Media for Species Identification by MALDI-TOF MS: Which Agar Is the Fastest?

Microbiology Spectrum
Neele J FroböseFrieder Schaumburg

Abstract

Short incubation of positive blood cultures on solid media is now increasingly applied to speed up species identification by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Although Columbia blood agar (CBA) and chocolate agar (Choc) are widely used, a direct comparison of standard agars is lacking. We therefore compared the time to species identification of blood cultures incubated on CBA, Choc, and MacConkey agar (MAC, for Gram-negative rods). Positive aerobic/anaerobic blood cultures (2 drops = 50 μl) were incubated on CBA, Choc, MAC, and the required time of incubation to low-confidence identification (score of ≥1.7 to <2) and high-confidence identification (score of ≥2) by MALDI-TOF MS was measured. Exclusion criteria were (i) false-positive blood cultures, (ii) mixed cultures with different species, (iii) growth of anaerobes/fungi, and (iv) a total number of isolates of one group (i.e., Gram-positive/-negative cocci/rods) of <30. A total of 187 blood cultures with Gram-positive cocci (n = 124) and Gram-negative rods (n = 63) were included in the final analysis. The shortest median time to high-confidence identification (score of ≥2) was achieved on MAC for Gram-negative rods (2...Continue Reading

References

Apr 5, 2014·Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases·E A IdelevichK Becker
Nov 3, 2016·Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America·Tristan T TimbrookKerry L LaPlante
Apr 14, 2019·Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases·Evgeny A IdelevichUNKNOWN ESCMID Study Group for Bloodstream Infections, Endocarditis and Sepsis (ESGBIES)
Nov 25, 2019·Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases·Brigitte LamyUNKNOWN ESCMID Study Group for Bloodstream Infections, Endocarditis and Sepsis (ESGBIES)

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