A differential centrifugation protocol and validation criterion for enhancing mass spectrometry (MALDI-TOF) results in microbial identification using blood culture growth bottles

• Published in: European journal of clinical microbiology & infectious diseases Vol. 32; no. 5; pp. 699 - 704
• Main Authors: March–Rosselló, G. A., Muñoz–Moreno, M. F., García-Loygorri–Jordán de Urriés, M. C., Bratos–Pérez, M. A.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-05-2013; Springer; Springer Nature B.V
• Subjects: Bacteremia - microbiology; Bacteria; Bacteria - chemistry; Bacteria - classification; Bacteria - isolation & purification; Bacteriological Techniques - methods; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Blood; Centrifugation; Centrifugation - methods; Centrifuges; Enterobacteriaceae; Enterococcus; Gram-positive bacteria; Humans; Identification; Infectious diseases; Internal Medicine; Laboratories; Mass spectrometry; Medical Microbiology; Medical sciences; Microbiology; Microorganisms; Parasitology; Proteins; Scientific imaging; Sediments; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Staphylococcus; Streptococcus; Spain; Blood Culture Bottle; Valid Identification; Blood Culture; Acinetobacter Baumannii; Validation Standard; Infection; Microbiological investigation; Microbiology; Criterion; Growth; Identification; Matrix assisted laser desorption ionization; Blood culture; Mass spectrometry
• ISSN: 0934-9723; 1435-4373
• DOI: 10.1007/s10096-012-1797-1

Matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry (MALDI-TOF) is a widely used tool in clinical microbiology for rapidly identifying microorganisms. This technique can be applied directly on positive blood cultures without the need for its culturing, thereby, reducing the time required for microbiological diagnosis. The present study proposes an innovative identification protocol applied to positive blood culture bottles using MALDI-TOF. We have processed 100 positive blood culture bottles, of which 36 of 37 Gram-negative bacteria (97.3 %) were correctly identified directly with 100 % of
Enterobacteriaceae
and other Gram-negative rods and 87.5 % of non-fermenting Gram-negative rods. We also correctly identified directly 62 of 63 of Gram-positive bacteria (98.4 %) with 100 % of
Streptococcus
,
Enterococcus
, and Gram-positive bacilli and 98 % of
Staphylococcus
. Applying the differential centrifugation protocol at the moment the automatic blood culture incubation system gives a positive reading together with the proposed validation criterion offers 98 % sensitivity (95 % confidence interval: 95.2–100 %). The MALDI-TOF system, thus, provides a rapid and reliable system for identifying microorganisms from blood culture growth bottles.