MALDI-TOF mass spectrometry following short incubation on a solid medium is a valuable tool for rapid pathogen identification from positive blood cultures.
Int J Med Microbiol
; 305(4-5): 469-79, 2015.
Article
em En
| MEDLINE
| ID: mdl-25953498
ABSTRACT
INTRODUCTION:
Rapid identification of the causative microorganism is a key element in appropriate antimicrobial therapy of bloodstream infections. Whereas traditional analysis of positive blood cultures requires subculture over at least 16-24h prior to pathogen identification by, e.g. matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), sample preparation procedures enabling direct MALDI-TOF MS, i.e. without preceding subculture, are associated with additional effort and costs. Hence, we integrated an alternative MALDI-TOF MS approach in diagnostic routine using a short incubation on a solid medium. MATERIALS ANDMETHODS:
Positive blood cultures were routinely plated on chocolate agar plates and incubated for 4h (37 °C, 5% CO2). Subsequently, MALDI-TOF MS using a Microflex LT instrument (Bruker Daltonics) and direct smear method was performed once per sample. For successful identification of bacteria at species level, score cut-off values were used as proposed by the manufacturer (≥ 2.0) and in a modified form (≥ 1.5 for MALDI-TOF MS results referring to Gram-positive cocci and ≥ 1.7 for MALDI-TOF MS results referring to bacteria other than Gram-positive cocci). Further data analysis also included an assessment of the clinical impact of the MALDI-TOF MS result.RESULTS:
Applying the modified score cut-off values, our approach led to an overall correct species identification in 69.5% with misidentification in 3.4% (original cut-offs 49.2% and 1.8%, respectively); for Gram-positive cocci, correct identification in 68.4% (100% for Staphylococcus aureus and enterococci, 80% for beta-hemolytic streptococci), for Gram-negative bacteria, correct identification in 97.6%. In polymicrobial blood cultures, in 72.7% one of the pathogens was correctly identified. Results were not reliable for Gram-positive rods and yeasts. The approach was easy to implement in diagnostic routine. In cases with available clinical data and successful pathogen identification, in 51.1% our approach allowed an optimized treatment recommendation.CONCLUSION:
MALDI-TOF MS following 4h pre-culture is a valuable tool for rapid pathogen identification from positive blood cultures, allowing easy integration in diagnostic routine and the opportunity of considerably earlier treatment adaptation.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Bactérias
/
Sangue
/
Técnicas Bacteriológicas
/
Sepse
/
Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
/
Meios de Cultura
Tipo de estudo:
Diagnostic_studies
/
Evaluation_studies
/
Guideline
/
Prognostic_studies
/
Screening_studies
Limite:
Humans
Idioma:
En
Ano de publicação:
2015
Tipo de documento:
Article