Photobleaching with phloxine B sensitizer to reduce food matrix interference for detection of Escherichia coli serotype O157:H7 in fresh spinach by flow cytometry.
Food Microbiol
; 36(2): 416-25, 2013 Dec.
Article
in En
| MEDLINE
| ID: mdl-24010624
ABSTRACT
A flow cytometric method (RAPID-B™) with detection sensitivity of one viable cell of Escherichia coli serotype O157H7 in fresh spinach (Spinacia oleracea) was developed and evaluated. The major impediment to achieving this performance was mistaking autofluorescing spinach particles for tagged target cells. Following a 5 h non-selective enrichment, artificially inoculated samples were photobleached, using phloxine B as a photosensitizer. Samples were centrifuged at high speed to concentrate target cells, then gradient centrifuged to separate them from matrix debris. In external laboratory experiments, RAPID-B and the reference method both correctly detected E. coli O157H7 at inoculations of ca. 15 cells. In a follow-up study, after 4 cell inoculations of positives and 6 h enrichment, RAPID-B correctly identified 92% of 25 samples. The RAPID-B method limit of detection (LOD) was one cell in 25 g. It proved superior to the reference method (which incorporated real time-PCR, selective enrichment, and culture plating elements) in accuracy and speed.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Photosensitizing Agents
/
Eosine I Bluish
/
Spinacia oleracea
/
Escherichia coli O157
/
Flow Cytometry
Type of study:
Diagnostic_studies
/
Evaluation_studies
/
Observational_studies
/
Prognostic_studies
Language:
En
Journal:
Food Microbiol
Journal subject:
CIENCIAS DA NUTRICAO
/
MICROBIOLOGIA
Year:
2013
Type:
Article
Affiliation country:
United States