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Isolation of Shiga toxin-producing Escherichia coli serogroups O26, O45, O103, O111, O121, and O145 from ground beef using modified rainbow agar and post-immunomagnetic separation acid treatment.
- Source :
-
Journal of food protection [J Food Prot] 2012 Sep; Vol. 75 (9), pp. 1548-54. - Publication Year :
- 2012
-
Abstract
- It is estimated that at least 70% of human illnesses due to non-O157 Shiga toxin-producing Escherichia coli (STEC) in the United States are caused by strains from the top six serogroups (O26, O45, O103, O111, O121, and O145). Procedures for isolating STEC from food products often use plating media that include antimicrobial supplements at concentrations that inhibit background microflora growth but can also inhibit target STEC growth. In this study, an agar medium with lower supplement concentrations, modified Rainbow agar (mRBA), was evaluated for recovery of STEC serogroups O26, O45, O103, O111, O121, and O145 from ground beef enrichments. A post-immunomagnetic separation (IMS) acid treatment step was additionally used to reduce background microflora and increase recovery of target STEC strains. Ground beef samples (325 g) were artificially contaminated with STEC and confounding organisms and enriched for 15 h. Recovery of the target STEC was attempted on the enrichments using IMS and plating onto mRBA and Rainbow agar (RBA). Additionally, acid treatment was performed on the post-IMS eluate followed by plating onto mRBA. Using the combination of mRBA and acid treatment, target STEC were isolated from 103 (85.8%) of 120 of the low-inoculated samples (1 to 5 CFU/325-g sample) compared with 68 (56.7%) of 120 using no acid treatment and plating onto RBA with higher levels of novobiocin and potassium tellurite. The combination of acid treatment and mRBA provides a significant improvement over the use of RBA for isolation of STEC serogroups O26, O45, O103, O111, O121, and O145 from raw ground beef.
- Subjects :
- Animals
Cattle
Colony Count, Microbial instrumentation
Colony Count, Microbial methods
Consumer Product Safety
Food Microbiology
Humans
Hydrogen-Ion Concentration
Serotyping
Agar
Food Contamination analysis
Immunomagnetic Separation methods
Meat Products microbiology
Shiga-Toxigenic Escherichia coli isolation & purification
Subjects
Details
- Language :
- English
- ISSN :
- 1944-9097
- Volume :
- 75
- Issue :
- 9
- Database :
- MEDLINE
- Journal :
- Journal of food protection
- Publication Type :
- Academic Journal
- Accession number :
- 22947460
- Full Text :
- https://doi.org/10.4315/0362-028X.JFP-12-110