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Enumeration and identification of pediococci in powder-based products using selective media and rapid PFGE
P J Simpson1, G F Fitzgerald, C Stanton
1Teagasc, Biotechnology Centre, Moorepark, Fermoy, Co., Cork, Ireland.
Abstract:
In this study, pediococci selective medium (PSM) was evaluated for the enumeration of Pediococcus acidilactici and Pediococcus pentosaceus from probiotic animal feed and silage inoculants. PSM is based on the complex basal medium MRS supplemented with cysteine hydrochloride, novobiocin, vancomycin, and nystatin. No significant change in electivity was observed when pediococci where recovered from culture or powder-based products following incubation at 37 degrees C under anaerobic conditions for 24 h. The medium was suitable for the enumeration of pediococci in samples also containing bacilli, bifidobacteria, enterococci, lactobacilli, lactococci, propionibacteria, streptococci, and yeast components. However, to inhibit Lactobacillus plantarum and Lactobacillus casei, ampicillin was added and the revised medium, termed PSM+A, was also considered to be suitably elective for pediococci recovered from powder. In addition, a rapid PFGE protocol is presented, which allows Pediococcus species and strain verification from colonies in less than 3 days.
Insights
This study evaluates pediococci selective medium (PSM) for enumerating Pediococcus species in animal feed and inoculants. The revised PSM+A medium effectively quantifies Pediococcus acidilactici and Pediococcus pentosaceus.
Area of Science:
- Microbiology
- Food Science
- Animal Nutrition
Background:
- Accurate enumeration of Pediococcus species is crucial for probiotic animal feed and silage inoculants.
- Existing methods may lack specificity or efficiency for complex matrices.
- Pediococcus acidilactici and Pediococcus pentosaceus are key probiotic species.
Purpose of the Study:
- To evaluate the efficacy of pediococci selective medium (PSM) for enumerating Pediococcus species.
- To assess the performance of PSM in probiotic animal feed and silage inoculants.
- To develop an improved medium (PSM+A) and a rapid verification protocol.
Main Methods:
- Evaluation of PSM based on MRS medium with specific supplements (cysteine hydrochloride, novobiocin, vancomycin, nystatin).
- Testing PSM and PSM+A (with ampicillin) for selectivity against common contaminants (bacilli, bifidobacteria, lactobacilli, etc.).
- Development and application of a rapid Pulse Field Gel Electrophoresis (PFGE) protocol for species and strain verification.
Main Results:
- PSM demonstrated effective enumeration of Pediococcus species from culture and powder products.
- The medium showed selectivity in the presence of various bacterial and yeast contaminants.
- PSM+A, with ampicillin, improved selectivity against Lactobacillus plantarum and Lactobacillus casei.
- The rapid PFGE protocol enabled Pediococcus species and strain verification in under 3 days.
Conclusions:
- PSM is a suitable medium for enumerating Pediococcus acidilactici and Pediococcus pentosaceus in probiotic animal feed and inoculants.
- PSM+A offers enhanced selectivity, particularly against common Lactobacillus species.
- The rapid PFGE protocol provides an efficient method for Pediococcus species and strain identification.
