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ANNUAL CONFERENCE :: Abstract Library
Abstract Library
2003 Conference Abstract
| Type of Submission |
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Submission Type: |
Poster Presentation |
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Subject Category: |
Applied Microbiology |
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| Session Information |
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Presentation Date: |
May 26, 2003 |
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Abstract ID: |
A26 |
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Session: |
Poster 1 |
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Time: |
14:00 |
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| Presenting Author |
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| Other Authors |
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L. MUTHARIA, Department of Microbioloty, University of Guelph
M. RAYMOND, Department of Microbiology, University of Guelph
J. ODUMERU, Laboratory Services Division, University of Guelph
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| Title |
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Decontamination of raw milk for isolation of Mycobacterium paratuberculosis |
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| Abstract Text |
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Mycobacterium paratuberculosis (Mptb) is the causative agent of Johne’s disease in cattle and there are suggestions that this organism may be associated with Crohn’s disease in human. Cows at the advanced stage of the disease shed this organism into both milk and feces. Although live Mptb can be isolated from milk, the microflora of milk often result in contamination of culture thereby limiting the recovery of this organism from milk by culture method. The purpose of this study is to develop a procedure for decontamination of milk prior to culture of Mptb. Raw milk (50 ml) samples were seeded with Mptb cells, and the samples kept at 4°C for 1-7 days prior to isolation and culture of the bacterium. Pellet was processed after centrifugation at 2,500 X g for 30 min. When one-week old milk samples were tested, decontamination in 0.75% (w/v) hexadecylpyridinium chloride (HPC) resulted in higher recovery of Mptb than the procedure involving the use of 0.75% HPC in ½ strength brain-heart infusion (BHI) broth. Higher recoveries of Mptb were obtained after five hours of decontamination than at 2, 24 and 48 h of decontamination at room temperature. For milk samples less than 3 days old, decontamination in 0.75% HPC for 2 – 3 h produced good recovery. However, for over 10-day old milk samples, decontamination was not effective in reducing the background flora. Prolonged decontamination did result in loss of viability of Mptb. We found that 24 h of decontamination in 0.75% HPC killed significantly higher number of Mptb cells (42%) compared to 5 h decontamination at room temperature. Incubation for 48 h in antibiotic brew (antibiotics in ½-strength BHI) killed about 45% of Mptb cells when compared to samples not subjected to the antibiotic brew treatment (N = 46, factorial ANOVA, P < 0.01). Decontamination for 24 h in 0.75% HPC at 37°C resulted in no recovery of live Mptb organisms. We recommend decontamination procedure involving the use of 0.75% HPC for 2 – 5 h at room temperature for raw milk 3 – 6 days old. Overnight decontamination in 0.75% HPC is not recommended because of the loss in viability of the Mptb bacterial cells. |
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