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Enumeration of the contaminating bacterial microbiota in unfermented pasteurized milks enriched with probiotic bacteria.
Can J Microbiol. 2009 Apr; 55(4):410-8.CJ

Abstract

Pasteurized and unfermented milks supplemented with probiotic bacteria are appearing on the market. It then becomes a challenge to ascertain the undesirable contamination microbiota in the presence of a largely superior population of probiotic bacteria. A method to enumerate the contaminating microbial microbiota in such probiotic-enriched milks was developed. The probiotic cultures, Lactobacillus rhamnosus Lb-Immuni-T and Bifidobacterium animalis subsp. lactis BB-12(R), were added to a pasteurized unfermented milk to reach a minimum of 1 billion CFU per 250 mL portion, as ascertained by plating on de Man - Rogosa - Sharpe (MRS) agar in anaerobic conditions. No growth of B. animalis subsp. lactis BB-12 was noted on plate count agar (PCA) or Petrifilm plates, and the presence of this culture did not affect standard plate counts (SPC) of contaminating bacteria. However, L. rhamnosus formed colonies on PCA and Petrifilm plates. Attempts were thus made to inhibit the growth of the probiotic lactobacilli in PCA. The addition of 2% sodium phosphate (SP) or 5% glycerophosphate (GP) inhibited the growth of the lactobacilli in broths, but pin-point colonies of L. rhamnosus Lb-Immuni-T nevertheless appeared on PCA supplemented with phosphates. SPC could be obtained on PCA + 2% SP by only counting the large colonies, but this resulted in a significant (4.4 fold) underestimation of SPC values. On Petrifilm AC, at dilutions 0 to 2, all colonies were considered as being contaminants, while at dilutions 3 and 4, only large colonies were counted for SPC determinations. There was a direct correlation (R2 = 0.99) between SPC values with Petrifilm in uninoculated milks and those obtained on probiotic-enriched milks. The high correlation obtained over the 102 to 106 CFU/mL range of SPC values show that this Petrifilm method is appropriate to evaluate the microbiological quality of pasteurized milks enriched with L. rhamnosus Lb-Immuni-T and B. animalis subsp. lactis BB-12.

Authors+Show Affiliations

Agriculture and Agri-Food Canada, Food Research and Development Centre, 3600 Casavant Blvd. West, St-Hyacinthe, QC J2S 8E3, Canada. Claude.Champagne@agr.gc.caNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Evaluation Study
Journal Article

Language

eng

PubMed ID

19396241

Citation

Champagne, C P., et al. "Enumeration of the Contaminating Bacterial Microbiota in Unfermented Pasteurized Milks Enriched With Probiotic Bacteria." Canadian Journal of Microbiology, vol. 55, no. 4, 2009, pp. 410-8.
Champagne CP, Raymond Y, Gonthier J, et al. Enumeration of the contaminating bacterial microbiota in unfermented pasteurized milks enriched with probiotic bacteria. Can J Microbiol. 2009;55(4):410-8.
Champagne, C. P., Raymond, Y., Gonthier, J., & Audet, P. (2009). Enumeration of the contaminating bacterial microbiota in unfermented pasteurized milks enriched with probiotic bacteria. Canadian Journal of Microbiology, 55(4), 410-8. https://doi.org/10.1139/w08-151
Champagne CP, et al. Enumeration of the Contaminating Bacterial Microbiota in Unfermented Pasteurized Milks Enriched With Probiotic Bacteria. Can J Microbiol. 2009;55(4):410-8. PubMed PMID: 19396241.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Enumeration of the contaminating bacterial microbiota in unfermented pasteurized milks enriched with probiotic bacteria. AU - Champagne,C P, AU - Raymond,Y, AU - Gonthier,J, AU - Audet,P, PY - 2009/4/28/entrez PY - 2009/4/28/pubmed PY - 2009/7/31/medline SP - 410 EP - 8 JF - Canadian journal of microbiology JO - Can J Microbiol VL - 55 IS - 4 N2 - Pasteurized and unfermented milks supplemented with probiotic bacteria are appearing on the market. It then becomes a challenge to ascertain the undesirable contamination microbiota in the presence of a largely superior population of probiotic bacteria. A method to enumerate the contaminating microbial microbiota in such probiotic-enriched milks was developed. The probiotic cultures, Lactobacillus rhamnosus Lb-Immuni-T and Bifidobacterium animalis subsp. lactis BB-12(R), were added to a pasteurized unfermented milk to reach a minimum of 1 billion CFU per 250 mL portion, as ascertained by plating on de Man - Rogosa - Sharpe (MRS) agar in anaerobic conditions. No growth of B. animalis subsp. lactis BB-12 was noted on plate count agar (PCA) or Petrifilm plates, and the presence of this culture did not affect standard plate counts (SPC) of contaminating bacteria. However, L. rhamnosus formed colonies on PCA and Petrifilm plates. Attempts were thus made to inhibit the growth of the probiotic lactobacilli in PCA. The addition of 2% sodium phosphate (SP) or 5% glycerophosphate (GP) inhibited the growth of the lactobacilli in broths, but pin-point colonies of L. rhamnosus Lb-Immuni-T nevertheless appeared on PCA supplemented with phosphates. SPC could be obtained on PCA + 2% SP by only counting the large colonies, but this resulted in a significant (4.4 fold) underestimation of SPC values. On Petrifilm AC, at dilutions 0 to 2, all colonies were considered as being contaminants, while at dilutions 3 and 4, only large colonies were counted for SPC determinations. There was a direct correlation (R2 = 0.99) between SPC values with Petrifilm in uninoculated milks and those obtained on probiotic-enriched milks. The high correlation obtained over the 102 to 106 CFU/mL range of SPC values show that this Petrifilm method is appropriate to evaluate the microbiological quality of pasteurized milks enriched with L. rhamnosus Lb-Immuni-T and B. animalis subsp. lactis BB-12. SN - 0008-4166 UR - https://www.unboundmedicine.com/medline/citation/19396241/Enumeration_of_the_contaminating_bacterial_microbiota_in_unfermented_pasteurized_milks_enriched_with_probiotic_bacteria_ DB - PRIME DP - Unbound Medicine ER -