RESUMEN
Measuring the viability of probiotic microorganisms in food products using plate count methodology is a common practice due to the simplicity [ease of performance], inexpensive and routine testing characters of this method. In present study, the suitability of de man rogosa and sharpe agar [MRS] bile agar medium for the selective enumeration of mixed probiotic bacteria [Lactobacillus acidophilus LA-5, L. casei 431 and Bifidobacterium lactis BB-12] in presence of mesophilic lactic cultures [Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. Cremoris] and yoghurt bacteria [Streptococcus thermophilus and Lactobacillus delbrueckii ssp. Bulgaricus] was investigated. Yoghurt bacteria did not grow neither in presence of 0.15% nor 0.30% of bile salts, as was expected. Mesophilic lactic starters could grow at both concentrations of bile salts at all incubation temperatures except 37°C. According to these results, MRS-bile agar [0.15 bile salts] could be successfully used for selective enumeration of mixed probiotic cultures in presence of mesophilic culture and/or yoghurt bacteria when plates were incubated at 37°C for 72 h