Here are some probiotic cultures from kefir:

From: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3064404/

Some of the bacteria that were identified in kefir include: Lactobacillus brevis, Lb. helveticus, Lb. kefir, Lb. viridescens, Lb. casei, Lb. kefiranofaciens, Lb. kefirgranum, Lb. parakefir, Lb. plantarum, Lb. acidophilus, Lb. delbrueckii, Lb. rhamnosis, Lb. paracasei, Lb. fructirorans, Lb. hilgardii, Lb. fermentum, Lb. riridescens, Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Streptococcus thermophilus, Enterococci durans, Leuconostocs sp., Leuconostocs mesenteroides, Acetobacter sp., Bacillus sp., Bacillus subtilis, Micrococcus sp., Escherechia coli, Kluyveromyces lactis, Kluyveromyces marxianus, and Pichia fermentans3,4,7 Metabolites produced by the yeasts add to the taste and mouthfeel of kefir and provide a milieu for the growth of kefir bacteria.3 Some of the yeasts that were identified in kefir include: Saccharomyces sp., Saccharomyces cerevisiae, Saccharomyces unisporus, Saccharomyces exiguus, Saccharomyces turicensis, Saccharomyces delbrueckii, Saccharomyces dairensis, Saccharomyces unisporus, Saccharomyces lipolytica, Candida pseudotropicalis, Candida friedrichii, Candida tenuis, Candida maris, Candida inconspicu, Candida lambica, Candida tannotelerans, Candida valida, Candida holmii, Candida kefir, Candida holmii, Torulaspora delbrueckii, Brettanomyces anomalus, Issatchenkia occidentalis, Pichia fermentans, and Kluyveromyces marxianus.3,7 Both bacteria and yeasts in kefir grains are surrounded by a polysaccharide matrix, which contains a water-soluble branched glucogalactan,8 produced by lactobacilli within the grains. The polysaccharide, named kefiran, is composed of a hexasaccharide-repeating unit and has been reported to possess many health benefits.

There is also lot of info in this paper: Probiotic bacteria in fermented foods: product characteristics and starter organisms

It looks like kefir is unbeatable