title: M-RTLV agar, a novel selective medium to distinguish Lactobacillus casei and Lactobacillus paracasei from Lactobacillus rhamnosus.
abstract: We developed a novel selective medium, modified-rhamnose-2,3,5-triphenyltetrazolium chloride-LBS-vancomycin agar (M-RTLV agar), that utilizes the fermentability of L-rhamnose to distinguish Lactobacillus casei and Lactobacillus paracasei from Lactobacillus rhamnosus. Whereas L. casei and L. paracasei formed red colonies on the M-RTLV agar, L. rhamnosus formed either pink-toned colonies or white colonies with a red spot. An intervention study was conducted to confirm the capability of M-RTLV agar to detect ingested L. casei when recovered from human feces. Subjects consumed one bottle daily of a fermented milk product (Yakult or Yakult Light, which contains L. casei strain Shirota; LcS) for 7 days. Diluents of the fecal samples were cultivated on M-RTLV agar. We were able to enumerate circular medium-sized red colonies, which were morphologically similar to L. casei/L. paracasei but clearly distinguishable from the remaining colonies owing to the color difference. These colonies were then subjected to enzyme-linked immunosorbent assay in order to identify the LcS. The viable counts of LcS were 6.6+/-0.7 log(10) CFU/g feces after intake of Yakult and 6.5+/-0.6 log(10) CFU/g feces after intake of Yakult Light (mean+/-SD).
authors.affiliation: Yakult Honsha European Research Center for Microbiology ESV, Technologiepark 4, 9052 Zwijnaarde, Belgium. takafumi.sakai@yher.be
authors.forename: Takafumi
authors.initials: T
authors.lastname: Sakai
authors.forename: Kenji
authors.initials: K
authors.lastname: Oishi
authors.forename: Takashi
authors.initials: T
authors.lastname: Asahara
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Takada
authors.forename: Norikatsu
authors.initials: N
authors.lastname: Yuki
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Koji
authors.initials: K
authors.lastname: Nomoto
authors.forename: Akira
authors.initials: A
authors.lastname: Kushiro
mesh_terms: D000328:Adult; D000362:Agar / Q000737:chemistry*; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry*; D043302:Cultured Milk Products / Q000382:microbiology; D005243:Feces / Q000382:microbiology; D005260:Female; D005285:Fermentation; D006801:Humans; D007780:Lacticaseibacillus casei / Q000302:isolation & purification*; D052201:Lacticaseibacillus rhamnosus / Q000302:isolation & purification*; D008297:Male; D008875:Middle Aged; D012210:Rhamnose / Q000737:chemistry; D055815:Young Adult
chemical_list: D003470:Culture Media; D000362:Agar; D012210:Rhamnose