Antibiotic Susceptibility Profile and Survival of Bifidobacterium adolescentis and Bifidobacterium catenulatum of Human and Avian Origin in Stored Yoghurt
Bifidobacteria are categorized as health-promoting microorganisms (probiotics) in the gastrointestinal tracts of humans and animals. Antibiotic susceptibility is a key criterion for probiotic agent selection. Good survival of probiotics during storage at selected storage temperature(s) is highly desirable. Bifidobacteria isolated from human and chicken were thus characterized phenotypically by their ability to produce fructose-6-phosphoketolase enzyme. Eight selected isolates were then characterized on molecular basis employing genus-specific and species-specific 16S rRNA gene primers, and their antibiotic susceptibilities were also evaluated. Isolates were confirmed to be strains of B. catenulatum
(4) and B. adolescentis (4). Studied strains were resistant to streptomycin, gentamycin, cloxacillin and cotrimoxazole but susceptible to chloramphenicol, augmentin, amoxicillin and erythromycin. Three strains (B. catenulatum HM2, B. catenulatum HM3 and B. catenulatum HM5) showed atypical tetracycline resistance. B. catenulatum HM2, B. adolescentis CH2 and B. adolescentis CH3 showed significant reduction in counts (p < 0.05) and survived in adequate amount in yoghurt stored at 4¢ªC and -18¢ªC for 4 weeks. In addition to presenting acceptable antibiotic susceptibility profile and exhibiting good survival in stored yoghurt, the bifidobacteria isolates inhibited Staphylococcus aureus ATCC 25925 and Escherichia coli ATCC 25922 in-vitro and demonstrated potential for application as probiotic agents for human and agricultural purposes.
Keywords: Bifidobacterium, probiotics, 16S rRNA, survival at low temperature.