Fifty-one strains of the genus Bifidobacterium have been found to accumulate indole-3-lactic acid in culture broth. The isolated metabolite was identified through mass and nuclear magnetic resonance spectroscopy. All the microorganisms tested, as resting cells, have been shown to be able to convert L-tryptophan into L-indole-3-lactic acid.
The hydrolysis of sodium taurocholate and glycocholate was a common feature among 52 strains from 14 species belonging to the genus Bijidobacteriurn. Forty-eight strains were able to hydrolyse both these conjugated bile acids, yet four strains failed to split the amide bond of either. Twenty-eight strains were checked for the ability to transform sodium cholate, chenodeoxycholate, deoxycholate and lithocholate; only 13 of these strains formed minimal quantities of monochetoderivatives from cholic acid. while none of them was able to transform the other tested bile acids.
The ecosystem of the dental plaque in periodontal diseases is very complex: the study of such micro-organisms, which are mostly strict anaerobes, requires the use of specific techniques under conditions of strict anaerobiosis. The aim of the present study was to design a rapid method to evaluate the activity of antimicrobials on mixed bacterial plaque of subjects with periodontal diseases. The study was carried out using a computerised instrument generally used for simultaneous diagnostic tests with aerobic bacteria. Operative and methodological modifications were made to obtain conditions of strict anaerobiosis and the balanced growth of all the microbial forms present in the mixed cultures of the plaque. Penicillins and cephalosporins were active on all the samples, whereas colistin, gentamicin, kanamycin and nalidixic acid showed no activity. Clindamycin, tetracycline, erythromycin and penicillin G were effective only against some samples. The activity of the antimicrobials towards isolated strains was analogous to that towards the corresponding mixed culture.
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