| Popis: |
The balance and the composition of the intestinal microbiota are important for the well-being and the ability of our bodies to resist to the invasion of phatogens. Many causes can alter this delicate balance, but the ingestion of antimicrobial agents is the most important. Then, to help the bowel and to increase the natural resistance of the host to infection, probiotic microorganisms such as lactobacilli and bifidobacteria can be consumed. The safety of these probiotic strains is essential, particularly that they should not be able to transfer to other bacteria any possible resistance to antimicrobial agents. Antibiotic resistance is an emerging issue nowadays. We have studied the antibiotic resistance of some probiotic microorganisms, for two reasons: to verify their ability to survive if taken at the same time as antibiotic therapy, and to increase the selective properties of media used for their isolation from samples containing mixed bacterial populations. We have isolated from commercial dairy and pharmaceutical products, 34 strains declared as probiotics, belonging to the genera Bifidobacterium [1] and Lactobacillus [2], and 21 strains of starter culture bacteria. All the microorganisms were identified using electrophoresis of the soluble proteins. The bifidobacteria were Bifidobacterium animalis except for one Bifidobacterium longum. Sometimes the identification showed that the strain found was not the one indicated on the label. The lactobacilli were L. acidophilus, L. casei, and Lactobacillus delbrueckii subsp. bulgaricus. The minimum inhibitory concentration (MIC) of 24 common antibiotic substances was measured using the broth microdiluition method. All the isolated strains were sensitive to ampicillin, bacitracin, clindamycin, dicloxacillin, erytromycin, lincomycin, novobiocin, penicillin G, rifampicin, vancomycin (MIC90 ≤ 5 µg/ml). For chloramphenicol, cephalothin and tetracycline MIC90 was ≤ 50 µg/ml, while for cycloserine, kanamycin, metronidazole, gentamicin, nalidixic acid, polymyxin B, neomycin, paromomycin, aztreonam, spectinomycin, streptomycin, the MIC90 was ≥ 50 µg/ml. |
