Antibiotic resistance of lactic acid bacteria and Bifidobacterium spp. isolated from dairy and pharmaceutical products.

The outlines of antibiotic resistance of some probiotic microorganisms were studied. This study was conducted with the double purpose of verifying their ability to survive if they are taken simultaneously with an antibiotic therapy and to increase the selective properties of suitable media for the isolation of samples containing mixed bacterial populations. We isolated from commercial dairy and pharmaceutical products, 34 strains declared as probiotics, belonging to the genera Bifidobacterium and Lactobacillus, and 21 strains of starter culture bacteria. All the microorganisms have been compared by electrophoresis of the soluble proteins for the purpose of identifying them. A Multiplex-PCR with genus- and species-specific primers was used to detect for Bifidobacterium animalis subsp. lactis presence. All bifidobacteria were B. animalis subsp. lactis except one Bifidobacterium longum. Sometimes the identification showed that the used strain was not the one indicated on the label. The lactobacilli were Lactobacillus acidophilus, Lactobacillus casei, and Lactobacillus delbrueckii subsp. bulgaricus. The streptococci were all Streptococcus thermophilus. The minimal inhibitory concentration (MIC) of 24 common antibiotic substances has been valued by the broth microdilution method. All tested strains were susceptible to ampicillin, bacitracin, clindamycin, dicloxacillin, erytromycin, novobiocin, penicillin G, rifampicin (MIC(90) ranging from 0.01 to 4 mug/ml); resistant to aztreonam, cycloserin, kanamycin, nalidixic acid, polymyxin B and spectinomycin (MIC(90) ranging from 64 to >1000 mug/ml). The susceptibility to cephalothin, chloramphenicol, gentamicin, lincomycin, metronidazole, neomycin, paromomycin, streptomycin, tetracycline and vancomycin was variable and depending on the species

Antibiotic resistance of Lactobacillus spp. isolated from dairy and pharmaceutical products

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

FOLATE PRODUCTION IN BIFIDOBACTERIA FROM INFANT AND ADULT HUMANS

Folates \u2013 the natural chemically reduced forms of folic acid (vitamin B9) - are cofactors in essential metabolic pathways such as DNA synthesis and methylation pathways. Humans cannot synthesize folate and depend on intake both from the diet (green vegetables, cereals, rice, milk, fermented milk products, etc.) and from indigenous folate synthesizing bacteria of the intestinal microbiota. Low folate levels increase the risk for neural tube defects and may increase the risk for e.g. certain cancer forms, cardiovascular disease and Alzheimer\u2019s. Screening for folate production of the bifidobacteria isolates from human adult and infant (1-6 month old) was performed. Strains typical of infants, such as Bifidobacterium longum subsp. infantis and B. breve, and of adults ( B. adolescentis) were selected for characterization. The aim of the present work was to investigate bifidobacteria from human host of different age with different feeding habits in order to establish a possible correlation between diet and the folate production. Folate is present in many different forms in humans. The detectable forms studied in the present work are 5-CH3-H4, H4 and total folate content. Bifidobacteria strains were cultivated in folate free synthetic media. Validated HPLC method was used to analyze deconjugated folates extracted from bacterial biomass