Antibiotic Susceptibility of Lactobacillus and Bifidobacterium Species from the Human Gastrointestinal Tract

Hundred and 22 strains of Bifidobacterium and Lactobacillus species have been compared with 12 antibiotics and two antibiotic mixtures of a commercial system, and tested (Trek Diagnostic Systems Sensititre Anaero3). The ceilings of some minimum inhibitory concentrations (MICs) were completed on MRS agar plates by the NCCLS method. All strains were sensitive to chloramphenicol and imipenem, and most of the strains were resistant to metronidazole. Bifidobacteria isolates were susceptible to cefoxitin, whereas about half of the lactobacilli were resistant. About 30% of the Bifidobacterium isolates were resistant to tetracycline, and five different Lactobacillus strains from four species. None of the tested Bifidobacterium isolates was resistant to vancomycin, whereas a species-dependent resistance of the lactobacilli was found. Individual strains of Bifidobacterium longum, Bifidobacterium pseudocatenulatum, Lactobacillus acidophilus, Lactobacillus rhamnosus and Lactobacillus brevis were resistant to erythromycin and / or clindamycin. Most of the observed resistance seemed to be intrinsic, but some others could be compatible with transmissible determinants.
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