title: Molecular characterization of intrinsic and acquired antibiotic resistance in lactic acid bacteria and bifidobacteria.
abstract: The minimum inhibitory concentrations (MICs) of 6 different antibiotics (chloramphenicol, clindamycin, erythromycin, streptomycin, tetracycline and vancomycin) were determined for 143 strains of lactic acid bacteria and bifidobacteria using the Etest. Different MICs were found for different species and strains. Based on the distribution of these MIC values, most of the strains were either susceptible or intrinsically resistant to these antibiotics. However, the MIC range of some of these antibiotics showed a bimodal distribution, which suggested that some of the tested strains possess acquired antibiotic resistance. Screening for resistance genes was performed by PCR using specific primers, or using a DNA microarray with around 300 nucleotide probes representing 7 classes of antibiotic resistance genes. The genes identified encoded resistance to tetracycline [tet(M), tet(W), tet(O) and tet(O/W)], erythromycin and clindamycin [erm(B)] and streptomycin [aph(E) and sat(3)]. Internal portions of some of these determinants were sequenced and found to be identical to genes described in other bacteria. All resistance determinants were located on the bacterial chromosome, except for tet(M), which was identified on plasmids in Lactococcus lactis. The contribution of intrinsic multidrug transporters to the antibiotic resistance was investigated by cloning and measuring the expression of Bifidobacterium breve genes in L. lactis.
authors.affiliation: Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Carretera de Infiesto s/n, Villaviciosa, Spain. ammor@ipla.csic.es
authors.forename: Mohammed Salim
authors.initials: MS
authors.lastname: Ammor
authors.forename: Ana Belén
authors.initials: AB
authors.lastname: Flórez
authors.forename: Angela H A M
authors.initials: AH
authors.lastname: van Hoek
authors.forename: Clara G
authors.initials: CG
authors.lastname: de Los Reyes-Gavilán
authors.forename: Henk J M
authors.initials: HJ
authors.lastname: Aarts
authors.forename: Abelardo
authors.initials: A
authors.lastname: Margolles
authors.forename: Baltasar
authors.initials: B
authors.lastname: Mayo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001644:Bifidobacterium / Q000187:drug effects* / Q000235:genetics; D015169:Colony Count, Microbial; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D006801:Humans; D007778:Lactobacillus / Q000187:drug effects* / Q000235:genetics; D017045:Lactococcus / Q000187:drug effects* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins