Molecular characterization of intrinsic and acquired antibiotic resistance in lactic acid bacteria and bifidobacteria.
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.
Ammor
Mohammed Salim
MS
Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Carretera de Infiesto s/n, Villaviciosa, Spain. ammor@ipla.csic.es
Flórez
Ana Belén
AB
van Hoek
Angela H A M
AH
de Los Reyes-Gavilán
Clara G
CG
Aarts
Henk J M
HJ
Margolles
Abelardo
A
Mayo
Baltasar
B
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
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins