Antibiotic susceptibility profiles of Lactobacillus reuteri and Lactobacillus fermentum.
Lactobacillus reuteri and Lactobacillus fermentum, which are commonly used as food processing aids and probiotics, can potentially act as reservoirs of antibiotic resistance genes. Acquired resistance genes may be transferred via the food chain or in the gastrointestinal tract to pathogenic bacteria. Knowledge of the distributions of antibiotic MICs for a species is needed when using a phenotypic method to assess the presence of acquired resistance genes. In the present study, 56 L. reuteri and 56 L. fermentum strains that differed by source and spatial and temporal origin were assessed for antibiotic susceptibility using an Etest kit and a broth microdilution protocol. L. fermentum strains displayed a uniform distribution of MICs for all six antibiotics tested. L. reuteri strains had a bimodal distribution of MICs or a distribution with MICs above the test range for 7 of the 14 antibiotics tested. Genetic relatedness was observed among L. reuteri strains with high MICs for both ampicillin and tetracycline and among strains with high MICs for both erythromycin and clindamycin. Results obtained with the Etest and the broth microdilution method corresponded well with each other. Thus, further research may make it possible to define microbiological breakpoints for distinguishing between strains with and without acquired resistance genes.
Egervärn
Maria
M
National Food Administration, P.O. Box 622, SE-751 26 Uppsala, Sweden. mia.egervarn@slv.se
Danielsen
Morten
M
Roos
Stefan
S
Lindmark
Hans
H
Lindgren
Sven
S
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005516:Food Microbiology; D052197:Limosilactobacillus fermentum / Q000187:drug effects*; D052200:Limosilactobacillus reuteri / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D019936:Probiotics; D013045:Species Specificity
D000900:Anti-Bacterial Agents