University of Natural Resources and Life Sciences, Vienna (BOKU) - Research portal
Gewählte Master / Diploma Thesis:
Firew Hailu Birru
(2010):
Evaluation of Broth Microdilution Based Method and Comparison of Standards for Antibiotic Susceptibility Testing of Non-enterococcal Lactic Acid Bacteria and Bifidobacteria.
Master / Diploma Thesis - Institut für Lebensmittelwissenschaften,
BOKU-Universität für Bodenkultur,
pp 194.
UB BOKU
obvsg
- Abstract:
- Lactic acid bacteria (LAB) and bifidobacteria are indigenous members of the gastrointestinal microbiota of humans. The main threat associated with these bacteria is that they can transfer resistance genes to pathogenic bacteria. Hence, bacterial strains intended to be used as probiotics in feed systems have to be systematically examined for antibiotic susceptibility. In order to avoid the spread of antibiotic-resistant determinants, a consistent approach should be adopted for microbial products in the food chain. Considering this point, it is necessary to dispose of a normalized method for MIC determination which employs a suitable test medium having little or no antagonistic effects towards studied antibiotics. Broth microdilution using LAB susceptibility test medium (LSM) was reported to provide the most optimal method in terms of growth support of non-enterococcal LAB and correct indication of minimum inhibitory concentrations (MICs) of international control strains. Therefore, the aim of this work was to further evaluate the applicability of the broth microdilution using LSM medium. Additionally, the performance of the recently published ISO/IDF standard with the CLSI guideline was compared for susceptibility testing of lactobacilli. The repeatability, reproducibility, and correct indication of MICs of the broth microdilution method were evaluated using commercial microdilution plates (VetMICTM National Veterinary Institute, Uppsala, Sweden) and the LSM medium for Bifidobacterium longum, Lactobacillus paracasei, Lactobacillus rhamnosus, Lactobacillus acidophilus, Lactococcus lactis, and Streptococcus thermophilus strains to 16 antimicrobial agents. Furthermore, the performances of the two standards were compared using self prepared microdilution plates for 22 Lactobacillus species to eight antibiotics. The broth microdilution method using LSM medium was found to be highly repeatable, reproducible and displayed a correct indication of MICs. All strains tested showed sufficient growth on the LSM medium of the ISO/IDF standard while only 11 Lactobacillus strains, out of 22, did grow on the medium recommend by CLSI. In general, the results of this study showed that the recently published ISO/IDF standard using broth microdilution method and LSM medium is an applicable method for antimicrobial susceptibility testing of non-enterococcal LAB and bifidobacteria.
- Beurteilende(r): Kneifel Wolfgang
- 1.Mitwirkender: Domig Konrad
- 2.Mitwirkender: Mayrhofer Sigrid