Phenotypic and molecular assessment of antimicrobial resistance in Lactobacillus paracasei strains of food origin

Geert Huys (Corresponding Author), Klaas D'Haene, Morten Danielsen, Jaana Mättö, Maria Egervärn, Peter Vandamme

Research output: Contribution to journalArticleScientificpeer-review

42 Citations (Scopus)


Antimicrobial resistance data in food-associated lactic acid bacteria (LAB) such as lactobacilli are mostly based on nonstandardized methodologies and/or have been obtained for only a limited number of strains. This susceptibility study included a diverse collection of 115 isolates mainly of food origin originally identified as Lactobacillus paracasei or Lactobacillus casei. Upon reidentification and removal of potential replicate isolates using repetitive DNA element PCR fingerprinting, 65 genotypically unique L. paracasei strains and the L. casei type strain were selected for broth microdilution and Etest assays using the LAB susceptibility test medium. In both methodologies, strains appeared uniformly susceptible to ampicillin and clindamycin but exhibited natural resistance to streptomycin and gentamicin. Three L. paracasei strains from cheese displayed acquired resistance to tetracycline (MIC ≥ 32 μg/ml) and/or to erythromycin (MIC >16 μ g/ml), which was linked to the presence of a tet(M) or tet(W) gene and/or an erm(B) gene, respectively. Partial sequencing revealed that the tet(M) genes found in two of these strains belonged to two tet(M) sequence homology groups previously found in enterococci. Collectively, phenotypic and genotypic data allowed us to propose tentative epidemiological cutoffs for L. paracasei and L. casei for differentiating susceptible strains from those strains harboring one or more acquired resistance factors.
Original languageEnglish
Pages (from-to)339-344
JournalJournal of Food Protection
Issue number2
Publication statusPublished - 2008
MoE publication typeA1 Journal article-refereed


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