Phenotypic and Molecular Assessment of Antimicrobial Resistance in Lactobacillus paracasei Strains of Food Origin

Authors: Huys, Geert1; D'Haene, Klaas1; Danielsen, Morten2; Mättö, Jaana3; Egervärn, Maria4; Vandamme, Peter1

Source: Journal of Food Protection®, Number 2, February 2008, pp. 252-458 , pp. 339-344(6)

Publisher: International Association for Food Protection

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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 μg/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.

Document Type: Research Article

Affiliations: 1: Laboratory of Microbiology, Department of Physiology, Biochemistry and Microbiology, Faculty of Sciences, Ghent University, K. L. Ledeganckstraat 35, Ghent, Belgium 2: Chr. Hansen A/S, Hørsholm, Denmark 3: VTT Biotechnology, Espoo, Finland 4: National Food Administration, Uppsala, Sweden

Publication date: February 1, 2008

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    First published in 1937, the Journal of Food Protection®, is a refereed monthly publication. Each issue contains scientific research and authoritative review articles reporting on a variety of topics in food science pertaining to food safety and quality. The Journal is internationally recognized as the leading publication in the field of food microbiology with a readership exceeding 11,000 scientists from 70 countries. The Journal of Food Protection® is indexed in Index Medicus, Current Contents, BIOSIS, PubMed, Medline, and many others.

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