In this research, samples of artisanal and industrial Italian cheeses were acquired from different supermarkets in Sicily from September 2000 to February 2001, and were analysed for vancomycin-resistant enterococci (VRE). The analyzed cheeses could be divided into three categories, based on the number of enterococci as determined on Kanamycin Aesculin Agar Base (KAA). An enrichment step in Tripticase Soy Yeast Extract Broth (TSYE) supplemented with 8 g/mL vancomycin and subsequently plating out onto KAA containing vancomycin allowed the individuation of vancomycin-resistant lactic acid bacteria in 46.7% of the cheese samples analyzed. These bacteria were assigned, on the bases of their morphology and metabolic characteristics, to the genera Leuconostoc, Pediococcus and Lactobacillus, known for their intrinsic vancomycin resistance. Strains of VRE were detected in only 3 out of 30 (10%) samples of different cheeses, i.e. Asiago cheese, Pecorino Pepato cheese and grated cheese, all included in the category of cheeses with a high number of enterococci. The VRE isolates, identified as Enterococcus faecium by multiplex PCR and Specific And Random Amplification (SARA)-PCR analysis, were highly resistant to vancomycin and teicoplanin (MIC > 64 µg/mL) and harboured the vanA gene, as shown by both PCR techniques. The genetic fingerprints obtained with a RAPD-PCR assay revealed that the isolates were genotipically heterogenous thus suggesting that different VRE strains are able to colonise different Italian cheeses. Also the results obtained in this study indicate that the presence of bacteria with acquired antibiotic resistance should be closely monitored and controlled in order to make food safer.
Presenza di ceppi di Enterococcus faecium vancomicina-resistenti in formaggi italiani
TORRIANI, Sandra;
2001-01-01
Abstract
In this research, samples of artisanal and industrial Italian cheeses were acquired from different supermarkets in Sicily from September 2000 to February 2001, and were analysed for vancomycin-resistant enterococci (VRE). The analyzed cheeses could be divided into three categories, based on the number of enterococci as determined on Kanamycin Aesculin Agar Base (KAA). An enrichment step in Tripticase Soy Yeast Extract Broth (TSYE) supplemented with 8 g/mL vancomycin and subsequently plating out onto KAA containing vancomycin allowed the individuation of vancomycin-resistant lactic acid bacteria in 46.7% of the cheese samples analyzed. These bacteria were assigned, on the bases of their morphology and metabolic characteristics, to the genera Leuconostoc, Pediococcus and Lactobacillus, known for their intrinsic vancomycin resistance. Strains of VRE were detected in only 3 out of 30 (10%) samples of different cheeses, i.e. Asiago cheese, Pecorino Pepato cheese and grated cheese, all included in the category of cheeses with a high number of enterococci. The VRE isolates, identified as Enterococcus faecium by multiplex PCR and Specific And Random Amplification (SARA)-PCR analysis, were highly resistant to vancomycin and teicoplanin (MIC > 64 µg/mL) and harboured the vanA gene, as shown by both PCR techniques. The genetic fingerprints obtained with a RAPD-PCR assay revealed that the isolates were genotipically heterogenous thus suggesting that different VRE strains are able to colonise different Italian cheeses. Also the results obtained in this study indicate that the presence of bacteria with acquired antibiotic resistance should be closely monitored and controlled in order to make food safer.
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