Safety of Bacteriocinogenic Strains Isolated from Traditional Smoked Meat Products from North Portugal

Introduction : LAB capable of producing bacteriocins have technological applications in smoked meat products' biopreservation. However, presence of virulences factors, antibiotic resistance or biogenic amine genes are critical in determining the safety aspects for LAB.

 

Purpose: To screen for the presence of genes encoding bacteriocin, virulence factors, antibiotic resistance and biogenic amines in LAB able to produce antimicrobial compounds, isolated from smoked meat products. 

 

Methods: The microbiological status (presence of Listeria spp., Aeromonas spp., LAB and total microbial count) of 43 industrial smoked and fermented meat products from Portugal, produced without starter cultures, was studied. Isolated LAB were identified by 16s rDNA sequencing and tested for the production of bacteriocins against various Listeria monocytogenes strains and screened by PCR for genes encoding bacteriocins, virulence factors, antibiotic resistance and biogenic amines formation.

 

Results : The microbiological status of tested meat products showed that fermentation was dominated by LAB (10⁷ CFU/g), consisting of “wild” strains of Lactobacillus spp. and Enterococcus spp.  The presence of L. innocua in tested products was recorded in 32 of 43 samples. L. monocytogenes, L. ivanovii and Aeromonas spp. were not detected in any of the samples. Six bacteriocinogenic strains (2 strains of Lactobacillus plantarum, 3 strains of Lb. sakei and 1 strain of Enterococcus faecium) were selected and tested for production of bacteriocins against L. monocytogenes from different serological groups. No evidences for presence of genes for ornithine decarboxylase, hystidine decarboxylase, tyrosine decarboxylase, gelatinase, aggregation substance, cytolisin, endocarditis antigen and vancomycin A were recorded in all tested strains. Vancomycin B gene was detected in Lb. sakei ST153Ch and Lb. plantarum ST216Ch; adhesion of collagen protein gene generated positive results for Lb. sakei ST22Ch and ST153Ch and Lb. plantarum ST216Ch; enterococcal surface protein and hyaluronidase were present in Lb. sakei ST154Ch.

Significance : Lb. plantarum ST202Ch and ST216Ch, Lb. sakei ST22Ch, ST153Ch and ST154Ch and E. faecium ST211Ch produce antilisterial bacteriocins, harbored at least one bacteriocin gene and presented low levels of presence of virulence genes. These strains present interesting potential for technological applications in the meat industry.