Antibiotic resistance in lactic acid bacteria and Micrococcaceae/Staphylococcaceae isolates from artisanal raw milk cheeses, and potential implications on cheese making.
ABSTRACT Antibiotic susceptibility against 19 antimicrobial agents was evaluated in isolates of the genera Lactococcus (46 isolates), Leuconostoc (22), Lactobacillus (19), Staphylococcus (8), Enterococcus (7), and Microccoccus/Kocuria (5) obtained from the predominant microflora of nonrecent and recent types of artisanal raw cow's milk cheeses. Beta-lactams showed broad activity against all genera, although leuconostocs and lactobacilli were highly resistant to oxacillin (80% to 95.5%). Resistance to aminoglycosides was frequent for lactococci and enterococci (particularly for streptomycin), whereas lower rates of resistance were detected for lactobacilli and leuconostocs. Technologically interesting traits for the food industry were distributed among isolates that showed different degrees of resistance to common antibiotics. However, isolates showing resistance to less than 2 antibiotics were mainly those with properties of greatest technological interest (acidifying activity, proteolytic/lipolytic activities, or diacetyl production).
Article: 2 3 Characterization of new strain Lactobacillus paracasei I-N-10 with proteolytic activity: Potential role in decrease in β-casein immuno-reactivity[show abstract] [hide abstract]
ABSTRACT: The proteolytic activity of thirty-three LAB isolates from Mongolian tarag was tested on skimmed milk. The strain displaying the highest proteolytic activity was purified and presented by 16S rDNA sequencing 99.9 % homology with Lactobacillus paracasei 1-4-2A. It was named L. paracasei I-N-10. Proteases of L. paracasei I-N-10 hydrolyze predominately b-casein and in some level aS2-casein; hydrolysis of aS1-casein was not observed. Proteolytic activity was optimal at 42 �C and neutral pH. Proteases of L. paracasei I-N-10 were inhibited by serineand metalloproteases inhibitors. PCR amplification revealed the presence of prtP gene, which was identical to prtP gene of L. paracasei genus. Mass spectrometry analysis of b-casein hydrolysate allowed to characterize 7 peptides resulting from proteolysis by L. paracasei I-N-10. The isolated strain was able to cleave b-casein in different sites including 2 of the major linear epitopes implicated in its allergenicity. Being sensitive to main antibiotics classes, L. paracasei I-N-10 could be considered as safe and used as starter culture with a potential role in decreasing b-casein immuno-reactivity.European Food Research and Technology 01/2012; 235:447. · 1.57 Impact Factor
Article: Antilisterial activity of nisin-like bacteriocin-producing Lactococcus lactis subsp. lactis isolated from traditional Sardinian dairy products.[show abstract] [hide abstract]
ABSTRACT: With the aim of selecting LAB strains with antilisterial activity to be used as protective cultures to enhance the safety of dairy products, the antimicrobial properties of 117 Lactococcus lactis subsp. lactis isolated from artisanal Sardinian dairy products were evaluated, and six strains were found to produce bacteriocin-like substances. The capacity of these strains to antagonize Listeria monocytogenes during cocultivation in skimmed milk was evaluated, showing a reduction of L. monocytogenes counts of approximately 4 log units compared to the positive control after 24 h of incubation. In order for a strain to be used as bioprotective culture, it should be carefully evaluated for the presence of virulence factors, to determine what potential risks might be involved in its use. None of the strains tested was found to produce biogenic amines or to possess haemolytic activity. In addition, all strains were sensitive to clinically important antibiotics such as ampicillin, tetracycline, and vancomycin. Our results suggest that these bac+ strains could be potentially applied in cheese manufacturing to control the growth of L. monocytogenes.Journal of Biomedicine and Biotechnology 01/2012; 2012:376428. · 2.44 Impact Factor