Identification and in vitro characterisation of Lactobacillus plantarum strains from artisanal Bulgarian white brined cheeses

Abstract

Lactobacillus plantarum strains were isolated from fully ripened, white brined Bulgarian home-made cheeses. Strains were derived from phenotypically homogenous Lactobacillus group and were identified as L. plantarum based on both phenotypic and molecular identification (species-specific and multiplex PCR) methods. Heterogeneity of L. plantarum isolates was evaluated by Rep-PCR analysis. Further antimicrobial activity, antibiotic susceptibility and transit tolerance of the strains were evaluated. Most of them showed broad spectrum of activity against Gram-negative bacteria (including human pathogens) independent on the presence of organic acids or hydrogen peroxide. All strains were sensitive to amoxicillin and sulfamethoxazole/trimethoprim, resistant to clinically relevant beta -lactame antibiotics (penicillin and ampicillin) and to nalidixic acid, ciprofloxacin, streptomycin, and vancomycin. Significant variability in the sensitivity to tetracycline was noted. The tolerance to low pH, bile salts, pepsin and pancreatin at concentrations similar to those in the gastrointestinal tract was strain-dependent. The exposure to bile salts was less destructive than exposure to pH 2.0 for all tested strains. Based on their combined responses to the above selection criteria, four L. plantarum strains, RL29, RL34, RL36 and RL37, were selected as potential probiotics for in vivo studies.

Modulation of Escherichia coli biofilm growth by cell-free spent cultures from lactobacilli

“…Based on these results, strains LB6 and LB7 were considered as probiotic candidate strains with strong transit tolerance and biological activity [22][23][24]. The present results are in support of this.…”

“…They are a part of laboratory collection and were identified to the species level in our previous work [22,26] Escherichia coli PU-3 Urine, woman with pyelonephritis, BM-PU [42] Escherichia coli PU-13 Am-r, Sxt-r Urine, man with cystitis, BM-PU [42] Lactobacillus strains:…”

“…As a source of CFS, 11 Lactobacillus vaginal and dairy-product isolates from the laboratory collection of the Institute of Microbiology were selected on the basis of their recently reported broad-spectrum antibacterial activities [22][23][24]. We collected evidence suggesting that highly diluted noninhibitory amounts of CFS (10 -2 to 10 -4 ) can still have a biofilm-modulation capacity and that this is probably due to factors different from those involved in their antibacterial activity.…”

Technological and probiotic characteristics of Lactobacillus plantarum strains isolated from traditionally produced fermented vegetables

“…Among the strains tested, L. plantarum 66 was the most sensitive considering its high susceptibility to the antibiotics used (8/13). Additionally, L. plantarum strains showed variable behavior towards penicillin and tetracycline ( Georgieva et al (2008) tested the resistance to some antibiotics of some L. plantarum strains isolated from white brined cheese; similar susceptibility results were obtained as in this study except for ampicillin. Variations in resistance of Lactobacillus to penicillin and tetracycline was previously reported by Temmerman et al (2003) and attributed to the potential transferability of antibiotic resistance determinants.…”

Survival of cheese bacteria in a gastrointestinal tract simulator

“…Non-starter lactic acid bacteria (NSLAB) from species of Lactobacillus (L.) plantarum, Lactobacillus rhamnosus, and Lactobacillus casei isolated from various cheese types have been tested for selection criteria of probiotics (Georgieva et al, 2008;Kask et al, 2003;Succi et al, 2005;Ugarte et al, 2006). Tolerance of these lactobacilli to low pH, bile salts, pepsin and pancreatin at biological concentrations has been shown to be strain-dependent (Georgieva et al, 2008;Haller et al, 2001) but often comparable with that of well-known probiotic strains.…”