BACTIBASE second release: a database and tool platform for bacteriocin characterization.

BACKGROUND: BACTIBASE is an integrated open-access database designed for the characterization of bacterial antimicrobial peptides, commonly known as bacteriocins. DESCRIPTION: For its second release, BACTIBASE has been expanded and equipped with additional functions aimed at both casual and power users. The number of entries has been increased by 44% and includes data collected from published literature as well as high-throughput datasets. The database provides a manually curated annotation of bacteriocin sequences. Improvements brought to BACTIBASE include incorporation of various tools for bacteriocin analysis, such as homology search, multiple sequence alignments, Hidden Markov Models, molecular modelling and retrieval through our taxonomy Browser. CONCLUSION: The provided features should make BACTIBASE a useful tool in food preservation or food safety applications and could have implications for the development of new drugs for medical use. BACTIBASE is available at http://bactibase.pfba-lab-tun.org.

On Lactococcus lactis UL719 competitivity and nisin (Nisaplin(®)) capacity to inhibit Clostridium difficile in a model of human colon.

Clostridium difficile is the most frequently identified enteric pathogen in patients with nosocomially acquired, antibiotic-associated diarrhea and pseudomembranous colitis. Although metronidazole and vancomycin were effective, an increasing number of treatment failures and recurrence of C. difficile infection are being reported. Use of probiotics, particularly metabolically active lactic acid bacteria, was recently proposed as an alternative for the medical community. The aim of this study was to assess a probiotic candidate, nisin Z-producer Lactococcus lactis UL719, competitivity and nisin (Nisaplin(®)) capacity to inhibit C. difficile in a model of human colon. Bacterial populations was enumerated by qPCR coupled to PMA treatment. L. lactis UL719 was able to survive and proliferate under simulated human colon, did not alter microbiota composition, but failed to inhibit C. difficile. While a single dose of 19 µmol/L (5× the MIC) was not sufficient to inhibit C. difficile, nisin at 76 µmol/L (20×the MIC) was effective at killing the pathogen. Nisin (at 76 µmol/L) caused some temporary changes in the microbiota with Gram-positive bacteria being the mostly affected. These results highlight the capacity of L. lactis UL719 to survive under simulated human colon and the efficacy of nisin as an alternative in the treatment of C. difficile infections.

Antibiotic and antimicrobial peptide combinations: synergistic inhibition of Pseudomonas fluorescens and antibiotic-resistant variants.

Variants resistant to penicillin G (RvP), streptomycin (RvS), lincomycin (RvL) and rifampicin (RvR) were developed from a colistin-sensitive isolate of Pseudomonas fluorescens LRC-R73 (P. fluorescens). Cell fatty acid composition, K(+) efflux and sensitivity to antimicrobial peptides (nisin Z, pediocin PA-1/AcH and colistin) alone or combined with antibiotics were determined. P. fluorescens was highly sensitive to kanamycin, tetracycline and chloramphenicol at minimal inhibitory concentrations of 0.366, 0.305 and 0.732 µg/ml respectively. P. fluorescens, RvP, RvS, RvL and RvR were resistant to nisin Z and pediocin PA-1/AcH at concentrations ≥100 µg/ml but sensitive to colistin at 0.076, 0.043, 0.344, 0.344 and 0.258 µg/ml respectively. A synergistic inhibitory effect (FICI ≤0.5) was observed when resistant variants were treated with peptide/antibiotic combinations. No significant effect on K(+) efflux from the resistant variants in the presence of antibiotics or peptides alone or combined was observed. The proportion of C16:0 was significantly higher in antibiotic-resistant variants than in the parent strain, accounting for 32.3%, 46.49%, 43.3%, 40.1% and 44.1% of the total fatty acids in P. fluorescens, RvP, RvS, RvL and RvR respectively. Combination of antibiotics with antimicrobial peptides could allow reduced use of antibiotics in medical applications and could help slow the emergence of bacteria resistant to antibiotics.