Anti-Proliferative and Anti-Biofilm Potentials of Bacteriocins Produced by Non-Pathogenic Enterococcus sp

Peptide-based strategies for overcoming biofilm-associated infections: a comprehensive review

Biofilms represent resilient microbial communities responsible for inducing chronic infections in human subjects. Given the escalating challenges associated with antibiotic therapy failures in clinical infections linked to biofilm formation, a peptide-based approach emerges as a promising alternative to effectively combat these notoriously resistant biofilms. Contrary to conventional antimicrobial peptides, which predominantly target cellular membranes, antibiofilm peptides necessitate a multifaceted approach, addressing various "biofilm-specific factors." These factors encompass Extracellular Polymeric Substance (EPS) degradation, membrane targeting, cell signaling, and regulatory mechanisms. Recent research endeavors have been directed toward assessing the potential of peptides as potent antibiofilm agents. However, to translate these peptides into viable clinical applications, several critical considerations must be meticulously evaluated during the peptide design process. This review serves to furnish an all-encompassing summary of the pivotal factors and parameters that necessitate contemplation for the successful development of an efficacious antibiofilm peptide.

Susceptibility to postbiotics - enterocins of methicillin-resistant Staphylococcus aureus strains isolated from rabbits

There is a major problem with the rising occurrence of highly virulent and multiply-resistant strains, including methicillin-resistant Staphylococcus aureus (MRSA), because of their difficult treatment. This study aimed to evaluate the antibacterial and antibiofilm effect of new enterocins (Ent) against potential pathogenic MRSA strains isolated from rabbits. Staphylococci were identified with PCR and screened for methicillin/oxacillin/cefoxitin resistance (MR) using the disk diffusion method and the PBP2' Latex Agglutination Test Kit. Enzyme production, hemolysis, DNase activity, slime production, and biofilm formation were tested in MRSA strains. The susceptibility of MRSA to eight partially-purified enterocins (Ent) produced by E. faecium and E. durans strains was checked using agar spot tests. The antibiofilm activity of Ents was tested using a quantitative plate assay. Out of 14 MRSA, PBP testing confirmed MR in 8 strains. The majority of MRSA showed DNase activity and β-hemolysis. Slime production and moderate biofilm formation were observed in all strains. MRSA were susceptible to tested Ents (100-12,800 AU/mL; except Ent4231). The antibiofilm effect of Ents (except Ent4231) was noted in the high range (64.9-97.0%). These results indicate that enterocins offer a promising option for the prevention and treatment of bacterial infections caused by biofilm-forming MRSA.

Genomic and phenotypic characterisation of Enterococcus mundtii AM_AQ_BC8 for its anti-biofilm, antimicrobial and probiotic potential

Enterococcus mundtii AM_AQ_BC8 isolated from biofouled filtration membrane was characterised as a potential probiotic bacterium showing strong L-lactic acid-producing capability. Experimental studies revealed that E. mundtii AM_AQ_BC8 possess antibiofilm and antimicrobial ability too, as tested against strong biofilm-forming bacteria like Pseudomonas spp. The present study has evaluated the genetic potential of E. mundtii AM_AQ_BC8 through genome sequencing. Whole genome analysis revealed the presence of key genes like ldh_1 and ldh_2 responsible for lactic acid production along with genes encoding probiotic features such as acid and bile salt resistance (dnaK, dnaJ, argS), fatty acid synthesis (fabD, fabE) and lactose utilisation (lacG, lacD). The phylogenomic analysis based on OrthoANI (99.85%) and dDDH (96.8%) values revealed that the strain AM_AQ_BC8 shared the highest homology with E. mundtii. The genome sequence of strain AM_AQ_BC8 has been deposited to NCBI and released with GenBank accession no. SAMN32531201. The study primarily demonstrated the probiotic potential of E. mundtii AM_AQ_BC8 isolate, for L-lactate synthesis in high concentration (8.98 g/L/day), which also showed anti-biofilm and antimicrobial activities.

Impact of lactic acid bacteria strains against Listeria monocytogenes biofilms on various food-contact surfaces

Listeria monocytogenes is one of the most important foodborne pathogens, causing listeriosis, a disease characterized by high mortality rates. This microorganism, commonly found in food production environments and transmitted to humans by consuming contaminated food, has the ability to form biofilms by attaching to a wide variety of surfaces. Traditional hygiene and sanitation procedures are not effective enough to completely remove L. monocytogenes biofilms from food-contact surfaces, which makes them a persistent threat to food safety. Alternative approaches to combating Listeria biofilms are needed, and the use of lactic acid bacteria (LAB) and their antimicrobial compounds shows promise. The present study investigated the effect of Lactobacillus strains, previously isolated from various foods and known to possess antimicrobial properties, on the biofilm formation of L. monocytogenes on three different food-contact surfaces. To study L. monocytogenes IVb ATCC 19115 type, culture was preferred to represent serotype IVb, which is responsible for the vast majority of listeriosis cases. The results demonstrated that cell-free supernatants (CFSs) of LAB strains inhibited biofilm formation by up to 51.57% on polystyrene, 60.96% on stainless steel, and 30.99% on glass surfaces. Moreover, these CFSs were effective in eradicating mature biofilms, with reductions of up to 78.86% on polystyrene, 73.12% on stainless steel, and 72.63% on glass surfaces. The strong inhibition rates of one strain of L. curvatus (P3X) and two strains of L. sakei (8.P1, 28.P2) used in the present study imply that they may provide an alternate technique for managing Listeria biofilms in food production environments.

Importance of microbial amphiphiles: interaction potential of biosurfactants, amyloids, and other exo-polymeric-substances

Microorganisms produce a diverse group of biomolecules having amphipathic nature (amphiphiles). Microbial amphiphiles, including amyloids, bio-surfactants, and other exo-polymeric substances, play a crucial role in various biological processes and have gained significant attention recently. Although diverse in biochemical composition, these amphiphiles have been reported for common microbial traits like biofilm formation and pathogenicity due to their ability to act as surface active agents with active interfacial properties essential for microbes to grow in various niches. This enables microbes to reduce surface tension, emulsification, dispersion, and attachment at the interface. In this report, the ecological importance and biotechnological usage of important amphiphiles have been discussed. The low molecular weight amphiphiles like biosurfactants, siderophores, and peptides showing helical and antimicrobial activities have been extensively reported for their ability to work as quorum-sensing mediators. While high molecular weight amphiphiles make up amyloid fibers, exopolysaccharides, liposomes, or magnetosomes have been shown to have a significant influence in deciding microbial physiology and survival. In this report, we have discussed the functional similarities and biochemical variations of several amphipathic biomolecules produced by microbes, and the present report shows these amphiphiles showing polyphyletic and ecophysiological groups of microorganisms and hence can `be replaced in biotechnological applications depending on the compatibility of the processes.

Resistance, Tolerance, Virulence and Bacterial Pathogen Fitness-Current State and Envisioned Solutions for the Near Future

The current antibiotic crisis and the global phenomena of bacterial resistance, inherited and non-inherited, and tolerance-associated with biofilm formation-are prompting dire predictions of a post-antibiotic era in the near future. These predictions refer to increases in morbidity and mortality rates as a consequence of infections with multidrug-resistant or pandrug-resistant microbial strains. In this context, we aimed to highlight the current status of the antibiotic resistance phenomenon and the significance of bacterial virulence properties/fitness for human health and to review the main strategies alternative or complementary to antibiotic therapy, some of them being already clinically applied or in clinical trials, others only foreseen and in the research phase.

Isolation and phenotypic characterization of bacteriophage SA14 with lytic- and anti-biofilm activity against multidrug-resistant Enterococcus faecalis

Background

Antimicrobial resistance is a growing global health concern demanding more attention and action at the international-, national- and regional levels. In the present study, bacteriophage was sought as a potential alternative to traditional antibiotics.

Results

Vancomycin-resistant Enterococcus faecalis was isolated from a urine sample. Partial 16S rRNA-gene sequencing and VITEK®2 system were employed for its identification, biochemical characterization, and antibiotic susceptibility testing. The isolate was resistant to eight antibiotics (out of 11): vancomycin, gentamicin (high-level synergy), streptomycin (high-level synergy), ciprofloxacin, levofloxacin, erythromycin, quinupristin/dalfopristin, and tetracycline. Bacteriophage SA14 was isolated from sewage water using the multidrug-resistant isolate as a host. Transmission electron micrographs revealed that phage SA14 is a member of the Siphoviridae family displaying the typical circular head and long non-contractile tail. The phage showed characteristic stability to a wide range of solution pH and temperatures, with optimal stability at pH 7.4 and 4 °C, while showing high specificity toward their host. Based on the one-step growth curve, the phage's latent period was 25 min, and the burst size was 20 PFU/ml. The lytic activity of phage SA14 was evaluated at various multiplicities of infection (MOI), all considerably suppressed the growth of the host organism. Moreover, phage SA14 displayed a characteristic anti-biofilm activity as observed by the reduction in adhered biomass and -viable cells in the pre-formed biofilm by 19.1-fold and 2.5-fold, respectively.

Conclusion

Phage therapy can be a valuable alternative to antibiotics against multi-drug resistant microorganisms.

Anti-cancer and antimicrobial potential of five soil Streptomycetes: a metabolomics-based study

Lack of new anti-cancer and anti-infective agents directed the pharmaceutical research to natural products' discovery especially from actinomycetes as one of the major sources of bioactive compounds. Metabolomics- and dereplication-guided approach has been used successfully in chemical profiling of bioactive actinomycetes. We aimed to study the metabolomic profile of five bioactive actinomycetes to investigate the interesting metabolites responsible for their antimicrobial and anti-cancer activities. Three actinomycetes, namely, Streptomyces sp. SH8, SH10 and SH13, were found to exhibit broad spectrum of antimicrobial activities, whereas isolate SH4 showed the broadest antimicrobial activity against all tested strains. In addition, isolates SH8, SH10 and SH12 displayed potent cytotoxicity against the breast cancer cell line Michigan Cancer Foundation-7 (MCF-7), whereas isolates SH4 and SH12 exhibited potent anti-cancer activity against the hepatoma cell line hepatoma G2 (HepG2) compared with their weak inhibitory properties on the normal breast cells MCF-10A and normal liver cells transformed human liver epithelial-2 (THLE2), respectively. All bioactive isolates were molecularly identified as Streptomyces sp. via 16S rRNA gene sequencing. Our actinobacterial dereplication analysis revealed putative identification of several bioactive metabolites including tetracycline, oxytetracycline and a macrolide antibiotic, novamethymycin. Together, chemical profiling of bioactive Streptomycetes via dereplication and metabolomics helped in assigning their unique metabolites and predicting the bioactive compounds instigating their diverse bioactivities.

The Application of Bacillus subtilis for Adhesion Inhibition of Pseudomonas and Preservation of Fresh Fish

Inhibiting the growth of spoilage bacteria, such as Pseudomonas spp., is key to reducing spoilage in fish. The mucus adhesion test in vitro showed that the adhesion ability of Bacillus subtilis was positively correlated with its inhibition ability to Pseudomonas spp. In vivo experiments of tilapia showed that dietary supplementation with B. subtilis could reduce the adhesion and colonization of Pseudomonas spp. in fish intestines and flesh, as well as reduce total volatile basic nitrogen (TVB-N) production. High throughput and metabolomic analysis showed treatment with B. subtilis, especially C6, reduced the growth of Pseudomonas spp., Aeromonas spp., Fusobacterium spp., and Enterobacterium spp., as well as aromatic spoilage compounds associated with these bacteria, such as indole, 2,4-bis(1,1-dimethylethyl)-phenol, 3-methyl-1-butanol, phenol, and 1-octen-3-ol. Our work showed that B. subtilis could improve the flavor of fish by changing the intestinal flora of fish, and it shows great promise as a microecological preservative.

Exploring clinically isolated Staphylococcus sp. bacteriocins revealed the production of amonabactin, micrococcin, and α-circulocin

Background and Objectives:

Bacteriocins are considered alternative non-conventional antimicrobials produced by certain bacteria with activity against closely related species. The present study focuses on screening, characterization, and partial purification of bacteriocins produced by Staphylococcus sp. isolated from different clinical sources such as pus and blood.

Materials and Methods:

A total of 100 Staphylococcus isolates were screened for bacteriocin production using spot on lawn assay and agar diffusion method against five indicator bacteria. Bacteriocins from five selected highly active isolates were subjected to proteinase-K enzyme, different pH, and heating at different temperatures, and investigated the stabilities of their antimicrobials. Two selected isolates, MK65 and MK88, were molecularly identified by 16S rRNA gene sequencing, explored for the presence of 18 bacteriocin genes, and liquid chromatography-high resolution electrospray ionization mass spectrometry (LC-HRESIMS) was used to identify their different metabolites.

Results:

Twenty isolates exhibited inhibitory effect against at least one indicator bacteria. Micrococcus luteus ATCC 4698 showed the highest sensitivity to such bacteriocins. Proteinase K, acidic pH, and heating at 100°C triggered marked activity inhibition. However, amylase enzyme, alkaline pH, and heating at 80°C caused trivial effects. Four out of eighteen bacteriocin genes were detected using PCR. Fermentation, partial purification, and LC-HRESIMS of total protein extracts of two selected isolates, MK65 and MK88, revealed the production of different antimicrobial peptides.

Conclusion:

To the best of our knowledge, this is the first study to report the production of micrococcin and α-circulocin from Staphylococcus aureus MK65 and the production of amonabactin from Staphylococcus epidermidis MK88.