Molecular characterization of aureocin 4181: a natural N-formylated aureocin A70 variant with a broad spectrum of activity

Methicillin-resistant Staphylococcus aureus and coagulase-negative Staphylococcus produce antimicrobial substances against members of the skin microbiota in children with atopic dermatitis

Coagulase-negative Staphylococcus (CoNS) species inhibiting Staphylococcus aureus has been described in the skin of atopic dermatitis (AD) patients. This study evaluated whether Staphylococcus spp. from the skin and nares of AD and non-AD children produced antimicrobial substances (AMS). AMS production was screened by an overlay method and tested against NaOH, proteases and 30 indicator strains. Clonality was assessed by pulsed-field gel electrophoresis. Proteinaceous AMS-producers were investigated for autoimmunity by the overlay method and presence of bacteriocin genes by polymerase chain reaction. Two AMS-producers had their genome screened for AMS genes. A methicillin-resistant S. aureus (MRSA) produced proteinaceous AMS that inhibited 51.7% of the staphylococcal indicator strains, and it was active against 60% of the colonies selected from the AD child where it was isolated. On the other hand, 57 (8.8%) CoNS from the nares and skin of AD and non-AD children, most of them S. epidermidis (45.6%), reduced the growth of S. aureus and other CoNS species. Bacteriocin-related genes were detected in the genomes of AMS-producers. AMS production by CoNS inhibited S. aureus and other skin microbiota species from children with AD. Furthermore, an MRSA colonizing a child with AD produced AMS, reinforcing its contribution to dysbiosis and disease severity.

The role of proteinaceous toxins secreted by Staphylococcus aureus in interbacterial competition

Staphylococcus aureus is highly adapted to colonization of the mammalian host. In humans the primary site of colonization is the epithelium of the nasal cavity. A major barrier to colonization is the resident microbiota, which have mechanisms to exclude S. aureus. As such, S. aureus has evolved mechanisms to compete with other bacteria, one of which is through secretion of proteinaceous toxins. S. aureus strains collectively produce a number of well-characterized Class I, II, and IV bacteriocins as well as several bacteriocin-like substances, about which less is known. These bacteriocins have potent antibacterial activity against several Gram-positive organisms, with some also active against Gram-negative species. S. aureus bacteriocins characterized to date are sporadically produced, and often encoded on plasmids. More recently the type VII secretion system (T7SS) of S. aureus has also been shown to play a role in interbacterial competition. The T7SS is encoded by all S. aureus isolates and so may represent a more widespread mechanism of competition used by this species. T7SS antagonism is mediated by the secretion of large protein toxins, three of which have been characterized to date: a nuclease toxin, EsaD; a membrane depolarizing toxin, TspA; and a phospholipase toxin, TslA. Further study is required to decipher the role that these different types of secreted toxins play in interbacterial competition and colonization of the host.

Fighting antibiotic resistance in the local management of bovine mastitis

Bovine mastitis is a widespread infectious disease with a significant economic burden, accounting for 80 % of the antibiotic usage in dairy animals. In recent years, extensive research has focused on using biomimetic approaches such as probiotics, bacteriocins, bacteriophages, or phytochemicals as potential alternatives to antibiotics. The local administration of therapeutic molecules through the intramammary route is one of the most commonly strategies to manage bovine mastitis. This review highlights the most important findings in this field and discusses their local application in mastitis therapy. In contrast to antibiotics, the proposed alternatives are not limited to promote bacterial death but consider other factors associated to the host microenvironments. To this end, the proposed biomimetic strategies can modulate different stages of infection by modifying the local microbiota, preventing oxidative stress, reducing bacterial adhesion to epithelial cells, modulating the immune response, or mediating the inflammatory process. Numerous in vitro studies support the antimicrobial, antibiofilm or antioxidant properties of these alternatives. However, in vivo studies incorporating these components within pharmaceutical formulations with potential clinical application are limited. The development of secure, stable, and effective drug delivery systems based on the proposed options is necessary to achieve real alternatives to antibiotics in the clinic.

Comprehensive Approaches for the Search and Characterization of Staphylococcins

Novel and sustainable approaches are required to curb the increasing threat of antimicrobial resistance (AMR). Within the last decades, antimicrobial peptides, especially bacteriocins, have received increased attention and are being explored as suitable alternatives to antibiotics. Bacteriocins are ribosomally synthesized antimicrobial peptides produced by bacteria as a self-preservation method against competitors. Bacteriocins produced by Staphylococcus, also referred to as staphylococcins, have steadily shown great antimicrobial potential and are currently being considered promising candidates to mitigate the AMR menace. Moreover, several bacteriocin-producing Staphylococcus isolates of different species, especially coagulase-negative staphylococci (CoNS), have been described and are being targeted as a good alternative. This revision aims to help researchers in the search and characterization of staphylococcins, so we provide an up-to-date list of bacteriocin produced by Staphylococcus. Moreover, a universal nucleotide and amino acid-based phylogeny system of the well-characterized staphylococcins is proposed that could be of interest in the classification and search for these promising antimicrobials. Finally, we discuss the state of art of the staphylococcin applications and an overview of the emerging concerns.

Effects of the natural antimicrobial peptide aureocin A53 on cells of Staphylococcus aureus and Streptococcus agalactiae involved in bovine mastitis in the excised teat model

Aureocin A53 is an N-formylated antimicrobial peptide (AMP) produced by Staphylococcus aureus. Aureocin A53 has a broad spectrum of antimicrobial activity against human and animal pathogens. In the present study, its antagonistic activity was investigated towards 30 strains of S. aureus and 30 strains of Streptococcus spp. isolated from bovine mastitis cases in Brazil. Bovine mastitis is a disease that causes a major economic impact worldwide. Aureocin A53 inhibited the growth of all 60 strains tested, including multidrug-resistant streptococcal isolates and strains of S. aureus belonging to different pulsotypes. This AMP proved to be bactericidal against the six target strains randomly selected among staphylococci and streptococci, also exhibiting a lytic mode of action against the staphylococcal cells. Furthermore, it was determined that 2,048 AU/mL of the AMP were required to inhibit 99.99% of the cell growth of the strain less sensitive to aureocin A53. Aureocin A53 was not toxic to bovine mammary gland epithelial cells after a 24-h exposure and maintained its antimicrobial activity when tested in the excised-teat model against strains of S. aureus and Streptococcus agalactiae, the species responsible for most intramammary infections, not only in Brazil but in other countries as well. Therefore, the use of aureocin A53 in the development of new pharmacological products for the prophylaxis and/or treatment of bovine mastitis was considered promising.

Biological Dark Matter Exploration using Data Mining for the Discovery of Antimicrobial Natural Products

The discovery of novel antimicrobials has significantly slowed down over the last three decades. At the same time, humans rely increasingly on antimicrobials because of the progressive antimicrobial resistance in medical practices, human communities, and the environment. Data mining is currently considered a promising option in the discovery of new antibiotics. Some of the advantages of data mining are the ability to predict chemical structures from sequence data, anticipation of the presence of novel metabolites, the understanding of gene evolution, and the corroboration of data from multiple omics technologies. This review analyzes the state-of-the-art for data mining in the fields of bacteria, fungi, and plant genomic data, as well as metabologenomics. It also summarizes some of the most recent research accomplishments in the field, all pinpointing to innovation through uncovering and implementing the next generation of antimicrobials.

Comparative genomic analysis of Staphylococcus aureus isolates associated with either bovine intramammary infections or human infections demonstrates the importance of restriction-modification systems in host adaptation

Staphylococcus aureus is a major etiological agent of clinical and subclinical bovine mastitis. The versatile and adaptative evolutionary strategies of this bacterium have challenged mastitis control and prevention globally, and the high incidence of S. aureus mastitis increases concerns about antimicrobial resistance (AMR) and zoonosis. This study aims to describe the evolutionary relationship between bovine intramammary infection (IMI)-associated S. aureus and human pathogenic S. aureus and further elucidate the specific genetic composition that leads to the emergence of successful bovine IMI-associated S. aureus lineages. We performed a phylogenomic analysis of 187 S. aureus isolates that originated from either dairy cattle or humans. Our results revealed that bovine IMI-associated S. aureus isolates showed distinct clades compared to human-originated S. aureus isolates. From a pan-genome analysis, 2070 core genes were identified. Host-specific genes and clonal complex (CC)-specific genes were also identified in bovine S. aureus isolates, mostly located in mobile genetic elements (MGEs). Additionally, the genome sequences of three apparent human-adapted isolates (two from CC97 and one from CC8), isolated from bovine mastitis samples, may provide an snapshot of the genomic characteristics in early host spillover events. Virulence and AMR genes were not conserved among bovine IMI-associated S. aureus isolates. Restriction-modification (R-M) genes in bovine IMI-associated S. aureus demonstrated that the Type I R-M system was lineage-specific and Type II R-M system was sequence type (ST)-specific. The distribution of exclusive, virulence, and AMR genes were closely correlated with the presence of R-M systems in S. aureus, suggesting that R-M systems may contribute to shaping clonal diversification by providing a genetic barrier to the horizontal gene transfer (HGT). Our findings indicate that the CC or ST lineage-specific R-M systems may limit genetic exchange between bovine-adapted S. aureus isolates from different lineages.

Heterologous overexpression and preliminary antimicrobial activity test of salmocin M, a novel colicin M-like bacteriocin against Salmonella sp

Currently, it is extremely important to identify and describe new alternative compounds with potential antimicrobial properties. Since various natural biological systems are capable of producing active compounds with such properties, many of them have been the subject of intensive study. The aim of this work was to heterologously overexpress, purify and preliminarily investigate the antimicrobial activity of a novel bacteriocin found in Salmonella species. Overexpressed protein shows an amino acid structure homologous to the well-known colicin M and was never expressed previously in the E. coli platform. Purified salmocin M showed an inhibition spectrum against Salmonella and E. coli strains. To determine its potential as an antimicrobial agent for use in medicine or the food industry, preliminary antimicrobial tests against pathogenic bacteria were carried out. Our research demonstrates that bacteriocin can be produced efficiently in bacterial expression systems, which are one of the cheapest and the most popular platforms for recombinant protein production. Moreover, preliminary results of microbiological tests showed its activity against most of the bacterial strains in a dose-dependent manner.