Soil Bacteria in Urban Community Gardens Have the Potential to Disseminate Antimicrobial Resistance Through Horizontal Gene Transfer

Genotypic diversity of staphylococcal enterotoxin B gene (seb) and its association with molecular characterization and antimicrobial resistance of Staphylococcus aureus from retail food

To investigate the expression pattern of staphylococcal enterotoxin B (SEB) in food and the genotypic diversity of SEB-encoding gene in association with molecular characteristics and antimicrobial resistance of S. aureus, 498 isolates from retail food were screened for seb gene and detected for SEB production in S. aureus. In addition, the seb nucleotide sequences, virulence genes, resistance genes, antimicrobial susceptibility and molecular characteristics of S. aureus were examined. A total of 45 (9.0 %) seb-positive S. aureus strains were identified, all of which expressed SEB. The detection rate of SEB-production strains was significantly higher from dairy-related sources than those from other sources (P < 0.05). In vitro simulations showed that S. aureus could grow and express SEB in both milk and pork, with SEB expression exceeding 20 ng/g after 1 day of storage at room temperature. There were 2 distinct SEB genotyping (SEB1 and SEB2) in the SEB amino acid sequences of the 45 isolates, including 4 amino acid differences (Ala-13Val, Ser14Ala, Asn192Ser, and Met222Leu). There was no significant difference (P > 0.05) in SEB production between SEB1 and SEB2 genotyping strains. Based on MLST clustering analysis, the same molecular type strains were found to have the same SEB genotyping, virulence gene profile, resistance gene profile and drug resistance profile. Among them, the dominant molecular types of SEB1 and SEB2 strains were CC1-ST188-t189 and CC59-ST59-t437, respectively. Compared to the CC1-ST188-t189 clonal strain, the CC59-ST59-t437 clonal strain carried a higher number of virulence and resistance genes and exhibited a broader resistance profile. Therefore, understanding the characteristics of the strains and their expression patterns in food can be effective in preventing food poisoning incidents.

The Safety of Bacteriophages in Treatment of Diseases Caused by Multidrug-Resistant Bacteria

Given the urgency due to the rapid emergence of multidrug-resistant (MDR) bacteria, bacteriophages (phages), which are viruses that specifically target and kill bacteria, are rising as a potential alternative to antibiotics. In recent years, researchers have begun to elucidate the safety aspects of phage therapy with the aim of ensuring safe and effective clinical applications. While phage therapy has generally been demonstrated to be safe and tolerable among animals and humans, the current research on phage safety monitoring lacks sufficient and consistent data. This emphasizes the critical need for a standardized phage safety assessment to ensure a more reliable evaluation of its safety profile. Therefore, this review aims to bridge the knowledge gap concerning phage safety for treating MDR bacterial infections by covering various aspects involving phage applications, including phage preparation, administration, and the implications for human health and the environment.

Prevalence and mobility of integrative and conjugative elements within a Streptomyces natural population

Horizontal Gene Transfer (HGT) is a powerful force generating genomic diversity in bacterial populations. HGT in Streptomyces is in large part driven by conjugation thanks to plasmids, Integrative and Conjugative elements (ICEs) and Actinomycete ICEs (AICEs). To investigate the impact of ICE and AICE conjugation on Streptomyces genome evolution, we used in silico and experimental approaches on a set of 11 very closely related strains isolated from a millimeter scale rhizosphere population. Through bioinformatic searches of canonical conjugation proteins, we showed that AICEs are the most frequent integrative conjugative elements, with the central chromosome region being a hotspot for integrative element insertion. Strains exhibited great variation in AICE composition consistent with frequent HGT and/or gene loss. We found that single insertion sites can be home to different elements in different strains (accretion) and conversely, elements belonging to the same family can be found at different insertion sites. A wide variety of cargo genes was present in the AICEs with the potential to mediate strain-specific adaptation (e.g., DNA metabolism and resistance genes to antibiotic and phages). However, a large proportion of AICE cargo genes showed hallmarks of pseudogenization, consistent with deleterious effects of cargo genes on fitness. Pock assays enabled the direct visualization of conjugal AICE transfer and demonstrated the transfer of AICEs between some, but not all, of the isolates. Multiple AICEs were shown to be able to transfer during a single mating event. Although we did not obtain experimental evidence for transfer of the sole chromosomal ICE in this population, genotoxic stress mediated its excision from the chromosome, suggesting its functionality. Our results indicate that AICE-mediated HGT in Streptomyces populations is highly dynamic, with likely impact on strain fitness and the ability to adapt to environmental change.