Allelic diversity uncovers protein domains contributing to the emergence of antimicrobial resistance

Allelic variations and gene cluster modularity act as nonlinear bottlenecks for cholera emergence

The underlying factors that lead to specific strains within a species to emerge as human pathogens remain mostly enigmatic. The diarrheal disease cholera is caused by strains from a phylogenetically confined group within the Vibrio cholerae species, the pandemic cholera group (PCG), making it an ideal model system to tackle this puzzling phenomenon. Comprehensive analyses of over 1,840 V. cholerae genomes, including environmental isolates from this study, reveal that the species consists of eleven groups, with the PCG belonging to the largest and located within a lineage shared with environmental strains. This hierarchical classification provided us with a framework to unravel the ecoevolutionary dynamics of the genetic determinants associated with the emergence of toxigenic V. cholerae. Our analyses indicate that this phenomenon is largely dependent on the acquisition of unique modular gene clusters and allelic variations that confer a competitive advantage during intestinal colonization. We determined that certain PCG-associated alleles are essential for successful colonization whereas others provide a nonlinear competitive advantage, acting as a critical bottleneck that clarifies the isolated emergence of PCG. For instance, toxigenic strains encoding non-PCG alleles of a) tcpF or b) a sextuple allelic exchange mutant for genes tcpA, toxT, VC0176, VC1791, rfbT, and ompU, lose their ability to colonize the intestine. Interestingly, these alleles do not play a role in the colonization of newly established model environmental reservoirs. Our study uncovers the evolutionary roots of toxigenic V. cholerae offering a tractable approach for investigating the emergence of pathogenic clones within an environmental population.

Anti-vibriosis bioactive molecules from marine-derived variant Streptomyces sp. ZZ741A

The infection of vibrio is an important cause of huge economic losses in aquaculture industry. At present, antibiotics are mainly used to prevent and reduce the infection of the vibrio, which has accelerated the emergence of multi-drug-resistant strains. New generation alternative anti-vibrio drugs were in urgent to solve this problem. In this study, six compounds (1-6) were isolated from the Streptomyces sp. ZZ741A, a marine-derived Streptomyces variant, including one new compound, 2-carbamoylphenyl isobutyrate (1), five known ones, nocardamine (2), dehydroxynocardamine (3), phenylacetic acid (4), thiophenol (5) and 2,3-dihydroxybenzoic acid (6). The anti-vibriosis assay showed that compounds 2 and 3 had specific inhibition activity against Vibrio vulnificus, Vibrio alginolyticus, and Vibrio parahaemolyticus with the MIC values ranging from 8 to 128 μg/mL. The molecular docking study of their possible mechanism of anti-vibriosis activity showed that the activity might come from the inhibition of Outer membrane protein U (OmpU).

(p)ppGpp and DksA play a crucial role in reducing the efficacy of β-lactam antibiotics by modulating bacterial membrane permeability

The key signaling molecules in the bacterial stress-sensing pathway, the alarmone (p)ppGpp and the transcription factor DksA, play a crucial role in bacterial survival during nutritional deprivation and exposure to xenobiotics by modulating cellular metabolic pathways. In Vibrio cholerae, (p)ppGpp metabolism is solely linked with the functions of three proteins: RelA, SpoT, and RelV. The effects of threshold or elevated concentrations of (p)ppGpp on cellular metabolites and proteins, both in the presence and absence of DksA, have not yet been comprehensively studied in V. cholerae or other bacteria. We engineered the genome of V. cholerae to develop DksA null mutants in the presence and absence of (p)ppGpp biosynthetic enzymes. We observed that the N16:ΔrelAΔrelVΔspoTΔdksA V. cholerae mutant, which lacks both (p)ppGpp and DksA, exhibits higher sensitivity to different ꞵ-lactam antibiotics compared with the wild-type (WT) strain. Our whole-cell metabolomic and proteome analysis revealed that the cell membrane and peptidoglycan biosynthesis pathways are significantly altered in the N16:ΔrelAΔrelVΔspoT, N16:ΔdksA, and N16:ΔrelAΔrelVΔspoTΔdksA V. cholerae strains. Furthermore, the mutant strains displayed enhanced inner and outer membrane permeabilities in comparison to the WT strains. These results correlate with V. cholerae's tolerance and survival against β-lactam antibiotics and may inform the development of adjuvants that inhibit stringent response modulators.IMPORTANCEThe (p)ppGpp biosynthetic pathway is widely conserved in bacteria. Intracellular levels of (p)ppGpp and the transcription factor DksA play crucial roles in bacterial multiplication and viability in the presence of antibiotics and/or other xenobiotics. The present findings have shown that (p)ppGpp and DksA significantly reduce the efficacy of ꞵ-lactam and other antibiotics by modulating the availability of peptidoglycan and cell membrane-associated metabolites by reducing membrane permeability. Nevertheless, the whole-cell proteome analysis of N16:ΔrelAΔrelVΔspoT, N16:ΔdksA, and N16:ΔrelAΔrelVΔspoTΔdksA strains identified the biosynthetic pathways and associated enzymes that are directly modulated by the stringent response effector molecules. Thus, the (p)ppGpp metabolic pathways and DksA could be a potential target for increasing the efficacy of antibiotics and developing antibiotic adjuvants.

Beyond antibiotics: exploring multifaceted approaches to combat bacterial resistance in the modern era: a comprehensive review

Antibiotics represent one of the most significant medical breakthroughs of the twentieth century, playing a critical role in combating bacterial infections. However, the rapid emergence of antibiotic resistance has become a major global health crisis, significantly complicating treatment protocols. This paper provides a narrative review of the current state of antibiotic resistance, synthesizing findings from primary research and comprehensive review articles to examine the various mechanisms bacteria employ to counteract antibiotics. One of the primary sources of antibiotic resistance is the improper use of antibiotics in the livestock industry. The emergence of drug-resistant microorganisms from human activities and industrial livestock production has presented significant environmental and public health concerns. Today, resistant nosocomial infections occur following long-term hospitalization of patients, causing the death of many people, so there is an urgent need for alternative treatments. In response to this crisis, non-antibiotic therapeutic strategies have been proposed, including bacteriophages, probiotics, postbiotics, synbiotics, fecal microbiota transplantation (FMT), nanoparticles (NPs), antimicrobial peptides (AMPs), antibodies, traditional medicines, and the toxin-antitoxin (TA) system. While these approaches offer innovative solutions for addressing bacterial infections and preserving the efficacy of antimicrobial therapies, challenges such as safety, cost-effectiveness, regulatory hurdles, and large-scale implementation remain. This review examines the potential and limitations of these strategies, offering a balanced perspective on their role in managing bacterial infections and mitigating the broader impact of antibiotic resistance.

The Impact of Vp-Porin, an Outer Membrane Protein, on the Biological Characteristics and Virulence of Vibrio Parahaemolyticus

Porins are crucial proteins located in the outer membrane that directly influence antimicrobial resistance mechanisms and virulence in bacteria. In this study, a porin gene (Vp-porin) was cloned in V. parahaemolyticus, and the function of Vp-Porin in biological characteristics and virulence was investigated. The results of sequence analysis showed that Vp-Porin is highly conserved in Vibrio spp., and the predicted 3D structure showed it could form a 20-strand transmembrane β-barrel domian. Membrane permeabilization provides evidence that the membrane integrity of ∆Vp-porin was damaged and the sensitivity to tetracycline, polymyxin B, rifampicin and cephalothin of ∆Vp-porin obviously increased. In addition, loss of Vp-porin damaged motility due to downregulated flagellar synthesis. In addition, ∆Vp-porin exhibited attenuated cytotoxicity to Tetrahymena. The relative survival rate of Tetrahymena infection with ∆Vp-porin was 86%, which is much higher than that with WT (49%). Taken together, the results of this study indicate that Vp-Porin in V. parahaemolyticus plays various roles in biological characteristics in membrane integrity, antimicrobial resistance and motility and contributes to virulence.

The Combination of Antibiotic and Non-Antibiotic Compounds Improves Antibiotic Efficacy against Multidrug-Resistant Bacteria

Bacterial antibiotic resistance, especially the emergence of multidrug-resistant (MDR) strains, urgently requires the development of effective treatment strategies. It is always of interest to delve into the mechanisms of resistance to current antibiotics and target them to promote the efficacy of existing antibiotics. In recent years, non-antibiotic compounds have played an important auxiliary role in improving the efficacy of antibiotics and promoting the treatment of drug-resistant bacteria. The combination of non-antibiotic compounds with antibiotics is considered a promising strategy against MDR bacteria. In this review, we first briefly summarize the main resistance mechanisms of current antibiotics. In addition, we propose several strategies to enhance antibiotic action based on resistance mechanisms. Then, the research progress of non-antibiotic compounds that can promote antibiotic-resistant bacteria through different mechanisms in recent years is also summarized. Finally, the development prospects and challenges of these non-antibiotic compounds in combination with antibiotics are discussed.