Aminoglycoside Revival: Review of a Historically Important Class of Antimicrobials Undergoing Rejuvenation

Application of pulsed electric field (PEF) as a strategy to enhance aminoglycosides efficacy against Gram-negative bacteria

In this study, two aminoglycosides (AGs), Kanamycin and Gentamicin, with similar modes of action and molecular weights, were combined with PEF treatment to enhance the inactivation of E. coli cells. Various PEF strengths were applied to assess the combined effect. To compare the inactivation efficacy of different AGs, bacterial growth measurements in suspension were performed at 3 and 10 h intervals over a 10-h period after PEF treatment. Interestingly, it was found that the additive effect of PEF treatment on E. coli growth inhibition was significantly greater with Kanamycin (IC50) than with Gentamicin (IC50). Further analysis revealed that the combined treatment with Kanamycin (IC50) was most effective within a timeframe of around 3 h. Our findings suggest that PEF treatment can significantly enhance the efficacy of AGs against Gram-negative bacteria; however, the extent of the additive effect varies depending on the specific antibiotic and the intensity of the applied PEF treatment.

Single-cell analysis of antimicrobial compound-induced cell death of bacterial cells

Due to the stochasticity of metabolic reactions and cell cycles of bacterial cells, it is necessary to examine the antibacterial activities of antimicrobial compounds (AMCs) such as antibiotics and antimicrobial peptides (AMPs) at the single-cell level. Here, we review recent studies of the bactericidal activities of AMCs at the single-cell level. First, we discuss recent investigations of the interaction of various AMPs with single bacterial cells, as monitored in real time using optical microscopy. This strategy provides information on AMP-induced membrane damage in single cells [e.g. the onset time of damage to the cell membrane (CM) and outer membrane of single cells]. The rate of AMP-induced CM damage is estimated as the fraction of cells with CM damage [Pdamage (t)] at a specific interaction time t. Second, we discuss the use of single-cell analysis of the bactericidal activity of AMCs. The fraction of dead cells after the exposure to AMCs for time t is determined as the fraction of the microcolonies containing only one cell [Psingle (t)]. For some AMPs, the Pdamage (t) and Psingle (t) values are similar, indicating that AMP-induced CM damage is the direct cause of cell death. Third, we discuss single-cell analysis of the processes and mechanisms of antibiotic-induced cell death. For example, fluoroquinolones and aminoglycosides are observed to induce cytoplasmic condensation and cell lysis, leading to cell death. Based on these studies, we provide our perspective on future investigations using single-cell analysis to assess the processes and the mechanisms of the bactericidal activities of AMCs.

A review of antibiotic safety in pregnancy-2025 update

Antibiotics constitute the majority of prescriptions for women during pregnancy. Common bacterial infections, including urinary tract infections, skin and soft tissue infections, and upper and lower respiratory tract infections, are expected in pregnancy, similar to the general public. These infections carry additional risks to both the woman and fetus; thus, antibiotics are often prescribed. Antibiotics, like other drugs, are not benign and may carry additional risks to the fetus beyond commonly encountered adverse drug events seen across most patient populations. Since 2014, 19 new antibiotics have been approved by the United States Food and Drug Administration. Additionally, in 2018, the previously held pregnancy category rating expired, and all manufacturers' labeling was updated with new narrative language reflecting safety in pregnancy, lactation, and males and females of reproductive potential. This review provides a comprehensive summary of available data and an update to the 2015 publication regarding the safe use of antibiotics in pregnancy. The primary focus of this review is on newly approved antibiotics, along with any additional published evidence on previously reviewed antibiotics. Data on lactation or antiviral or antifungal use in pregnancy are not included. Clinicians should remain updated on current available evidence and vigilant to provide safe and effective antibiotic decision-making in pregnant women.

Antioxidant Therapies in the Treatment of Aminoglycoside-Induced Ototoxicity: A Meta-Analysis

OBJECTIVE

A feared complication of aminoglycoside treatment is ototoxicity, which is theorized to be attributed to the production of aminoglycoside-induced reactive oxygen species. Previous studies using animal models have suggested that numerous therapies targeting reducing oxidative stress may prevent ototoxicity from aminoglycosides. However, few clinical studies have been conducted on these antioxidants. This systematic review and meta-analysis examines the effectiveness of antioxidant therapies in the treatment of aminoglycoside-induced ototoxicity.

DATA SOURCES

PubMed, Embase, Web of Science, and ClinicalTrials.gov.

REVIEW METHOD

A literature search was conducted in August 2024. This review sought randomized controlled trials to be conducted on humans to examining otologic outcomes in aminoglycoside-induced ototoxicity following administration of medications intended to reduce oxidative stress.

RESULTS

A systematic review yielded 2037 results, of which seven studies met inclusion criteria. N-acetylcysteine (NAC) was investigated in four studies, aspirin in two studies, and vitamin E in one study. Six studies examined the benefit of antioxidant treatments for up to 8 weeks after administration while one study tested subjects' hearing after 1 year. In pooled analysis, two studies assessing NAC showed the greatest reduction in ototoxicity (RR 0.112, 95% CI, 0.032-0.395; p = 0.0007; I2 = 18%), followed by two studies examining aspirin (RR 0.229, 95% CI, 0.080-0.650; p = 0.0057; I2 = 0%). One study performed with vitamin E did not find a reduction in ototoxicity compared to the placebo (RR 0.841, 95% CI, 0.153-4.617; p = 0.8416).

CONCLUSIONS

Multiple studies have shown that NAC and aspirin are effective in reducing ototoxicity from treatment with aminoglycosides. However, there is a lack of high-quality evidence. Additional studies should examine whether aspirin and N-acetylcysteine provide long-term benefit, and which of the other promising antioxidants translate from animal models.

LEVEL OF EVIDENCE

NA Laryngoscope, 135:1278-1286, 2025.

Identification of a novel aminoglycoside nucleotidyltransferase gene in Morganella morganii from farm sewage

BACKGROUND

Aminoglycosides are important broad-spectrum antimicrobial agents. When combined with β-lactam drugs, these agents can be used to treat severe infections such as those causing sepsis. Identifying additional resistance mechanisms will guarantee the successful application of aminoglycoside agents in clinical practice.

METHODS

The isolate Morganella morganii A19 was obtained from a sewage sample from an animal farm by means of agar plate streaking. The agar dilution method was used to determine the minimum inhibitory concentrations (MICs) of the antimicrobial agents. Cloning of the predicted resistance gene was conducted, and its resistance function was assessed through MIC testing. The protein was expressed in E. coli, and the kinetic parameters were quantified. The analysis of novel resistance gene-related sequences, including their structures and evolutionary relationships, was performed using bioinformatic tools.

RESULTS

In Morganella morganii A19, a newly discovered chromosome-encoded aminoglycoside resistance gene named aadA37 was identified and characterized. The protein AadA37 exhibited the highest amino acid identity (57.14%) with the functionally characterized aminoglycoside adenylyltransferase AadA33. aadA37 confers resistance to spectinomycin, streptomycin and ribostamycin, and enzyme kinetic analysis also demonstrated that it had adenosine transfer activities against spectinomycin and streptomycin, with kcat/Km values of 0.66 × 103 M- 1 s- 1 and 1.63 × 103 M- 1 s- 1, respectively. The aadA37 gene and its homologs were not related to any mobile genetic element (MGE), and they were all found to be encoded on the chromosomes of the M. morganii strains.

CONCLUSION

A novel aminoglycoside resistance gene was identified from an environmental bacterium and characterized in this work. Identifying new resistance mechanisms will aid in the effective clinical use of antimicrobial agents for treating infectious diseases caused by pathogens harboring the same resistance genes.

Food substances alter gut resistome: Mechanisms, health impacts, and food components

Antibiotics are effective in treating bacterial infections, but their widespread use has spurred antibiotic resistance, which is linked closely with human disease. While dietary components are known to influence the gut microbiome, specific effects on the gut resistome-the collection of antibiotic-resistant genes in the gut-remain underexplored. This review outlines the mechanisms of antibiotic action and the development of resistance, emphasizing the connection between the gut resistome and human diseases such as metabolic disorders, cardiovascular disease, liver disease, and nervous system disorders. It also discusses the effects of diet habits and dietary components, including bioactive macronutrients, phytochemicals, and probiotics, on the composition of the gut resistome by enhancing antibiotic efficacy and potentially reducing resistance. This review highlights the emerging trend of increasing interest in functional foods aimed at targeting the gut resistome and a growing focus on bioactive plant compounds with the potential to modulate antibiotic resistance.

Reno-protective impact of diosmin and perindopril in amikacin-induced nephrotoxicity rat model: modulation of SIRT1/p53/C-FOS, NF-κB-p65, and keap-1/Nrf2/HO-1 signaling pathways

PURPOSE

Amikacin (AMC), an aminoglycoside antibiotic known for its rapid and potent bactericidal activity, is also associated with nephrotoxicity. Diosmin and perindopril have been reported to improve renal function and hold promise as therapeutic agents for preventing drug-induced nephrotoxicity. This study aimed to investigate the protective effect of Diosmin and perindopril, either alone or in combination, against renal damage induced by AMC toxicity and to elucidate the underlying mechanisms.

MATERIALS AND METHODS

The researchers evaluated the impact of Diosmin (50 mg/kg, orally) and perindopril (2 mg/kg, intraperitoneally) on AMC-induced kidney injury (1.2 g/kg, intraperitoneally) in rats. Invasive blood pressure, serum kidney function and toxicity parameters, oxidative stress biomarkers, and inflammatory cytokine levels in serum and renal tissue were assessed. Histopathological changes in the kidney were examined using hematoxylin and eosin (H&E) staining, electron microscopy, and immunohistochemical analysis. The molecular mechanisms underlying the protective effect of the combination pretreatment on kidney injury were investigated using enzyme-linked immunosorbent assay (ELISA) and Western blotting techniques.

RESULTS

The findings demonstrated that the combination therapy improved kidney function by attenuating pathological changes observed in H&E staining including tubular necrosis and glomerular damage, in addition to reducing levels of kidney function including serum levels of creatinine compared to the AMC group, blood urea nitrogen (BUN) uric acid, and albumin. Mean arterial blood pressure, and toxicity markers including Kidney Injury Molecule-1 (KIM-1), Cystatin-c were also decreased in samples of combination group compared to AMC group. Furthermore, the protective combination therapy downregulated NF-κB-p65, P53, Keap-1, and C-FOS, while upregulating Mammalian sirtuin 1 (SIRT1), inhibitor of nuclear factor kappa B (Iκβ), nuclear factor erythroid 2-related factor 2 (Nrf2), and Heme oxygenase-1 (HO-1) levels.

CONCLUSIONS

The findings reveal the potential clinical application of combining Diosmin and perindopril to reduce AMC-induced nephrotoxicity, which requires further research in clinical settings.

Staphylococcal Drug Resistance: Mechanisms, Therapies, and Nanoparticle Interventions

The increasing incidence of antibiotic resistance in Staphylococcus aureus (S. aureus) poses a substantial threat to global public health. In recent decades, the evolution of bacteria and the misuse of antibiotics have led to a progressive development in drug resistance of S. aureus, resulting in a worldwide rise in methicillin-resistant S. aureus (MRSA) infection rates. Understanding the molecular mechanisms underlying staphylococcal drug resistance, the treatments for staphylococcal infections, and the efficacy of nanomaterials in addressing multi-drug resistance is crucial. This review explores the resistance mechanisms, which include limiting drug uptake, target modification, drug inactivation through the production of degrading enzymes, and active efflux of drugs. It also examines the current therapeutic strategies, such as antibiotic combination therapy, phage therapy, monoclonal antibody therapy, and nanoparticle therapy, with a particular emphasis on the role of silver-based nanomaterials. Nanoparticles possess the ability to overcome multi-drug resistance, offering a novel avenue for the management of drug-resistant bacteria. The nanomaterials have demonstrated potent antibacterial activity against S. aureus through various mechanisms, including cell membrane disruption, generation of reactive oxygen species (ROS), and inhibition of essential cellular processes. It also highlights the need for further research to optimize nanoparticle design, enhance their antibacterial potency, and ensure their biocompatibility and biodegradability. The review ultimately concludes by emphasizing the importance of a multifaceted approach to treatment, including the development of new antibiotics, investment in stewardship programs to prevent antibiotic misuse, and the exploration of natural compounds and bacteriocins as potential antimicrobial agents.

Over-the-counter antibiotics compromising aminoglycoside activity

INTRODUCTION

Antimicrobial resistance (AMR) is a global issue that needs addressing. While antibiotic stewardship has improved often by restricting antibiotic use, some antibiotics that are still sold legally over the counter (OTC), notably in sore throat medications. Recent findings suggest OTC antibiotics could trigger cross-resistance to antibiotics used in clinical treatments, whether systemic or topical. Here we investigated the impact of three antibiotics contained in OTC sore throat medicines on emerging AMR in vitro.

METHODS

Bacterial pathogens were exposed to a bactericidal concentration of an aminoglycoside in the presence or absence of a during-use concentration of bacitracin, gramicidin or tyrothricin in a time-kill assay. Damage to the bacterial membrane was also investigated by measuring potassium leakage and membrane potential alteration post-OTC antibiotic exposure.

RESULTS

Gramicidin (15 µg/mL) significantly decreased the bactericidal activity of amikacin, tobramycin or gentamicin in Acinetobacter baumannii. It also decreased gentamicin bactericidal activity in Enterobacter cloacae, Escherichia coli and Klebsiella pneumoniae, while tyrothricin decreased the aminoglycoside efficacy in E. cloacae and E. coli. Gramicidin significantly decreased bacterial membrane potential and caused significant potassium leakage.

CONCLUSION

Gramicidin and to some extent tyrothricin impacted aminoglycoside efficacy by affecting membrane potential, which is essential for aminoglycosides uptake. Thus, some OTC antibiotics can interfere with aminoglycoside activity, which could in turn affect treatment efficacy. Although the likelihood of OTC antibiotics and aminoglycosides being used at the same time might not be common, this research highlights one potential reason for OTC antibiotics' usage to result in treatment failure and their contribution to AMR development.

Identification and characterization of a novel chromosome-encoded aminoglycoside O-nucleotidyltransferase gene, ant(9)-Id, in Providencia sp. TYF-12 isolated from the marine fish intestine

Background

The mechanisms underlying the resistance of the genus Providencia to aminoglycosides are complex, which poses a challenge for the efficient treatment of infectious diseases caused by these pathogens. To help clinicians treat infections more effectively, a more comprehensive understanding of antibiotic resistance mechanisms is urgently needed.

Methods

Plates were streaked to isolate bacteria from the intestinal contents of fish. The standard agar dilution method was used to determine the minimum inhibitory concentrations (MICs) of the antimicrobial agents. Molecular cloning was carried out to study the function of the novel antibiotic inactivation gene ant(9)-Id. The kinetic parameters of ANT(9)-Id were measured by a SpectraMax multifunctional microplate reader. Whole-genome sequencing and bioinformatic analysis were conducted to elucidate the sequence structure and evolutionary relationships of similar genes.

Results

The novel aminoglycoside O-nucleotidyltransferase gene ant(9)-Id was encoded on the chromosome of a species-unclassified isolate designated Providencia sp. TYF-12, which was isolated from the intestine of a marine fish. Among the 11 aminoglycosides tested, ant(9)-Id was resistant to only spectinomycin. The MIC of spectinomycin for the recombinant strain carrying ant(9)-Id (pUCP20-ant(9)-Id/DH5α) increased 64-fold compared with that of the control strain (pUCP20/DH5ɑ). ANT(9)-Id shares the highest amino acid (aa) identity of 46.70% with the known drug resistance enzyme ANT(9)-Ic. Consistent with the MIC results, ANT(9)-Id showed high affinity and catalytic efficiency for spectinomycin, with a K m of 8.94 ± 2.50 μM and a k cat/K m of 26.15 μM-1·s-1. This novel resistance gene and its close homologs are conserved in Providencia strains from various sources, including some of clinical significance. No mobile genetic elements (MGEs) surrounding the ant(9)-Id(-like) genes were identified.

Conclusion

This work revealed and characterized a novel spectinomycin resistance gene, ant(9)-Id, along with its biological features. Identifying novel resistance genes in pathogens can assist in rational medication use and the identification of additional antimicrobial resistance mechanisms in microbial populations.

Aminoglycoside heteroresistance in Enterobacter cloacae is driven by the cell envelope stress response

Enterobacter cloacae is a Gram-negative nosocomial pathogen of the ESKAPE (Enterococcus, Staphylococcus, Klebsiella, Acinetobacter, Pseudomonas, and Enterobacter spp.) priority group with increasing multi-drug resistance via the acquisition of resistance plasmids. However, E. cloacae can also display forms of antibiotic refractoriness, such as heteroresistance and tolerance. Here, we report that E. cloacae displays transient heteroresistance to aminoglycosides, which is accompanied with the formation of small colony variants (SCVs) with increased minimum inhibitor concentration (MIC) of gentamicin and other aminoglycosides used in the clinic, but not other antibiotic classes. To explore the underlying mechanisms, we performed RNA sequencing of heteroresistant bacteria, which revealed global gene expression changes and a signature of the CpxRA cell envelope stress response. Deletion of the cpxRA two-component system abrogated aminoglycoside heteroresistance and SCV formation, pointing to its indispensable role in these processes. The introduction of a constitutively active allele of cpxA led to high aminoglycoside MICs, consistent with cell envelope stress response driving these behaviors in E. cloacae. Cell envelope stress can be caused by environmental cues, including heavy metals. Indeed, bacterial exposure to copper increased gentamicin MIC in the wild-type but not in the ΔcpxRA mutant. Moreover, copper exposure also elevated the gentamicin MICs of clinical isolates from bloodstream infections, suggesting that CpxRA- and copper-dependent aminoglycoside resistance is broadly conserved in E. cloacae strains. Altogether, we establish that E. cloacae relies on transcriptional reprogramming via the envelope stress response pathway for transient resistance to a major class of frontline antibiotic.IMPORTANCEEnterobacter cloacae is a bacterium that belongs to the WHO high-priority group and an increasing threat worldwide due its multi-drug resistance. E. cloacae can also display heteroresistance, which has been linked to treatment failure. We report that E. cloacae shows heteroresistance to aminoglycoside antibiotics. These are important frontline microbicidal drugs used against Gram-negative bacterial infections; therefore, understanding how resistance develops among sensitive strains is important. We show that aminoglycoside resistance is driven by the activation of the cell envelope stress response and transcriptional reprogramming via the CpxRA two-component system. Furthermore, heterologous activation of envelope stress via copper, typically a heavy metal with antimicrobial actions, also increased aminoglycoside MICs of the E. cloacae type strain and clinical strains isolated from bloodstream infections. Our study suggests aminoglycoside recalcitrance in E. cloacae could be broadly conserved and cautions against the undesirable effects of copper.

The evolution of knowledge for treating Gram-negative bacterial infections

PURPOSE OF REVIEW

Infections caused by nonprimarily pathogenic Gram-negative bacilli (GNB) have been increasingly reported from the second half of the 20th century to the present. This phenomenon has expanded during the antibiotic era and in the presence of immunodeficiency.Before the discovery of sulphonamides and penicillin G, infections caused by GNB were rare compared to Gram-positive infections. The advent of anticancer therapy, the expansion of surgical procedures, the use of corticosteroids, and the implantation of prosthetic materials, along with better control of Gram-positive infections, have promoted the current increase in GNB infections.GNB have similar antimicrobial targets to Gram-positive bacteria. However, only antibiotics that can penetrate the double membrane of GNB and remain in them for a sufficient duration have antibacterial activity against them.

RECENT FINDINGS

Sulphonamides and early penicillins had limited activity against GNB. Ampicillin and subsequent beta-lactams expanded their spectrum to treat GNB. Aminoglycosides may re-surge with less toxic drugs, as highly resistant to beta-lactams GNB rise. Polymyxins, tetracyclines, and fluoroquinolones are also used for GNB. Combinations with other agents may be needed in specific cases, such as in the central nervous system and prostate, where beta-lactams may have difficulty reaching the infection site.Alternatives to current treatments must be sought in the discovery of new drug families and therapies such as phage therapy combined with antibiotics.

SUMMARY

Narrower-spectrum immunosuppressive therapies and antibiotics, antimicrobials that minimally intervene with the human microbiota, and instant diagnostic methods are necessary to imagine a future where currently dominant bacteria in infectious pathology lose their preeminence.

Nosocomial Pneumonia in Georgia: A Study of Extended Spectrum Beta-Lactamase (ESBL)-Producing Versus Non-extended ESBL Gram-Negative Bacterial Profiles

BACKGROUND

Nosocomial pneumonia is a significant healthcare challenge, particularly in the face of rising antimicrobial resistance among Gram-negative bacteria. The production of extended spectrum beta-lactamase (ESBL) exacerbates treatment complexities.

AIM

This study investigates the prevalence and resistance patterns of ESBL-producing and non-ESBL Gram-negative bacteria in nosocomial pneumonia cases in Georgian hospitals to inform antibiotic stewardship and treatment strategies. To our knowledge, this is the first study of its kind conducted in Georgia, offering critical insights into bacterial resistance in this region.

METHODS

This prospective observational study analyzed a total of 357 pulmonary samples from patients diagnosed with nosocomial pneumonia in Georgian hospitals between December 2022 and February 2024. Gram-negative bacterial identification and ESBL determination were performed using the combination disk method, adhering to European Committee on Antimicrobial Susceptibility Testing (EUCAST) standards. The analyses were conducted at TEST-IMP Laboratory and the Richard Lugar Center for Public Health Research to investigate the prevalence and resistance patterns of ESBL-producing versus non-ESBL Gram-negative bacteria.

RESULTS

Among the 256 Gram-negative isolates, 201 (78.5%) were ESBL producers. Pseudomonas aeruginosa (63.7%), Acinetobacter baumannii (18.4%), and Klebsiella pneumoniae (17.9%) were the most prevalent. Non-ESBL producers accounted for 21.5% but exhibited notable beta-lactamase activity. The remaining 101 samples were evaluated as an additional analysis, revealing the distribution of Gram-positive bacteria and fungi as outlined in the results. However, the primary emphasis of this study remains on the resistance patterns and prevalence of Gram-negative pathogens.

CONCLUSIONS

The study highlights a concerning prevalence of ESBL-producing bacteria in nosocomial pneumonia cases, emphasizing the urgent need for improved antibiotic stewardship and infection control practices in Georgian hospitals. Non-ESBL producers displayed susceptibility to advanced antibiotics, presenting potential therapeutic opportunities, though vigilance is required to prevent further resistance development.

Antibiotic-mediated selection of randomly mutagenized and cytokine-expressing oncolytic viruses

Optimization of oncolytic viruses for therapeutic applications requires the strategic removal or mutagenesis of virulence genes alongside the insertion of transgenes that enhance viral replication, spread and immunogenicity. However, the complexity of many viral genomes and the labour-intensive nature of methods for the generation and isolation of recombinant viruses have hindered the development of therapeutic oncolytic viruses. Here we report an iterative strategy that exploits the preferential susceptibility of viruses to certain antibiotics to accelerate the engineering of the genomes of oncolytic viruses for the insertion of immunomodulatory cytokine transgenes, and the identification of dispensable genes with regard to replication of the recombinant oncolytic viruses in tumour cells. We applied the strategy by leveraging insertional mutagenesis via the Sleeping Beauty transposon system, combined with long-read nanopore sequencing, to generate libraries of herpes simplex virus type 1 and vaccinia virus, identifying stable transgene insertion sites and gene deletions that enhance the safety and efficacy of the viruses.

First Detection of High-Level Aminoglycoside-Resistant Klebsiella pneumoniae and Enterobacter cloacae Isolates Due to 16S rRNA Methyltransferases with and Without blaNDM in Uruguay

BACKGROUND

The increase in antimicrobial resistance includes emerging mechanisms such as 16S ribosomal RNA methylases, which confer high-level resistance to aminoglycosides. In this regard, the most predominant genes observed worldwide are rmtB and armA, but their presence in Uruguay is unknown.

OBJECTIVES

We describe the genomic characterization of isolates carrying rmtB and rmtC, together with blaNDM-5 and blaNDM-1, respectively, and rmtD in our country. Methology: Five isolates from patients admitted to three hospitals were studied. Identification and antibiotic susceptibility testing were performed using the Vitek2 System. Whole Genome Sequencing was conducted, and hybrid assembly was performed with Unicycler. In silico analysis using the Center for Genomic Epidemiology's tools was undertaken to predict antibiotic resistance determinants, plasmid incompatibility groups, and sequence types.

RESULTS

We report three K. pneumoniae ST307 isolates with an IncR plasmid carrying blaNDM-5/blaCTX-M-15/blaTEM-1B/rmtB/dfrA14/dfrA12/sul1/qacEΔ1/ermB/mphA, one K. pneumoniae ST258 harboring an IncC plasmid containing rmtC/blaNDM-1/blaCMY-6/aac(6')-Ib/sul1, and one E. cloacae ST88 isolate with an IncFIB/II plasmid hosting rmtD, within a novel Tn21-like transposon named Tn7825, alongside blaOXA-101/sul1/tet(G)/floR, and a new variant of blaTEM assigned as blaTEM-258. One of the strains, named UH_B2, also carried an IncM1 plasmid encoding qnrE1/blaTEM-1/blaCTX-M-8 associated with ISEcp1.

CONCLUSIONS

This is the first description of plasmids harboring 16S rRNA methyltransferases in Uruguay. The association and dissemination of diverse antibiotic-resistant genes underpin the health threat they represent, highlighting the lack of available antibiotics effective against multidrug-resistant microorganisms.

Enhancing Gentamicin Antibacterial Activity by Co-Encapsulation with Thymoquinone in Liposomal Formulation

BACKGROUND AND PURPOSE

Gentamicin (GEN) is a broad-spectrum antibiotic that cannot be prescribed freely because of its toxicity. Thymoquinone (THQ), a phytochemical, has antibacterial, antioxidant, and toxicity-reducing properties. However, its hydrophobicity and light sensitivity make it challenging to utilize. This incited the idea of co-encapsulating GEN and THQ in liposomes (Lipo-GEN-THQ).

METHOD

Lipo-GEN-THQ were characterized using the zeta-potential, dynamic light scattering, Fourier transform infrared spectroscopy, and transmission electron microscope (TEM). The liposomes' stability was evaluated under different storage and biological conditions. Lipo-GEN-THQ's efficacy was investigated by the minimum inhibitory/bactericidal concentrations (MICs-MBCs), time-kill curves, and antibiofilm and antiadhesion assays. Bacterial interactions with the empty and GEN-THQ-loaded liposomes were evaluated using TEM.

RESULTS

The Lipo-GEN-THQ were spherical, monodispersed, and negatively charged. The Lipo-GEN-THQ were relatively stable and released GEN sustainably over 24 h. The liposomes exhibited significantly higher antibacterial activity than free GEN, as evidenced by the four-fold lower MIC and biofilm eradication in resistant E. coli strain (EC-219). TEM images display how the empty liposomes fused closely to the tested bacteria and how the loaded liposomes caused ultrastructure damage and intracellular component release. An antiadhesion assay showed that the Lipo-GEN-THQ and free GEN (0.125 mg/L) similarly inhibited Escherichia coli (EC-157) adhesion to the A549 cells (68% vs. 64%).

CONCLUSIONS

The Lipo-THQ-GEN enhanced GEN by combining it with THQ within the liposomes, reducing the effective dose. The reduction in the GEN dose after adding THQ may indirectly reduce the toxicity and aid in developing an enhanced and safer form of GEN.

Defense mechanisms of Salmonella against antibiotics: a review

Salmonella is a foodborne pathogenic bacterium that causes salmonellosis worldwide. Also, Salmonella is considered a serious problem for food safety and public health. Several antimicrobial classes including aminoglycosides, tetracyclines, phenols, and β-Lactams are used to treat Salmonella infections. Antibiotics have been prescribed for decades to treat infections caused by bacteria in human and animal healthcare. However, intensive use of antibiotics resulted in antibiotic resistance (AR) among several foodborne bacteria including Salmonella. Furthermore, multi-drug resistance (MDR) of Salmonella has increased dramatically. In addition to MDR Salmonella, extensively drug resistant (XDR) as well as pan drug resistant (PDR) Salmonella were reported globally. Therefore, increasing AR is becoming a serious universal public health crisis. Salmonella developed many mechanisms to ensure its survival against antimicrobials. The most prominent defense mechanisms against these antibiotics include enzymatic inactivation, expelling drugs from the cell through efflux pumps, altering the structure of drugs, and changing or protecting the targets of drugs. Additionally, the formation of biofilms and plasmid-mediated AR by Salmonella, enhancing its resistance to various antibiotics, making it a challenging pathogen in both healthcare and food industry settings. This review focuses exclusively on providing a detailed overview of the mechanisms of AR in Salmonella.

Stalled ribosome rescue factors exert different roles depending on types of antibiotics in Escherichia coli

Escherichia coli possesses three stalled-ribosome rescue factors, tmRNA·SmpB (primary factor), ArfA (alternative factor to tmRNA·SmpB), and ArfB. Here, we examined the susceptibility of rescue factor-deficient strains from E. coli SE15 to various ribosome-targeting antibiotics. Aminoglycosides specifically decreased the growth of the ΔssrA (tmRNA gene) strain, in which the levels of reactive oxygen species were elevated. The decrease in growth of ΔssrA could not be complemented by plasmid-borne expression of arfA, arfB, or ssrAAA to DD mutant gene possessing a proteolysis-resistant tag sequence. These results highlight the significance of tmRNA·SmpB-mediated proteolysis during growth under aminoglycoside stress. In contrast, tetracyclines or amphenicols decreased the growth of the ΔarfA strain despite the presence of tmRNA·SmpB. Quantitative RT-PCR revealed that tetracyclines and amphenicols, but not aminoglycosides, considerably induced mRNA expression of arfA. These findings indicate that tmRNA·SmpB, and ArfA exert differing functions during stalled-ribosome rescue depending on the type of ribosome-targeting antibiotic.

Metagenomics analysis of sewage for surveillance of antimicrobial resistance in South Africa

Our 24-month study used metagenomics to investigate antimicrobial resistance (AMR) abundance in raw sewage from wastewater treatment works (WWTWs) in two municipalities in Gauteng Province, South Africa. At the AMR class level, data showed similar trends at all WWTWs, showing that aminoglycoside, beta-lactam, sulfonamide and tetracycline resistance was most abundant. AMR abundance differences were shown between municipalities, where Tshwane Metropolitan Municipality (TMM) WWTWs showed overall higher abundance of AMR compared to Ekurhuleni Metropolitan Municipality (EMM) WWTWs. Also, within each municipality, there were differing trends in AMR abundance. Notably, within TMM, certain AMR classes (macrolides and macrolides_streptogramin B) were in higher abundance at a WWTW serving an urban high-income area, while other AMR classes (aminoglycosides) were in higher abundance at a WWTW serving a semi-urban low income area. At the AMR gene level, all WWTWs samples showed the most abundance for the sul1 gene (encoding sulfonamide resistance). Following this, the next 14 most abundant genes encoded resistance to sulfonamides, aminoglycosides, macrolides, tetracyclines and beta-lactams. Notably, within TMM, some macrolide-encoding resistance genes (mefC, msrE, mphG and mphE) were in highest abundance at a WWTW serving an urban high-income area; while sul1, sul2 and tetC genes were in highest abundance at a WWTW serving a semi-urban low income area. Differential abundance analysis of AMR genes at WWTWs, following stratification of data by season, showed some notable variance in six AMR genes, of which blaKPC-2 and blaKPC-34 genes showed the highest prevalence of seasonal abundance differences when comparing data within a WWTW. The general trend was to see higher abundances of AMR genes in colder seasons, when comparing seasonal data within a WWTW. Our study investigated wastewater samples in only one province of South Africa, from WWTWs located within close proximity to one another. We would require a more widespread investigation at WWTWs distributed across all regions/provinces of South Africa, in order to describe a more comprehensive profile of AMR abundance across the country.

Prevalence and mechanisms of aminoglycoside resistance among drug-resistant Pseudomonas aeruginosa clinical isolates in Iran

BACKGROUND

Aminoglycosides have been a cornerstone of the treatment of nosocomial infections caused by Pseudomonas aeruginosa for over 80 years. However, escalating emergence of resistance poses a significant challenge. Therefore, this study aimed to investigate the prevailing patterns of aminoglycoside resistance among clinical isolates of P. aeruginosa in Iran; as well as the underlying resistance mechanisms observed in patients referred to Ardabil hospitals.

METHODS

A total of 200 isolates from five hospitals were evaluated. The resistance profiles of P. aeruginosa isolates to tobramycin, amikacin, and netilmicin were determined using the disk diffusion method. The capacity of aminoglycoside-resistant isolates to form biofilms was assessed through a phenotypic assay, and the results were confirmed using the gene amplification technique. The presence of genes associated with aminoglycoside resistance was detected using polymerase chain reaction (PCR). Quantitative reverse transcription PCR (qRT-PCR) was performed to measure the expression levels of genes encoding the MexXY-OprM efflux pump and PhoPQ two-component system (TCS).

RESULTS

The prevalence of aminoglycoside-resistant P. aeruginosa isolates was 48%, with 94.7% demonstrating multidrug resistance (MDR). All aminoglycoside-resistant P. aeruginosa strains exhibited biofilm-forming capabilities and harbored all the genes associated with biofilm production. Among the nine genes encoding 16S rRNA methylase and aminoglycoside-modifying enzymes, three genes were detected in these isolates: aac(6')-Ib (85.4%), ant(2'')-Ia (18.7%), and aph(3')-VI (3.1%). Additionally, all aminoglycoside-resistant P. aeruginosa isolates carried mexY and phoP genes, although the expression levels of mexY and phoP were 75% and 87.5%, respectively.

CONCLUSION

Given the considerably high prevalence of aminoglycoside-resistant P. aeruginosa strains, urgent measures are warranted to transition towards the use of novel aminoglycosides and to uphold vigilant surveillance of resistance patterns.

Evolution of polyamine resistance in Staphylococcus aureus through modulation of potassium transport

Microbes must adapt to diverse biotic and abiotic factors encountered in host environments. Polyamines are an abundant class of aliphatic molecules that play essential roles in fundamental cellular processes across the tree of life. Surprisingly, the bacterial pathogen Staphylococcus aureus is highly sensitive to polyamines encountered during infection, and acquisition of a polyamine resistance locus has been implicated in spread of the prominent USA300 methicillin-resistant S. aureus lineage. At present, alternative pathways of polyamine resistance in staphylococci are largely unknown. Here we applied experimental evolution to identify novel mechanisms and consequences of S. aureus adaption when exposed to increasing concentrations of the polyamine spermine. Evolved populations of S. aureus exhibited striking evidence of parallel adaptation, accumulating independent mutations in the potassium transporter genes ktrA and ktrD. Mutations in either ktrA or ktrD are sufficient to confer polyamine resistance and function in an additive manner. Moreover, we find that ktr mutations provide increased resistance to multiple classes of unrelated cationic antibiotics, suggesting a common mechanism of resistance. Consistent with this hypothesis, ktr mutants exhibit alterations in cell surface charge indicative of reduced affinity and uptake of cationic molecules. Finally, we observe that laboratory-evolved ktr mutations are also present in diverse natural S. aureus isolates, suggesting these mutations may contribute to antimicrobial resistance during human infections. Collectively this study identifies a new role for potassium transport in S. aureus polyamine resistance with consequences for susceptibility to both host-derived and clinically-used antimicrobials.

Expanding antibiotic, vaccine, and diagnostics development and access to tackle antimicrobial resistance

The increasing number of bacterial infections globally that do not respond to any available antibiotics indicates a need to invest in-and ensure access to-new antibiotics, vaccines, and diagnostics. The traditional model of drug development, which depends on substantial revenues to motivate investment, is no longer economically viable without push and pull incentives. Moreover, drugs developed through these mechanisms are unlikely to be affordable for all patients in need, particularly in low-income and middle-income countries. New, publicly funded models based on public-private partnerships could support investment in antibiotics and novel alternatives, and lower patients' out-of-pocket costs, making drugs more accessible. Cost reductions can be achieved with public goods, such as clinical trial networks and platform-based quality assurance, manufacturing, and product development support. Preserving antibiotic effectiveness relies on accurate and timely diagnosis; however scaling up diagnostics faces technological, economic, and behavioural challenges. New technologies appeared during the COVID-19 pandemic, but there is a need for a deeper understanding of market, physician, and consumer behaviour to improve the use of diagnostics in patient management. Ensuring sustainable access to antibiotics also requires infection prevention. Vaccines offer the potential to prevent infections from drug-resistant pathogens, but funding for vaccine development has been scarce in this context. The High-Level Meeting of the UN General Assembly in 2024 offers an opportunity to rethink how research and development can be reoriented to serve disease management, prevention, patient access, and antibiotic stewardship.

Interplay between mistranslation and oxidative stress in Escherichia coli

Mistakes in translation are mostly associated with toxic effects in the cell due to the production of functionally aberrant and misfolded proteins. However, under certain circumstances mistranslation can have beneficial effects and enable cells to preadapt to other stress conditions. Mistranslation may be caused by mistakes made by aminoacyl-tRNA synthetases, essential enzymes that link amino acids to cognate tRNAs. There is an Escherichia coli strain expressing isoleucyl-tRNA synthetase mutant variant with inactivated editing domain which produces mistranslated proteomes where valine (Val) and norvaline (Nva) are misincorporated into proteins instead of isoleucine. We compared this strain with the wild-type to determine the effects of such mistranslation on bacterial growth in oxidative stress conditions. When the cells were pre-incubated with 0.75 mmol/L Nva or 1.5 mmol/L Val or Nva and exposed to hydrogen peroxide, no beneficial effect of mistranslation was observed. However, when the editing-deficient strain was cultivated in medium supplemented with 0.75 mmol/L Val up to the early or mid-exponential phase of growth and then exposed to oxidative stress, it slightly outgrew the wild-type grown in the same conditions. Our results therefore show a modest adaptive effect of isoleucine mistranslation on bacterial growth in oxidative stress, but only in specific conditions. This points to a delicate balance between deleterious and beneficial effects of mistranslation.

Navigating Antibacterial Frontiers: A Panoramic Exploration of Antibacterial Landscapes, Resistance Mechanisms, and Emerging Therapeutic Strategies

The development of effective antibacterial solutions has become paramount in maintaining global health in this era of increasing bacterial threats and rampant antibiotic resistance. Traditional antibiotics have played a significant role in combating bacterial infections throughout history. However, the emergence of novel resistant strains necessitates constant innovation in antibacterial research. We have analyzed the data on antibacterials from the CAS Content Collection, the largest human-curated collection of published scientific knowledge, which has proven valuable for quantitative analysis of global scientific knowledge. Our analysis focuses on mining the CAS Content Collection data for recent publications (since 2012). This article aims to explore the intricate landscape of antibacterial research while reviewing the advancement from traditional antibiotics to novel and emerging antibacterial strategies. By delving into the resistance mechanisms, this paper highlights the need to find alternate strategies to address the growing concern.

Gentamicin loaded niosomes against intracellular uropathogenic Escherichia coli strains

Urinary tract infections (UTIs) are the most common bacterial infections and uropathogenic Escherichia coli (UPEC) is the main etiological agent of UTIs. UPEC can persist in bladder cells protected by immunological defenses and antibiotics and intracellular behavior leads to difficulty in eradicating the infection. The aim of this paper is to design, prepare and characterize surfactant-based nanocarriers (niosomes) able to entrap antimicrobial drug and potentially to delivery and release antibiotics into UPEC-infected cells. In order to validate the proposed drug delivery system, gentamicin, was chosen as "active model drug" due to its poor cellular penetration. The niosomes physical-chemical characterization was performed combining different techniques: Dynamic Light Scattering Fluorescence Spectroscopy, Transmission Electron Microscopy. Empty and loaded niosomes were characterized in terms of size, ζ-potential, bilayer features and stability. Moreover, Gentamicin entrapped amount was evaluated, and the release study was also carried out. In addition, the effect of empty and loaded niosomes was studied on the invasion ability of UPEC strains in T24 bladder cell monolayers by Gentamicin Protection Assay and Confocal Microscopy. The observed decrease in UPEC invasion rate leads us to hypothesize a release of antibiotic from niosomes inside the cells. The optimization of the proposed drug delivery system could represent a promising strategy to significatively enhance the internalization of antimicrobial drugs.

Comparative Pharmacokinetics of Gentamicin C1, C1a and C2 in Healthy and Infected Piglets

Gentamicin, an aminoglycoside antibiotic, is a mixture of therapeutically active C1, C1a, C2 and other minor components. Despite its decades-long use in pigs and other species, its intramuscular (IM) pharmacokinetics/pharmacodynamics (PKs/PDs) are unknown in piglets. Furthermore, the PKs of many drugs differ between healthy and sick animals. Therefore, we investigated the PKs of gentamicin after a single IM dose (10 mg/kg) in healthy piglets and piglets that were intranasally co-infected with Actinobacillus pleuropneumoniae and Pasteurella multocida (PM). The plasma concentrations were measured using validated liquid chromatography/mass spectrometry. The gentamicin exposure was 36% lower based on the area under the plasma concentration-time curve and 16% lower based on the maximum plasma concentration (Cmax) in the infected piglets compared to the healthy piglets, while it was eliminated faster (shorter half-life and larger clearance) in the infected piglets compared to the healthy piglets. The clearance and volume of distribution were the highest for the C1 component. C1, C1a and C2 accounted for 22-25%, 33-37% and 40-42% of the total gentamicin exposure, respectively. The PK/PD target for the efficacy of aminoglycosides (Cmax/minimum inhibitory concentration (MIC) > 10) could be exceeded for PM, with a greater magnitude in the healthy piglets. We suggest integrating this PK information with antibiotic susceptibility data for other bacteria to make informed antibiotic and dosage regimen selections against piglet infections.

Antibacterial activity of deer musk and Ziziphus spina-christi against carbapebem resis-tant gram negative bacteria isolated from patients with burns and wounds

Bacteria were isolated from 250 specimens obtained from patients attending the Plastic Reconstructive and Burn Surgery Hospital in the Sulaymaniyah (Kurdistan region) and the burn and wound care units of the Azadi Teaching Hospital (Kirkuk), Iraq. Gram-negative bacteria were isolated from 100 (40%) of the samples which identified by BD phoenix, 66 isolates (66%) were carbapenem-resistant species, Rapidec® Carba NP test and sensitivity tests revealed 17 different genera and species of carbapenem-resistant bacteria. The BD Phoenix system was used to evaluate the susceptibility test of the isolates to 18 different antibiotics. The number of isolates that exhibited resistance to the carbapenem antibiotics, ertapenem, imipenem and meropenem, was 40 (61%), 35 (54%) and 28 (42%) respectively. Meanwhile, the number of isolates resistant to the penicillin antibiotics, ampicillin, amoxicillin-clavulanic acid and piperacillin-tazobactam, was 61 (92%), 54 (82%) and 24 (36%) respectively. The isolates were also evaluated for their resistance to the cephalosporins, cefazolin, cefuroxime, ceftazidime, ceftriaxone, cefepime, and ceftolozane-tazobactam; the respective number of resistant isolates were 60 (91%), 60 (91%), 39 (59%), 48 (73%), 42 (64%) and 27(41%). In contrast, a fraction of Ziziphus spina-christi leaves that was extracted using ethyl acetate inhibited all of the carbapenem-resistant isolates studied. The zone of inhibition (ZoI) Ø was between 19 and 24 mm. The ZoI Ø of black deer musk was 11–19 mm. The minimum inhibitory concentration (MICs) of ethyl acetate extract of Ziziphus spina-christi leaves for Acinetobacter baumannii (PDR), CR-Citrobacter farmeri, CR-Escherichia coli, CR-Proteus mirabilis, CR-Pseudomonas fluorescens, CR-Escherichia vulneris, CR-Kluyvera ascorbata, CR-Pantoea agglomerans, CR-Pseudomonas putida and CR-Serratia marcescens, was 6.25 mg/mL. Meanwhile, the MIC for Acinetobacter calcoaceticus–baumannii complex, Citrobacter freundii, Enterobacter cloacae, Klebsiella pneumoniae, Morganella morganii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia was 12.5 mg/mL. High-performance liquid chromatography (HPLC) was used to analyse the components of the ethyl acetate-extract of Ziziphus spina-christi leaves. The analysis found gallic acid (760.3 ppm/mL), caffeine (84.0 ppm/mL) and quercetin (2.2 ppm/mL); the total phenolic content was 846.5 ppm/mL. The evidence obtained from this study indicates that leaves of this plant (named sidr in the Middle East) have the potential to be used as a natural antibiotic against carbapenem-resistant Gram-negative bacteria. Thus, the leaves of this tree present an important opportunity in the development of novel therapeutic agents. The study found the MIC of deer musk for CR-Citrobacter farmeri, CR-Citrobacter freundii, CR-Enterobacter cloacae, CR-Escherichia vulneris, CR-Klebsiella pneumoniae, CR-Kluyvera ascorbata, CR-Morganella morganii, CR-Pantoea agglomerans, CR-Proteus mirabilis, CR-Pseudomonas fluorescens, CR-Pseudomonas putida and CR-Serratia marcescens to be 50 mg/mL. In contrast, the MIC of deer musk was 100 mg/mL for Acinetobacter baumannii (PDR), CR-Acinetobacter calcoaceticus–baumannii complex, CR-Escherichia coli, CR-Pseudomonas aeruginosa and CR-Stenotrophomonas maltophilia. The results of the gas chromatography–mass spectrometry (GC–MS) indicate that the primary constituents of musk were1,4,4-tetramethyltetralin, 7-acetyl-6-ethyl-1, diethyl phthalate and tonalid; their contribution to the whole ranged from 12.2% to 19.6%. Black musk exhibits considerable antibacterial activity, able to inhibit seventeen different species of carbapenem-resistant Gram-negative bacteria. The non-natural form of black musk can be used to scent detergent.

Application of tobramycin benzyl ether as an antibiotic adjuvant capable of sensitizing multidrug-resistant Gram-negative bacteria to rifampicin

The emergence of aminoglycoside resistance has prompted the development of amphiphilic aminoglycoside derivatives which target bacterial membranes. Tobramycin and nebramine ether derivatives initially designed for this purpose were optimized and screened for their potential application as outer membrane (OM) permeabilizing adjuvants. Structure-activity relationship (SAR) studies revealed that the tobramycin benzyl ether was the most optimal OM permeabilizer, capable of potentiating rifampicin, novobiocin, vancomycin, minocycline, and doxycycline against Gram-negative bacteria. The innovative use of this compound as an adjuvant is highlighted by its ability to sensitize multidrug-resistant (MDR) Gram-negative bacteria to rifampicin and restore the susceptibility of MDR Escherichia coli to minocycline.

Improved characterization of aminoglycoside penetration into human lung epithelial lining fluid via population pharmacokinetics

Aminoglycosides are important treatment options for serious lung infections, but modeling analyses to quantify their human lung epithelial lining fluid (ELF) penetration are lacking. We estimated the extent and rate of penetration for five aminoglycosides via population pharmacokinetics from eight published studies. The area under the curve in ELF vs plasma ranged from 50% to 100% and equilibration half-lives from 0.61 to 5.80 h, indicating extensive system hysteresis. Aminoglycoside ELF peak concentrations were blunted, but overall exposures were moderately high.

Association of Diabetes Mellitus With Increased Mortality in Carbapenem-Resistant Enterobacterales Infections

Introduction Carbapenem-resistant Enterobacterales (CRE) infections have high mortality. We aimed to examine the diabetes mellitus (DM) association with CRE mortality. Methodology Our study is a retrospective cohort study including patients who were admitted to the medical wards in the main district hospital (New Jahra Hospital, Kuwait) between January 1, 2022, and January 1, 2023, and diagnosed with CRE infections during hospitalization. The patients were divided into diabetic and non-diabetic groups. Clinical and laboratory data were collected. The presence of carbapenemase genes was detected. The primary outcome was 30-day hospital mortality. We assessed the effect of glycemic control on the outcomes. Results We included 47 patients in the diabetic group and 39 patients in the non-diabetic group. Females represented 54.7% of patients, and the median age was 73 and 55 years in the two groups, respectively. Klebsiella pneumonia (86%) and Escherichia coli (12.8%) were the most frequently isolated CRE. Carbapenemase genes were detected in all patients: NDM-1 in 67.4%, OXA-48 in 18.6%, and both genes coexisted in 14%. The 30-day hospital mortality was significantly higher in the diabetic group compared to the non-diabetic group (48.9% vs. 28.2%, P = 0.041). Among the diabetic patients, there was no significant difference between survivors and non-survivors regarding median glucose or glycated hemoglobin (HbA1c) levels (P = 0.465 and 0.932, respectively). Moreover, levels of glucose (odds ratio (OR) 0.928, confidence interval (CI) 0.763-1.13, P = 0.457) and HbA1c (OR 0.89, CI 0.63-1.26, P = 0.507) were not risk factors for increased mortality among diabetic patients.  Conclusion We demonstrated the association between DM and increased CRE mortality regardless of the level of glycemic control. This study demonstrates the interaction between communicable and non-communicable diseases.

Combating Aminoglycoside Resistance: From Structural and Functional Characterisation to Therapeutic Challenges with RKAAT

A comprehensive knowledge of aminoglycoside-modifying enzymes (AMEs) and their role in bacterial resistance mechanisms is urgently required due to the rising incidence of antibiotic resistance, particularly in Klebsiella pneumoniae infections. This study explores the essential features of AMEs, including their structural and functional properties, the processes by which they contribute to antibiotic resistance, and the therapeutic importance of aminoglycosides. The study primarily examines the Recombinant Klebsiella pneumoniae Aminoglycoside Adenylyl Transferase (RKAAT), particularly emphasizing its biophysical characteristics and the sorts of resistance it imparts. Furthermore, this study examines the challenges presented by RKAAT-mediated resistance, an evaluation of treatment methods and constraints, and options for controlling infection. The analysis provides a prospective outlook on strategies to address and reduce antibiotic resistance. This extensive investigation seeks to provide vital insights into the continuing fight against bacterial resistance, directing future research efforts and medicinal approaches.

Aminoglycoside uptake, stress, and potentiation in Gram-negative bacteria: new therapies with old molecules

SUMMARYAminoglycosides (AGs) are long-known molecules successfully used against Gram-negative pathogens. While their use declined with the discovery of new antibiotics, they are now classified as critically important molecules because of their effectiveness against multidrug-resistant bacteria. While they can efficiently cross the Gram-negative envelope, the mechanism of AG entry is still incompletely understood, although this comprehension is essential for the development of new therapies in the face of the alarming increase in antibiotic resistance. Increasing antibiotic uptake in bacteria is one strategy to enhance effective treatments. This review aims, first, to consolidate old and recent knowledge about AG uptake; second, to explore the connection between AG-dependent bacterial stress and drug uptake; and finally, to present new strategies of potentiation of AG uptake for more efficient antibiotic therapies. In particular, we emphasize on the connection between sugar transport and AG potentiation.

Risk assessment of Enterococcus faecium, Klebsiella pneumoniae, and Pseudomonas aeruginosa in environmental water sources: Development of surrogate models for antibiotic resistance genes

The presence of Enterococcus faecium (E. faecium), Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa (P. aeruginosa), and the aminoglycoside resistance genes, aac(6')-Ib and aac(6')-aph(2″), was investigated in environmental water sources obtained from informal settlements in the Western Cape (South Africa). Using ethidium monoazide bromide quantitative polymerase chain reaction (EMA-qPCR) analysis, E. faecium, K. pneumoniae, and P. aeruginosa were detected in 88.9 %, 100 %, and 93.3 % of the samples (n = 45), respectively, with a significantly higher mean concentration recorded for K. pneumoniae (7.83 × 104 cells/100 mL) over the sampling period. The aac(6')-Ib gene was detected in 95.6 % (43/45) of the environmental water samples [mean concentration of 7.07 × 106 gene copies (GC)/100 mL], while the aac(6')-aph(2″) gene was detected in 100 % (n = 45) of the samples [mean concentration of 6.68 × 105 GC/100 mL]. Quantitative microbial risk assessment (QMRA) subsequently indicated that the risks posed by K. pneumoniae and P. aeruginosa were linked to intentional drinking, washing/bathing, cleaning of the home, and swimming, in the samples collected from the various sampling sites. Surrogate risk assessment models were then designed and applied for Gram-positive [aac(6')-aph(2″) gene] and Gram-negative [aac(6')-Ib gene] pathogens that may exhibit aminoglycoside resistance. The results indicated that only the Gram-negative pathogens posed a risk (>10-4) in all the samples for cleaning of the home and intentional drinking, as well as for washing laundry by hand, garden hosing, garden work, washing/bathing, accidental consumption, and swimming at the stream and marsh sites. Thus, while environmental waters may pose a health risk of exposure to pathogenic bacteria, the results obtained indicate that screening for antibiotic resistant genes, associated with multiple genera/species, could serve as a surrogate model for estimating risks with the target group under investigation.

Within-Host Resistance and Virulence Evolution of a Hypervirulent Carbapenem-Resistant Klebsiella pneumoniae ST11 Under Antibiotic Pressure

Background

Hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) has recently aroused an extremely severe health challenge and public concern. However, the underlying mechanisms of fitness costs that accompany antibiotic resistance acquisition remain largely unexplored. Here, we report a hv-CRKP-associated fatal infection and reveal a reduction in virulence due to the acquisition of aminoglycoside resistance.

Methods

The bacterial identification, antimicrobial susceptibility, hypermucoviscosity, virulence factors, MLST and serotypes were profiled.The clonal homology and plasmid acquisition among hv-CRKP strains were detected by XbaI and S1-PFGE. The virulence potential of the strains was evaluated using Galleria mellonella larvae infection model, serum resistance assay, capsular polysaccharide quantification, and biofilm formation assay. Genomic variations were identified using whole-genome sequencing (WGS).

Results

Four K. pneumoniae carbapenemase (KPC)-producing CRKP strains were consecutively isolated from an 86-year-old patient with severe pneumonia. Whole-genome sequencing (WGS) showed that all four hv-CRKP strains belonged to the ST11-KL64 clone. PFGE analysis revealed that the four ST11-KL64 hv-CRKP strains could be grouped into the same PFGE type. Under the pressure of antibiotics, the antimicrobial resistance of the strains increased and the virulence potential decreased. Further sequencing, using the Nanopore platform, was performed on three representative isolates (WYKP586, WYKP589, and WYKP594). Genomic analysis showed that the plasmids of these three strains underwent a large number of breaks and recombination events under antibiotic pressure. We found that as aminoglycoside resistance emerged via acquisition of the rmtB gene, the hypermucoviscosity and virulence of the strains decreased because of internal mutations in the rmpA and rmpA2 genes.

Conclusion

This study shows that ST11-KL64 hv-CRKP can further evolve to acquire aminoglycoside resistance accompanied by decreased virulence to adapt to antibiotic pressure in the host.

The potential role of upregulated PARP-1/RIPK1 expressions in amikacin-induced oxidative damage and nephrotoxicity in Wistar rats

This study aimed to investigate the gene expression levels associated with nephrotoxic action of amikacin, as well as the post-treatment effect of diuretics on its nephrotoxic effects. Sixty male rats were divided equally into six groups, including the control group receiving saline intra-peritoneally (ip), and the five treated groups including therapeutic and double therapeutic dose groups, injected ip (15 and 30 mg/kg b.wt./day) respectively for seven days, and another two rat groups treated as therapeutic and double therapeutic dose groups then administered the diuretic orally for seven days and the last group received amikacin ip at a rate of 15 mg/kg/day for seven days, then given free access to water without diuretics for another seven days and was kept as a self-recovery group. Amikacin caused kidney injury, which was exacerbated by the double therapeutic dose, as evidenced by abnormal serum renal injury biomarkers, elevated renal MDA levels, inhibition of renal catalase and SOD enzyme activities, with renal degenerative and necrotic changes. Moreover, comet assays also revealed renal DNA damage. Interestingly, amikacin administration markedly elevated expression levels of the PARP-1, RIP1, TNF-α, IL-1β, and iNOS genes as compared to the control group. However, compared to the self-recovery group, post-amikacin diuretic treatment modulates amikacin-induced altered findings and alleviates amikacin nephrotoxic effects more efficiently. Our findings suggested the potential role of PARP-1 and RIPK1 expressions that influence the expression of proinflammatory cytokines such as IL-1β and TNF-α by exaggerating oxidative stress which may contribute to the pathogenesis of amikacin-induced nephrotoxicity.

Restoring susceptibility to aminoglycosides: identifying small molecule inhibitors of enzymatic inactivation

Growing resistance to antimicrobial medicines is a critical health problem that must be urgently addressed. Adding to the increasing number of patients that succumb to infections, there are other consequences to the rise in resistance like the compromise of several medical procedures and dental work that are heavily dependent on infection prevention. Since their introduction in the clinics, aminoglycoside antibiotics have been a critical component of the armamentarium to treat infections. Still, the increase in resistance and their side effects led to a decline in their utilization. However, numerous current factors, like the urgent need for antimicrobials and their favorable properties, led to renewed interest in these drugs. While efforts to design new classes of aminoglycosides refractory to resistance mechanisms and with fewer toxic effects are starting to yield new promising molecules, extending the useful life of those already in use is essential. For this, numerous research projects are underway to counter resistance from different angles, like inhibition of expression or activity of resistance components. This review focuses on selected examples of one aspect of this quest, the design or identification of small molecule inhibitors of resistance caused by enzymatic modification of the aminoglycoside. These compounds could be developed as aminoglycoside adjuvants to overcome resistant infections.

Extensive screening reveals previously undiscovered aminoglycoside resistance genes in human pathogens

Antibiotic resistance is a growing threat to human health, caused in part by pathogens accumulating antibiotic resistance genes (ARGs) through horizontal gene transfer. New ARGs are typically not recognized until they have become widely disseminated, which limits our ability to reduce their spread. In this study, we use large-scale computational screening of bacterial genomes to identify previously undiscovered mobile ARGs in pathogens. From ~1 million genomes, we predict 1,071,815 genes encoding 34,053 unique aminoglycoside-modifying enzymes (AMEs). These cluster into 7,612 families (<70% amino acid identity) of which 88 are previously described. Fifty new AME families are associated with mobile genetic elements and pathogenic hosts. From these, 24 of 28 experimentally tested AMEs confer resistance to aminoglycoside(s) in Escherichia coli, with 17 providing resistance above clinical breakpoints. This study greatly expands the range of clinically relevant aminoglycoside resistance determinants and demonstrates that computational methods enable early discovery of potentially emerging ARGs.

Changes in Antibiotic Resistance of Acinetobacter baumannii and Pseudomonas aeruginosa Clinical Isolates in a Multi-Profile Hospital in Years 2017-2022 in Wroclaw, Poland

In recent years, we have witnessed increasing drug resistance among bacteria, which is associated with the use and availability of an increasing number of broad-spectrum antimicrobials, as well as with their irrational and excessive use. The present study aims to analyze changes in the drug resistance of Gram-negative Pseudomonas aeruginosa and Acinetobacter baumannii, isolated from infections in a multi-profile hospital over a five-year period (from 2017 to 2022). Among the practical results of the evaluation of these data will be the possibility to determine changes in susceptibility to the antibiotics used in the hospital. This, in turn, will help propose new therapeutic options, especially for empirical therapy, which is essential in severe infections. Analysis of the use of different antibiotic groups has made it possible to identify the causes of increasing resistance in the analyzed Gram-negative bacilli. The highest antibiotic use was observed in the hospital between 2020 and 2022, most probably due to the COVID-19 pandemic and the higher number of patients in severe condition requiring hospitalization. Unfortunately, during the period analyzed, the number of multi-resistant strains of A. baumannii was successively increasing; this seems to be related to the increased use, especially during the pandemic period, of broad-spectrum antibiotics, mainly penicillins with inhibitors, third-generation cephalosporins and carbapenems.

Identification of the active mechanism of aminoglycoside entry in V. cholerae through characterization of sRNA ctrR, regulating carbohydrate utilization and transport

The possible active entry of aminoglycosides in bacterial cells has been debated since the development of this antibiotic family. Here we report the identification of their active transport mechanism in Vibrio species. We combined genome-wide transcriptional analysis and fitness screens to identify alterations driven by treatment of V. cholerae with sub-minimum inhibitory concentrations (sub-MIC) of the aminoglycoside tobramycin. RNA-seq data showed downregulation of the small non-coding RNA ncRNA586 during such treatment, while Tn-seq revealed that inactivation of this sRNA was associated with improved fitness in the presence of tobramycin. This sRNA is located near sugar transport genes and previous work on a homologous region in Vibrio tasmaniensis suggested that this sRNA stabilizes gene transcripts for carbohydrate transport and utilization, as well as phage receptors. The role for ncRNA586, hereafter named ctrR, in the transport of both carbohydrates and aminoglycosides, was further investigated. Flow cytometry on cells treated with a fluorescent aminoglycoside confirmed the role of ctrR and of carbohydrate transporters in differential aminoglycoside entry. Despite sequence diversity, ctrR showed functional conservation across the Vibrionales. This system in directly modulated by carbon sources, suggesting regulation by carbon catabolite repression, a widely conserved mechanism in Gram-negative bacteria, priming future research on aminoglycoside uptake by sugar transporters in other bacterial species.

Evaluation of the Ability to Form Biofilms in KPC-Producing and ESBL-Producing Klebsiella pneumoniae Isolated from Clinical Samples

The appearance of Klebsiella pneumoniae strains producing extended-spectrum β-lactamase (ESBL), and carbapenemase (KPC) has turned into a significant public health issue. ESBL- and KPC-producing K. pneumoniae's ability to form biofilms is a significant concern as it can promote the spread of antibiotic resistance and prolong infections in healthcare facilities. A total of 45 K. pneumoniae strains were isolated from human infections. Antibiograms were performed for 17 antibiotics, ESBL production was tested by Etest ESBL PM/PML, a rapid test was used to detect KPC carbapenemases, and resistance genes were detected by PCR. Biofilm production was detected by the microtiter plate method. A total of 73% of multidrug resistance was found, with the highest resistance rates to ampicillin, trimethoprim-sulfamethoxazole, cefotaxime, amoxicillin-clavulanic acid, and aztreonam. Simultaneously, the most effective antibiotics were tetracycline and amikacin. bla_CTX-M, bla_TEM, bla_SHV, aac(3)-II, aadA1, tetA, cmlA, catA, gyrA, gyrB, parC, sul1, sul2, sul3, bla_KPC, bla_OXA, and bla_PER genes were detected. Biofilm production showed that 80% of K. pneumoniae strains were biofilm producers. Most ESBL- and KPC-producing isolates were weak biofilm producers (40.0% and 60.0%, respectively). There was no correlation between the ability to form stronger biofilms and the presence of ESBL and KPC enzymes in K. pneumoniae isolates.

ANT(9)-Ic, a Novel Chromosomally Encoded Aminoglycoside Nucleotidyltransferase from Brucella intermedia

Aminoglycoside-modifying enzymes are among the most important mechanisms of resistance to aminoglycoside antibiotics, typically conferring high-level resistance by enzymatic drug inactivation. Previously, we isolated a multidrug-resistant Brucella intermedia strain ZJ499 from a cancer patient, and whole-genome sequencing revealed several putative novel aminoglycoside-modifying enzyme genes in this strain. Here, we report the characterization of one of them that encodes an intrinsic, chromosomal aminoglycoside nucleotidyltransferase designated ANT(9)-Ic, which shares only 33.05% to 47.44% amino acid identity with the most closely related ANT(9)-I enzymes. When expressed in Escherichia coli, ANT(9)-Ic conferred resistance only to spectinomycin and not to any other aminoglycosides tested, indicating a substrate profile typical of ANT(9)-I enzymes. Consistent with this, deletion of ant(9)-Ic in ZJ499 resulted in a specific and significant decrease in MIC of spectinomycin. Furthermore, the purified ANT(9)-Ic protein showed stringent substrate specificity for spectinomycin with a Km value of 44.83 μM and a kcat/Km of 2.8 × 104 M-1 s-1, echoing the above observations of susceptibility testing. In addition, comparative genomic analysis revealed that the genetic context of ant(9)-Ic was conserved in Brucella, with no mobile genetic elements found within its 20-kb surrounding region. Overall, our results demonstrate that ANT(9)-Ic is a novel member of the ANT(9)-I lineage, contributing to the intrinsic spectinomycin resistance of ZJ499. IMPORTANCE The emergence, evolution, and worldwide spread of antibiotic resistance present a significant global public health crisis. For aminoglycoside antibiotics, enzymatic drug modification is the most common mechanism of resistance. We identify a novel chromosomal aminoglycoside nucleotidyltransferase from B. intermedia, called ANT(9)-Ic, which shares the highest identity (47.44%) with the previously known ANT(9)-Ia and plays an important role in spectinomycin resistance of the host strain. Analysis of the genetic environment and origin of ant(9)-Ic shows that the gene and its surrounding region are widely conserved in Brucella, and no mobile elements are detected, indicating that ANT(9)-Ic may be broadly important in the natural resistance to spectinomycin of Brucella species.

Side effects of antibiotics and perturbations of mitochondria functions

Antibiotics are one of the greatest discoveries of medicine of the past century. Despite their invaluable contribution to infectious disease, their administration could lead to side effects that in some cases are serious. The toxicity of some antibiotics is in part due to their interaction with mitochondria: these organelles derive from a bacterial ancestor and possess specific translation machinery that shares similarities with the bacterial counterpart. In other cases, the antibiotics could interfere with mitochondrial functions even if their main bacterial targets are not shared with the eukaryotic cells. The purpose of this review is to summarize the effects of antibiotics administration on mitochondrial homeostasis and the opportunity that some of these molecules could represent in cancer treatment. The importance of antimicrobial therapy is unquestionable, but the identification of interaction with eukaryotic cells and in particular with mitochondria is crucial to reduce the toxicity of these drugs and to explore other useful medical applications.

The small mycobacterial ribosomal protein, bS22, modulates aminoglycoside accessibility to its 16S rRNA helix-44 binding site

Treatment of tuberculosis continues to be challenging due to the widespread latent form of the disease and the emergence of antibiotic-resistant strains of the pathogen, Mycobacterium tuberculosis. Bacterial ribosomes are a common and effective target for antibiotics. Several second line anti-tuberculosis drugs, e.g. kanamycin, amikacin, and capreomycin, target ribosomal RNA to inhibit protein synthesis. However, M. tuberculosis can acquire resistance to these drugs, emphasizing the need to identify new drug targets. Previous cryo-EM structures of the M. tuberculosis and M. smegmatis ribosomes identified two novel ribosomal proteins, bS22 and bL37, in the vicinity of two crucial drug-binding sites: the mRNA-decoding center on the small (30S), and the peptidyl-transferase center on the large (50S) ribosomal subunits, respectively. The functional significance of these two small proteins is unknown. In this study, we observe that an M. smegmatis strain lacking the bs22 gene shows enhanced susceptibility to kanamycin compared to the wild-type strain. Cryo-EM structures of the ribosomes lacking bS22 in the presence and absence of kanamycin suggest a direct role of bS22 in modulating the 16S rRNA kanamycin-binding site. Our structures suggest that amino-acid residue Lys-16 of bS22 interacts directly with the phosphate backbone of helix 44 of 16S rRNA to influence the micro-configuration of the kanamycin-binding pocket. Our analysis shows that similar interactions occur between eukaryotic homologues of bS22, and their corresponding rRNAs, pointing to a common mechanism of aminoglycoside resistance in higher organisms.

Connecting Gut Microbial Diversity with Plasma Metabolome and Fecal Bile Acid Changes Induced by the Antibiotics Tobramycin and Colistin Sulfate

The diversity of microbial species in the gut has a strong influence on health and development of the host. Further, there are indications that the variation in expression of gut bacterial metabolic enzymes is less diverse than the taxonomic profile, underlying the importance of microbiome functionality, particularly from a toxicological perspective. To address these relationships, the gut bacterial composition of Wistar rats was altered by a 28 day oral treatment with the antibiotics tobramycin or colistin sulfate. On the basis of 16S marker gene sequencing data, tobramycin was found to cause a strong reduction in the diversity and relative abundance of the microbiome, whereas colistin sulfate had only a marginal impact. Associated plasma and fecal metabolomes were characterized by targeted mass spectrometry-based profiling. The fecal metabolome of tobramycin-treated animals had a high number of significant alterations in metabolite levels compared to controls, particularly in amino acids, lipids, bile acids (BAs), carbohydrates, and energy metabolites. The accumulation of primary BAs and significant reduction of secondary BAs in the feces indicated that the microbial alterations induced by tobramycin inhibit bacterial deconjugation reactions. The plasma metabolome showed less, but still many alterations in the same metabolite groups, including reductions in indole derivatives and hippuric acid, and furthermore, despite marginal effects of colistin sulfate treatment, there were nonetheless systemic alterations also in BAs. Aside from these treatment-based differences, we also uncovered interindividual differences particularly centering on the loss of Verrucomicrobiaceae in the microbiome, but with no apparent associated metabolite alterations. Finally, by comparing the data set from this study with metabolome alterations in the MetaMapTox database, key metabolite alterations were identified as plasma biomarkers indicative of altered gut microbiomes resulting from a wide activity spectrum of antibiotics.

Inhibition of Enzymatic Acetylation-Mediated Resistance to Plazomicin by Silver Ions

Plazomicin is a recent U.S. Food and Drug Administration (FDA)-approved semisynthetic aminoglycoside. Its structure consists of a sisomicin scaffold modified by adding a 2(S)-hydroxy aminobutyryl group at the N1 position and a hydroxyethyl substituent at the 6' position. These substitutions produced a molecule refractory to most aminoglycoside-modifying enzymes. The main enzyme within this group that recognizes plazomicin as substrate is the aminoglycoside 2'-N-acetyltransferase type Ia [AAC(2')-Ia], which reduces the antibiotic's potency. Designing formulations that combine an antimicrobial with an inhibitor of resistance is a recognized strategy to extend the useful life of existing antibiotics. We have recently found that several metal ions inhibit the enzymatic inactivation of numerous aminoglycosides mediated by the aminoglycoside 6'-N-acetyltransferase type Ib [AAC(6')-Ib]. In particular, Ag+, which also enhances the effect of aminoglycosides by other mechanisms, is very effective in interfering with AAC(6')-Ib-mediated resistance to amikacin. Here we report that silver acetate is a potent inhibitor of AAC(2')-Ia-mediated acetylation of plazomicin in vitro, and it reduces resistance levels of Escherichia coli carrying aac(2')-Ia. The resistance reversion assays produced equivalent results when the structural gene was expressed under the control of the natural or the blaTEM-1 promoters. The antibiotic effect of plazomicin in combination with silver was bactericidal, and the mix did not show significant toxicity to human embryonic kidney 293 (HEK293) cells.

The Influence of Outer Membrane Protein on Ampicillin Resistance of Vibrio parahaemolyticus

The antibiotic resistance of the food-borne pathogen Vibrio parahaemolyticus has attracted researchers' attention in recent years, but its molecular mechanism remains poorly understood. In this study, 7 genes encoding outer membrane proteins (OMPs) were individually deleted in V. parahaemolyticus ATCC33846, and the resistance of these 7 mutants to 14 antibiotics was investigated. The results revealed that the resistance of the 7 mutants to ampicillin was significantly increased. Further exploration of 20-gene transcription changes by real time-qPCR (RT-qPCR) demonstrated that the higher ampicillin resistance might be attributed to the expression of β-lactamase and reduced peptidoglycan (PG) synthesis activity through reduced transcription of penicillin-binding proteins (PBPs), increased transcription of l,d-transpeptidases, downregulated d,d-carboxypeptidase, and alanine deficiency. This study provides a new perspective on ampicillin resistance in OMP mutants with respect to PG synthesis.

Role of necroptosis in kidney health and disease

Cell death, particularly that of tubule epithelial cells, contributes critically to the pathophysiology of kidney disease. A body of evidence accumulated over the past 15 years has ascribed a central pathophysiological role to a particular form of regulated necrosis, termed necroptosis, to acute tubular necrosis, nephron loss and maladaptive renal fibrogenesis. Unlike apoptosis, which is a non-immunogenic process, necroptosis results in the release of cellular contents and cytokines, which triggers an inflammatory response in neighbouring tissue. This necroinflammatory environment can lead to severe organ dysfunction and cause lasting tissue injury in the kidney. Despite evidence of a link between necroptosis and various kidney diseases, there are no available therapeutic options to target this process. Greater understanding of the molecular mechanisms, triggers and regulators of necroptosis in acute and chronic kidney diseases may identify shortcomings in current approaches to therapeutically target necroptosis regulators and lead to the development of innovative therapeutic approaches.

Antibiotics with Antiviral and Anti-Inflammatory Potential Against Covid-19: A Review

In Covid-19 cases, elderly patients in long-term care facilities, children younger than five years with moderate symptoms, and patients admitted to ICU or with comorbidities are at a high risk of coinfection, as suggested by the evidence. Thus, in these patients, antibiotic therapy based on empirical evidence is necessary. Finding appropriate antimicrobial agents, especially with antiviral and anti-inflammatory properties, is a promising approach to target the virus and its complications, hyper-inflammation, and microorganisms resulting in co-infection. Moreover, indiscriminate use of antibiotics can be accompanied by Clostridioides difficile colitis, the emergence of resistant microorganisms, and adverse drug reactions, particularly kidney damage and QT prolongation. Therefore, rational administration of efficient antibiotics is an important issue. The main objective of the present review is to provide a summary of antibiotics with possible antiviral activity against SARS-CoV-2 and anti-immunomodulatory effects to guide scientists for further research. Besides, the findings can help health professionals in the rational prescription of antibiotics in Covid-19 patients with a high risk of co-infection.

Antiphage small molecules produced by bacteria - beyond protein-mediated defenses

Bacterial populations face the constant threat of viral predation exerted by bacteriophages ('phages'). In response, bacteria have evolved a wide range of defense mechanisms against phage challenges. Yet the vast majority of antiphage defense systems described until now are mediated by proteins or RNA complexes acting at the single-cell level. Here, we review small molecule-based defense strategies against phage infection, with a focus on the antiphage molecules described recently. Importantly, inhibition of phage infection by excreted small molecules has the potential to protect entire bacterial communities, highlighting the ecological significance of these antiphage strategies. Considering the immense repertoire of bacterial metabolites, we envision that the list of antiphage small molecules will be further expanded in the future.

Surgical Site Infection in Cardiac Surgery

Surgical site infections (SSIs) are one of the most significant complications in surgical patients and are strongly associated with poorer prognosis. Due to their aggressive character, cardiac surgical procedures carry a particular high risk of postoperative infection, with infection incidence rates ranging from a reported 3.5% and 26.8% in cardiac surgery patients. Given the specific nature of cardiac surgical procedures, sternal wound and graft harvesting site infections are the most common SSIs. Undoubtedly, DSWIs, including mediastinitis, in cardiac surgery patients remain a significant clinical problem as they are associated with increased hospital stay, substantial medical costs and high mortality, ranging from 3% to 20%. In SSI prevention, it is important to implement procedures reducing preoperative risk factors, such as: obesity, hypoalbuminemia, abnormal glucose levels, smoking and S. aureus carriage. For decolonisation of S. aureus carriers prior to cardiac surgery, it is recommended to administer nasal mupirocin, together with baths using chlorhexidine-based agents. Perioperative management also involves antibiotic prophylaxis, surgical site preparation, topical antibiotic administration and the maintenance of normal glucose levels. SSI treatment involves surgical intervention, NPWT application and antibiotic therapy.