Revisiting Antibiotic Resistance: Mechanistic Foundations to Evolutionary Outlook

Bacterial Infections: Surveillance, Prevention and Control

Bacteria play a vital role in maintaining human health, but they may also be responsible for many different serious infections and diseases [...].

Antibiotic action and resistance: updated review of mechanisms, spread, influencing factors, and alternative approaches for combating resistance

Antibiotics represent a frequently employed therapeutic modality for the management of bacterial infections across diverse domains, including human health, agriculture, livestock breeding, and fish farming. The efficacy of antibiotics relies on four distinct mechanisms of action, which are discussed in detail in this review, along with accompanying diagrammatic illustrations. Despite their effectiveness, antibiotic resistance has emerged as a significant challenge to treating bacterial infections. Bacteria have developed defense mechanisms against antibiotics, rendering them ineffective. This review delves into the specific mechanisms that bacteria have developed to resist antibiotics, with the help of diagrammatic illustrations. Antibiotic resistance can spread among bacteria through various routes, resulting in previously susceptible bacteria becoming antibiotic-resistant. Multiple factors contribute to the worsening crisis of antibiotic resistance, including human misuse of antibiotics. This review also emphasizes alternative solutions proposed to mitigate the exacerbation of antibiotic resistance.

Evaluation of Expanded 2-Aminobenzothiazole Library for Inhibition of Pseudomonas aeruginosa Virulence Phenotypes

Bacterial resistance to antibiotics is a rapidly increasing threat to human health. New strategies to combat resistant organisms are desperately needed. One potential avenue is targeting two-component systems, which are the main bacterial signal transduction pathways used to regulate development, metabolism, virulence, and antibiotic resistance. These systems consist of a homodimeric membrane-bound sensor histidine kinase, and a cognate effector, the response regulator. The high sequence conservation in the catalytic and adenosine triphosphate-binding (CA) domain of histidine kinases and their essential role in bacterial signal transduction could enable broad-spectrum antibacterial activity. Through this signal transduction, histidine kinases regulate multiple virulence mechanisms including toxin production, immune evasion, and antibiotic resistance. Targeting virulence, as opposed to development of bactericidal compounds, could reduce evolutionary pressure for acquired resistance. Additionally, compounds targeting the CA domain have the potential to impair multiple two-component systems that regulate virulence in one or more pathogens. We conducted structure-activity relationship studies of 2-aminobenzothiazole-based inhibitors designed to target the CA domain of histidine kinases. We found these compounds have anti-virulence activities in Pseudomonas aeruginosa, reducing motility phenotypes and toxin production associated with the pathogenic functions of this bacterium.

Transposon-aided capture (TRACA) of plasmids from the human gut

The gut microbiota consists of a vast and diverse assemblage of microorganisms that play a pivotal role in maintaining host health. Nevertheless, a significant portion of the human gut microbiota remains uncultivated. Plasmids, a type of MGE, assume a critical function in the biological evolution and adaptation of bacteria to varying environments. To investigate the plasmids present within the gut microbiota community, we used the transposon-aided capture method (TRACA) to explore plasmids derived from the gut microbiota. In this study, fecal samples were collected from two healthy human volunteers and subsequently subjected to the TRACA method for plasmid isolation. Then, the complete sequence of the plasmids was obtained using the genome walking method, and sequence identity was also analyzed. A total of 15 plasmids were isolated. At last, 13 plasmids were successfully sequenced, of which 12 plasmids were highly identical to the plasmids in the National Center for Biotechnology Information (NCBI) database and were all small plasmids. Furthermore, a putative novel plasmid, named pMRPHD, was isolated, which had mobilized elements (oriT and oriV) and a potential type II restriction-modification (R-M) system encoded by DNA cytosine methyltransferase and type II restriction enzyme (Ban I), whose specific functions and applications warrant further exploration.

Antibacterial efficacy of an ultra-short palmitoylated random peptide mixture in mouse models of infection by carbapenem-resistant Klebsiella pneumoniae

Indiscriminate use of antibiotics has imposed a selective pressure for the rapid rise in bacterial resistance, creating an urgent need for novel therapeutics for managing bacterial infectious diseases while counteracting bacterial resistance. Carbapenem-resistant Klebsiella pneumoniae strains have become a major challenge in modern medicine due to their ability to cause an array of severe infections. Recently, we have shown that the 20-mer random peptide mixtures are effective therapeutics against three ESKAPEE pathogens. Here, we evaluated the toxicity, biodistribution, bioavailability, and efficacy of the ultra-short palmitoylated 5-mer phenylalanine:lysine (FK5P) random peptide mixtures against multiple clinical isolates of carbapenem-resistant K. pneumoniae and K. oxytoca. We demonstrate the FK5P rapidly and effectively killed various strains of K. pneumoniae, inhibited the formation of biofilms, and disrupted mature biofilms. FK5P displayed strong toxicity profiles both in vitro and in mice, with prolonged favorable biodistribution and a long half-life. Significantly, FK5P reduced the bacterial burden in mouse models of acute pneumonia and bacteremia and increased the survival rate in a mouse model of bacteremia. Our results demonstrate that FK5P is a safe and promising therapy against Klebsiella species as well as other ESKAPEE pathogens.

Therapeutic drug monitoring of carbapenem antibiotics in critically ill patients: an overview of principles, recommended dosing regimens, and clinical outcomes

INTRODUCTION

The importance of antibiotic treatment for sepsis in critically ill septic patients is well established. Consistently achieving the dose of antibiotics required to optimally kill bacteria, minimize the development of resistance, and avoid toxicity is challenging. The increasing understanding of the pharmacokinetic and pharmacodynamic (PK/PD) characteristics of antibiotics, and the effects of critical illness on key PK/PD parameters, is gradually re-shaping how antibiotics are dosed in critically ill patients.

AREAS COVERED

The PK/PD characteristics of commonly used carbapenem antibiotics, the principles of the application of therapeutic drug monitoring (TDM), and current as well as future methods of utilizing TDM to optimally devise dosing regimens will be reviewed. The limitations and evidence-base supporting the use of carbapenem TDM to improve outcomes in critically ill patients will be examined.

EXPERT OPINION

It is important to understand the principles of TDM in order to correctly inform dosing regimens. Although the concept of TDM is attractive, and the ability to utilize PK software to optimize dosing in the near future is expected to rapidly increase clinicians' ability to meet pre-defined PK/PD targets more accurately, current evidence provides only limited support for the use of TDM to guide carbapenem dosing in critically ill patients.

Assessing Contact Time and Concentration of Thymus vulgaris Essential Oil on Antibacterial Efficacy In Vitro

The overuse and misuse of antibiotics can pose the risk of spreading mutant strains that show antimicrobial resistance (AMR), with negative impacts on the management of bacterial infections and economic implications for healthcare systems. The research and development of natural antibacterial agents could be a priority in the next years to improve a number of effective antibacterial molecules and to reduce the AMR phenomenon and its development. The present study identified the most effective concentration and contact time of Thymus vulgaris L. essential oil (TEO) to obtain bactericidal effects in vitro against different Gram-positive and Gram-negative bacterial strains. Six clinically isolated (wild types) bacterial strains, (Citrobacter freundii, Enterococcus feciorum, Proteus mirabilis, Acinetobacter cioffi, Pseudomonas putrefaciens and Klebsiella pneumoniae) and two ATCCs (Staphylococcus aureus and Streptococcus mutans) were tested after 1 min, 3 min and 5 min of contact with TEO. The preliminary results on S. aureus after 24 h of incubation revealed a TEO concentration of 9.28 mg/mL (w/v) that completely inhibited bacteria growth, keeping cell viability. The total suppression of bacterial growth at all tested contact times was observed for all tested bacterial strains, and the results were confirmed after 48 h of incubation. Bacterial growth suppression was confirmed even with the presence of organic components. These preliminary results showed the in vitro antimicrobial efficacy of TEO against different Gram-positive and Gram-negative bacterial strains. Future studies are necessary to confirm the reproducibility of these results even on other strains and to define the exact molecular mechanisms of EOs in order to consider TEO as a valid alternative to classic antibiotic therapies and subsequently to reduce the occurrence of AMR.

Omadacycline for treatment of acute bacterial infections: a meta-analysis of phase II/III trials

OBJECTIVE

This study aims to assess the clinical efficacy and safety of omadacycline for the treatment of acute bacterial infections.

METHODS

A search of PubMed, Embase, Cochrane Library, and Clinical Trials was conducted up to July 1, 2022. We included only randomized controlled trials (RCTs), in which omadacycline and other antibiotics were evaluated for treating acute bacterial infections in adults. The primary outcomes were clinical response and microbiological response, whereas the secondary outcome was the risk of adverse events (AEs).

RESULTS

A total of seven RCTs involving 2841 patients with acute bacterial infection were included. Overall, our study illustrated that the clinical cure ratio of omadacycline was similar to the comparators in the treatment of acute bacterial infections (OR = 1.18, 95%CI = 0.96, 1.46, I² = 29%). Omadacycline had a microbiological eradication rate similar to comparators in the treatment of acute bacterial infections (OR = 1.02, 95%CI = 0.81, 1.29, I² = 42%). No statistical differences were observed between omadacycline and the comparators in terms of infection caused by Staphylococcus aureus (OR = 1.14, 95%CI = 0.80, 1.63, I² = 0%), methicillin-resistant S. aureus (MRSA, OR = 1.28, 95%CI = 0.73, 2.24, I² = 0%), methicillin-susceptible S. aureus (MSSA, OR = 1.12, 95%CI = 0.69, 1.81, I² = 0%), and Enterococcus faecalis (OR = 2.47, 95%CI = 0.36, 16.97, I² = 7%). A significant difference was found between omadacycline and the comparators for the risk of any AEs and treatment related AEs. The risk of discontinuation of the study drug due to an AEs was lower for omadacycline than for the comparators.

CONCLUSION

Omadacycline is as good as comparators in terms of efficacy and tolerance in the treatment of acute bacterial infections in adult patients. Thus, omadacycline is an appropriate option for antibiotic therapy in adult patients with acute bacterial infections.

Metal-Organic Frameworks and Their Biodegradable Composites for Controlled Delivery of Antimicrobial Drugs

Antimicrobial resistance (AMR) is a growing global crisis with an increasing number of untreatable or exceedingly difficult-to-treat bacterial infections, due to their growing resistance to existing drugs. It is predicted that AMR will be the leading cause of death by 2050. In addition to ongoing efforts on preventive strategies and infection control, there is ongoing research towards the development of novel vaccines, antimicrobial agents, and optimised diagnostic practices to address AMR. However, developing new therapeutic agents and medicines can be a lengthy process. Therefore, there is a parallel ongoing worldwide effort to develop materials for optimised drug delivery to improve efficacy and minimise AMR. Examples of such materials include functionalisation of surfaces so that they can become self-disinfecting or non-fouling, and the development of nanoparticles with promising antimicrobial properties attributed to their ability to damage numerous essential components of pathogens. A relatively new class of materials, metal-organic frameworks (MOFs), is also being investigated for their ability to act as carriers of antimicrobial agents, because of their ultrahigh porosity and modular structures, which can be engineered to control the delivery mechanism of loaded drugs. Biodegradable polymers have also been found to show promising applications as antimicrobial carriers; and, recently, several studies have been reported on delivery of antimicrobial drugs using composites of MOF and biodegradable polymers. This review article reflects on MOFs and polymer-MOF composites, as carriers and delivery agents of antimicrobial drugs, that have been studied recently, and provides an overview of the state of the art in this highly topical area of research.

Serratia marcescens antibiotic resistance mechanisms of an opportunistic pathogen: a literature review

Serratia marcescens is a ubiquitous bacterium from order Enterobacterales displaying a high genetic plasticity that allows it to adapt and persist in multiple niches including soil, water, plants, and nosocomial environments. Recently, S. marcescens has gained attention as an emerging pathogen worldwide, provoking infections and outbreaks in debilitated individuals, particularly newborns and patients in intensive care units. S. marcescens isolates recovered from clinical settings are frequently described as multidrug resistant. High levels of antibiotic resistance across Serratia species are a consequence of the combined activity of intrinsic, acquired, and adaptive resistance elements. In this review, we will discuss recent advances in the understanding of mechanisms guiding resistance in this opportunistic pathogen.

Novel tetrahydropyrimidinyl-substituted benzimidazoles and benzothiazoles: synthesis, antibacterial activity, DNA interactions and ADME profiling

A series of tetrahydropyrimidinyl-substituted benzimidazoles attached to various aliphatic or aromatic residues via phenoxymethylene were synthesised to investigate their antibacterial activities against selected Gram-positive and Gram-negative bacteria. The influence of the type of substituent at the C-3 and C-4 positions of the phenoxymethylene linker on the antibacterial activity was observed, showing that the aromatic moiety improved the antibacterial potency. Of all the evaluated compounds, benzoyl-substituted benzimidazole derivative 15a was the most active compound, particularly against the Gram-negative pathogens E. coli (MIC = 1 μg mL^-1) and M. catarrhalis (MIC = 2 μg mL^-1). Compound 15a also exhibited the most promising antibacterial activity against sensitive and resistant strains of S. pyogenes (MIC = 2 μg mL^-1). Significant stabilization effects and positive induced CD bands strongly support the binding of the most biologically active benzimidazoles inside the minor grooves of AT-rich DNA, in line with docking studies. The predicted physico-chemical and ADME properties lie within drug-like space except for low membrane permeability, which needs further optimization. Our findings encourage further development of novel structurally related 5(6)-tetrahydropyrimidinyl substituted benzimidazoles in order to optimize their antibacterial effect against common respiratory pathogens.

Polysorbate 21 Can Modulate the Antibacterial Potential of Two Pyrazol Derivatives

The combination of two compounds with known antimicrobial activity may, in some cases, be an effective way to limit the resistance to antibiotics of specific pathogens. Molecules carrying pyrazole moiety are well known for their bioactive properties and have wide applicability in the medical and pharmaceutical field. Surfactants have, among other useful properties, the ability to affect the growth of microorganisms. The paper reports on the effect of the combination of two pyrazole derivatives, (1H-pyrazol-1-yl) methanol 1-hydroxymethylpyrazole (SAM1) and 1,1'methandiylbis (1H-pyrazol) (AM1), with sorbitan monolaurate (polysorbate 21, Tween 21, T21) on the growth of Gram-positive and Gram-negative bacteria. The results demonstrated a different ability of this combination to inhibit Staphylococcus aureus and Escherichia coli. T21 intensified the inhibitory activity of the pyrazoles to a greater extent in the Gram-negative bacteria compared to the Gram-positive ones, a fact confirmed by time-kill experiments. The experimental data showed that the association of T21 with the pyrazoles led to the increased release of intracellular material and a more intense uptake of crystal violet, which indicates that the potentiation of the antibacterial effect was based on the modification of the normal permeability of bacterial cells. T21 acted as a modulating factor and increased the permeability of the membrane, allowing the accelerated penetration of the pyrazoles inside the bacterial cells. This fact is important in controlling the global increase in microbial resistance to antibiotics and antimicrobials and finding viable solutions to overcome the antibiotic crisis. The paper highlights the possibility of using non-toxic surfactant molecules in antimicrobial combinations with practical applications. This could widen the range of adjuvants in applications which would be useful in the control of resistant microorganisms.

The Spread of Antibiotic Resistance Genes In Vivo Model

Infections caused by antibiotic-resistant bacteria are a major public health threat. The emergence and spread of antibiotic resistance genes (ARGs) in the environment or clinical setting pose a serious threat to human and animal health worldwide. Horizontal gene transfer (HGT) of ARGs is one of the main reasons for the dissemination of antibiotic resistance in vitro and in vivo environments. There is a consensus on the role of mobile genetic elements (MGEs) in the spread of bacterial resistance. Most drug resistance genes are located on plasmids, and the spread of drug resistance genes among microorganisms through plasmid-mediated conjugation transfer is the most common and effective way for the spread of multidrug resistance. Experimental studies of the processes driving the spread of antibiotic resistance have focused on simple in vitro model systems, but the current in vitro protocols might not correctly reflect the HGT of antibiotic resistance genes in realistic conditions. This calls for better models of how resistance genes transfer and disseminate in vivo. The in vivo model can better mimic the situation that occurs in patients, helping study the situation in more detail. This is crucial to develop innovative strategies to curtail the spread of antibiotic resistance genes in the future. This review aims to give an overview of the mechanisms of the spread of antibiotic resistance genes and then demonstrate the spread of antibiotic resistance genes in the in vivo model. Finally, we discuss the challenges in controlling the spread of antibiotic resistance genes and their potential solutions.

A one health approach versus Acanthamoeba castellanii, a potential host for Morganella morganii

Acanthamoeba castellanii, known as the “Trojan horse of the microbial world,” is known to host a variety of microorganisms including viruses, yeasts, protists, and bacteria. Acanthamoeba can act as a vector and may aid in the transmission of various bacterial pathogens to potential hosts and are found in a variety of places, thus impacting the health of humans, animals, and the environment. These are interconnected in a system known as “one health.” With the global threat of antibiotic resistance, bacteria may avoid harsh conditions, antibiotics, and disinfectants by sheltering within Acanthamoeba. In this study, Acanthamoeba castellanii interaction with Morganella morganii, a Gram-negative bacterium was studied. Escherichia coli K1 interaction with Acanthamoeba was carried out as a control. Association, invasion, and survival assays were accomplished. Morganella morganii was found to associate, invade, and survive within Acanthamoeba castellanii. Additionally, Escherichia coli K1 was also found to associate, invade, and survive within the Acanthamoeba at a higher number in comparison to Morganella morganii. For the first time, we have shown that Morganella morganii interact, invade, and survive within Acanthamoeba castellanii, suggesting that Acanthamoeba may be a potential vector in the transmission of Morganella morganii to susceptible hosts. Taking a one health approach to tackle and develop disinfectants to target Acanthamoeba is warranted, as the amoebae may be hosting various microbes such as multiple drug-resistant bacteria and even viruses such as the novel coronavirus.