Antibacterial Drug Development: A New Approach Is Needed for the Field to Survive and Thrive

Phage-antibiotic synergism against Salmonella typhi isolated from stool samples of typhoid patients

BACKGROUND

Typhoid fever is a fatal disease in humans that is caused by Salmonella typhi. S. typhi infections need immediate antibiotic therapy, and their extensive use has led to multidrug-resistant (MDR) pathogens. The use of bacteriophages is becoming a new way to treat these resistant bacteria. This research was directed to bacteriophage isolation against S. typhi and to determine phage-antibiotic synergism.

AIMS

To isolate bacteriophages targeting S. typhi, the causative agent of typhoid fever, and investigate their potential synergistic effects when combined with antibiotics.

STUDY DESIGN

A cross-sectional study.

METHODS

The Widal test was positive; twenty diarrheal stool samples were taken, and for confirmation of S. typhi, different biochemical tests were performed. The disc-diffusion technique was used to determine antimicrobial resistance, and the double agar overlay method was used for bacteriophage isolation from sewage water against S. typhi. To test antibiotic-phage synergism, the S. typhi bacteria was treated by phages together with varying antibiotic concentrations.

RESULTS

Eleven samples were positive for S. typhi with black colonies on SS-agar. These were catalase and MR positive with alkali butt on TSI. Clear plaques were observed after the agar overlay. Isolated phages were stable at various pH and temperature levels. Synergism was observed on agar plate. The zone was enlarged when phages were combined with bacterial lawn culture and ciprofloxacin disk. Bacterial growth inhibition had a significant p-value of 0.03 in titration plates, with the phage-ciprofloxacin combination being more effective than the phage and antibiotic alone.

CONCLUSION

The study highlights the synergistic effects of isolated bacteriophages with antibiotics, which are not only effective against S. typhi infection but also decrease antibiotic resistance.

Antimicrobial activity in Asterceae: The selected genera characterization and against multidrug resistance bacteria

Plants from the Asteraceae family are widely used as ethno medicines to treatment parasitic, malaria, hematemesis, pruritus, pyretic, anthelmintic, wound healing. The aim of this review is to provide an overview of Asteraceae plants antimicrobial activity. The most relevant results from the published studies are summarized and discussed. The species in genus of Artemisia, Echinacea, Centaurea, Baccharis, and Calendula showed antimicrobial activity. Most of these species are usually used as ethno medicines to treat infection, inflammation, and parasitics. The effective part or component for antimicrobial was essential oil and crude extract, and essential oil attracted more attention. It was also reported that nanoparticles coated with crude extract were effective against multidrug resistant bacteria. For multidrug resistant bacteria study, the species in Armtemisia were the most investigated, and Staphylococcus aureus and Escherichia coli were the most studied multidrug resistant strains. The antimicrobial activity was evaluated mainly based on the results of minimum inhibitory concentration (MIC). Few reports have been reported on minimum bactericide concentration (MBC) and its antibacterial mechanisms. According to the reported study results, some plants in Asteraceae have the potential to be developed as bacteriostatic agents and against multidrug resistant bacteria. However, most studies are still in vitro, further clinical and applied studies are needed.

Evaluation of the efficacy of the antimicrobial peptide HJH-3 in chickens infected with Salmonella Pullorum

As a promising substitute for antibiotics, increasing attention has been given to the clinical application of antimicrobial peptides (AMPs). In this study, the mode of action of the HJH-3 against Salmonella Pullorum was investigated. The structure and properties of HJH-3 were examined in silico, and minimum inhibitory concentrations (MICs) were determined to evaluate its antimicrobial spectrum. The time-kill kinetics of HJH-3 was determined. The hemolytic activity of HJH-3 was determined by measuring the hemoglobin ultraviolet absorption value, and the cytotoxicity was determined using a CCK-8 kit. The protective effect of HJH-3 on chickens infected with S. Pullorum was evaluated in vivo. The results demonstrated that HJH-3 exhibited strong antibacterial activity against Gram-negative pathogens at MIC values of 1.5625-25 μg/mL and against Gram-positive pathogens at MIC values of 25-50 μg/mL. HJH-3 also showed activity against the Candida albicans (100 μg/mL) and Bacillus subtilis (6.25-12.5 μg/mL). HJH-3 at 100 μg/mL completely killed S. Pullorum after co-incubation for 6 h. Likewise, the hemolysis rate of CRBCs treated with 100 μg/mL HJH-3 (7.31%) was lower than that of CRBCs treated with 100 μg/mL pexiganan (40.43%). Although the hemolysis rate of CRBCs treated with 400 μg/mL HJH-3 was increased to 13.37%, it was much lower than that of 400 μg/mL pexiganan (57.27%). In regards to cytotoxicity, HJH-3 had almost no-effect on the CEF proliferation, pexiganan decreased CEFs proliferation from 56.93 to 31.00% when increasing the concentration from 50 to 200 μg/mL. In a chicken infection model, the results showed that the antibiotic prevention and HJH-3 prevention groups exhibited the best treatment effect, with the chickens being protected from the lethal dose of S. Pullorum, a decreased number of bacteria in the blood and spleen, and less pathological changes in intestinal segments. The prevention of infection by HJH-3 was similar to that by Ampicillin; the effect of treatment after infection was lower than that of treatment before infection, and the survival rate of infected chicks treated with HJH-3 was 70%, which was still higher than that of the infected chickens. These results suggest that HJH-3 has good clinical application potential and can be used as a substitute for antibiotics for the prevention and treatment of S. Pullorum infection.

Promising advances in nanobiotic-based formulations for drug specific targeting against multidrug-resistant microbes and biofilm-associated infections

Antimicrobial agents and alternative strategies to combat bacterial infections have become urgent due to the rapid development of multidrug-resistant bacteria caused by the misuse and overuse of antibiotics, as well as the ineffectiveness of antibiotics against difficult-to-treat infectious diseases. Nanobiotics is one of the strategies being explored to counter the increase in antibiotic-resistant bacteria. Nanobiotics are antibiotic molecules encapsulated in nanoparticles or artificially engineered pure antibiotics that are ≤ 100 nm in size in at least one dimension. Formulation scientists recognize nanobiotic delivery systems as an effective strategy to overcome the limitations associated with conventional antibiotic therapy. This review highlights the general mechanisms by which nanobiotics can be used to target resistant microbes and biofilm-associated infections. We focus on the design elements, properties, characterization, and toxicity assessment of organic nanoparticles, inorganic nanoparticle and molecularly imprinted polymer-based nano-formulations that can be designed to improve the efficacy of nanobiotic formulation.

The importance of pharmacokinetics and pharmacodynamics in antimicrobial drug development and their influence on the success of agents developed to combat resistant gram negative pathogens: A review

A deep understanding of an antimicrobial’s critical pharmacokinetic and pharmacodynamic properties is crucial towards optimizing its use in patients and bolstering the drug development program. With the growing threat of antimicrobial resistance and decline in antimicrobial development, the advancement of complex and rigorous pharmacokinetic and pharmacodynamic studies over a short time span has renewed confidence in the value of pharmacokinetic and pharmacodynamic studies and allowed it to become fundamental component of a robust drug development program with high chances of successful approval. In addition, recent guidance by various regulatory bodies have reinforced that a strong and dedicated focus on pharmacokinetics and pharmacodynamics throughout research and development lead to the use of an optimized dosing regimen in Phase 3 trials, improving the probability of drug approval. The objective of this review is to demonstrate the importance of pharmacokinetic and pharmacodynamic studies in the drug development decision-making process by highlighting the developments in pharmacokinetic and pharmacodynamic methods and discuss the role of pharmacokinetic and pharmacodynamic studies in antimicrobial successes and failures.

Benefits of Combined Phage–Antibiotic Therapy for the Control of Antibiotic-Resistant Bacteria: A Literature Review

With the increase in bacterial resistance to antibiotics, more and more therapeutic failures are being reported worldwide. The market for antibiotics is now broken due to the high cost of developing new molecules. A promising solution to bacterial resistance is combined phage–antibiotic therapy, a century-old method that can potentiate existing antibiotics by prolonging or even restoring their activity against specific bacteria. The aim of this literature review was to provide an overview of different phage–antibiotic combinations and to describe the possible mechanisms of phage–antibiotic synergy.

Nanoantibiotics to fight multidrug resistant infections by Gram-positive bacteria: hope or reality?

The spread of antimicrobial resistance in Gram-positive pathogens represents a threat to human health. To counteract the current lack of novel antibiotics, alternative antibacterial treatments have been increasingly investigated. This review covers the last decade's developments in using nanoparticles as carriers for the two classes of frontline antibiotics active on multidrug-resistant Gram-positive pathogens, i.e., glycopeptide antibiotics and daptomycin. Most of the reviewed papers deal with vancomycin nanoformulations, being teicoplanin- and daptomycin-carrying nanosystems much less investigated. Special attention is addressed to nanoantibiotics used for contrasting biofilm-associated infections. The status of the art related to nanoantibiotic toxicity is critically reviewed.

Improved bactericidal efficacy and thermostability of Staphylococcus aureus-specific bacteriophage SA3821 by repeated sodium pyrophosphate challenges

As antibiotic resistance is being a threat to public health worldwide, bacteriophages are re-highlighted as alternative antimicrobials to fight with pathogens. Various wild-type phages isolated from diverse sources have been tested, but potential mutant phages generated by genome engineering or random mutagenesis are drawing increasing attention. Here, we applied a chelating agent, sodium pyrophosphate, to the staphylococcal temperate Siphoviridae phage SA3821 to introduce random mutations. Through 30 sequential sodium pyrophosphate challenges and random selections, the suspected mutant phage SA3821^M was isolated. SA3821^M maintained an intact virion morphology, but exhibited better bactericidal activity against its host Staphylococcous aureus CCARM 3821 for up to 17 h and thermostability than its parent, SA3821. Sodium pyrophosphate-mediated mutations in SA3821^M were absent in lysogenic development genes but concentrated (83.9%) in genes related to the phage tail, particularly in the tail tape measure protein, indicating that changes in the tail module might have been responsible for the altered traits. This intentional random mutagenesis through controlled treatments with sodium pyrophosphate could be applied to other phages as a simple but potent method to improve their traits as alternative antimicrobials.

Understanding eco-immunology of bacterial zoonoses and alternative therapeutics toward "One Health"

The current review identifies key bacterial zoonoses, the understanding of comparative immunology, evolutionary trade-offs between emerging bacterial pathogens and their dynamics on both arms of immunity. The several gaps in the literature limit our understanding of spread of prominent bacterial zoonotic diseases and the host-pathogen interactions that may change in response to environmental and social factors. Gaining a more comprehensive understanding of how anthropogenic activities affects the spread of emerging zoonotic diseases, is essential for predicting and mitigating future disease emergence through fine-tuning of surveillance and control measures with respect to different pathogens. This review highlights the urgent need to increase understanding of the comparative immunity of animal reservoirs, design of vaccines according to the homology in host-pathogen interactions, and the alternative strategies to counter the risk of bacterial pathogenic spillover to humans with eventual spread of zoonotic diseases.

Challenges and opportunities in the discovery, development, and commercialization of pathogen-targeted antibiotics

The use of antibiotics directly correlates with the increase in antimicrobial resistance (AMR). Targeting novel antibiotics to patients with multidrug-resistant (MDR) pathogens should enhance their durability and slow development of resistance. The discovery, development, and clinical adoption of pathogen-targeted antibiotics have been hampered by technical and regulatory challenges. Growing insights into bacterial physiology and mechanisms of resistance, innovative clinical trial designs, streamlined regulatory approval pathways, and availability of rapid bacterial diagnostics are recent developments that can help address those challenges. Pathogen-targeted antibiotics provide an opportunity to treat patients with the right drug at the right time, leading to improved patient outcomes and better antimicrobial stewardship. Patient-centered pricing and reimbursement reform is needed to incentivize innovation.

Anti-phage serum antibody responses and the outcome of phage therapy

We examined the appearance of serum anti-phage antibodies in 25 patients with chronic sinusitis treated with phage therapy (PT). Approximately 30% of patients with weak antibody responses responded positively to PT, which was similar to the results of treatment achieved in a group of patients with high antibody production. In addition, there was no correlation between antibody level and the outcome of PT. These data, derived from a homogenous group of patients, confirm our earlier findings suggesting that the prognostic significance of serum anti-phage antibodies for the outcome of PT should be determined by relevant clinical trials.