Antimicrobials

Unlocking the microbial treasure trove: advances in Streptomyces derived secondary metabolites in the battle against cancer

Streptomyces is widely recognized as the "biological factory" of specialized metabolites comprising a huge variety of bioactive molecules with diverse chemical properties. The potential of this Gram-positive soil bacteria to produce such diversified secondary metabolites with significant biological properties positions them as an ideal candidate for anticancer drug discovery. Some of the Streptomyces-derived secondary metabolites include siderophores (enterobactin, desferrioxamine), antibiotics (xiakemycin, dinactin) pigments (prodigiosin, melanin), and enzymes (L-methioninase, L-asperginase, cholesterol oxidase) which exhibit a pronounced anticancer effect on both in vitro and in vivo system. These secondary metabolites are endowed with antiproliferative, pro-apoptotic, antimetastatic, and antiangiogenic properties, presenting several promising characteristics that make them suitable candidates in the battle against this deadly disease. In this comprehensive review, we have dived deep and explored their history of discovery, their role as anticancer agents, underlying mechanisms, the approaches for the discovery of anticancer molecules from the secondary metabolites of Streptomyces (isolation of Streptomyces, characterization of bacterial strain, screening for anticancer activity and determination of in vitro and in vivo toxicity, structure-activity relationship studies, clinical translation, and drug development studies). The hurdles and challenges associated with this process and their future prospect were also illustrated. This review highlights the efficacy of Streptomyces as a "microbial treasure island" for novel anticancer agents, which warrants sustained research and exploration in this field to disclose more molecules from Streptomyces that are unidentified and to translate the clinical application of these secondary metabolites for cancer patients.

Novel antibacterial agents and emerging therapies in the fight against multidrug-resistant Acinetobacter baumannii

Acinetobacter baumannii, a multidrug-resistant pathogen, poses a critical challenge in healthcare settings due to its adaptability and limited treatment options. The global rise in antimicrobial resistance (AMR) has underscored the urgent need for novel therapeutic strategies to combat infections caused by extensively drug-resistant (EDR) and pan-drug-resistant (PDR) A. baumannii. Traditional antibiotic discovery methods, such as whole-cell screening, have fallen short, consistently identifying drugs prone to resistance. This review explores the discovery of new anti-bacterial agents targeting A. baumannii, focusing on emerging therapeutic approaches, including nanoparticle-based therapies, antimicrobial peptides, and antibiotic combination therapies. Nanoparticle-based approaches, leveraging enhanced penetration and multi-mechanistic action, show promise in overcoming resistance, though challenges such as toxicity and biocompatibility persist. Additionally, combination therapies, such as polymyxins with carbapenems, have demonstrated efficacy in clinical settings. This review also highlights the limitations of current therapies, the mechanisms of bacterial resistance, and the role of alternative strategies like bacteriophage therapy. Emphasis is placed on the need for further research into overcoming cross-resistance and enhancing therapeutic efficacy against A. baumannii. The review concludes by discussing the importance of advancing research into novel agents, optimizing dosage strategies, and addressing the challenges posed by toxicity to ensure the effective treatment of A. baumannii infections in both hospital and community settings.

Antibiotic use among hospitalised patients in Sierra Leone: a national point prevalence survey using the WHO survey methodology

OBJECTIVE

Inappropriate use of antibiotics is a major driver of antibiotic resistance. A few studies conducted in Africa have documented that about half of hospitalised patients who receive antibiotics should not have received them. A few hospital-based studies that have been conducted in Sierra Leone have documented a high usage of antibiotics in hospitals. Therefore, we conducted a nationwide point prevalence survey on antibiotic use among hospitalised patients in Sierra Leone.

DESIGN

We conducted a hospital-based, cross-sectional survey on the use of antibiotics using the WHO point prevalence survey methodology.

SETTING

The study was conducted in 26 public and private hospitals that are providing inpatient healthcare services.

PARTICIPANTS

All patients admitted to paediatric and adult inpatient wards before or at 08:00 on the survey date were enrolled.

OUTCOME MEASURES

Prevalence of antibiotic use, antibiotics Access, Watch and Reserve (AWaRe) categorisation, indication for antibiotic use prevalence and proportion of bacteria culture done.

RESULTS

Of the 1198 patient records reviewed, 883 (73.7%, 95% CI 71.1% to 76.2%) were on antibiotics. Antibiotic use was highest in the paediatric wards (306, 85.7%), followed by medical wards (158, 71.2%), surgical wards (146, 69.5%), mixed wards (97, 68.8%) and lowest in the obstetrics and gynaecology wards (176, 65.7%). The most widely prescribed antibiotics were metronidazole (404, 22.2%), ceftriaxone (373, 20.5%), ampicillin (337, 18.5%), gentamicin (221, 12.1%) and amoxicillin (90, 5.0%). Blood culture was only done for one patient and antibiotic treatments were given empirically. The most common indication for antibiotic use was community-acquired infection (484, 51.9%) followed by surgical prophylaxis (222, 23.8%).

CONCLUSION

There was high usage of antibiotics in hospitals in Sierra Leone as the majority of patients admitted received an antibiotic. This has the potential to increase the burden of antibiotic resistance in the country. We, therefore, recommend the establishment of hospital antimicrobial stewardship programmes according to the WHO core components.

Crosspteryx fibrifuga leaf extract enhances host resistance to Trypanosoma congolense infection in mice by regulating host immune response and disrupting the activity of parasite superoxide dismutase enzyme

African trypanosomiasis, a neglected tropical disease, is caused by diverse species of the protozoan parasite belonging to the genus Trypanosoma. Although anti-trypanosomal medications exist, the increase in drug resistance and persistent antigenic variation has necessitated the development of newer and more efficacious therapeutic agents which are selectively toxic to the parasite. In this study, we assessed the trypanocidal efficacy of Crosspteryx fibrifuga leaf extract (C.f/L-extract) in vitro. Following treatment of T. congolense parasites with C.f/L-extract, we observed a significant decrease in parasite number and an elevation in the expression of the apoptotic markers, Annexin V and 7-Aminoactinomycin D (7AAD). Interestingly, at the same concentration (50 μg/mL), C.f/L-extract was not cytotoxic to murine whole splenocytes. We also observed a significant increase in pro-inflammatory cytokines and nitric oxide secretion by bone marrow derived macrophages following treatment with C.f/L-extract (10 μg/mL and 50 μg/mL) compared to PBS treated controls, suggesting that the extract possesses an immune regulatory effect. Treatment of T. congolense infected mice with C.f/L-extract led to significant decrease in parasite numbers and a modest increase in mouse survival compared to PBS treated controls. In addition, there was a significant increase in CD4+IFN-γ+ T cells and a decrease in CD4+IL-10+ T cells in the spleens of T. congolense infected mice treated with C.f/L-extract. Interestingly, C.f/L-extract treatment decreased the activity of superoxide dismutase (an enzyme that protects unicellular organisms from oxidative stress) in T. congolense parasites but not in splenocytes. Collectively, our study has identified C.f/L-extract as a potential anti-trypanosomal agent that warrant further investigation and possibly explored as a treatment option for T. congolense infection.

Prevalence and Antimicrobial Susceptibility Profile of Salmonella and Shigella among Diarrheic Patients Attending Selected Health Facilities in Addis Ababa, Ethiopia

Diarrhea is one of the important public health problems in developing countries. Salmonella and Shigella species are the major bacterial causal agents of diarrhea. The increasing burden of antimicrobial resistance is posing difficulty in the treatment of these pathogens. This study aimed to assess the occurrence of Salmonella and Shigella in the feces of diarrheic patients receiving health services in Addis Ababa, Ethiopia, and to determine their antimicrobial susceptibility profile. A cross-sectional study involving 13 health centers was conducted where 428 diarrheic patients were recruited. Standard microbiology techniques were used to isolate Salmonella and Shigella from stool samples. In addition, Salmonella isolates were confirmed by polymerase chain reaction (PCR). The Kirby-Bauer disc diffusion method was employed to assess susceptibility to 11 antimicrobials for each of the Salmonella and Shigella isolates. The prevalence of Salmonella and Shigella spp. among diarrheic patients was 8.4%; n = 36 and 5.6%; n = 24, respectively. Thirty (83.3%) of Salmonella isolates were susceptible to all antimicrobials tested, whereas 4 (10.8%) of isolates were resistant to 2 or more antimicrobials and 2 (5.6%) were multidrug resistant. Resistance to ampicillin was recorded in only one (2.7%) of Salmonella isolates; however, resistance to ampicillin was recorded in 12 (50%) of the Shigella isolates. Half of the Shigella isolates (n = 12) were resistant to 2 or more antimicrobials while 5 (20.8%) of them were resistant to 3 or more antimicrobials. The overall rate of resistance to antimicrobials was more common in Shigella compared to Salmonella isolates. In conclusion, Salmonella and Shigella were isolated from the feces of diarrheic patients, with a higher rate of antimicrobial resistance in Shigella isolates, which could make the treatment of shigellosis challenging. Therefore, increasing hygienic practices during food preparation to reduce the burden of Salmonella and Shigella infection and prudent use of antimicrobials are recommended to limit the spread of antimicrobial resistant strains.

Nanotechnology Involved in Treating Urinary Tract Infections: An Overview

Considered as the most frequent contaminations that do not require hospitalization, urinary tract infections (UTIs) are largely known to cause significant personal burdens on patients. Although UTIs overall are highly preventable health issues, the recourse to antibiotics as drug treatments for these infections is a worryingly spread approach that should be addressed and gradually overcome in a contemporary, modernized healthcare system. With a virtually alarming global rise of antibiotic resistance overall, nanotechnologies may prove to be the much-needed 'lifebuoy' that will eventually suppress this prejudicial phenomenon. This review aims to present the most promising, currently known nano-solutions, with glimpses on clinical and epidemiological aspects of the UTIs, prospective diagnostic instruments, and non-antibiotic treatments, all of these engulfed in a comprehensive overview.

Antimicrobial agents and microbial ecology

Antimicrobials are therapeutic substances used to prevent or treat infections. Disinfectants are antimicrobial agents applied to non-living surfaces. Every year, several thousand tonnes of antimicrobials and their by-products are released into the environment and in particular into the aquatic environment. This type of xenobiotic has ecological consequences in the natural environment but also in technological environments such as wastewater treatment plants and methane fermentation sewage sludge treatment plants. The constant exposure of microbial communities not only to high concentrations but also to sub-inhibitory concentrations of antibiotics is a key element in the development of antibiotic resistance in aquatic environments and in soils. The future of antimicrobials lies in the development of biosourced or bioinspired molecules. The observation and deciphering of interactions between living organisms is the key to this development.

The war against bacteria, from the past to present and beyond

INTRODUCTION

The human defense against microorganisms dates back to the ancient civilizations, with attempts to use substances from vegetal, animal, or inorganic origin to fight infections. Today, the emerging threat of multidrug-resistant bacteria highlights the consequences of antibiotics inappropriate use, and the urgent need for novel effective molecules.

METHODS AND MATERIALS

We extensively researched on more recent data within PubMed, Medline, Web of Science, Elsevier's EMBASE, Cochrane Review for the modern pharmacology in between 1987 - 2021. The historical evolution included a detailed analysis of past studies on the significance of medical applications in the ancient therapeutic field.

AREAS COVERED

We examined the history of antibiotics development and discovery, the most relevant biochemical aspects of their mode of action, and the biomolecular mechanisms conferring bacterial resistance to antibiotics.

EXPERT OPINION

The list of pathogens showing low sensitivity or full resistance to most currently available antibiotics is growing worldwide. Long after the 'golden age' of antibiotic discovery, the most novel molecules should be carefully reserved to treat serious bacterial infections of susceptible bacteria. A correct diagnostic and therapeutic procedure can slow down the spreading of nosocomial and community infections sustained by multidrug-resistant bacterial strains.