Mechanisms of antimicrobial resistance: their clinical relevance in the new millennium

Anti-bacterial efficacy of Boron Nanosheet against clinical isolates and its in vivo toxicity assessment using Artemiasalina

Microbes have been increasing their potential against newly developed drugs and antibiotics daily. The increased microbial drug resistance is still a challenging societal inconvenience. 2D nanomaterials, such as graphene, fascinate researchers with their unique physical and chemical properties and have a major role in current science and technology. Nowadays, researchers have been replacing graphene with its analogous 2D material, borophene, which is a single layer of boron with a honeycomb plane. Boron nanosheets which are theoretically investigated, have been synthesized by various top-down and bottom-up approaches. Our study focuses on synthesizing boron-based material from the precursor MgB2 which possesses a honeycomb boron structure with sandwiched Mg atoms. The Mg atoms have been selectively removed using the chelating agents at alkaline pH. The synthesized boron nanosheets have been characterized by FT-IR, Raman, XRD, FESEM, EDS, and TGA. The formation of B-H-B, B-B and B-O bond is confirmed by FT-IR and Raman spectra. It is also evident from XPS spectra which possess B1s spectra at 193 eV. The efficient chelation and exfoliation is confirmed by EDS and FESEM analysis which shows the presence of boron and trace amount of Mg with bark like projections. Though there are several studies on antibacterial activity of compounds, generally the studies are with laboratory cultures of bacterial strains. Clinical studies offer more valid results and are very sparse in literature. The use of clinical strains in the present study is one of the novelty. It has also been analyzed for its anti-bacterial activity against clinical strains of B. subtilis, S. aureus, E. coli, and K. pneumonia. Boron nanosheets possess an enhanced zone of inhibition (8 mm, 11 mm) against clinical strains of B. subtilis where the micro dilution studies show MIC and MBC values as 125 μg and 62.5 μg. The in vivo toxicity studies carried out using Brine Shrimp Lethality Assay reveal higher LC50 values of boron nanosheets (>1 mg/ml), which in turn portrays its non-toxic nature. Thus, the synthesized boron nanosheets are toxic to multidrug-resistant B. subtilis where it is non-toxic to mammalian cells. Thus, the study could advance the applications of borophene in biomedical applications.

Application research and progress of microalgae as a novel protein resource in the future

Economic growth and health awareness spotlight opportunities and challenges in the food industry, particularly with decreasing arable land, climate change, dwindling freshwater resources, and pollution affecting traditional protein sources. Microalgae have emerged as a promising alternative, with higher protein content, better nutritional quality, and greater environmental resilience compared to conventional crops. They offer a protein balance comparable to meat, making them a sustainable protein source with health benefits like antioxidants, cardiovascular support, and anti-inflammatory properties. Improving the protein content of microalgae through optimized cultivation techniques is crucial to fully realize its potential as a novel food source. While there are already microalgae-based food products in the market, challenges remain in utilizing microalgal protein for widespread food production, emphasizing the need for further research. This review article explores the impact of microalgae culture conditions on protein content, the physicochemical and nutritional characteristics of microalgal protein, the health advantages of microalgal proteins and their derivatives, as well as research on separating and purifying microalgal proteins and their derivatives. It also delves into the current opportunities and obstacles of microalgal proteins and their derivatives as food, highlighting the potential for investigating the link between microalgal protein food and human health.

Antimicrobial Resistance in the WHO African Region: A Systematic Literature Review 2016-2020

Antimicrobial resistance (AMR) is a significant global public health threat. This review presents the most recent in-depth review of the situation of the main AMR types in relation to the most commonly prescribed antibiotics in the World Health Organization (WHO) African Region. Underlying genes of resistance have been analyzed where possible. A search to capture published research data on AMR from articles published between 2016 and 2020 was done using PubMed and Google Scholar, with rigorous inclusion/exclusion criteria. Out of 48003 articles, only 167 were included. Among the tested gram-negative bacteria species, Klebsiella spp. remain the most tested, and generally the most resistant. The highest overall phenotypic resistance for imipenem was reported in E. coli, whereas for meropenem, E. coli and Haemophilus spp. showed an equal resistance proportion at 2.5%. For gram-positive bacteria, Streptococcus pneumoniae displayed high resistance percentages to trimethoprim/sulfamethoxazole (64.3%), oxacillin (32.2%), penicillin (23.2%), and tetracycline (28.3%), whereas Staphylococcus aureus contributed to 22.8% and 10% resistance to penicillin and oxacillin, respectively. This review shows that AMR remains a major public health threat. The present findings will help public health decision-makers in developing efficient preventive strategies and adequate policies for antibiotic stewardship and surveillance in line with the global action plan for AMR.

Facile Synthesis of 5-Bromo-N-Alkylthiophene-2-Sulfonamides and Its Activities Against Clinically Isolated New Delhi Metallo-β-Lactamase Producing Klebsiella pneumoniae ST147

Introduction

New Delhi Metallo-β-lactamase producing Klebsiella pneumoniae (NDM-1-KP) sequence type (ST) 147 poses a significant threat in clinical settings due to its evolution into two distinct directions: hypervirulence and carbapenem resistance. Hypervirulence results from a range of virulence factors, while carbapenem resistance stems from complex biological mechanisms. The NDM-1-KP ST147 clone has emerged as a recent addition to the family of successful clones within the species.

Methods

In this study, we successfully synthesized 5-bromo-N-alkylthiophene-2-sulfonamides (3a-c) by reacting 5-bromothiophene-2-sulfonamide (1) with various alkyl bromides (2) using LiH. We also synthesized a series of compounds (4a-g) from compound (3b) using the Suzuki-Miyaura cross-coupling reaction with fair to good yields (56-72%). Further, we screened the synthesized molecules against clinically isolated New Delhi Metallo-β-lactamase producing Klebsiella pneumoniae ST147. Subsequently, we conducted in-silico tests on compound 3b against a protein extracted from NDM-KP ST147 with PDB ID: 5N5I.

Results

The compound (3b) with favourable drug candidate status, MIC of 0.39 μg/mL, and MBC of 0.78 μg/mL. This low molecular weight compound exhibited the highest potency against the resistant bacterial strains. The in-silico tests revealed that the compound 3b against a protein extracted from NDM-KP ST147 with PDB ID: 5N5I demonstrated H-bond and hydrophobic interactions.

Conclusion

The 5-bromo-N-alkylthiophene-2-sulfonamides displayed antibacterial efficacy against New Delhi Metallo-β-lactamase producing Klebsiella pneumoniae ST147. After the in-vivo trial, this substance might offer an alternative therapeutic option.

Climate warming, environmental degradation and pollution as drivers of antibiotic resistance

Antibiotic resistance is a major challenge to public health, but human-caused environmental changes have not been widely recognized as its drivers. Here, we provide a comprehensive overview of the relationships between environmental degradation and antibiotic resistance, demonstrating that the former can potentially fuel the latter with significant public health outcomes. We describe that (i) global warming favors horizontal gene transfer, bacterial infections, the spread of drug-resistant pathogens due to water scarcity, and the release of resistance genes with wastewater; (ii) pesticide and metal pollution act as co-selectors of antibiotic resistance mechanisms; (iii) microplastics create conditions promoting and spreading antibiotic resistance and resistant bacteria; (iv) changes in land use, deforestation, and environmental pollution reduce microbial diversity, a natural barrier to antibiotic resistance spread. We argue that management of antibiotic resistance must integrate environmental goals, including mitigation of further increases in the Earth's surface temperature, better qualitative and quantitative protection of water resources, strengthening of sewage infrastructure and improving wastewater treatment, counteracting the microbial diversity loss, reduction of pesticide and metal emissions, and plastic use, and improving waste recycling. These actions should be accompanied by restricting antibiotic use only to clinically justified situations, developing novel treatments, and promoting prophylaxis. It is pivotal for health authorities and the medical community to adopt the protection of environmental quality as a part of public health measures, also in the context of antibiotic resistance management.

In Silico Identification and Characterization of Drug Targets in Streptococcus pneumoniae ATCC 700669 (Serotype 23F) by Subtractive Genomics

Streptococcus pneumoniae (S. pneumoniae) is an important pathogen worldwide that causes pneumococcal infections which are related to high rates of morbidity and mortality especially in young children, older adults, and immune-compromised persons. Antibiotic resistance in S. pneumoniae is a serious problem across the world from time to time, resulting in treatment failure and diminished value of older medicines. Therefore, the objective of this study was to identify new putative drug targets against S. pneumoniae serotype 23F by using subtractive genomics. By using bioinformatics tools such as NCBI, UniProt KB, PDB, KEGG, DEG, PSORTb, CD hit, DrugBank database, and other softwares, proteins involved in unique metabolic pathways of S. pneumoniae serotype 23F were studied. The result indicates that this serotype consists of 97 metabolic pathways of which 74 are common with that of human, and 23 pathways are unique to the serotype 23F. After investigation and analysis of essentiality, nonhomology, subcellular localization, having drug targets, and enzymatic activity, four proteins were prioritized as druggable targets. These druggable proteins include UDP-N-acetylglucosamine 1-carboxyvinyltransferase, UDP-N-acetyl muramate dehydrogenase, D-alanine-D-alanine ligase, and alanine racemase that are found in S. pneumoniae serotype 23F. All these four proteins are essential, are nonhomologous with human proteins, have drug targets, and are located in cell cytoplasm. Therefore, the authors recommend these proteins to be used for efficient drug design against S. pneumoniae serotype 23F after experimental validation for essentiality and druggability.

Study of Antimicrobial Resistance (AMR) in Shigella spp. in India

Antimicrobial agents are essential in reducing illness and mortality brought on by infectious diseases in both humans and animals. However, the therapeutic effect of antibiotics has diminished due to an increase in antimicrobial drug resistance (AMR). This article provides a retrospective analysis of AMR in Shigella infections in India, showing a rise in resistance that has contributed to a global burden. Shigella spp. are widespread and the second-leading cause of diarrheal death in people of all ages. The frequency and mortality rates of Shigella infections are decreased by antibiotic treatment. However, the growth of broad-spectrum antibiotic resistance is making it more difficult to treat many illnesses. Reduced cell permeability, efflux pumps, and the presence of enzymes that break down antibiotics are the causes of resistance. AMR is a multifaceted and cross-sectoral problem that affects humans, animals, food, and the environment. As a result, there is a growing need for new therapeutic approaches, and ongoing surveillance of Shigella spp. infections which should definitely be improved for disease prevention and management. This review emphasizes on the epidemiological data of India, and antimicrobial resistance in Shigella spp.

pH Window for High Selectivity of Ionizable Antimicrobial Polymers toward Bacteria

Antimicrobial polymers exhibit great potential for treating drug-resistant bacteria; however, designing antimicrobial polymers that can selectively kill bacteria and cause relatively low toxicity to normal tissues/cells remains a key challenge. Here, we report a pH window for ionizable polymers that exhibit high selectivity toward bacteria. Ionizable polymer PC6A showed the greatest selectivity (131.6) at pH 7.4, exhibiting low hemolytic activity and high antimicrobial activity against bacteria, whereas a very high or low protonation degree (PD) produced relatively low selectivity (≤35.6). Bactericidal mechanism of PC6A primarily comprised membrane lysis without inducing drug resistance even after consecutive incubation for 32 passages. Furthermore, PC6A demonstrated synergistic effects in combination with antibiotics at pH 7.4. Hence, this study provides a strategy for designing selective antimicrobial polymers.

An insight into endophytic antimicrobial compounds: an updated analysis

Resistance in micro-organisms against antimicrobial compounds is an emerging phenomenon in the modern era as compared to the traditional world which brings new challenges to discover novel antimicrobial compounds from different available sources, such as, medicinal plants, various micro-organisms, like, bacteria, fungi, algae, actinomycetes, and endophytes. Endophytes reside inside the plants without exerting any harmful impact on the host plant along with providing ample of benefits. In addition, they are capable of producing diverse antimicrobial compounds similar to their host, allowing them to serve as useful micro-organism for a range of therapeutic purposes. In recent years, a large number of studies on the antimicrobial properties of endophytic fungi have been carried out globally. These antimicrobials have been used to treat various bacterial, fungal, and viral infections in humans. In this review, the potential of fungal endophytes to produce diverse antimicrobial compounds along with their various benefits to their host have been focused on. In addition, classification systems of endophytic fungi as well as the need for antimicrobial production with genetic involvement and some of the vital novel antimicrobial compounds of endophytic origin can further be utilized in the pharmaceutical industries for various formulations along with the role of nanoparticles as antimicrobial agents have been highlighted.

Potential of nanocarriers using ABC transporters for antimicrobial resistance

Some existing therapies such as antimicrobial regimens, drug combinations, among others, are employed for the treatment of infections that are a threat to the healthcare industry owing to low drug efficacy, increasing dosage regimes, mutation in bacteria and poor pharmacokinetics/pharmacodynamics properties of drugs. Overuse of antibiotics is fostering the emergence and spread of inherent microorganisms that confer temporary and permanent resistance. Nanocarriers accompanying the ABC transporter efflux mechanism are considered 'magic bullets' (i.e., effective antibacterial agents) and can traverse the multidrug-resistant obstacle owing to their multifunctional capabilities (e.g., nanostructure, variability in in vivo functions, etc.) by interfering with normal cell activity. This review focuses on novel applications of the ABC transporter pump by nanocarriers to overcome the resistance caused by the various organs of the body. Teaser: Nanocarriers, the ABC transporter and overcoming multidrug resistance.

Phage-bacterial evolutionary interactions: experimental models and complications

Phage treatment of bacterial infections has offered some hope even as the crisis of antimicrobial resistance continues to be on the rise. However, bacterial resistance to phage is another looming challenge capable of undermining the effectiveness of phage therapy. Moreover, the consideration of including phage therapy in modern medicine calls for more careful research around every aspect of phage study. In an attempt to adequately prepare for the events of phage resistance, many studies have attempted to experimentally evolve phage resistance in different bacterial strains, as well as train phages to evolve counter-infectivity of resistant bacterial mutants, in view of answering such questions as coevolutionary dynamics between phage and bacteria, mechanisms of phage resistance, fitness costs of phage resistance on bacteria, etc. In this review, we summarised many such studies and by careful examination, highlighted critical issues to the outcome of phage therapy. We also discuss the insufficiency of many of these in vitro studies to represent actual disease conditions during phage application, alongside other complications that exist in phage-bacterial evolutionary interactions. Conclusively, we present the exploitation of phage-bacterial interactions for successful infection managements, as well as some future perspectives to direct phage research.

Fragment-Based Lead Discovery Strategies in Antimicrobial Drug Discovery

Fragment-based lead discovery (FBLD) is a powerful application for developing ligands as modulators of disease targets. This approach strategy involves identification of interactions between low-molecular weight compounds (100-300 Da) and their putative targets, often with low affinity (K_D ~0.1-1 mM) interactions. The focus of this screening methodology is to optimize and streamline identification of fragments with higher ligand efficiency (LE) than typical high-throughput screening. The focus of this review is on the last half decade of fragment-based drug discovery strategies that have been used for antimicrobial drug discovery.

Antimicrobial Peptides and Cationic Nanoparticles: A Broad-Spectrum Weapon to Fight Multi-Drug Resistance Not Only in Bacteria

In the last few years, antibiotic resistance and, analogously, anticancer drug resistance have increased considerably, becoming one of the main public health problems. For this reason, it is crucial to find therapeutic strategies able to counteract the onset of multi-drug resistance (MDR). In this review, a critical overview of the innovative tools available today to fight MDR is reported. In this direction, the use of membrane-disruptive peptides/peptidomimetics (MDPs), such as antimicrobial peptides (AMPs), has received particular attention, due to their high selectivity and to their limited side effects. Moreover, similarities between bacteria and cancer cells are herein reported and the hypothesis of the possible use of AMPs also in anticancer therapies is discussed. However, it is important to take into account the limitations that could negatively impact clinical application and, in particular, the need for an efficient delivery system. In this regard, the use of nanoparticles (NPs) is proposed as a potential strategy to improve therapy; moreover, among polymeric NPs, cationic ones are emerging as promising tools able to fight the onset of MDR both in bacteria and in cancer cells.

An Overview of Antimicrobial Stewardship Optimization: The Use of Antibiotics in Humans and Animals to Prevent Resistance

Antimicrobials are a type of agent widely used to prevent various microbial infections in humans and animals. Antimicrobial resistance is a major cause of clinical antimicrobial therapy failure, and it has become a major public health concern around the world. Increasing the development of multiple antimicrobials has become available for humans and animals with no appropriate guidance. As a result, inappropriate use of antimicrobials has significantly produced antimicrobial resistance. However, an increasing number of infections such as sepsis are untreatable due to this antimicrobial resistance. In either case, life-saving drugs are rendered ineffective in most cases. The actual causes of antimicrobial resistance are complex and versatile. A lack of adequate health services, unoptimized use of antimicrobials in humans and animals, poor water and sanitation systems, wide gaps in access and research and development in healthcare technologies, and environmental pollution have vital impacts on antimicrobial resistance. This current review will highlight the natural history and basics of the development of antimicrobials, the relationship between antimicrobial use in humans and antimicrobial use in animals, the simplistic pathways, and mechanisms of antimicrobial resistance, and how to control the spread of this resistance.

Intravenous antimicrobial administration through peripheral venous catheters - establishing risk profiles from an analysis of 5252 devices

INTRODUCTION

Peripheral venous catheters (PVCs) are used to administer antimicrobials, but many fail prior to completion of therapy. While some antimicrobials are known to increase the PVC failure rate, risk profiles for many are unclear.

OBJECTIVE

To synthesize data from prospective PVC studies conducted between 2013 and 2019 to determine associations between common antimicrobials and PVC failure.

METHODS

A secondary analysis was undertaken of seven randomized controlled trials and two prospective cohort studies from three quaternary hospitals (two adult and one paediatric) in Australia between 2013 and 2019. The primary outcome was PVC failure due to vessel injury (occlusion, infiltration or extravasation) or irritation (pain or phlebitis). Associations between antimicrobial use and PVC failure were explored using multi-variable Cox regression.

RESULTS

In total, 5252 PVCs (4478 patients) were analysed; vessel injury and irritations occurred in 19% and 11% of all PVCs, respectively. Vessel injury was significantly associated with cefepime hydrochloride [hazard ratio (HR) 2.50; 95% confidence interval (CI) 1.44-4.34], ceftazidime pentahydrate (HR 1.91, 95% CI 1.11-3.31), flucloxacillin sodium (HR 1.84, 95% CI 1.45-2.33), lincomycin hydrochloride (HR 1.67, 95% CI 1.10-2.52) and vancomycin hydrochloride (HR 1.73, 95% CI 1.25-2.40). Irritation was significantly associated with flucloxacillin sodium (HR 2.58, 95% CI 1.96-3.40).

CONCLUSIONS

This study identified several antimicrobials associated with increased PVC failure, including some that were already known to be associated and some that had not been identified previously. Research is needed urgently to determine superior modes of delivery (e.g. dilution, infusion time, device type) that may prevent PVC failure.

Molecular Characterization of Salmonella Detected along the Broiler Production Chain in Trinidad and Tobago

This cross-sectional study determined the serovars, antimicrobial resistance genes, and virulence factors of Salmonella isolated from hatcheries, broiler farms, processing plants, and retail outlets in Trinidad and Tobago. Salmonella in silico serotyping detected 23 different serovars where Kentucky 20.5% (30/146), Javiana 19.2% (28/146), Infantis 13.7% (20/146), and Albany 8.9% (13/146) were the predominant serovars. There was a 76.0% (111/146) agreement between serotyping results using traditional conventional methods and whole-genome sequencing (WGS) in in silico analysis. In silico identification of antimicrobial resistance genes conferring resistance to aminoglycosides, cephalosporins, peptides, sulfonamides, and antiseptics were detected. Multidrug resistance (MDR) was detected in 6.8% (10/146) of the isolates of which 100% originated from broiler farms. Overall, virulence factors associated with secretion systems and fimbrial adherence determinants accounted for 69.3% (3091/4463), and 29.2% (1302/4463) counts, respectively. Ten of 20 isolates of serovar Infantis (50.0%) showed MDR and contained the bla_CTX-M-65 gene. This is the first molecular characterization of Salmonella isolates detected along the entire broiler production continuum in the Caribbean region using WGS. The availability of these genomes will help future source tracking during epidemiological investigations associated with Salmonella foodborne outbreaks in the region and worldwide.

Sensitivity Patterns, Plasmid Profiles and Clonal Relatedness of Multi-Drug Resistant Pseudomonas aeruginosa Isolated From the Ashanti Region, Ghana

Pseudomonas aeruginosa is a major cause of most opportunistic nosocomial infections in Ghana. The study sought to characterize P. aeruginosa isolates from market environments, poultry farms and clinical samples of patients from 2 district hospitals in the Ashanti region of Ghana. The genetic relatedness, plasmid profiles and antimicrobial sensitivity of the isolates were investigated. Culture based isolation and oprL gene amplification were used to confirm the identity of the isolates. Susceptibility testing was conducted using the Kirby Bauer disk diffusion method. Random whole genome typing of the P. aeruginosa strains was done using Enterobacterial repetitive-intergenic consensus based (ERIC) PCR assay. The most active agents against P. aeruginosa isolates were ceftazidime (90%), piperacillin (85%), meropenem, cefipeme and ticarcillin/clavulanic acid (81.6%). The isolates were most resistant to gentamycin (69%), ciprofloxacin (62.1%), ticarcillin (56.3%) and aztreonam (25%). About 65% (n = 38) of the multi-drug resistant (MDR) P. aeruginosa isolates harbored 1 to 5 plasmids with sizes ranging from 2 to 116.8 kb. A total of 27 clonal patterns were identified. Two major clones were observed with a clone showing resistance to all the test antipseudomonal agents. There is therefore a need for continued intensive surveillance to control the spread and development of resistant strains.

Prodigiosin inhibits bacterial growth and virulence factors as a potential physiological response to interspecies competition

Prodigiosin, a red linear tripyrrole pigment, has long been recognised for its antimicrobial property. However, the physiological contribution of prodigiosin to the survival of its producing hosts still remains undefined. Hence, the aim of this study was to investigate the biological role of prodigiosin from Serratia marcescens, particularly in microbial competition through its antimicrobial activity, towards the growth and secreted virulence factors of four clinical pathogenic bacteria (methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa) as well as Staphylococcus aureus and Escherichia coli. Prodigiosin was first extracted from S. marcescens and its purity confirmed by absorption spectrum, high performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrophotometry (LC-MS/MS). The extracted prodigiosin was antagonistic towards all the tested bacteria. A disc-diffusion assay showed that prodigiosin is more selective towards Gram-positive bacteria and inhibited the growth of MRSA, S. aureus and E. faecalis and Gram-negative E. coli. A minimum inhibitory concentration of 10 μg/μL of prodigiosin was required to inhibit the growth of S. aureus, E. coli and E. faecalis whereas > 10 μg/μL was required to inhibit MRSA growth. We further assessed the effect of prodigiosin towards bacterial virulence factors such as haemolysin and production of protease as well as on biofilm formation. Prodigiosin did not inhibit haemolysis activity of clinically associated bacteria but was able to reduce protease activity for MRSA, E. coli and E. faecalis as well as decrease E. faecalis, Salmonella Typhimurium and E. coli biofilm formation. Results of this study show that in addition to its role in inhibiting bacterial growth, prodigiosin also inhibits the bacterial virulence factor protease production and biofilm formation, two strategies employed by bacteria in response to microbial competition. As clinical pathogens were more resistant to prodigiosin, we propose that prodigiosin is physiologically important for S. marcescens to compete against other bacteria in its natural soil and surface water environments.

Dehydroabietic Acid Microencapsulation Potential as Biofilm-Mediated Infections Treatment

The antimicrobial activity of dehydroabietic acid (DHA) for its use as an antibiofilm agent was tested in this work. DHA was assayed against a collection of Gram-positive, Gram-negative sensitive and resistant bacteria and yeasts through the minimum inhibitory concentration (MIC), MIC with Bioburden challenge, minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), MBIC with Bioburden challenge and growth curve studies. Toxicological studies (Artemia salina, sulforhodamine B (SRB) assay) were done to assess if the compound had antimicrobial and not cytotoxic properties. Furthermore, microencapsulation and stability studies were carried out to evaluate the chemical behavior and stability of DHA. On MIC results, Gram-positive bacteria Staphylococcus aureus ATCC 1228 and Mycobacterium smegmatis ATCC 607 presented a high efficiency (7.81 µg/mL), while on Gram-negative bacteria the highest MIC value of 125 µg/mL was obtained by all Klebsiella pneumoniae strains and Escherichia coli isolate strain HSM 303. Bioburden challenge showed that MIC, MBIC and percentage biofilm inhibition (BI) values suffered alterations, therefore, having higher concentrations. MBIC values demonstrated that DHA has a higher efficiency against S. aureus ATCC 43866 with a percentage of BI of 75.13 ± 0.82% at 0.49 µg/mL. Growth curve kinetic profiles of DHA against S. aureus ATCC 25923 were observed to be bacteriostatic. DHA-alginate beads had a average size of 2.37 ± 0.20 and 2.31 ± 0.17 × 103 µm2 with an encapsulation efficiency (EE%) around 99.49 ± 0.05%, a protection percentage (PP%) of 60.00 ± 0.05% in the gastric environment and a protection efficiency (PE%) around 88.12 ± 0.05% against UV light. In toxicological studies DHA has shown IC50 of 19.59 ± 7.40 µg/mL and a LC50 of 21.71 ± 2.18%. The obtained results indicate that DHA is a promising antimicrobial candidate against a wide range of bacteria and biofilm formation that must be further explored.

Genotypic Characterization of Antimicrobial Resistant Salmonella spp. Strains from Three Poultry Processing Plants in Colombia

The poultry industry in Colombia has implemented several changes and measures in chicken processing to improve sanitary operations and control pathogens’ prevalence. However, there is no official in-plant microbial profile reference data currently available throughout the processing value chains. Hence, this research aimed to study the microbial profiles and the antimicrobial resistance of Salmonella isolates in three plants. In total, 300 samples were collected in seven processing sites. Prevalence of Salmonella spp. and levels of Enterobacteriaceae were assessed. Additionally, whole-genome sequencing was conducted to characterize the isolated strains genotypically. Overall, the prevalence of Salmonella spp. in each establishment was 77%, 58% and 80% for plant A, B, and C. The mean levels of Enterobacteriaceae in the chicken rinsates were 5.03, 5.74, and 6.41 log CFU/mL for plant A, B, and C. Significant reductions were identified in the counts of post-chilling rinsate samples; however, increased levels were found in chicken parts. There were six distinct Salmonella spp. clusters with the predominant sequence types ST32 and ST28. The serotypes Infantis (54%) and Paratyphi B (25%) were the most commonly identified within the processing plants with a high abundance of antimicrobial resistance genes.

Polyphenols against infectious diseases: Controlled release nano-formulations

The emergence of multi-drug resistant (MDR) pathogens has become a global threat and a cause of significant morbidity and mortality around the world. Natural products have been used as a promising approach to counter the infectious diseases associated with these pathogens. The application of natural products and their derivatives especially polyphenolic compounds as antibacterial agents is an active area of research, and prior studies have successfully treated a variety of bacterial infections using these polyphenolic compounds. However, delivery of polyphenolic compounds has been challenging due to their physicochemical properties and often poor aqueous solubility. In this regard, nanotechnology-based novel drug delivery systems offer many advantages, including improving bioavailability and the controlled release of polyphenolic compounds. This review summarizes the pharmacological mechanism and use of nano-formulations in developing controlled release delivery systems of naturally occurring polyphenols in infectious diseases.

The Role of Urban Wastewater in the Environmental Transmission of Antimicrobial Resistance: The Current Situation in Italy (2010-2019)

Scientific studies show that urban wastewater treatment plants (UWWTP) are among the main sources of release of antibiotics, antibiotic resistance genes (ARG) and antibiotic-resistant bacteria (ARB) into the environment, representing a risk to human health. This review summarizes selected publications from 1 January 2010 to 31 December 2019, with particular attention to the presence and treatment of ARG and ARB in UWWTPs in Italy. Following a brief introduction, the review is divided into three sections: (i) phenotypic assessment (ARB) and (ii) genotypic assessment (ARG) of resistant microorganisms, and (iii) wastewater treatment processes. Each article was read entirely to extract the year of publication, the geographical area of the UWWTP, the ARB and ARG found, and the type of disinfection treatment used. Among the ARB, we focused on the antibiotic resistance of Escherichia coli, Klebsiella pneumoniae, and Enterococci in UWWTP. The results show that the information presented in the literature to date is not exhaustive; therefore, future scientific studies at the national level are needed to better understand the spread of ARB and ARG, and also to develop new treatment methods to reduce this spread.

A simple, inexpensive, and rapid method to assess antibiotic effectiveness against exoelectrogenic bacteria

A sufficiently fast and simple antimicrobial susceptibility testing (AST) is urgently required to guide effective antibiotic usages and to surveil the antimicrobial resistance rate. Here, we establish a rapid, quantitative, and high-throughput phenotypic AST by measuring electrons transferred from the interiors of microbial cells to external electrodes. Because the transferred electrons are based on microbial metabolic activities and are inversely proportional to the concentration of potential antibiotics, the changes in electrical outputs can be readily used as a transducing signal to efficiently monitor bacterial growth and antibiotic susceptibility. The sensing is performed by directly measuring the total energy, or all the accumulated microbial electricity, generated by microbial fuel cells (MFCs) arranged in a large-capacity disposable, paper-based testbed. A common Gram-negative pathogenic bacterium Pseudomonas aeruginosa wild-type PAO1 and first-line antibiotic gentamicin (GEN) are used in our experiments. The minimum inhibitory concentration (MIC) values generated from our technique are validated by the gold standard broth microdilution (BMD). Our new approach provides quantitative, actionable MIC results within just 5 h because it measures electricity produced by bacterial metabolism instead of the days needed for growth-observation methods. Moreover, as the equipment needed is simple, common, and inexpensive, our test has immense potential to be adopted in the field or resource-limited hospitals and labs to provide insightful assessments for research and clinical practices.

Synthetic macromolecules as therapeutics that overcome resistance in cancer and microbial infection

Synthetic macromolecular antimicrobials have shown efficacy in the treatment of multidrug resistant (MDR) pathogens. These synthetic macromolecules, inspired by Nature's antimicrobial peptides (AMPs), mitigate resistance by disrupting microbial cell membrane or targeting multiple intracellular proteins or genes. Unlike AMPs, these polymers are less prone to degradation by proteases and are easier to synthesize on a large scale. Recently, various studies have revealed that cancer cell membrane, like that of microbes, is negatively charged, and AMPs can be used as anticancer agents. Nevertheless, efforts in developing polymers as anticancer agents has remained limited. This review highlights the recent advancement in the development of synthetic biodegradable antimicrobial polymers (e.g. polycarbonates, polyesters and polypeptides) and anticancer macromolecules including peptides and polymers. Additionally, strategies to improve their in vivo bioavailability and selectivity towards bacteria and cancer cells are examined. Lastly, future perspectives, including use of artificial intelligence or machine learning, in the development of antimicrobial and anticancer macromolecules are discussed.

Resurrection of antibiotics that methicillin-resistant Staphylococcus aureus resists by silver-doped bioactive glass-ceramic microparticles

This work describes a novel strategy to combat methicillin-resistant Staphylococcus aureus (MRSA) via the reactivation of inert antibiotics. This strategy exploits a multifunctional system consisting of bioactive glass-ceramic microparticles with antibacterial properties combined with various antibiotics to kill MRSA. Specifically, sol-gel derived silver-doped bioactive glass-ceramic microparticles (Ag-BG) combined with antibiotics that MRSA resists such as oxacillin or fosfomycin, significantly decreased the viability of MRSA. Ag-BG also potentiated the activity of vancomycin on static bacteria, which are typically resistant to this antibiotic. Notably, the synergistic activity is restricted to cell-envelope acting antibiotics as Ag-BG supplementation did not increase the efficacy of gentamicin. Bacteria viability assays and electron microscopy images demonstrate that Ag-BG synergizes to restore antibacterial activity to antibiotics that MRSA resists. The low cytotoxicity previously studied against oral bacteria, together with the known regenerative properties presented in previous studies, and the unique antibacterial properties observed in this work when they are combined with antibiotics, make this multifunctional system a promising approach for healing infected tissue. STATEMENT OF SIGNIFICANCE: This study addresses a very significant issue in the field of antibiotic resistance presenting an innovative way to clear MRSA, by utilizing bioactive glass-ceramic microparticles in combination with antibiotics. Multifunctional glass-ceramic microparticles doped with silver ions (Ag-BG) have been previously observed to exhibit bioactive and antibacterial properties. In this study Ag-BG microparticles were observed to synergize with antibiotics restoring their sensitivity against MRSA. This research work presents a novel approach to resurrect ineffective antibiotics and render them effective against MRSA. Cytotoxicity to eukaryotic cells is not anticipated, as it has been previously observed that these microparticles can trigger hard and soft dental tissue regeneration, when they are utilized in certain concentrations. This study opens a new avenue in the treatment of multidrug resistance bacteria.

Graphene oxide decorated with zinc oxide nanoflower, silver and titanium dioxide nanoparticles: fabrication, characterization, DNA interaction, and antibacterial activity

The fabrication, characterization, and antibacterial activity of novel nanocomposites based on graphene oxide (GO) nanosheets decorated with silver, titanium dioxide nanoparticles, and zinc oxide nanoflowers were examined. The fabricated nanocomposites were characterized by various techniques including X-ray diffraction, ultraviolet-visible light absorption and fluorescence spectroscopy, Brunauer–Emmett–Teller theory analysis, Fourier transform infrared, and scanning electron microscopy. The antibacterial activity of the GO–metal oxide nanocomposites against two Gram-positive and two Gram-negative bacteria was examined by using the standard counting plate methodology. The results showed that the fabricated nanocomposites on the surface of GO could inhibit the growth of microbial adhered cells, and consequently prevent the process of biofilm formation in food packaging and medical devices. To confirm the antibacterial activity of the examined GO-nanocomposites, we examined their interactions with bovine serum albumin (BSA) and circulating tumor DNA (ctDNA) by steady-state fluorescence spectroscopy. Upon addition of different amounts of fabricated GO-nanocomposites, the fluorescence intensities of the singlet states of BSA and ctDNA were considerably quenched. The higher quenching was observed in the case of GO–Ag–TiO₂@ZnO nanocomposite compared with other control composites.

The fabrication, characterization, and antibacterial activity of novel nanocomposites based on graphene oxide (GO) nanosheets decorated with silver, titanium dioxide nanoparticles, and zinc oxide nanoflowers were examined.

Effect of UVA/LED/TiO2 photocatalysis treated sulfamethoxazole and trimethoprim containing wastewater on antibiotic resistance development in sequencing batch reactors

Controlling of antibiotics is the crucial step for preventing antibiotic resistance genes (ARGs) dissemination; UV photocatalysis has been identified as a promising pre-treatment technology for antibiotics removal. However, information about the effects of intermediates present in the treated antibiotics wastewater on the downstream biological treatment processes or ARGs development is very limited. In the present study, continuous UVA/LED/TiO₂ photocatalysis removed more than 90% of 100 ppb sulfamethoxazole (SMX)/trimethoprim (TMP), the treated wastewater was fed into SBR systems for over one year monitoring. Residual SMX/TMP (2-3 ppb) and intermediates present in the treated wastewater did not adversely affect SBR performance in terms of TOC and TN removal. SMX and TMP resistance genes (sulI, sulII, sulIII, dfrII, dfrV and dfr13) were also quantified in SBRs microbial consortia. Results suggested that continuous feeding of treated SMX/TMP containing wastewaters did not trigger any ARGs promotion during the one year operation. By stopping the input of 100 ppb SMX/TMP, abundance of sulII and dfrV genes were reduced by 83% and 100%, respectively. sulI gene was identified as the most persistence ARG, and controlling of 100 ppb SMX input did not achieve significant removal of sulI gene. A significant correlation between sulI gene and class 1 integrons was found at the level of p = 1.4E-10 (r = 0.94), and sulII gene positively correlated with the plasmid transfer efficiency (r = 2.442E-10, r = 0.87). Continuous input of 100 ppb SMX enhanced plasmid transfer efficiency in the SBR system, resulting in sulII gene abundance increasing more than 40 times.

Antibiotic Resistance Patterns and Serotypes of Salmonella spp. Isolated at Jeollanam-do in Korea

OBJECTIVES

Few long-term studies have been conducted on the serotype and antibiotic resistance patterns of Salmonella speices (spp.) The aim of this study was to determine the serotypes and antibiotic resistance patterns of Salmonella spp. isolated at Jeollanam-do in Korea from 2004 to 2014.

METHODS

A total of 276 Salmonella samples were evaluated. Serotyping was carried out according to the Kauffmann-White scheme. Antibiotic susceptibility was determined using the Vitek II system with an AST-N169 card.

RESULTS

A total of 22 different serotypes were identified, and the major serotypes were Salmonella Enteritidis (116 strains, 42.0%) and Salmonella Typhimurium (60 strains, 21.7%). The highest resistance was observed in response to nalidixic acid (43.4%), followed by ampicillin (40.5%) and tetracycline (31.6%). Resistance to nalidixic acid was detected in 81.0% of S. Enteritidis. Multidrug resistance was detected in 43.3% of Salmonella spp. S. Enteritidis and S. Typhimurium presented the highest resistance (98.3%) and multidrug resistance rate (73.3%), respectively. The most highly observed antibiotic resistance pattern among Salmonella spp. in this study was ampicillin-chloramphenicol (14 strains, 5.7%).

CONCLUSION

Overall, S. Enteritidis and S. Typhimurium showed higher antibiotic resistance than the other Salmonella serotypes tested in this study. Our study will provide useful information for investigating the sources of Salmonella infections, as well as selecting effective antibiotics for treatment.

Decomposition of sulfamethoxazole and trimethoprim by continuous UVA/LED/TiO2 photocatalysis: Decomposition pathways, residual antibacterial activity and toxicity

In this study, continuous LED/UVA/TiO₂ photocatalytic decomposition of sulfamethoxazole (SMX) and trimethoprim (TMP) was investigated. More than 90% of SMX and TMP were removed within 20min by the continuous photoreactor (with the initial concentration of 400ppb for each). The removal rates of SMX and TMP decreased with higher initial antibiotics loadings. SMX was much easier decomposed in acidic condition, while pH affected little on TMP's decomposition. 0.003% was found to be the optimum H₂O₂ dosage to enhance SMX photocatalytic decomposition. Decomposition pathways of SMX and TMP were proposed based on the intermediates identified by using LC-MS-MS and GC-MS. Aniline was identified as a new intermediate generated during SMX photocatalytic decomposition. Antibacterial activity study with a reference Escherichia coli strain was also conducted during the photocatalytic process. Results indicated that with every portion of TMP removed, the residual antibacterial activity decreased by one portion. However, the synergistic effect between SMX and TMP tended to slow down the antibacterial activity removal of SMX and TMP mixture. Chronic toxicity studies conducted with Vibrio fischeri exhibited 13-20% bioluminescence inhibition during the decomposition of 1ppm SMX and 1ppm TMP, no acute toxicity to V. fischeri was observed during the photocatalytic process.

Structure-based analysis of Bacilli and plasmid dihydrofolate reductase evolution

Dihydrofolate reductase (DHFR), a key enzyme in tetrahydrofolate-mediated biosynthetic pathways, has a structural motif known to be highly conserved over a wide range of organisms. Given its critical role in purine and amino acid synthesis, DHFR is a well established therapeutic target for treating a wide range of prokaryotic and eukaryotic infections as well as certain types of cancer. Here we present a structural-based computer analysis of bacterial (Bacilli) and plasmid DHFR evolution. We generated a structure-based sequence alignment using 7 wild-type DHFR x-ray crystal structures obtained from the RCSB Protein Data Bank and 350 chromosomal and plasmid homology models we generated from sequences obtained from the NCBI Protein Database. We used these alignments to compare active site and non-active site conservation in terms of amino acid residues, secondary structure and amino acid residue class. With respect to amino acid sequences and residue classes, active-site positions in both plasmid and chromosomal DHFR are significantly more conserved than non-active site positions. Secondary structure conservation was similar for active site and non-active site positions. Plasmid-encoded DHFR proteins have greater degree of sequence and residue class conservation, particularly in sequence positions associated with a network of concerted protein motions, than chromosomal-encoded DHFR proteins. These structure-based were used to build DHFR specific phylogenetic trees from which evidence for horizontal gene transfer was identified.

Altered antibiotic tolerance in anaerobic digesters acclimated to triclosan or triclocarban

Bench-scale anaerobic digesters were amended to elevated steady-state concentrations of triclosan (850 mg/kg) and triclocarban (150 mg/kg) using a synthetic feed. After more than 9 solids retention time (SRT) values of acclimatization, biomass from each digester (and a control digester that received no antimicrobials) was used to assess the toxicity of three antibiotics. Methane production rate was measured as a surrogate for activity in microcosms that received doses of antibiotics ranging from no-antibiotic to inhibitory concentrations. Biomass amended with triclocarban was more sensitive to tetracycline compared to the control indicating synergistic inhibitory effects between this antibiotic and triclocarban. In contrast, biomass amended with triclosan was able to tolerate statistically higher levels of ciprofloxacin indicating that triclosan can induce functional resistance to ciprofloxacin in an anaerobic digester community.

Omics for Investigating Chitosan as an Antifungal and Gene Modulator

Chitosan is a biopolymer with a wide range of applications. The use of chitosan in clinical medicine to control infections by fungal pathogens such as Candida spp. is one of its most promising applications in view of the reduced number of antifungals available. Chitosan increases intracellular oxidative stress, then permeabilizes the plasma membrane of sensitive filamentous fungus Neurospora crassa and yeast. Transcriptomics reveals plasma membrane homeostasis and oxidative metabolism genes as key players in the response of fungi to chitosan. A lipase and a monosaccharide transporter, both inner plasma membrane proteins, and a glutathione transferase are main chitosan targets in N. crassa. Biocontrol fungi such as Pochonia chlamydosporia have a low content of polyunsaturated free fatty acids in their plasma membranes and are resistant to chitosan. Genome sequencing of P. chlamydosporia reveals a wide gene machinery to degrade and assimilate chitosan. Chitosan increases P. chlamydosporia sporulation and enhances parasitism of plant parasitic nematodes by the fungus. Omics studies allow understanding the mode of action of chitosan and help its development as an antifungal and gene modulator.

Genetic Mechanisms of Antimicrobial Resistance of Acinetobacter baumannii

OBJECTIVE

To summarize published data identifying known genetic mechanisms of antibiotic resistance in Acinetobacter baumannii and the correlating phenotypic expression of antibiotic resistance.

DATA SOURCES

MEDLINE databases (1966-July 15, 2010) were searched to identify original reports of genetic mechanisms of antibiotic resistance in A. baumannii.

DATA SYNTHESIS

Numerous genetic mechanisms of resistance to multiple classes of antibiotics are known to exist in A. baumannii, a gram-negative bacterium increasingly implicated in nosocomial infections. Mechanisms may be constitutive or acquired via plasmids, integrons, and transposons. Methods of resistance include enzymatic modification of antibiotic molecules, modification of antibiotic target sites, expression of efflux pumps, and downregulation of cell membrane porin channel expression. Resistance to β-lactams appears to be primarily caused by β-lactamase production, including extended spectrum β-lactamases (b/aTEM, blaSHV, b/aTX-M,b/aKPC), metallo-β-lactamases (blaMP, blaVIM, bla, SIM), and most commonly, oxacillinases (blaOXA). Antibiotic target site alterations confer resistance to fluoroquinolones (gyrA, parC) and aminoglycosides (arm, rmt), and to a much lesser extent, β-lactams. Efflux pumps (tet, ade, abe) contribute to resistance against β-lactams, tetracyclines, fluoroquinolones, and aminoglycosides. Finally, porin channel deletion (carO, oprD) appears to contribute to β-lactam resistance and may contribute to rarely seen polymyxin resistance. Of note, efflux pumps and porin deletions as solitary mechanisms may not render clinical resistance to A. baumannii.

CONCLUSIONS

A. baumannii possesses copious genetic resistance mechanisms. Knowledge of local genotypes and expressed phenotypes for A. baumannii may aid clinicians more than phenotypic susceptibilities reported in large epidemiologic studies.

Spread of Efflux Pump Overexpressing-Mediated Fluoroquinolone Resistance and Multidrug Resistance in Pseudomonas aeruginosa by using an Efflux Pump Inhibitor

Background

Fluoroquinolone resistance in Pseudomonas aeruginosa may be due to efflux pump overexpression and/or target mutations. We designed this study to investigate the efflux pump mediated fluoroquinolone resistance and check the increasing effectiveness of fluoroquinolones in combination with an efflux pumps inhibitor among P. aeruginosa isolates from burn wounds infections.

Materials and Methods

A total of 154 consecutive strains of P. aeruginosa were recovered from separate patients hospitalized in a burn hospital, Tehran, Iran. The isolates first were studied by disk diffusion antibiogram for 11 antibiotics and then minimum inhibitory concentration (MIC) experiments were performed to detect synergy between ciprofloxacin and the efflux pump inhibitor, carbonyl cyanide-m-chlorophenyl hydrazone (CCCP). Then to elucidate the inducing of multi drug resistance due to different efflux pumps activation in Fluoroquinolone resistant isolates, synergy experiments were also performed in random ciprofloxacin resistant isolates which have overexpressed efflux pumps phenotypically, using CCCP and selected antibiotics as markers for Beta-lactams and Aminoglycosides. The isolates were also tested by polymerase chain reaction (PCR) for the presence of the MexA, MexC and MexE, which encode the efflux pumps MexAB-OprM, MexCD-OprJ and MexEF-OprN.

Results

Most of the isolates were resistant to 3 or more antibiotics tested. More than half of the ciprofloxacin resistant isolates exhibited synergy between ciprofloxacin and CCCP, indicating the efflux pump activity contributed to the ciprofloxacin resistance. Also increased susceptibility of random ciprofloxacin resistant isolates of P. aeruginosa to other selected antibiotics, in presence of CCCP, implied multidrug extrusion by different active efflux pump in fluoroquinolones resistant strains. All of Ciprofloxacin resistant isolates were positive for MexA, MexC and MexE genes simultaneously.

Conclusion

In this burn hospital, where multidrug resistant P. aeruginosa isolates were prevalent, ciprofloxacin resistance and multidrug resistance due to the overexpression of fluoroquinolones mediated efflux pumps has also now emerged. Early recognition of this resistance mechanism should allow the use of alternative antibiotics and use an efflux pumps inhibitor in combination with antibiotic therapy.

Salmonella enterica: survival, colonization, and virulence differences among serovars

Data indicate that prevalence of specific serovars of Salmonella enterica in human foodborne illness is not correlated with their prevalence in feed. Given that feed is a suboptimal environment for S. enterica, it appears that survival in poultry feed may be an independent factor unrelated to virulence of specific serovars of Salmonella. Additionally, S. enterica serovars appear to have different host specificity and the ability to cause disease in those hosts is also serovar dependent. These differences among the serovars may be related to gene presence or absence and expression levels of those genes. With a better understanding of serovar specificity, mitigation methods can be implemented to control Salmonella at preharvest and postharvest levels.

Awareness of antibiotic prescribing and resistance in primary dental care

Dentists in primary care account for approximately one in ten of all therapeutic antibiotic prescriptions, but many of these prescriptions may be unnecessary and will contribute to the critically important problem of bacterial resistance. Emerging guidance on antimicrobial stewardship is discussed and the annual European Antibiotic Awareness Day (EAAD), which takes place on 18 November, is highlighted.

Relação da idade na presença de bactérias resistentes a antimicrobianos em rebanhos leiteiros no Rio Grande do Sul

A mastite bovina é uma doença importante na bovinocultura de leite, devido à sua alta incidência e perdas econômicas associadas principalmente com a produção de leite reduzida e aos custos do tratamento. O uso de antimicrobianos para o tratamento de casos clínicos e no período seco tem levantado preocupações quanto à seleção de cepas bacterianas resistentes. Isso também pode refletir na saúde pública, uma vez que bactérias resistentes, como o Staphylococcus aureus meticilina-resistente (MRSA), podem ser transmitidas aos seres humanos por contato direto com animais infectados ou produtos lácteos. A resistência das bactérias aos agentes antimicrobianos aumentou, em geral, devido a tratamentos ineficazes. Estudos realizados no Brasil com amostras não planejadas mostram aumento no padrão de resistência, principalmente em S. aureus. A exposição ao tratamento antimicrobiano repetido ao longo das lactações consecutivas de vacas pode ser um fator predisponente para o desenvolvimento da resistência antimicrobiana em bactérias que infectam o úbere. Assim, o objetivo deste estudo foi determinar a possível associação causal entre resistência antimicrobiana em bactérias isoladas a partir do leite bovino e dados como idade e período de lactação. As amostras de leite foram coletadas de 21 rebanhos leiteiros do Rio Grande do Sul, Brasil, selecionados aleatoriamente a partir da população-alvo de 1.656 explorações leiteiras semi-intensivas, estratificada por tamanho do rebanho. A bactéria foi considerada a unidade amostral, e para a estimativa de prevalência foram utilizados os seguintes parâmetros: uma frequência de 35% de Staphylococcus sp. resistentes à penicilina; um nível de confiança de 90%; e uma precisão absoluta de 12%. As bactérias foram isoladas de amostras de leite compostas de todos os quartos mamários de cada vaca após descartar os primeiros três ou quatro jatos de leite. Para acessar os potenciais fatores de risco, características dos animais foram obtidas através de uma entrevista com os produtores. Os exames laboratoriais foram realizados de acordo com as recomendações do National Mastitis Council. Um total de 242 isolados foi obtido de 195 vacas a partir da amostra do rebanho total (251 vacas). A prevalência de infecções foi descrita em grupos de acordo com o perfil epidemiológico: bactérias ambientais, contagiosas e outras. Estas perfizeram 57,3%, 26,3% e 11,2%, respectivamente, dos animais amostrados. Testes de suscetibilidade antimicrobiana contra 12 diferentes antimicrobianos foram realizados em 159 isolados. No total, 30% dos isolados testados mostraram resistência a pelo menos três grupos diferentes de antimicrobianos e foram classificados como multirresistentes. Foram observadas as freqüências mais elevadas de resistência contra a ampicilina para os estafilococos coagulase-negativo, seguida de eritromicina para estafilococos coagulase-positivo e tetraciclina para estreptococos. A análise de regressão logística mostrou uma relação significativa entre a idade das vacas e a presença de estafilococos coagulase-positivo multirresistentes e distribuição de classes diferentes de bactérias nos diferentes estratos etários, o que sugere uma concorrência dinâmica ao longo do tempo (p < 0,05). Animais com três a quatro anos tiveram 13,7 vezes mais chances (IC95% 1,4 - 130,2, p = 0,02) de ter estafilococos coagulase-positivo multirresistentes em comparação com aqueles com dois ou três anos. O tempo de exposição a agentes infecciosos e consequentes terapias sugere uma maior chance de colonização do úbere por patógenos resistentes devido à pressão de seleção repetida durante a vida.

Antibacterial activity of alkaloids produced by endophytic fungus Aspergillus sp. EJC08 isolated from medical plant Bauhinia guianensis

Bauhinia guianensis is a typical plant in the Amazon region belonging to the family Leguminosea, used by local populations for the treatment of infectious and renal diseases. Previous work on the plant B. guianensis led to the isolation of substances with anti-inflammatory and analgesic activities. Thus, compounds isolated from B. guianensis with antimicrobial activities had not been identified. Given that there is a possibility of biological activity reported for a given plant being found in the endophytic fungi, we decided to isolate endophytic fungi from B. guianensis and test their antimicrobial activities. The alkaloids known as fumigaclavine C and pseurotin A were isolated by column chromatography and identified by 1D and 2D NMR techniques and mass spectrometry. The alkaloids are first reported as broad-spectrum antibacterial agents with good activity.

Cefepime

Cefepime (Maxipime), Maxcef, Cepimax, Cepimex, Axepim, a parenteral fourth-generation cephalosporin, is active against many organisms causative in pneumonia. Cefepime has in vitro activity against Gram-positive organisms including Staphylococcus aureus and penicillin-sensitive, -intermediate and -resistant Streptococcus pneumoniae similar to that of cefotaxime and ceftriaxone. Cefepime also has good activity against Gram-negative organisms, including Pseudomonas aeruginosa, similar to that of ceftazidime. Importantly, cefepime is stable against many of the common plasmid- and chromosome-mediated beta-lactamases and is a poor inducer of AmpC beta-lactamases. As a result, it retains activity against Enterobacteriaceae that are resistant to third-generation cephalosporins, such as derepressed mutants of Enterobacter spp. Cefepime may be hydrolyzed by the extended-spectrum beta-lactamases produced by some members of the Enterobacteriaceae, but to a lesser extent than the third-generation cephalosporins. Monotherapy with cefepime 1 or 2g, usually administered intravenously twice daily, was as effective for clinical and bacteriological response as ceftazidime, ceftriaxone or cefotaxime monotherapy (1 or 2g two or three times daily) in a number of randomized, clinical trials in hospitalized adult, or less commonly, pediatric, patients with generally moderate to severe community-acquired or nosocomial pneumonia. More limited data indicated that monotherapy with cefepime 2g three times daily was also as effective in treating patients with nosocomial pneumonia as imipenem/cilostatin 0.5g four times daily, and when combined with amikacin, cefepime was as effective as ceftazidime plus amikacin. Patients with pneumonia who failed to respond to previous antibacterial therapy with penicillins or other cephalosporins responded to treatment with cefepime. Cefepime is generally well tolerated, with a tolerability profile similar to those of other parenteral cephalosporins. In clinical trials, the majority of adverse events experienced by cefepime recipients were mild to moderate and reversible. The most common adverse events with a causal relationship to cefepime reported in clinical trials included rash and diarrhea. Other, less common, adverse events included pruritus, urticaria, nausea, vomiting oral candidiasis, colitis, headache, fever, erythema and vaginitis.

CONCLUSION

Cefepime is an established and generally well tolerated parenteral drug with a broad spectrum of antibacterial activity which, when administered twice daily, provides coverage of most of the pathogens that may be causative in pneumonia. In randomized clinical trials in hospitalized patients with generally moderate to severe community-acquired or nosocomial pneumonia, cefepime monotherapy exhibited good clinical and bacteriological efficacy. Cefepime may become a preferred antibacterial agent for infections caused by Enterobacter spp. With prudent use in order to prevent the emergence of resistant organisms, cefepime will continue to be a suitable option for the empiric treatment of pneumonia.

Klebsiella pneumoniae carbapenemases in Enterobacteriaceae: history, evolution, and microbiology concerns

Since the discovery of penicillin 80 years ago, gram-negative bacteria have become proficient at evading the lethal activity of β-lactam antibiotics, principally through the production of β-lactamases. The rapid emergence of penicillinases in both gram-positive and gram-negative bacteria led to the development of cephalosporin β-lactam antibiotics, but production of plasmid-mediated extended-spectrum cephalosporinases (or extended-spectrum β-lactamases) and AmpC enzymes resulted in resistance to this drug class. Because carbapenems were the only β-lactam agents active against such extended-spectrum β-lactamase-producing strains, appropriate and inappropriate use soon resulted in Enterobacteriaceae resistance. As a result, two distinct types of carbapenemases-the metallo-β-lactamases and Klebsiella pneumoniae carbapenemases (KPCs)-were soon identified. The KPCs comprise 10 variants that differ from one another by one to three amino acid substitutions (KPC-2 to KPC-11). The KPC-producing Enterobacteriaceae are not only multidrug resistant but are also difficult to detect routinely in the clinical microbiology laboratory. Tigecycline, polymyxins (colistin and polymyxin B), and aminoglycosides are possible candidate therapies for infections caused by KPC-producing organisms, although well-conducted clinical trials are required to fully define their roles in patient management. The shortage of new antimicrobial agents on the immediate horizon suggests that enhanced adherence with infection prevention procedures and antimicrobial stewardship programs are needed to curb patient-to-patient transmission and to reduce the selection of multidrug-resistant bacteria.

Effect of an alkaloidal fraction of Tabernaemontana elegans (Stapf.) on selected micro-organisms

ETHNOPHARMACOLOGICAL RELEVANCE

Bacterial infections remain a significant threat to human health. Due to the emergence of widespread antibiotic resistance, development of novel antibiotics is required in order to ensure that effective treatment remains available. There are several reports on the ethnomedical use of Tabernaemontana elegans pertaining to antibacterial activity.

AIM OF THE STUDY

The aim of this study was to isolate and identify the fraction responsible for the antimicrobial activity in Tabernaemontana elegans (Stapf.) root extracts.

MATERIALS AND METHODS

The active fraction was characterized by thin layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS). Antibacterial activity was determined using the broth micro-dilution assay and antimycobacterial activity using the BACTEC radiometric assay. Cytotoxicity of the crude extract and fractions was assessed against primary cell cultures; lymphocytes and fibroblasts; as well as a hepatocarcinoma (HepG2) and macrophage (THP-1) cell line using the Neutral Red uptake and MTT assays.

RESULTS

The crude root extracts were found to contain a high concentration of alkaloids (1.2%, w/w). GC-MS analysis identified the indole alkaloids, voacangine and dregamine, as major components. Antibacterial activity was limited to the Gram-positive bacteria and Mycobacterium species, with MIC values in the range of 64-256μg/ml. When combined with antibiotics, additive antibacterial effects were observed. Marked cytotoxicity to all cell lines tested was evident in the MTT and Neutral Red uptake assays, with IC(50) values <9.81μg/ml.

CONCLUSIONS

This study confirms the antibacterial activity of Tabernaemontana elegans and supports its potential for being investigated further for the development of a novel antibacterial compound.

Antimicrobial activity of flavonoids from Piper lanceaefolium and other Colombian medicinal plants against antibiotic susceptible and resistant strains of Neisseria gonorrhoeae

BACKGROUND

The successful treatment of Neisseria gonorrhoeae (NG) infections is increasingly problematic because of the resistance of this pathogen to multiple antimicrobial agents. This development underscores the need for new antimicrobial sources. In the current study, 21 crude methanol extracts, from 19 plants used in Colombian traditional medicine for cutaneous infections, were screened for antimicrobial activity against NG.

METHODS

Extracts were screened by disc susceptibility assay. In addition, the minimum inhibitory concentrations of active compounds from P. lanceaefolium were assayed using a panel of 26 NG strains comprising 12 antibiotic-resistant phenotypes.

RESULTS

In all, 71% of the crude extracts exhibited antibacterial activity against the antibiotic susceptible NG strain WHO V, whereas 10% of the extracts inhibited penicillinase-producing NG strain GC1-182. The crude extract of Piper lanceaefolium was the only extract to show significant activity without ultraviolet (UV) light activation. Preliminary screening identified 3 compounds in this plant possessing antimicrobial activity: the flavonoids 5,7-dihydroxyflavanone (pinocembrin), 2',4',6'-trihydroxychalcone (pinocembrin chalcone), and the prenylated benzoic acid derivative cyclolanceaefolic acid methyl ester. Pinocembrin and pinocembrin chalcone inhibited 100% of the NG panel at 64 μg/mL and 128 μg/mL, respectively, whereas cyclolanceaefolic acid methyl ester inhibited 44% of the strains at 128 μg/mL.

CONCLUSIONS

This is the first report of the antibacterial activity of Columbian plants against NG. The activity of the 2 flavonoids, pinocembrin, and pinocembrin chalcone, toward both susceptible and resistant NG strains makes them promising candidates for further research.

Antibacterial nanomedicine

Recent advances in the field of nanotechnology led several groups to recognize the promise of recruiting nanomaterials to the ongoing battle against pathogenic bacteria. A large battery of newly discovered and developed nanomaterials has been accumulating during the last decade, therefore, it could be anticipated that it should only be a matter of time until such preliminary nanomedicine applications are presented. We review some of these pioneering studies in which nanomaterials have been evaluated as potential therapeutics, antiseptics or disinfectants. These studies can be divided roughly into two groups. The first are studies of antibacterial nanomedicines that are based solely on synthetic (artificial) materials. The second group comprises studies of antibacterial nanomaterials that are based on biological substances used in their natural or in a modified form. We will discuss the physicochemical and antibacterial highlights of each material and present the future perspectives of this emerging field.