Overcoming resistance to β-lactam antibiotics

The effect of novel β-lactam derivatives synthesized from substituted phenethylamines on resistance genes of MRSA isolates

This study focuses on the activity of previously reported imine and β-lactam derivatives against methicillin-resistant Staphylococcus aureus (MRSA) isolates. The presence of mecA and blaZ genes in the isolates was determined, and the minimum inhibitory concentration (MIC) values were determined based on the antibacterial activity against these isolates. Active compounds were selected and their ability to act against resistant isolates in vitro was determined. Concurrently, biochemical (nitrocefin) and molecular (qRT-PCR) tests were used to investigate the ability of the compounds to induce resistance genes in MRSA isolates. The cytotoxicity of the compounds on human dermal fibroblasts (HDF) was investigated. The MIC values of compounds (10) and (12) against MSSA and MRSA isolates were 7.81 and 15.62 μg ml-1, respectively. The most active compounds were identified as (10) and (12), and it was observed that the isolates did not develop resistance to these compounds in vitro. These compounds were found to inhibit β-lactamase, reduce the expression of resistance genes, and exhibit reduced HDF cell toxicity in a dose-dependent manner. According to the findings of the study, it can be concluded that these compounds show promise as hits with an interesting mechanism of action for further chemical modifications to develop new MRSA inhibitors.

Antimicrobial Resistance Elements in Coastal Water of Llanquihue Lake, Chile

Antimicrobial resistance has been stated to be a global health problem. In Chile, the use of antibiotics should be declared by medical prescription, but it is unknown what happens to the drugs once the treatment ends. Among the possibilities for their disposal are the trash or the drain; regardless of which scenario arises, antibiotics could accumulate in the environment, stimulating the emergence of antimicrobial resistance mechanisms and their transfer between microorganisms. Unfortunately, sometimes wastewater ends up in bodies of water, due to the dragging of elements by rain, or by the presence of illegal water discharges. In this work, shotgun metagenomics was used to elucidate the functional and microbial composition of biohazard elements in the bay of Puerto Varas City, Chile. As expected, a high diversity of microorganisms was found, including bacterial elements described as human or animal pathogens. Also, a diverse repertory of antimicrobial resistant genes (ARGs) was detected, which confers mainly resistance to macrolides, beta-lactams, and tetracyclines, consistent with the families of antibiotics most used in Chile. Similar ARGs were identified in DNA mobile elements. In addition, we tested the antimicrobial susceptibility in 14 bacterial strains isolated from Llanquihue Lake. This is the first report of the presence of genomic elements that could constitute a health problem, considering the importance of the interconnection between environmental, animal, and human health, a concept known as One Health.

Spermacoce alata Aubl. Essential Oil: Chemical Composition, In Vitro Antioxidant Activity, and Inhibitory Effects of Acetylcholinesterase, α-Glucosidase and β-Lactamase

Spermacoce alata Aubl. is widely available in the market as traditional Chinese medicine and animal feed, due to its properties of clearing heat and treating malaria and its high-protein and crude fiber content. In this study, the essential oil of S. alata was obtained through hydrodistillation. GC-MS and GC-FID methods were used to identify the chemical components and their relative abundance. Furthermore, the antioxidant capacity was measured using DPPH, ABTS, and FRAP assays, and the inhibitory effects of acetylcholinesterase, α-glucosidase, and β-lactamase were also evaluated. A total of 67 compounds were identified, with the major constituents being palmitic acid (30.74%), linoleic acid (16.13%), and phenylheptatriyne (8.07%). The essential oil exhibited moderate antioxidant activity against DPPH (IC50 > 10 mg/mL), while the IC50 value for the ABTS assay was 3.84 ± 2.12 mg/mL and the FRAP assay value was 87.22 ± 12.22 µM/g. Additionally, the essential oil showed moderate anti-acetylcholinesterase activity (IC50 = 286.0 ± 79.04 μg/mL), significant anti-α-glucosidase activity (IC50 = 174.7 ± 13.12 μg/mL), and potent anti-β-lactamase activity (IC50 = 37.56 ± 3.48 μg/mL). The results suggest that S. alata has the potential for application in pharmacology, warranting further exploration and investigation.

Prevalence of Extended-Spectrum β-Lactamases (ESBLs) Producing Aeromonas spp. Isolated from Lamellidens marginalis (Lamark, 1819) of Sewage-Fed Wetland: A Phenotypic and Genotypic Approach

The global rise of zoonotic bacteria resistant to multiple antimicrobial classes and the growing occurrence of infections caused by Aeromonas spp. resistant to β-lactam antibiotics pose a severe threat to animal and human health. However, the contribution of natural environments, particularly aquatic ecosystems, as ideal settings for the development and spread of antimicrobial resistance (AMR) is a key concern. Investigating the phenotypic antibiotic resistance and detection of β-lactamase producing Aeromonas spp. in Lamellidens marginalis, which inhabit all freshwater ecosystems of the Indian subcontinent, is essential for implications in monitoring food safety and drug resistance. In the present investigation, 92 isolates of Aeromonas spp. were recovered from 105 bivalves and screened for their antimicrobial resistance patterns. In vitro antibiotic resistance profiling showed a higher Multiple Antibiotic Resistance (MAR) index of 0.8 with the highest resistance against ampicillin/sulbactam (82%), while 58, 44, 39 and 38% of the isolates were resistant to cephalothin, erythromycin, cefoxitin and imipenem, respectively. PCR results revealed that these isolates carried the blaTEM gene (94%), which was followed by the blaCTX-M gene (51%) and the blaSHV gene (45%). A combination of blaSHV, blaCTX-M, and blaTEM genes was found in 17% of the isolates, indicating the presence of all three resistance genes. This is the first investigation which highlights the importance of multidrug-resistant Aeromonas spp. in L. marginalis. The identification of extended-spectrum-β-lactamases (ESBLs) genes demand the necessity of continuous surveillance and systematic monitoring, considering its potential health risks for both animals and human beings.

Prevalence of diverse antimicrobial resistance genes and bacteria in sewage treatment plant-derived sludge environment

Antimicrobial resistance (AMR) contamination in the environment is one of the most significant worldwide threats of the 21st century. Since sludge is heavily exposed to diverse contaminants, including pharmaceuticals, the inhabitant bacterial population is expected to exhibit resistance to antimicrobial agents. In this study, sewage treatment plant (STP) sludge samples were analyzed to assess the antibiotic-resistant bacterial population, abundance of AMR genes (ermF, qnrS, Sul1, blaGES, blaCTX-M, and blaNDM), and mobile genetic elements (intl1 and IS26). Out of 16, six bacterial isolates exhibited resistance to 13 antibiotics with a high multiple antibiotic resistance index (MARI) (0.93) and high metal tolerance. Quantitative polymerase chain reaction showed the abundance of target genes ranging from 6.6 × 103 to 6.5 × 108 copies g-1 sludge. The overall outcome reveals that STP sludge comprised varied multidrug-resistant bacterial populations. It will give insights into the functions of heavy metals and biofilm development in the selection and spread of AMR genes and the associated bacteria. Therefore, the application of sludge needs proper screening for AMR and metal contamination prior to its countless applications. This study will contribute immensely to the risk analysis of STP effluents on environmental health, including control of AMR transmission.

Physical compatibility of sulbactam/durlobactam with select intravenous drugs during simulated Y-site administration

PURPOSE

Sulbactam/durlobactam is a combination antibiotic designed to target Acinetobacter baumannii, including carbapenem-resistant and multidrug-resistant strains. The objective of this study was to determine the physical compatibility of sulbactam/durlobactam solution during simulated Y-site administration with 95 intravenous (IV) drugs.

METHODS

Vials of sulbactam/durlobactam solution were diluted in 0.9% sodium chloride injection to a volume of 100 mL (the final concentration of both drugs was 15 mg/mL). All other IV drugs were reconstituted according to the manufacturer's recommendations and diluted with 0.9% sodium chloride injection to the upper range of concentrations used clinically or tested undiluted as intended for administration. Y-site conditions were simulated by mixing 5 mL of sulbactam/durlobactam with 5 mL of the tested drug solutions in a 1:1 ratio. Solutions were inspected for physical characteristics (clarity, color, and Tyndall effect), turbidity, and pH changes before admixture, immediately post admixture, and over 4 hours. Incompatibility was defined as any observed precipitation, significant color change, positive Tyndall test, or turbidity change of ≥0.5 nephelometric turbidity unit during the observation period.

RESULTS

Sulbactam/durlobactam was physically compatible with 38 out of 42 antimicrobials tested (90.5%) and compatible overall with 86 of 95 drugs tested (90.5%). Incompatibility was observed with albumin, amiodarone hydrochloride, ceftaroline fosamil, ciprofloxacin, daptomycin, levofloxacin, phenytoin sodium, vecuronium, and propofol.

CONCLUSION

The Y-site compatibility of sulbactam/durlobactam with 95 IV drugs was described. These compatibility data will assist pharmacists and nurses to safely coordinate administration of IV medications with sulbactam/durlobactam.

Kinship analysis of mecA gene of methicillin-resistant Staphylococcus aureus isolated from milk and risk factors from the farmers in Blitar, Indonesia

Background and Aim

There are numerous reports of subclinical mastitis cases in Blitar, which is consistent with the region's high milk production and dairy cattle population. Staphylococcus aureus, which is often the cause of mastitis cases, is widely known because of its multidrug-resistant properties and resistance to β-lactam antibiotic class, especially the methicillin-resistant S. aureus (MRSA) strains. This study aimed to molecular detection and sequence analysis of the mecA gene in milk and farmer's hand swabs to show that dairy cattle are reservoirs of MRSA strains.

Materials and Methods

A total of 113 milk samples and 39 farmers' hand swab samples were collected from a dairy farm for the isolation of S. aureus using Mannitol salt agar. The recovered isolates were further characterized using standard microbiological techniques. Isolates confirmed as S. aureus were tested for sensitivity to antibiotics. Oxacillin Resistance Screening Agar Base testing was used to confirm the presence of MRSA, whereas the mecA gene was detected by polymerase chain reaction and sequencing.

Results

A total of 101 samples were confirmed to be S. aureus. There were 2 S. aureus isolates that were multidrug-resistant and 14 S. aureus isolates that were MRSA. The mecA gene was detected in 4/14 (28.6%) phenotypically identified MRSA isolates. Kinship analysis showed identical results between mecA from milk and farmers' hand swabs. No visible nucleotide variation was observed in the two mecA sequences of isolates from Blitar, East Java.

Conclusion

The spread of MRSA is a serious problem because the risk of zoonotic transmission can occur not only to people who are close to livestock in the workplace, such as dairy farm workers but also to the wider community through the food chain.

Multimodal learning in clinical proteomics: enhancing antimicrobial resistance prediction models with chemical information

MOTIVATION

Large-scale clinical proteomics datasets of infectious pathogens, combined with antimicrobial resistance outcomes, have recently opened the door for machine learning models which aim to improve clinical treatment by predicting resistance early. However, existing prediction frameworks typically train a separate model for each antimicrobial and species in order to predict a pathogen's resistance outcome, resulting in missed opportunities for chemical knowledge transfer and generalizability.

RESULTS

We demonstrate the effectiveness of multimodal learning over proteomic and chemical features by exploring two clinically relevant tasks for our proposed deep learning models: drug recommendation and generalized resistance prediction. By adopting this multi-view representation of the pathogenic samples and leveraging the scale of the available datasets, our models outperformed the previous single-drug and single-species predictive models by statistically significant margins. We extensively validated the multi-drug setting, highlighting the challenges in generalizing beyond the training data distribution, and quantitatively demonstrate how suitable representations of antimicrobial drugs constitute a crucial tool in the development of clinically relevant predictive models.

AVAILABILITY AND IMPLEMENTATION

The code used to produce the results presented in this article is available at https://github.com/BorgwardtLab/MultimodalAMR.

Extended-spectrum β-lactamases producing Enterobacteriaceae (ESBL-PE) prevalence in Nepal: A systematic review and meta-analysis

An alarming increase in the occurrence of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE) has threatened the treatment and management of bacterial infections. This systematic review and meta-analysis aimed to provide a quantitative estimate of the prevalence of ESBL among the members of the Enterobacteriaceae family by analyzing the community-based and clinical studies published between 2011 and 2021 from Nepal and determine if ESBL-PE correlates with multidrug resistance (MDR). The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were followed for systematic review and meta-analysis and the articles' quality was assessed using the Newcastle-Ottawa scale. Of the 2529 articles screened, 65 articles were systematically reviewed, data extracted, and included in in-depth meta-analysis. The overall pooled prevalence of ESBL-producers in Enterobacteriaceae was 29 % (95 % CI: 26-32 %) with high heterogeneity (I2 = 96 %, p < 0.001). Escherichia coli was the predominant ESBL-producing member of the Enterobacteriaceae family, followed by Citrobacter spp. and Klebsiella spp. The prevalence of ESBL-PE increased from 18.7 % in 2011 to 29.5 % in 2021. A strong positive correlation (r = 0.98) was observed between ESBL production and MDR in Enterobacteriaceae. ESBL-PE isolates showed high resistance to ampicillin, cephalosporins, and amoxicillin-clavulanic acid, and blaCTX-M type was the most reported gene variant among ESBL-PE. In conclusion, this study demonstrated an increased prevalence of ESBL-PE in Nepal over the last decade, and such isolates showed a high level of MDR against the β-lactams and non-β-lactam antibiotics. Tackling the rising antibiotic resistance (AR) and MDR in ESBL-PE would require concerted efforts from all stakeholders to institute effective infection control programs in the community and clinical settings.

Two-Dose Ceftiofur Treatment Increases Cephamycinase Gene Quantities and Fecal Microbiome Diversity in Dairy Cows Diagnosed with Metritis

Antimicrobial resistance is a significant concern worldwide; meanwhile, the impact of 3rd generation cephalosporin (3GC) antibiotics on the microbial communities of cattle and resistance within these communities is largely unknown. The objectives of this study were to determine the effects of two-dose ceftiofur crystalline-free acid (2-CCFA) treatment on the fecal microbiota and on the quantities of second-and third-generation cephalosporin, fluoroquinolone, and macrolide resistance genes in Holstein-Friesian dairy cows in the southwestern United States. Across three dairy farms, 124 matched pairs of cows were enrolled in a longitudinal study. Following the product label regimen, CCFA was administered on days 0 and 3 to cows diagnosed with postpartum metritis. Healthy cows were pair-matched based on lactation number and calving date. Fecal samples were collected on days 0, 6, and 16 and pooled in groups of 4 (n = 192) by farm, day, and treatment group for community DNA extraction. The characterization of community DNA included real-time PCR (qPCR) to quantify the following antibiotic resistance genes: blaCMY-2, blaCTX-M, mphA, qnrB19, and the highly conserved 16S rRNA back-calculated to gene copies per gram of feces. Additionally, 16S rRNA amplicon sequencing and metagenomics analyses were used to determine differences in bacterial community composition by treatment, day, and farm. Overall, blaCMY-2 gene copies per gram of feces increased significantly (p ≤ 0.05) in the treated group compared to the untreated group on day 6 and remained elevated on day 16. However, blaCTX-M, mphA, and qnrB19 gene quantities did not differ significantly (p ≥ 0.05) between treatment groups, days, or farms, suggesting a cephamycinase-specific enhancement in cows on these farms. Perhaps unexpectedly, 16S rRNA amplicon metagenomic analyses showed that the fecal bacterial communities from treated animals on day 6 had significantly greater (p ≤ 0.05) alpha and beta diversity than the untreated group. Two-dose ceftiofur treatment in dairy cows with metritis elevates cephamycinase gene quantities among all fecal bacteria while paradoxically increasing microbial diversity.

β_lactam antibiotics against drug addiction: A novel therapeutic option

Drug addiction as a problem for the health of the individual and the society is the result of a complex process in which there is an interaction between brain nuclei and neurotransmitters (such as glutamate). β-lactam antibiotics, due to their enhancing properties on the glutamate transporter glutamate transporter-1, can affect and counteract the addictive mechanisms of drugs through the regulation of extracellular glutamate. Since glutamate is a key neurotransmitter in the development of drug addiction, it seems that β-lactams can be considered as a promising treatment for addiction. However, more research in this field is necessary to identify other mechanisms involved in their effectiveness. This article is a review of the studies conducted on the effect of β-lactam administration in preventing the development of drug addiction, as well as their possible cellular and molecular mechanisms. This review suggests the clinical use of β-lactam antibiotics that have weak antimicrobial properties (such as clavulanic acid) in the treatment of drug dependence.

Proteomic Changes in Methicillin-Resistant Staphylococcus aureus Exposed to Cannabinoids

Methicillin-resistant Staphylococcus aureus (MRSA) is a major human pathogen that causes a wide range of infections. Its resistance to β-lactam antibiotics complicates treatment due to the limited number of antibiotics with activity against MRSA. To investigate development of alternative therapeutics, the mechanisms that mediate antibiotic resistance in MRSA need to be fully understood. In this study, MRSA cells were subjected to antibiotic stress from methicillin in combination with three cannabinoid compounds and analyzed using proteomics to assess the changes in physiology. Subjecting MRSA to nonlethal levels of methicillin resulted in an increased production of penicillin-binding protein 2 (PBP2). Exposure to cannabinoids showed antibiotic activity against MRSA, and differential proteomics revealed reduced levels of proteins involved in the energy production as well as PBP2 when used in combination with methicillin.

In silico designing and immunoinformatics analysis of a novel peptide vaccine against metallo-beta-lactamase (VIM and IMP) variants

The rapid spread of acquired metallo-beta-lactamases (MBLs) among gram negative pathogens is becoming a global concern. Improper use of broad-spectrum antibiotics can trigger the colonization and spread of resistant strains which lead to increased mortality and significant economic loss. In the present study, diverse immunoinformatic approaches are applied to design a potential epitope-based vaccine against VIM and IMP MBLs. The amino acid sequences of VIM and IMP variants were retrieved from the GenBank database. ABCpred and BCPred online Web servers were used to analyze linear B cell epitopes, while IEDB was used to determine the dominant T cell epitopes. Sequence validation, allergenicity, toxicity and physiochemical analysis were performed using web servers. Seven sequences were identified for linear B cell dominant epitopes and 4 sequences were considered as dominant CD4+ T cell epitopes, and the predicted epitopes were joined by KK and GPGPG linkers. Stabilized multi-epitope protein structure was obtained using molecular dynamics simulation. Molecular docking showed that the designed vaccine exhibited sustainable and strong binding interactions with Toll-like receptor 4 (TLR4). Finally, codon adaptation and in silico cloning studies were performed to design an effective vaccine production strategy. Immune simulation significantly provided high levels of immunoglobulins, T helper cells, T-cytotoxic cells and INF-γ. Even though the introduced vaccine candidate demonstrates a very potent immunogenic potential, but wet-lab validation is required to further assessment of the effectiveness of this proposed vaccine candidate.

Bifunctional antibiotic hybrids: A review of clinical candidates

Antibiotic resistance is a top threat to human health and a priority across the globe. This problematic issue is accompanied by the decline of new antibiotics in the pipeline over the past 30 years. In this context, an urgent need to develop new strategies to combat antimicrobial resistance is in great demand. Lately, among the possible approaches used to deal with antimicrobial resistance is the covalent ligation of two antibiotic pharmacophores that target the bacterial cells through a dissimilar mode of action into a single hybrid molecule, namely hybrid antibiotics. This strategy exhibits several advantages, including better antibacterial activity, overcoming the existing resistance towards individual antibiotics, and may ultimately delay the onset of bacterial resistance. This review sheds light on the latest development of the dual antibiotic hybrids pipeline, their potential mechanisms of action, and challenges in their use.

Combating Antimicrobial Resistance in the Post-Genomic Era: Rapid Antibiotic Discovery

Constantly evolving drug-resistant "superbugs" have caused an urgent demand for novel antimicrobial agents. Natural products and their analogs have been a prolific source of antimicrobial agents, even though a high rediscovery rate and less targeted research has made the field challenging in the pre-genomic era. With recent advancements in technology, natural product research is gaining new life. Genome mining has allowed for more targeted excavation of biosynthetic potential from natural sources that was previously overlooked. Researchers use bioinformatic algorithms to rapidly identify and predict antimicrobial candidates by studying the genome before even entering the lab. In addition, synthetic biology and advanced analytical instruments enable the accelerated identification of novel antibiotics with distinct structures. Here, we reviewed the literature for noteworthy examples of novel antimicrobial agents discovered through various methodologies, highlighting the candidates with potent effectiveness against antimicrobial-resistant pathogens.

Capture ELISA for KPC Detection in Gram-Negative Bacilli: Development and Standardisation

The detection of KPC-type carbapenemases is necessary for guiding appropriate antibiotic therapy and the implementation of antimicrobial stewardship and infection control measures. Currently, few tests are capable of differentiating carbapenemase types, restricting the lab reports to their presence or not. The aim of this work was to raise antibodies and develop an ELISA test to detect KPC-2 and its D179 mutants. The ELISA-KPC test was designed using rabbit and mouse polyclonal antibodies. Four different protocols were tested to select the bacterial inoculum with the highest sensitivity and specificity rates. The standardisation procedure was performed using 109 previously characterised clinical isolates, showing 100% of sensitivity and 89% of specificity. The ELISA-KPC detected all isolates producing carbapenemases, including KPC variants displaying the ESBL phenotype such as KPC-33 and -66.

Development of a combination antibiogram for empirical treatments of Pseudomonas aeruginosa at a university-affiliated teaching hospital

INTRODUCTION

The significantly higher mortality rate in the critical illness patients with Pseudomonas aeruginosa (PA) infection is linked to inappropriate selecting of empirical treatment. Traditional local antibiogram provides clinicians the resistant rate of a single antimicrobial agent to the pathogen in the specific setting. The information is valuable to the clinicians in selecting suitable empirical antibiotic therapy. However, traditional local antibiogram can only provide information for single agent empirical antibiotic not combination regimens. The combination antibiogram should be developed to facilitate the selection of appropriate antibiotics to broader the coverage rate of resistant PA.

METHODS

The susceptibility to the β-lactam antibiotics (piperacillin/tazobactam (PTZ), ceftazidime, cefepime, imipenem, or meropenem) or to those administered in combination with an aminoglycoside (gentamicin or amikacin) or fluoroquinolone (ciprofloxacin or levofloxacin) was calculated. The chi-square test was used to compare the differences of combination coverage rates between non-ICU and ICU isolates.

RESULTS

880 PA isolates were isolated during study period. The susceptibility of single agents ranged from 83.1% to 89.7%. The combination regimens containing amikacin provide the highest cover rate (98.9%-99.1%) and those containing levofloxacin provide less coverage rate (92.3%-93.9%). The susceptibility to five β-lactam single agents in ICU isolates significantly lower than non-ICU isolates. The non-ICU isolates exhibited significantly higher susceptibility to the PTZ-gentamicin (p = 0.002) and ceftazidime-gentamicin (p = 0.025) than ICU isolates.

CONCLUSION

Our results support the use of aminoglycosides instead of fluoroquinolones as additive agents in empirical combination treatments for patients with critical infections caused by PA.

An In Vitro Susceptibility Study of Cefotaxime-Sulbactam on Clinical Bacterial Isolates From Various Regions in India: A Comparison With Ceftriaxone-Sulbactam

Background and objective Combining sulbactam with cefotaxime/ceftriaxone augments its antimicrobial activity against β-lactamase-producing bacteria. They are widely used as empirical treatment for many clinical infections. However, there is a scarcity of data on the susceptibility of various organisms to these antibiotics in the Indian region. In light of this, the present in vitro study evaluated the susceptibility of bacterial isolates to cefotaxime-sulbactam and compared it with ceftriaxone-sulbactam. Methodology Clinical samples with positive bacterial cultures from various laboratories in India were subjected to antibiotic sensitivity testing using in vitro E-test strips and disk diffusion methods to determine the minimum inhibitory concentration (MIC) and zone of inhibition (ZOI), respectively. MIC₅₀ and MIC₉₀ values were determined along with the measurement of the ZOI for the effectiveness of antibiotics. Interpretations of MIC and ZOI values were made as per the criteria set by the Clinical and Laboratory Standards Institute (CLSI) guidelines to estimate the proportion of sensitive organisms. Results Among 400 clinical isolates evaluated, Escherichia coli (E. coli) (47.75%) was the most common organism isolated followed by Klebsiella (26%), Salmonella (7.75%), Proteus (3.8%), and Acinetobacter (2.8%). The mean ZOI was found significantly higher for E. coli, Klebsiella, and Salmonella in the cefotaxime-sulbactam group than in the ceftriaxone-sulbactam group. MIC₅₀ values for E. coli and Klebsiella were 0.25 and 0.19 µg/ml, respectively in the cefotaxime-sulbactam group as compared to 0.38 and 0.25 µg/ml, respectively for ceftriaxone-sulbactam. The proportion of sensitive isolates was also higher in the cefotaxime-sulbactam group for E. coli, Klebsiella, and Salmonella. Conclusions The in vitro effect of cefotaxime-sulbactam on organisms is similar to that of ceftriaxone-sulbactam in terms of MIC, ZOI, and proportion of sensitivity based on our study involving clinical isolates from various parts of India. Cefotaxime-sulbactam may be preferred in the empirical management of various clinical infections.

β-Lactam resistance genes present in UK pheasants and red-legged partridges

BACKGROUND

Despite considerable recent reductions in antimicrobial use, the UK gamebird industry continues to struggle with production diseases during the rearing season, necessitating significant antibiotic use. This observational study investigated the presence of genes conferring resistance to β-lactam antibiotics within industry-reared pheasants and red-legged partridges in the UK.

METHODS

DNA was extracted from 60 pooled caecal samples collected from gamebirds at routine postmortem examinations during the rearing season. Genes encoding extended-spectrum β-lactamases (ESBL) were detected by PCR and the corresponding alleles were determined.

RESULTS

Over half (53%) of the samples harboured genes encoding blaTEM resistance, with blaSHV identified in 20% of samples. The blaTEM gene was more common on sites with higher antibiotic use, whereas blaSHV was predominantly found in birds younger than 5 weeks. Genotyping of the identified resistance genes revealed the presence of blaTEM-1 , blaSHV-1 and blaSHV-11 alleles.

LIMITATIONS

This was a small-scale study conducted at four sites in southern England.

CONCLUSION

This is the first report of the presence of ESBL genes in gamebirds, highlighting the need for further research into antimicrobial resistance in UK gamebirds.

Synthesis of α-CF3 Amides via Palladium-Catalyzed Carbonylation of 2-Bromo-3,3,3-trifluoropropene

Amide compounds are important organic compounds, which play an important role in biomedical chemistry, materials science, life science, and other fields. The synthesis of α-CF₃ amides, especially compounds containing 3-(trifluoromethyl)-1,3,4,5-tetrahydro-2H-benzo[b][1,4]diazepine-2-one, has long been a challenge due to the tensile properties and instability of the rings. Here, we report an example of palladium-catalyzed carbonylation of CF₃-containing olefin to form α-CF₃ acrylamide. By controlling the ligands, we can get different amide compounds as products. This method has good substrate adaptability and functional group tolerance.

Pseudomonas aeruginosa and Staphylococcus aureus Display Differential Proteomic Responses to the Silver(I) Compound, SBC3

The urgent need to combat antibiotic resistance and develop novel antimicrobial therapies has triggered studies on novel metal-based formulations. N-heterocyclic carbene (NHC) complexes coordinate transition metals to generate a broad range of anticancer and/or antimicrobial agents, with ongoing efforts being made to enhance the lipophilicity and drug stability. The lead silver(I) acetate complex, 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene (NHC*) (SBC3), has previously demonstrated promising growth and biofilm-inhibiting properties. In this work, the responses of two structurally different bacteria to SBC3 using label-free quantitative proteomics were characterised. Multidrug-resistant Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) are associated with cystic fibrosis lung colonisation and chronic wound infections, respectively. SBC3 increased the abundance of alginate biosynthesis, the secretion system and drug detoxification proteins in P. aeruginosa, whilst a variety of pathways, including anaerobic respiration, twitching motility and ABC transport, were decreased in abundance. This contrasted the affected pathways in S. aureus, where increased DNA replication/repair and cell redox homeostasis and decreased protein synthesis, lipoylation and glucose metabolism were observed. Increased abundance of cell wall/membrane proteins was indicative of the structural damage induced by SBC3 in both bacteria. These findings show the potential broad applications of SBC3 in treating Gram-positive and Gram-negative bacteria.

Synergistic antimicrobial effect of the combination of beta-lactam antibiotics and chitosan derivative on multidrug-resistant bacteria

Dissemination of multidrug-resistant (MDR) bacteria with CTX-M-type extended-spectrum β-lactamases (blaCTX-M) has become the greatest challenge in public health care. This study aimed to investigate the synergistic antibacterial potential of N-alkylaminated chitosan nanoparticles (CNPs) combined with conventional β-lactam antibiotics (BLAs) against multidrug-resistant pathogen with blaCTX-M gene. The results of this study showed that the developed nano-formulation resensitized the studied E. coli MDR strain (E001) to ampicillin (AMP) and piperacillin (PIP) by causing a 1000-10,000-fold decrease in their MIC values (5000-50,000 mg/L to 5 mg/L). The conjugation of CNPs with cefoxitin (FOX) and ceftazidime (CAZ) showed a comparatively lower synergistic inhibitory effect owing to the higher susceptibility (MIC value = 0.5 mg/L-5 mg/L) of E001 to these antibiotics. The results indicate that CNPs could be effectively employed as an additive to augment the antibacterial effect of the BLAs for which MDR strains exhibit higher MIC values.

Drug Repurposing Approaches towards Defeating Multidrug-Resistant Gram-Negative Pathogens: Novel Polymyxin/Non-Antibiotic Combinations

Multidrug-resistant (MDR) Gram-negative pathogens remain an unmet public health threat. In recent times, increased rates of resistance have been reported not only to commonly used antibiotics, but also to the last-resort antibiotics, such as polymyxins. More worryingly, despite the current trends in resistance, there is a lack of new antibiotics in the drug-discovery pipeline. Hence, it is imperative that new strategies are developed to preserve the clinical efficacy of the current antibiotics, particularly the last-line agents. Combining conventional antibiotics such as polymyxins with non-antibiotics (or adjuvants), has emerged as a novel and effective strategy against otherwise untreatable MDR pathogens. This review explores the available literature detailing the latest polymyxin/non-antibiotic combinations, their mechanisms of action, and potential avenues to advance their clinical application.

Phage-Plasmids Spread Antibiotic Resistance Genes through Infection and Lysogenic Conversion

Antibiotic resistance is rapidly spreading via the horizontal transfer of resistance genes in mobile genetic elements. While plasmids are key drivers of this process, few integrative phages encode antibiotic resistance genes. Here, we find that phage-plasmids, elements that are both phages and plasmids, often carry antibiotic resistance genes. We found 60 phage-plasmids with 184 antibiotic resistance genes, providing resistance for broad-spectrum-cephalosporins, carbapenems, aminoglycosides, fluoroquinolones, and colistin. These genes are in a few hot spots, seem to have been cotranslocated with transposable elements, and are often in class I integrons, which had not been previously found in phages. We tried to induce six phage-plasmids with resistance genes (including four with resistance integrons) and succeeded in five cases. Other phage-plasmids and integrative prophages were coinduced in these experiments. As a proof of concept, we focused on a P1-like element encoding an extended spectrum β-lactamase, blaCTX-M-55. After induction, we confirmed that it is capable of infecting and converting four other E. coli strains. Its reinduction led to the further conversion of a sensitive strain, confirming that it is a fully functional phage. This study shows that phage-plasmids carry a large diversity of clinically relevant antibiotic resistance genes that they can transfer across bacteria. As plasmids, these elements seem plastic and capable of acquiring genes from other plasmids. As phages, they may provide novel paths of transfer for resistance genes because they can infect bacteria that are distant in time and space from the original host. As a matter of alarm, they may also mediate transfer to other types of phages. IMPORTANCE The dissemination of antimicrobial resistance is a major threat to global health. Here, we show that a group of temperate bacterial viruses (phages), termed phage-plasmids, commonly encode different and multiple types of resistance genes of high clinical importance, often in integrons. This is unexpected, as phages typically do not carry resistance genes and, hence, do not confer upon their hosts resistance via infection and genome integration. Our experiments with phage-plasmids isolated from clinical settings confirmed that they infect sensitive strains and render them antibiotic resistant. The spread of antibiotic resistance genes by phage-plasmids is worrisome because it dispenses cell-to-cell contact, which is necessary for canonical plasmid transfer (conjugation). Furthermore, their integrons become genetic platforms for the acquisition of novel resistance genes.

The Role of Outer Membrane Proteins in UPEC Antimicrobial Resistance: A Systematic Review

Uropathogenic Escherichia coli (UPEC) are one of the most common agents of urinary tract infection. In the last decade, several UPEC strains have acquired antibiotic resistance mechanisms and some have become resistant to all classes of antibiotics. UPEC outer membrane proteins (OMPs) seem to have a decisive role not only in the processes of invasion and colonization of the bladder mucosa, but also in mechanisms of drug resistance, by which bacteria avoid killing by antimicrobial molecules. This systematic review was performed according to the PRISMA guidelines, aiming to characterize UPEC OMPs and identify their potential role in antimicrobial resistance. The search was limited to studies in English published during the last decade. Twenty-nine studies were included for revision and, among the 76 proteins identified, seven were associated with antibiotic resistance. Indeed, OmpC was associated with β-lactams resistance and OmpF with β-lactams and fluoroquinolone resistance. In turn, TolC, OmpX, YddB, TosA and murein lipoprotein (Lpp) were associated with fluoroquinolones, enrofloxacin, novobiocin, β-lactams and globomycin resistances, respectively. The clinical implications of UPEC resistance to antimicrobial agents in both veterinary and human medicine must propel the implementation of new strategies of administration of antimicrobial agents, while also promoting the development of improved antimicrobials, protective vaccines and specific inhibitors of virulence and resistance factors.

In vitro activity of celastrol in combination with thymol against carbapenem-resistant Klebsiella pneumoniae isolates

Klebsiella pneumoniae is an opportunistic pathogen causing nosocomial and community-acquired infections. Klebsiella has developed resistance against antimicrobials including the last resort class; carbapenem. Currently, treatment options for carbapenem-resistant-Klebsiella (CRK) are very limited. This study aims to restore carbapenem effectiveness against CRK using celastrol and thymol. Clinical Klebsiella isolates were identified using biochemical and molecular methods. Antimicrobial susceptibility was determined using disk-diffusion method. Carbapenemase-production was tested phenotypically and genotypically. Celastrol and thymol-MICs were determined and the carbapenemase-inhibitory effect of sub-MICs was investigated. Among 85 clinical Klebsiella isolates, 72 were multi-drug-resistant and 43 were meropenem-resistant. Phenotypically, 39 isolates were carbapenemase-producer. Genotypically, bla_NDM1 was detected in 35 isolates, bla_VIM in 17 isolates, bla_OXA in 18 isolates, and bla_KPC was detected only in 6 isolates. Celastrol showed significant inhibitory effect against carbapenemase-hydrolytic activity. Meropenem-MIC did not decrease in presence of celastrol, only 2-fold decrease was observed with thymol, while 4-64 fold decrease was observed when meropenem was combined with both celastrol and thymol. Furthermore, thymol increased CRK cell wall-permeability. Molecular docking revealed that celastrol is superior to thymol for binding to KPC and VIM-carbapenemase. Our study showed that celastrol is a promising inhibitor of multiple carbapenemases. While meropenem-MIC were not affected by celastrol alone and decreased by only 2-folds with thymol, it decreased by 4-64 folds in presence of both celastrol and thymol. Thymol increases the permeability of CRK-envelope to celastrol. The triple combination (meropenem/celastrol/thymol) could be useful for developing more safe and effective analogues to restore the activity of meropenem and other β-lactams.

A patent review on pharmaceutical and therapeutic applications of oxadiazole derivatives for the treatment of chronic diseases (2013-2021)

INTRODUCTION

Oxadiazole is a unique class of heterocycle, possessing numerous important biomedical and therapeutic applications such as anti-bacterial, anti-cancer, anti-inflammatory, inhibitors for diverse enzymes, receptors modulators, and neuroprotective properties. The rapid development in the field of oxadiazole-containing structures is confirmed by the development of numerous clinical drugs such as doxazosin, nesapidil, pleconaril, fasiplon, ataluren, zibotentan, and prenoxdiazine as selected examples.

AREAS COVERED

This review provides a comprehensive overview of the range of biological applications of oxadiazole-containing drugs in a range of patents from 2013 to 2021. The information was collected from available data sources including SciFinder, Reaxys, MedLine, and Chemical Abstracts.

EXPERT OPINION

Oxadiazole is an established class of compounds with fascinating biological properties. The importance of oxadiazoles can be recognized by their enormous application in a wide spectrum of medicinal chemistry from anticancer, antibiotic, and antidiabetic to the use in agriculture and neuroprotection. For instance, the oxadiazole-based compounds have shown the ability to modulate a variety of receptors including the M4 receptor agonists, S1P1 receptor modulators, SSTR5 antagonists, orexin type-2 receptor agonists, liver X receptor agonists, and many more. This testifies to the special features associated with the oxadiazole scaffold making it a significant pharmacophore.

Different Chiral Ligands Assisted Enantioselective C-H Functionalization with Transition-Metal Catalysts

C–H bonds are common in organic molecules, and the functionalization of these inactive C–H bonds has become one of the most powerful methods used to assemble complicated bioactive molecules from readily available starting materials. However, a central challenge in these reactions is controlling their stereoselectivity. Recently, significant progress has been made in the development of enantioselective C–H activation enabled by different chiral ligands for the formation of C–C and C–X bonds bearing a chiral center. In this paper, we focus on some archetypal chiral ligands for enantioselective C–H functionalization developed in recent years and analyze the mechanism of these methods, aiming to accelerate related research and to search for more efficient strategies.

Emerging nanotechnologies for targeting antimicrobial resistance

Antimicrobial resistance is a leading cause of mortality worldwide. Without newly approved antibiotics and antifungals being brought to the market, resistance is being developed to the ones currently available to clinicians. The reason is the applied evolutionary pressure to bacterial and fungal species due to the wide overuse of common antibiotics and antifungals in clinical practice and agriculture. Biofilms harbour antimicrobial-resistant subpopulations, which make their antimicrobial treatment even more challenging. Nanoparticle-based technologies have recently been shown to successfully overcome antimicrobial resistance in both planktonic and biofilms phenotypes. This results from the combination of novel nanomaterial research and classic antimicrobial therapies which promise to deliver a whole new generation of high-performance active nanocarrier systems. This review discusses the latest developments of promising nanotechnologies with applications against resistant pathogens and evaluates their potential and feasibility for use in novel antimicrobial therapies.

N-Aryl Mercaptopropionamides as Broad-Spectrum Inhibitors of Metallo-β-Lactamases

Drug-resistant pathogens pose a global challenge to public health as they cause diseases that are extremely difficult to cure. Metallo-β-lactamases (MBLs) are a diverse set of zinc-containing enzymes that catalyze the hydrolysis of β-lactam drugs, including carbapenems, which are considered as the last resort to fight severe infections. To restore the activity of current β-lactam antibiotics and to offer an orthogonal strategy to the discovery of new antibiotics, we have identified a series of polar N-aryl mercaptopropionamide derivatives as potent inhibitors of several class B1 MBLs. We have identified a hit structure with high selectivity restoring the effect of imipenem and reducing minimum inhibitory concentration (MIC) values up to 256-fold in resistant isolates from Escherichia coli. Furthermore, the combination of imipenem with our inhibitor showed in vivo efficacy in a Galleria mellonella model, increasing the survival rate of infected larvae by up to 31%.

The rapid synthesis of intrinsic green-fluorescent poly(pyrogallol)-derived carbon dots for amoxicillin drug sensing in clinical samples

Detection of the amoxicillin drug using pyrogallol-derived carbon dots.

Effect of Imipenem and Amikacin Combination against Multi-Drug Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic nosocomial pathogen associated with high morbidity and mortality rates. Combination of antibiotics has been found to combat multi-drug resistant or extensively drug resistance P. aeruginosa. In this study we investigate the in vitro and in vivo effect of amikacin and imipenem combination against resistant P. aeruginosa. The checkerboard technique and time-killing curve have been performed for in vitro studies showed synergistic effect for combination. A peritonitis mouse model has been used for evaluation of the therapeutic efficacy of this combination which confirmed this synergistic effect. The in vitro and in vivo techniques showed synergistic interaction between tested drugs with fractional inhibitory concentration indices (FICIs) of ≤0.5. Conventional PCR and quantitative real-time PCR techniques were used in molecular detection of bla _IMP and aac(6')-Ib as 35.5% and 42.2% of P. aeruginosa harbored bla _IMP and aac(6')-Ib respectively. Drug combination viewed statistically significant reduction in bacterial counts (p value < 0.5). The lowest bla _IMP and aac(6')-Ib expression was observed after treatment with 0.25 MIC of imipenem + 0.5 MIC of amikacin. Morphological changes in P. aeruginosa isolates were detected by scanning electron microscope (SEM) showing cell shrinkage and disruption in the outer membrane of P. aeruginosa that were more prominent with combination therapy than with monotherapy.

Exploitation of E. coli for the production of penicillin G amidase: a tool for the synthesis of semisynthetic β-lactam antibiotics

BACKGROUND

Penicillin G amidase/acylases from microbial sources is a unique enzyme that belongs to the N-terminal nucleophilic hydrolase structural superfamily. It catalyzes the selective hydrolysis of side chain amide/acyl bond of penicillins and cephalosporins whereas the labile amide/acyl bond in the β-lactam ring remains intact. This review summarizes the production aspects of PGA from various microbial sources at optimized conditions. The minimal yield from wild strains has been extensively improved using varying strain improvement techniques like recombination and mutagenesis; further applied for the subsequent synthesis of 6-aminopenicillanic acid, which is an intermediate molecule for synthesis of a wide range of novel β-lactam antibiotics. Immobilization of PGA has also been attempted to enhance the durability of enzyme for the industrial purposes.

SHORT CONCLUSION

The present review provides an emphasis on exploitation of E. coli to enhance the microbial production of PGA. The latest achievements in the production of recombinant enzymes have also been discussed. Besides E. coli, other potent microbial strains with PGA activity must be explored to enhance the yields.

Plasmid-mediated catabolism for the removal of xenobiotics from the environment

The large-scale application of xenobiotics adversely affects the environment. The genes that are present in the chromosome of the bacteria are considered nonmobile, whereas the genes present on the plasmids are considered mobile genetic elements. Plasmids are considered indispensable for xenobiotic degradation into the contaminated environment. In the contaminated sites, bacteria with plasmids can transfer the mobile genetic element into another strain. This mechanism helps in spreading the catabolic genes into the bacterial population at the contaminated sites. The indigenous microbial strains with such degradative plasmids are important for the bioremediation of xenobiotics. Environmental factors play a critical role in the conjugation efficiency, which is involved in the bioremediation of the xenobiotics at the contaminated sites. However, there is still a need for more research to fill in the gaps regarding plasmids and their impact on bioremediation. This review explores the role of bacterial plasmids in the bioremediation of xenobiotics from contaminated environments.

Exploiting enzyme evolution for computational protein design

Recent years have seen an explosion of interest in understanding the physicochemical parameters that shape enzyme evolution, as well as substantial advances in computational enzyme design. This review discusses three areas where evolutionary information can be used as part of the design process: (i) using ancestral sequence reconstruction (ASR) to generate new starting points for enzyme design efforts; (ii) learning from how nature uses conformational dynamics in enzyme evolution to mimic this process in silico; and (iii) modular design of enzymes from smaller fragments, again mimicking the process by which nature appears to create new protein folds. Using showcase examples, we highlight the importance of incorporating evolutionary information to continue to push forward the boundaries of enzyme design studies.

Computationally designed peptide macrocycle inhibitors of New Delhi metallo-β-lactamase 1

The rise of antibiotic resistance calls for new therapeutics targeting resistance factors such as the New Delhi metallo-β-lactamase 1 (NDM-1), a bacterial enzyme that degrades β-lactam antibiotics. We present structure-guided computational methods for designing peptide macrocycles built from mixtures of l- and d-amino acids that are able to bind to and inhibit targets of therapeutic interest. Our methods explicitly consider the propensity of a peptide to favor a binding-competent conformation, which we found to predict rank order of experimentally observed IC₅₀ values across seven designed NDM-1- inhibiting peptides. We were able to determine X-ray crystal structures of three of the designed inhibitors in complex with NDM-1, and in all three the conformation of the peptide is very close to the computationally designed model. In two of the three structures, the binding mode with NDM-1 is also very similar to the design model, while in the third, we observed an alternative binding mode likely arising from internal symmetry in the shape of the design combined with flexibility of the target. Although challenges remain in robustly predicting target backbone changes, binding mode, and the effects of mutations on binding affinity, our methods for designing ordered, binding-competent macrocycles should have broad applicability to a wide range of therapeutic targets.

A general strategy for the synthesis of α-trifluoromethyl- and α-perfluoroalkyl-β-lactams via palladium-catalyzed carbonylation

β-Lactam compounds play a key role in medicinal chemistry, specifically as the most important class of antibiotics. Here, we report a novel one-step approach for the synthesis of α-(trifluoromethyl)-β-lactams and related products from fluorinated olefins, anilines and CO. Utilization of an advanced palladium catalyst system with the Ruphos ligand allows for selective cycloaminocarbonylations to give diverse fluorinated β-lactams in high yields.

Detection of Antimicrobial and Heavy-Metal Resistance Genes in Aeromonas spp. Isolated from Hard-Shelled Mussel (Mytilus Coruscus)

Hard-shelled mussel (Mytilus coruscus) is a popular seafood in South Korea because of its delicacy and high nutritional value. Our study aimed to identify antimicrobial and heavy-metal resistance determinants in Aeromonas isolates from marketed hard-shelled mussel in South Korea. A total of 33 Aeromonas species were isolated, and antimicrobial disk diffusion test was done to observe antimicrobial resistance patterns. In addition, broth microdilution test was performed to determine resistance to heavy-metals. PCR amplification was done to detect resistance genes. High resistance to amoxicillin (100.0%), ampicillin (93.9%), rifampicin (78.8%), and cephalothin (48.5%) was observed where least resistance to other antimicrobials was also detected. In addition, the isolates showed high resistance to cadmium (Cd) (57.6%), and 42.4% and 27.3% were resistant to chromium (Cr) and copper (Cu). The occurrence of antimicrobial resistance genes, such as blaTEM, blaSHV, blaCTX-M, tetB, tetE, and intI1 genes, was observed in 9 (27.3%), 8 (24.2%), 8 (24.2%), 6 (18.2%), 5 (15.2%), and 9 (27.3%) isolates, respectively. Also, heavy-metal resistance genes, czcA, copA, and merA were detected in 17 (51.5%), 11 (33.3%), and 7 (21.2%) of the isolates, respectively. The results suggest that mussels are a reservoir of multidrug and heavy-metal-resistant Aeromonas spp.

Evolution of β-lactamases and enzyme promiscuity

β-Lactamases represent one of the most prevalent resistance mechanisms against β-lactam antibiotics. Beyond their clinical importance, they have also become key models in enzymology and evolutionary biochemistry. A global understanding of their evolution and sequence and functional diversity can therefore aid a wide set of different disciplines. Interestingly, β-lactamases have evolved multiple times from distinct evolutionary origins, with ancestries that reach back billions of years. It is therefore no surprise that these enzymes exhibit diverse structural features and enzymatic mechanisms. In this review, we provide a bird's eye view on the evolution of β-lactamases within the two enzyme superfamilies-i.e. the penicillin-binding protein-like and metallo-β-lactamase superfamily-through phylogenetics. We further discuss potential evolutionary origins of each β-lactamase class by highlighting signs of evolutionary connections in protein functions between β-lactamases and other enzymes, especially cases of enzyme promiscuity.

Azetidinimines as a novel series of non-covalent broad-spectrum inhibitors of β-lactamases with submicromolar activities against carbapenemases KPC-2 (class A), NDM-1 (class B) and OXA-48 (class D)

The occurrence of resistances in Gram negative bacteria is steadily increasing to reach extremely worrying levels and one of the main causes of resistance is the massive spread of very efficient β-lactamases which render most β-lactam antibiotics useless. Herein, we report the development of a series of imino-analogues of β-lactams (namely azetidinimines) as efficient non-covalent inhibitors of β-lactamases. Despite the structural and mechanistic differences between serine-β-lactamases KPC-2 and OXA-48 and metallo-β-lactamase NDM-1, all three enzymes can be inhibited at a submicromolar level by compound 7dfm, which can also repotentiate imipenem against a resistant strain of Escherichia coli expressing NDM-1. We show that 7dfm can efficiently inhibit not only the three main clinically-relevant carbapenemases of Ambler classes A (KPC-2), B (NDM-1) and D (OXA-48) with Ki's below 0.3 μM, but also the cephalosporinase CMY-2 (class C, 86% inhibition at 10 μM). Our results pave the way for the development of a new structurally original family of non-covalent broad-spectrum inhibitors of β-lactamases.

Antibacterial and synergistic activity of 6β-hydroxy-3-oxolup-20(29)-en-28-oic acid (6β-hydroxy betunolic acid) isolated from Schumacheria castaneifolia vahl

Multi- drug resistant microbial pathogens are a serious global health problem and thus new antibacterial agents, which are effective both alone and in combination with traditional antibiotics, are urgently needed. Hence, the objective of the present study was to investigate the antibacterial activity of 6β-hydroxy-3-oxolup-20(29)-en-28-oic acid (6β-hydroxy betunolic acid) isolated from the bark of Schumacheria castaneifolia and its effect when combined with oxacillin. Antibacterial potential of 6β-hydroxy betunolic acid alone was performed using broth micro dilution assay against sixteen bacterial strains which included eight standard strains [Staphylococcus aureus (ATCC 29213 and ATCC 25923), Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 35218 and ATCC 25922), carbapenemase producing Kebsiella pneumonia (ATCC BAA 1705), carbapenemase non-producing K. pneumonia (ATCC BAA 1706) and Pseudomonas aeruginosa (ATCC 27853)] and four strains each of clinically isolated meropenem resistant Acinetobactor sp. and methicillin resistant S. aureus (MRSA) which were included in the urgent threat list and serious threat list, respectively in 2019 by the Centers for Disease Control and Prevention in the United States. Its effect when combined with oxacillin was tested against S. aureus (ATCC 29213) and MRSAs using a checkerboard dilution method. The results indicated that 6β-hydroxy betunolic acid had antibacterial activity against the tested Gram positive organisms with MICs ranging from 16 to 32 mg L^-1 (MIC of oxacillin and meropenem ranged from 0.25-16 and 0.03-128 mg L^-1 respectively). The high MIC values (>1024 mg L^-1) of 6β-hydroxy betunolic acid against Gram negative strains indicated a likely lack of activity. Further, 6β-hydroxy betunolic acid exhibited synergistic effect with oxacillin against Staphylococcus aureus (0.49) and showed an additive effect against all the tested MRSAs. The present study suggested that the antibacterial activity of the 6β-hydroxy betunolic acid is restricted to Staphylococcus isolates and possibly Enterococcus faecalis. Further testing on different types of Gram positives and identification of the exact mechanism of action would be of importance.

Extended-Spectrum Beta-Lactamase-Producing Gram-Negative Bacteria on Healthcare Workers' Mobile Phones: Evidence from Tikur Anbessa Specialized Hospital, Addis Ababa, Ethiopia

Background

Mobile phones are widely used in hospital settings for different purposes. Mobile phones of healthcare workers (HCWs) could be colonized or harbor extended-spectrum beta-lactamase (ESBL) producing gram-negative bacteria and may act as source of infectious agents. The aim of this study was to determine the rate of extended-spectrum beta-lactamase-producing Gram-negative bacteria on mobile phones of healthcare workers, to assess their antimicrobial susceptibility patterns and associated factors.

Methods

A laboratory-based cross-sectional study was conducted involving a total of 572 samples by rubbing swabs of the front screen, back, keypad, and metallic surfaces of mobile phones of healthcare workers using simple random sampling technique. All specimens were screened for ESBL using ESBL CHROME agar and confirmed using double-disk diffusion test (DDDT). Antibiotic susceptibility testing was done by the Kirby–Bauer disk diffusion technique on Mueller–Hinton agar. Data were analyzed using SPSS version 25, odds ratio and p-value was calculated to determine the association among variables.

Results

Overall, the number of mobile phones contaminated by gram-negative bacteria was 454 out of 572 (79.4%). Female sex (OR 0.651, p-value=0.039) and service year (OR 0.468, p-value=0.038) of healthcare workers were found to be the most significant factors associated with healthcare professionals’ mobile phone and bacterial contamination. Nine percent of the isolates were ESBL-producers. K. pneumoniae (27%) was the dominant ESBL-producing isolate followed by Acinetobacter spp. (14.5%) and E.coli (14.5%). ESBL-producers were highly resistant to ampicillin (95.8%), piperacillin (83.3%), cotrimoxazole (70.8%), and chloramphenicol (54.2%), but highly sensitive to meropenem (87.5%), amikacin (85.4%), and piperacillin-tazobactam (81.2%).

Conclusion

ESBL-producing Gram-negative bacteria were isolated from 8.3% of HCWs’ mobile phones. As high as 79.4% of the isolates were multidrug resistant. Mobile phones can lead to bacterial cross-contamination and could be a source of nosocomial infections.