Exploring the genetic mechanisms underlying amoxicillin-clavulanate resistance in waterborne Escherichia coli

Geospatial mapping and cluster analysis of antibiotic-resistant Escherichia coli in drinking water of semi-arid areas

Ensuring universal access to safe drinking water remains a global challenge, especially in semi-arid regions facing water scarcity, pollution, inadequate infrastructure, and rapid urbanization. The present study aimed to assess drinking water quality by analysing antibiotic-resistant Escherichia coli (E. coli) and their spatial distribution, identifying contamination hotspots using integrated physicochemical, microbial, and advanced geospatial assessments on 122 samples collected from surface and groundwater of semi-arid areas with key physicochemical parameters analysed using standard methods. Microbial contamination was assessed through heterotrophic plate counts and coliform tests, detecting E. coli (n = 83 isolates) that underwent antibiotic susceptibility testing via the Kirby-Bauer disk diffusion method against eleven antibiotics. Results showed that several key physicochemical (total dissolved solids, alkalinity, fluoride, and calcium) and microbial parameters exceeded WHO permissible limits. Correlation analysis revealed significant relationships among water quality indicators in both water sources. Advanced geospatial techniques, including Empirical Bayesian Kriging and Getis-Ord Gi cluster analysis, enabled spatial interpolation of studied parameters and identified significant antibiotic-resistant E. coli clusters in 15 wards. The antibiogram showed high resistance levels, with 91.6% of isolates resistant to oxacillin, 83.1% to amoxicillin, and 63.9% to ciprofloxacin, complemented by the Multiple Antibiotic Resistance Index reaching up to 0.83 indicating a high risk of contamination. Spatial-cluster analysis pinpointed high-risk areas exhibiting significant antibiotic-resistant E. coli clusters. This integrated approach underscores the urgent need for improved water treatment, antimicrobial resistance surveillance, and infrastructure upgrades to mitigate contamination risks in drinking water systems of rapidly urbanizing semi-arid regions worldwide.

In Vitro Antimicrobial Potential of Portuguese Propolis Extracts from Gerês against Pathogenic Microorganisms

Antimicrobial resistance (AMR) is one of humanity's main health problems today. Despite all the breakthroughs and research over the past few years, the number of microbial illnesses that are resistant to the available antibiotics is increasing at an alarming rate. In this article, we estimated the biomedical potential of Portuguese propolis harvested from the Gerês apiary over five years, evaluating the in vitro antimicrobial effect of five hydroalcoholic extracts prepared from five single propolis samples and of a hydroalcoholic extract obtained from the mixture of all samples. The antimicrobial potential was firstly assessed by determining the minimum inhibitory concentration (MIC) of these extracts against a panel of three Gram-positive (Bacillus subtilis, methicillin-sensitive Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus) and one Gram-negative bacteria (Escherichia coli), as well as two yeasts (Candida albicans and Saccharomyces cerevisiae). As MIC values against each bacterium were consistent across all the evaluated propolis extracts, we decided to further conduct a disk diffusion assay, which included three commercial antibiotics-erythromycin, vancomycin, and amoxicillin/clavulanic acid-for comparison purposes. In addition to displaying a concentration-dependent antibacterial effect, the hydroalcoholic extracts prepared with 70% ethanol exhibited stronger antimicrobial capacity than vancomycin against B. subtilis (% of increase ranged between 26 and 59%) and methicillin-sensitive S. aureus (% of increase ranged between 63 and 77%). Moreover, methicillin-resistant S. aureus (MRSA) showed susceptibility to the activity of the same extracts and resistance to all tested antibiotics. These findings support that propolis from Gerês is a promising natural product with promising antimicrobial activity, representing a very stimulating result considering the actual problem with AMR.

Antibacterial and Antibiofilm Effects of Different Samples of Five Commercially Available Essential Oils

Essential oils (EOs) have gained economic importance due to their biological activities, and increasing amounts are demanded everywhere. However, substantial differences between the same essential oil samples from different suppliers are reported-concerning their chemical composition and bioactivities-due to numerous companies involved in EOs production and the continuous development of online sales. The present study investigates the antibacterial and antibiofilm activities of two to four samples of five commercially available essential oils (Oregano, Eucalyptus, Rosemary, Clove, and Peppermint oils) produced by autochthonous companies. The manufacturers provided all EOs' chemical compositions determined through GC-MS. The EOs' bioactivities were investigated in vitro against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The antibacterial and antibiofilm effects (ABE% and, respectively, ABfE%) were evaluated spectrophotometrically at 562 and 570 nm using microplate cultivation techniques. The essential oils' calculated parameters were compared with those of three standard broad-spectrum antibiotics: Amoxicillin/Clavulanic acid, Gentamycin, and Streptomycin. The results showed that at the first dilution (D1 = 25 mg/mL), all EOs exhibited antibacterial and antibiofilm activity against all Gram-positive and Gram-negative bacteria tested, and MIC value > 25 mg/mL. Generally, both effects progressively decreased from D1 to D3. Only EOs with a considerable content of highly active metabolites revealed insignificant differences. E. coli showed the lowest susceptibility to all commercially available essential oils-15 EO samples had undetected antibacterial and antibiofilm effects at D2 and D3. Peppermint and Clove oils recorded the most significant differences regarding chemical composition and antibacterial/antibiofilm activities. All registered differences could be due to different places for harvesting the raw plant material, various technological processes through which these essential oils were obtained, the preservation conditions, and complex interactions between constituents.