The total phenolic content of extracts in decreasing order is ethanol extract (CDA Et) > acetone extract (CDA ACE) > phenolic extract (CDA MW) > n-hexane extract (CDA nHX)> chloroform extract (CDA CHL) > dichloromethane extract (CDA DCM). The ordering of extracts in terms of antioxidant activity from highest to lowest is CDA Et > CDA MW > CDA DCM > CDA CHL > CDA ACE > CDA nHX in DPPH, ABTS and FRAP assays. A significant relationship is found between antioxidant potential and total phenolic content, suggesting that phenolic compounds are the major contributors to the antioxidant activity of C. didymus.

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The goal of this study was to genotypically characterize extended-spectrum β-lactamase-producing Escherichia coli isolates from the western region of Saudi Arabia and to identify active antibiotics against these isolates using phenotypic and molecular modeling. In total, 211 ESBL-producing E. coli isolates recovered from heterogeneous clinical specimens were identified by MALDI-TOF. Thirty-two sequence types (STs) were identified from a multilocus sequence typing (MLST) analysis of ESBL-producing E. coli, including a novel ST (ST8162). The most common ST in the Saudi and expatriate population was ST131, followed by ST38. All the isolates were multidrug resistant (MDR), and >95% of the isolates were resistant to third-generation (ceftriaxone and ceftazidime) and fourth-generation (cefepime) cephalosporins. The ESBL-positive E. coli isolates primarily harbored the blaCTX-M and blaTEM genes. No resistance was observed against the carbapenem antibiotic group. All the ESBL-producing E. coli isolates were observed to be susceptible to a ceftazidime/avibactam combination. Molecular interaction analyses of the docked complexes revealed the amino acid residues crucial for the binding of antibiotics and inhibitors to the modeled CTX-M-15 enzyme. Importantly, avibactam displayed the most robust interaction with CTX-M-15 among the tested inhibitors in the docked state (∆G = −6.6 kcal/mol). The binding free energy values for clavulanate, tazobactam and sulbactam were determined to be −5.7, −5.9 and −5.2 kcal/mol, respectively. Overall, the study concludes that ‘ceftazidime along with avibactam’ should be carefully used as a treatment option against only carbapenem-resistant MDR ESBL-producing E. coli in this region.

Background: Enterococcus faecalis is a ubiquitous member of the gut microbiota and has emerged as a lifethreatening multidrug-resistant (MDR) nosocomial pathogen. The aim of this study was to survey the prevalence of multidrug-resistant and epidemiologically important strains of E. faecalis in the western region of Saudi Arabia using phenotypic and whole genome sequencing approaches. Methods: In total, 155 patients positive for E. faecalis infection were included in this study. The isolates were identified by MALDI-TOF, and screen for antimicrobial resistance using VITEK-2 system. Genome sequencing was performed with paired-end strategy using MiSeq platform. Results: Seventeen sequence types (STs) were identified through multilocus sequence typing (MLST) analysis of the E. faecalis genomes, including two novels STs (ST862 and ST863). The most common STs in the Saudi patients were ST179 and ST16 from clonal complex 16 (CC16). Around 96% (n = 149) isolates were MDR. The antibiotics quinupristin/dalfopristin, clindamycin, and erythromycin demonstrated almost no coverage, and high-level streptomycin, gentamycin, and ciprofloxacin demonstrated suboptimal coverage. Low resistance was observed against vancomycin, linezolid, and ampicillin. Moreover, 34 antimicrobial resistance genes and variants, and three families of insertion sequences were found in the E. faecalis genomes, which likely contributed to the observed antimicrobial resistance. Twenty-two virulence factors, which were mainly associated with biofilm formation, endocarditis, cell adherence, and colonization, were detected in the isolates. Conclusions: Diverse STs of E. faecalis, including strains associated with common nosocomial infections are circulating in the healthcare facility of Saudi Arabia and carried multi-drug resistance, which has important implications for infection control.